Move outbound channel constructor into `OutboundV1Channel` impl
[rust-lightning] / lightning / src / ln / channel.rs
index 00faeabbde562644bcdcd9529a8668e056cfcaa2..131b9b402499201fdda8d0c68f71b0bc87061aa4 100644 (file)
@@ -304,6 +304,85 @@ const MULTI_STATE_FLAGS: u32 = BOTH_SIDES_SHUTDOWN_MASK | ChannelState::PeerDisc
 
 pub const INITIAL_COMMITMENT_NUMBER: u64 = (1 << 48) - 1;
 
+pub const DEFAULT_MAX_HTLCS: u16 = 50;
+
+pub(crate) fn commitment_tx_base_weight(opt_anchors: bool) -> u64 {
+       const COMMITMENT_TX_BASE_WEIGHT: u64 = 724;
+       const COMMITMENT_TX_BASE_ANCHOR_WEIGHT: u64 = 1124;
+       if opt_anchors { COMMITMENT_TX_BASE_ANCHOR_WEIGHT } else { COMMITMENT_TX_BASE_WEIGHT }
+}
+
+#[cfg(not(test))]
+const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
+#[cfg(test)]
+pub const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
+
+pub const ANCHOR_OUTPUT_VALUE_SATOSHI: u64 = 330;
+
+/// The percentage of the channel value `holder_max_htlc_value_in_flight_msat` used to be set to,
+/// before this was made configurable. The percentage was made configurable in LDK 0.0.107,
+/// although LDK 0.0.104+ enabled serialization of channels with a different value set for
+/// `holder_max_htlc_value_in_flight_msat`.
+pub const MAX_IN_FLIGHT_PERCENT_LEGACY: u8 = 10;
+
+/// Maximum `funding_satoshis` value according to the BOLT #2 specification, if
+/// `option_support_large_channel` (aka wumbo channels) is not supported.
+/// It's 2^24 - 1.
+pub const MAX_FUNDING_SATOSHIS_NO_WUMBO: u64 = (1 << 24) - 1;
+
+/// Total bitcoin supply in satoshis.
+pub const TOTAL_BITCOIN_SUPPLY_SATOSHIS: u64 = 21_000_000 * 1_0000_0000;
+
+/// The maximum network dust limit for standard script formats. This currently represents the
+/// minimum output value for a P2SH output before Bitcoin Core 22 considers the entire
+/// transaction non-standard and thus refuses to relay it.
+/// We also use this as the maximum counterparty `dust_limit_satoshis` allowed, given many
+/// implementations use this value for their dust limit today.
+pub const MAX_STD_OUTPUT_DUST_LIMIT_SATOSHIS: u64 = 546;
+
+/// The maximum channel dust limit we will accept from our counterparty.
+pub const MAX_CHAN_DUST_LIMIT_SATOSHIS: u64 = MAX_STD_OUTPUT_DUST_LIMIT_SATOSHIS;
+
+/// The dust limit is used for both the commitment transaction outputs as well as the closing
+/// transactions. For cooperative closing transactions, we require segwit outputs, though accept
+/// *any* segwit scripts, which are allowed to be up to 42 bytes in length.
+/// In order to avoid having to concern ourselves with standardness during the closing process, we
+/// simply require our counterparty to use a dust limit which will leave any segwit output
+/// standard.
+/// See <https://github.com/lightning/bolts/issues/905> for more details.
+pub const MIN_CHAN_DUST_LIMIT_SATOSHIS: u64 = 354;
+
+// Just a reasonable implementation-specific safe lower bound, higher than the dust limit.
+pub const MIN_THEIR_CHAN_RESERVE_SATOSHIS: u64 = 1000;
+
+/// Used to return a simple Error back to ChannelManager. Will get converted to a
+/// msgs::ErrorAction::SendErrorMessage or msgs::ErrorAction::IgnoreError as appropriate with our
+/// channel_id in ChannelManager.
+pub(super) enum ChannelError {
+       Ignore(String),
+       Warn(String),
+       Close(String),
+}
+
+impl fmt::Debug for ChannelError {
+       fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+               match self {
+                       &ChannelError::Ignore(ref e) => write!(f, "Ignore : {}", e),
+                       &ChannelError::Warn(ref e) => write!(f, "Warn : {}", e),
+                       &ChannelError::Close(ref e) => write!(f, "Close : {}", e),
+               }
+       }
+}
+
+macro_rules! secp_check {
+       ($res: expr, $err: expr) => {
+               match $res {
+                       Ok(thing) => thing,
+                       Err(_) => return Err(ChannelError::Close($err)),
+               }
+       };
+}
+
 /// The "channel disabled" bit in channel_update must be set based on whether we are connected to
 /// our counterparty or not. However, we don't want to announce updates right away to avoid
 /// spamming the network with updates if the connection is flapping. Instead, we "stage" updates to
@@ -1450,420 +1529,463 @@ impl<Signer: ChannelSigner> ChannelContext<Signer> {
                }
                stats
        }
-}
 
-// Internal utility functions for channels
-
-/// Returns the value to use for `holder_max_htlc_value_in_flight_msat` as a percentage of the
-/// `channel_value_satoshis` in msat, set through
-/// [`ChannelHandshakeConfig::max_inbound_htlc_value_in_flight_percent_of_channel`]
-///
-/// The effective percentage is lower bounded by 1% and upper bounded by 100%.
-///
-/// [`ChannelHandshakeConfig::max_inbound_htlc_value_in_flight_percent_of_channel`]: crate::util::config::ChannelHandshakeConfig::max_inbound_htlc_value_in_flight_percent_of_channel
-fn get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis: u64, config: &ChannelHandshakeConfig) -> u64 {
-       let configured_percent = if config.max_inbound_htlc_value_in_flight_percent_of_channel < 1 {
-               1
-       } else if config.max_inbound_htlc_value_in_flight_percent_of_channel > 100 {
-               100
-       } else {
-               config.max_inbound_htlc_value_in_flight_percent_of_channel as u64
-       };
-       channel_value_satoshis * 10 * configured_percent
-}
+       /// Get the available balances, see [`AvailableBalances`]'s fields for more info.
+       /// Doesn't bother handling the
+       /// if-we-removed-it-already-but-haven't-fully-resolved-they-can-still-send-an-inbound-HTLC
+       /// corner case properly.
+       pub fn get_available_balances(&self) -> AvailableBalances {
+               let context = &self;
+               // Note that we have to handle overflow due to the above case.
+               let inbound_stats = context.get_inbound_pending_htlc_stats(None);
+               let outbound_stats = context.get_outbound_pending_htlc_stats(None);
 
-/// Returns a minimum channel reserve value the remote needs to maintain,
-/// required by us according to the configured or default
-/// [`ChannelHandshakeConfig::their_channel_reserve_proportional_millionths`]
-///
-/// Guaranteed to return a value no larger than channel_value_satoshis
-///
-/// This is used both for outbound and inbound channels and has lower bound
-/// of `MIN_THEIR_CHAN_RESERVE_SATOSHIS`.
-pub(crate) fn get_holder_selected_channel_reserve_satoshis(channel_value_satoshis: u64, config: &UserConfig) -> u64 {
-       let calculated_reserve = channel_value_satoshis.saturating_mul(config.channel_handshake_config.their_channel_reserve_proportional_millionths as u64) / 1_000_000;
-       cmp::min(channel_value_satoshis, cmp::max(calculated_reserve, MIN_THEIR_CHAN_RESERVE_SATOSHIS))
-}
+               let mut balance_msat = context.value_to_self_msat;
+               for ref htlc in context.pending_inbound_htlcs.iter() {
+                       if let InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::Fulfill(_)) = htlc.state {
+                               balance_msat += htlc.amount_msat;
+                       }
+               }
+               balance_msat -= outbound_stats.pending_htlcs_value_msat;
 
-/// This is for legacy reasons, present for forward-compatibility.
-/// LDK versions older than 0.0.104 don't know how read/handle values other than default
-/// from storage. Hence, we use this function to not persist default values of
-/// `holder_selected_channel_reserve_satoshis` for channels into storage.
-pub(crate) fn get_legacy_default_holder_selected_channel_reserve_satoshis(channel_value_satoshis: u64) -> u64 {
-       let (q, _) = channel_value_satoshis.overflowing_div(100);
-       cmp::min(channel_value_satoshis, cmp::max(q, 1000))
-}
+               let outbound_capacity_msat = context.value_to_self_msat
+                               .saturating_sub(outbound_stats.pending_htlcs_value_msat)
+                               .saturating_sub(
+                                       context.counterparty_selected_channel_reserve_satoshis.unwrap_or(0) * 1000);
 
-// Get the fee cost in SATS of a commitment tx with a given number of HTLC outputs.
-// Note that num_htlcs should not include dust HTLCs.
-#[inline]
-fn commit_tx_fee_sat(feerate_per_kw: u32, num_htlcs: usize, opt_anchors: bool) -> u64 {
-       feerate_per_kw as u64 * (commitment_tx_base_weight(opt_anchors) + num_htlcs as u64 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000
-}
+               let mut available_capacity_msat = outbound_capacity_msat;
 
-// Get the fee cost in MSATS of a commitment tx with a given number of HTLC outputs.
-// Note that num_htlcs should not include dust HTLCs.
-fn commit_tx_fee_msat(feerate_per_kw: u32, num_htlcs: usize, opt_anchors: bool) -> u64 {
-       // Note that we need to divide before multiplying to round properly,
-       // since the lowest denomination of bitcoin on-chain is the satoshi.
-       (commitment_tx_base_weight(opt_anchors) + num_htlcs as u64 * COMMITMENT_TX_WEIGHT_PER_HTLC) * feerate_per_kw as u64 / 1000 * 1000
-}
+               if context.is_outbound() {
+                       // We should mind channel commit tx fee when computing how much of the available capacity
+                       // can be used in the next htlc. Mirrors the logic in send_htlc.
+                       //
+                       // The fee depends on whether the amount we will be sending is above dust or not,
+                       // and the answer will in turn change the amount itself — making it a circular
+                       // dependency.
+                       // This complicates the computation around dust-values, up to the one-htlc-value.
+                       let mut real_dust_limit_timeout_sat = context.holder_dust_limit_satoshis;
+                       if !context.opt_anchors() {
+                               real_dust_limit_timeout_sat += context.feerate_per_kw as u64 * htlc_timeout_tx_weight(false) / 1000;
+                       }
 
-// TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
-// has been completed, and then turn into a Channel to get compiler-time enforcement of things like
-// calling channel_id() before we're set up or things like get_outbound_funding_signed on an
-// inbound channel.
-//
-// Holder designates channel data owned for the benefit of the user client.
-// Counterparty designates channel data owned by the another channel participant entity.
-pub(super) struct Channel<Signer: ChannelSigner> {
-       pub context: ChannelContext<Signer>,
-}
+                       let htlc_above_dust = HTLCCandidate::new(real_dust_limit_timeout_sat * 1000, HTLCInitiator::LocalOffered);
+                       let max_reserved_commit_tx_fee_msat = FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE * context.next_local_commit_tx_fee_msat(htlc_above_dust, Some(()));
+                       let htlc_dust = HTLCCandidate::new(real_dust_limit_timeout_sat * 1000 - 1, HTLCInitiator::LocalOffered);
+                       let min_reserved_commit_tx_fee_msat = FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE * context.next_local_commit_tx_fee_msat(htlc_dust, Some(()));
 
-#[cfg(any(test, fuzzing))]
-struct CommitmentTxInfoCached {
-       fee: u64,
-       total_pending_htlcs: usize,
-       next_holder_htlc_id: u64,
-       next_counterparty_htlc_id: u64,
-       feerate: u32,
-}
+                       // We will first subtract the fee as if we were above-dust. Then, if the resulting
+                       // value ends up being below dust, we have this fee available again. In that case,
+                       // match the value to right-below-dust.
+                       let mut capacity_minus_commitment_fee_msat: i64 = (available_capacity_msat as i64) - (max_reserved_commit_tx_fee_msat as i64);
+                       if capacity_minus_commitment_fee_msat < (real_dust_limit_timeout_sat as i64) * 1000 {
+                               let one_htlc_difference_msat = max_reserved_commit_tx_fee_msat - min_reserved_commit_tx_fee_msat;
+                               debug_assert!(one_htlc_difference_msat != 0);
+                               capacity_minus_commitment_fee_msat += one_htlc_difference_msat as i64;
+                               capacity_minus_commitment_fee_msat = cmp::min(real_dust_limit_timeout_sat as i64 * 1000 - 1, capacity_minus_commitment_fee_msat);
+                               available_capacity_msat = cmp::max(0, cmp::min(capacity_minus_commitment_fee_msat, available_capacity_msat as i64)) as u64;
+                       } else {
+                               available_capacity_msat = capacity_minus_commitment_fee_msat as u64;
+                       }
+               } else {
+                       // If the channel is inbound (i.e. counterparty pays the fee), we need to make sure
+                       // sending a new HTLC won't reduce their balance below our reserve threshold.
+                       let mut real_dust_limit_success_sat = context.counterparty_dust_limit_satoshis;
+                       if !context.opt_anchors() {
+                               real_dust_limit_success_sat += context.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000;
+                       }
 
-pub const DEFAULT_MAX_HTLCS: u16 = 50;
+                       let htlc_above_dust = HTLCCandidate::new(real_dust_limit_success_sat * 1000, HTLCInitiator::LocalOffered);
+                       let max_reserved_commit_tx_fee_msat = context.next_remote_commit_tx_fee_msat(htlc_above_dust, None);
 
-pub(crate) fn commitment_tx_base_weight(opt_anchors: bool) -> u64 {
-       const COMMITMENT_TX_BASE_WEIGHT: u64 = 724;
-       const COMMITMENT_TX_BASE_ANCHOR_WEIGHT: u64 = 1124;
-       if opt_anchors { COMMITMENT_TX_BASE_ANCHOR_WEIGHT } else { COMMITMENT_TX_BASE_WEIGHT }
-}
+                       let holder_selected_chan_reserve_msat = context.holder_selected_channel_reserve_satoshis * 1000;
+                       let remote_balance_msat = (context.channel_value_satoshis * 1000 - context.value_to_self_msat)
+                               .saturating_sub(inbound_stats.pending_htlcs_value_msat);
 
-#[cfg(not(test))]
-const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
-#[cfg(test)]
-pub const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
+                       if remote_balance_msat < max_reserved_commit_tx_fee_msat + holder_selected_chan_reserve_msat {
+                               // If another HTLC's fee would reduce the remote's balance below the reserve limit
+                               // we've selected for them, we can only send dust HTLCs.
+                               available_capacity_msat = cmp::min(available_capacity_msat, real_dust_limit_success_sat * 1000 - 1);
+                       }
+               }
 
-pub const ANCHOR_OUTPUT_VALUE_SATOSHI: u64 = 330;
+               let mut next_outbound_htlc_minimum_msat = context.counterparty_htlc_minimum_msat;
 
-/// The percentage of the channel value `holder_max_htlc_value_in_flight_msat` used to be set to,
-/// before this was made configurable. The percentage was made configurable in LDK 0.0.107,
-/// although LDK 0.0.104+ enabled serialization of channels with a different value set for
-/// `holder_max_htlc_value_in_flight_msat`.
-pub const MAX_IN_FLIGHT_PERCENT_LEGACY: u8 = 10;
+               // If we get close to our maximum dust exposure, we end up in a situation where we can send
+               // between zero and the remaining dust exposure limit remaining OR above the dust limit.
+               // Because we cannot express this as a simple min/max, we prefer to tell the user they can
+               // send above the dust limit (as the router can always overpay to meet the dust limit).
+               let mut remaining_msat_below_dust_exposure_limit = None;
+               let mut dust_exposure_dust_limit_msat = 0;
 
-/// Maximum `funding_satoshis` value according to the BOLT #2 specification, if
-/// `option_support_large_channel` (aka wumbo channels) is not supported.
-/// It's 2^24 - 1.
-pub const MAX_FUNDING_SATOSHIS_NO_WUMBO: u64 = (1 << 24) - 1;
+               let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if context.opt_anchors() {
+                       (context.counterparty_dust_limit_satoshis, context.holder_dust_limit_satoshis)
+               } else {
+                       let dust_buffer_feerate = context.get_dust_buffer_feerate(None) as u64;
+                       (context.counterparty_dust_limit_satoshis + dust_buffer_feerate * htlc_success_tx_weight(false) / 1000,
+                        context.holder_dust_limit_satoshis       + dust_buffer_feerate * htlc_timeout_tx_weight(false) / 1000)
+               };
+               let on_counterparty_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat;
+               if on_counterparty_dust_htlc_exposure_msat as i64 + htlc_success_dust_limit as i64 * 1000 - 1 > context.get_max_dust_htlc_exposure_msat() as i64 {
+                       remaining_msat_below_dust_exposure_limit =
+                               Some(context.get_max_dust_htlc_exposure_msat().saturating_sub(on_counterparty_dust_htlc_exposure_msat));
+                       dust_exposure_dust_limit_msat = cmp::max(dust_exposure_dust_limit_msat, htlc_success_dust_limit * 1000);
+               }
 
-/// Total bitcoin supply in satoshis.
-pub const TOTAL_BITCOIN_SUPPLY_SATOSHIS: u64 = 21_000_000 * 1_0000_0000;
-
-/// The maximum network dust limit for standard script formats. This currently represents the
-/// minimum output value for a P2SH output before Bitcoin Core 22 considers the entire
-/// transaction non-standard and thus refuses to relay it.
-/// We also use this as the maximum counterparty `dust_limit_satoshis` allowed, given many
-/// implementations use this value for their dust limit today.
-pub const MAX_STD_OUTPUT_DUST_LIMIT_SATOSHIS: u64 = 546;
-
-/// The maximum channel dust limit we will accept from our counterparty.
-pub const MAX_CHAN_DUST_LIMIT_SATOSHIS: u64 = MAX_STD_OUTPUT_DUST_LIMIT_SATOSHIS;
-
-/// The dust limit is used for both the commitment transaction outputs as well as the closing
-/// transactions. For cooperative closing transactions, we require segwit outputs, though accept
-/// *any* segwit scripts, which are allowed to be up to 42 bytes in length.
-/// In order to avoid having to concern ourselves with standardness during the closing process, we
-/// simply require our counterparty to use a dust limit which will leave any segwit output
-/// standard.
-/// See <https://github.com/lightning/bolts/issues/905> for more details.
-pub const MIN_CHAN_DUST_LIMIT_SATOSHIS: u64 = 354;
-
-// Just a reasonable implementation-specific safe lower bound, higher than the dust limit.
-pub const MIN_THEIR_CHAN_RESERVE_SATOSHIS: u64 = 1000;
-
-/// Used to return a simple Error back to ChannelManager. Will get converted to a
-/// msgs::ErrorAction::SendErrorMessage or msgs::ErrorAction::IgnoreError as appropriate with our
-/// channel_id in ChannelManager.
-pub(super) enum ChannelError {
-       Ignore(String),
-       Warn(String),
-       Close(String),
-}
-
-impl fmt::Debug for ChannelError {
-       fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-               match self {
-                       &ChannelError::Ignore(ref e) => write!(f, "Ignore : {}", e),
-                       &ChannelError::Warn(ref e) => write!(f, "Warn : {}", e),
-                       &ChannelError::Close(ref e) => write!(f, "Close : {}", e),
-               }
-       }
-}
-
-macro_rules! secp_check {
-       ($res: expr, $err: expr) => {
-               match $res {
-                       Ok(thing) => thing,
-                       Err(_) => return Err(ChannelError::Close($err)),
-               }
-       };
-}
-
-impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
-       fn get_initial_channel_type(config: &UserConfig, their_features: &InitFeatures) -> ChannelTypeFeatures {
-               // The default channel type (ie the first one we try) depends on whether the channel is
-               // public - if it is, we just go with `only_static_remotekey` as it's the only option
-               // available. If it's private, we first try `scid_privacy` as it provides better privacy
-               // with no other changes, and fall back to `only_static_remotekey`.
-               let mut ret = ChannelTypeFeatures::only_static_remote_key();
-               if !config.channel_handshake_config.announced_channel &&
-                       config.channel_handshake_config.negotiate_scid_privacy &&
-                       their_features.supports_scid_privacy() {
-                       ret.set_scid_privacy_required();
+               let on_holder_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat;
+               if on_holder_dust_htlc_exposure_msat as i64 + htlc_timeout_dust_limit as i64 * 1000 - 1 > context.get_max_dust_htlc_exposure_msat() as i64 {
+                       remaining_msat_below_dust_exposure_limit = Some(cmp::min(
+                               remaining_msat_below_dust_exposure_limit.unwrap_or(u64::max_value()),
+                               context.get_max_dust_htlc_exposure_msat().saturating_sub(on_holder_dust_htlc_exposure_msat)));
+                       dust_exposure_dust_limit_msat = cmp::max(dust_exposure_dust_limit_msat, htlc_timeout_dust_limit * 1000);
                }
 
-               // Optionally, if the user would like to negotiate the `anchors_zero_fee_htlc_tx` option, we
-               // set it now. If they don't understand it, we'll fall back to our default of
-               // `only_static_remotekey`.
-               #[cfg(anchors)]
-               { // Attributes are not allowed on if expressions on our current MSRV of 1.41.
-                       if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx &&
-                               their_features.supports_anchors_zero_fee_htlc_tx() {
-                               ret.set_anchors_zero_fee_htlc_tx_required();
+               if let Some(remaining_limit_msat) = remaining_msat_below_dust_exposure_limit {
+                       if available_capacity_msat < dust_exposure_dust_limit_msat {
+                               available_capacity_msat = cmp::min(available_capacity_msat, remaining_limit_msat);
+                       } else {
+                               next_outbound_htlc_minimum_msat = cmp::max(next_outbound_htlc_minimum_msat, dust_exposure_dust_limit_msat);
                        }
                }
 
-               ret
-       }
+               available_capacity_msat = cmp::min(available_capacity_msat,
+                       context.counterparty_max_htlc_value_in_flight_msat - outbound_stats.pending_htlcs_value_msat);
 
-       /// If we receive an error message, it may only be a rejection of the channel type we tried,
-       /// not of our ability to open any channel at all. Thus, on error, we should first call this
-       /// and see if we get a new `OpenChannel` message, otherwise the channel is failed.
-       pub(crate) fn maybe_handle_error_without_close(&mut self, chain_hash: BlockHash) -> Result<msgs::OpenChannel, ()> {
-               if !self.context.is_outbound() || self.context.channel_state != ChannelState::OurInitSent as u32 { return Err(()); }
-               if self.context.channel_type == ChannelTypeFeatures::only_static_remote_key() {
-                       // We've exhausted our options
-                       return Err(());
+               if outbound_stats.pending_htlcs + 1 > context.counterparty_max_accepted_htlcs as u32 {
+                       available_capacity_msat = 0;
                }
-               // We support opening a few different types of channels. Try removing our additional
-               // features one by one until we've either arrived at our default or the counterparty has
-               // accepted one.
-               //
-               // Due to the order below, we may not negotiate `option_anchors_zero_fee_htlc_tx` if the
-               // counterparty doesn't support `option_scid_privacy`. Since `get_initial_channel_type`
-               // checks whether the counterparty supports every feature, this would only happen if the
-               // counterparty is advertising the feature, but rejecting channels proposing the feature for
-               // whatever reason.
-               if self.context.channel_type.supports_anchors_zero_fee_htlc_tx() {
-                       self.context.channel_type.clear_anchors_zero_fee_htlc_tx();
-                       assert!(self.context.channel_transaction_parameters.opt_non_zero_fee_anchors.is_none());
-                       self.context.channel_transaction_parameters.opt_anchors = None;
-               } else if self.context.channel_type.supports_scid_privacy() {
-                       self.context.channel_type.clear_scid_privacy();
-               } else {
-                       self.context.channel_type = ChannelTypeFeatures::only_static_remote_key();
+
+               AvailableBalances {
+                       inbound_capacity_msat: cmp::max(context.channel_value_satoshis as i64 * 1000
+                                       - context.value_to_self_msat as i64
+                                       - context.get_inbound_pending_htlc_stats(None).pending_htlcs_value_msat as i64
+                                       - context.holder_selected_channel_reserve_satoshis as i64 * 1000,
+                               0) as u64,
+                       outbound_capacity_msat,
+                       next_outbound_htlc_limit_msat: available_capacity_msat,
+                       next_outbound_htlc_minimum_msat,
+                       balance_msat,
                }
-               Ok(self.get_open_channel(chain_hash))
        }
 
-       // Constructors:
-       pub fn new_outbound<ES: Deref, SP: Deref, F: Deref>(
-               fee_estimator: &LowerBoundedFeeEstimator<F>, entropy_source: &ES, signer_provider: &SP, counterparty_node_id: PublicKey, their_features: &InitFeatures,
-               channel_value_satoshis: u64, push_msat: u64, user_id: u128, config: &UserConfig, current_chain_height: u32,
-               outbound_scid_alias: u64
-       ) -> Result<Channel<Signer>, APIError>
-       where ES::Target: EntropySource,
-             SP::Target: SignerProvider<Signer = Signer>,
-             F::Target: FeeEstimator,
-       {
-               let holder_selected_contest_delay = config.channel_handshake_config.our_to_self_delay;
-               let channel_keys_id = signer_provider.generate_channel_keys_id(false, channel_value_satoshis, user_id);
-               let holder_signer = signer_provider.derive_channel_signer(channel_value_satoshis, channel_keys_id);
-               let pubkeys = holder_signer.pubkeys().clone();
-
-               if !their_features.supports_wumbo() && channel_value_satoshis > MAX_FUNDING_SATOSHIS_NO_WUMBO {
-                       return Err(APIError::APIMisuseError{err: format!("funding_value must not exceed {}, it was {}", MAX_FUNDING_SATOSHIS_NO_WUMBO, channel_value_satoshis)});
-               }
-               if channel_value_satoshis >= TOTAL_BITCOIN_SUPPLY_SATOSHIS {
-                       return Err(APIError::APIMisuseError{err: format!("funding_value must be smaller than the total bitcoin supply, it was {}", channel_value_satoshis)});
-               }
-               let channel_value_msat = channel_value_satoshis * 1000;
-               if push_msat > channel_value_msat {
-                       return Err(APIError::APIMisuseError { err: format!("Push value ({}) was larger than channel_value ({})", push_msat, channel_value_msat) });
-               }
-               if holder_selected_contest_delay < BREAKDOWN_TIMEOUT {
-                       return Err(APIError::APIMisuseError {err: format!("Configured with an unreasonable our_to_self_delay ({}) putting user funds at risks", holder_selected_contest_delay)});
-               }
-               let holder_selected_channel_reserve_satoshis = get_holder_selected_channel_reserve_satoshis(channel_value_satoshis, config);
-               if holder_selected_channel_reserve_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
-                       // Protocol level safety check in place, although it should never happen because
-                       // of `MIN_THEIR_CHAN_RESERVE_SATOSHIS`
-                       return Err(APIError::APIMisuseError { err: format!("Holder selected channel  reserve below implemention limit dust_limit_satoshis {}", holder_selected_channel_reserve_satoshis) });
-               }
+       pub fn get_holder_counterparty_selected_channel_reserve_satoshis(&self) -> (u64, Option<u64>) {
+               let context = &self;
+               (context.holder_selected_channel_reserve_satoshis, context.counterparty_selected_channel_reserve_satoshis)
+       }
 
-               let channel_type = Self::get_initial_channel_type(&config, their_features);
-               debug_assert!(channel_type.is_subset(&channelmanager::provided_channel_type_features(&config)));
+       /// Get the commitment tx fee for the local's (i.e. our) next commitment transaction based on the
+       /// number of pending HTLCs that are on track to be in our next commitment tx.
+       ///
+       /// Optionally includes the `HTLCCandidate` given by `htlc` and an additional non-dust HTLC if
+       /// `fee_spike_buffer_htlc` is `Some`.
+       ///
+       /// The first extra HTLC is useful for determining whether we can accept a further HTLC, the
+       /// second allows for creating a buffer to ensure a further HTLC can always be accepted/added.
+       ///
+       /// Dust HTLCs are excluded.
+       fn next_local_commit_tx_fee_msat(&self, htlc: HTLCCandidate, fee_spike_buffer_htlc: Option<()>) -> u64 {
+               let context = &self;
+               assert!(context.is_outbound());
 
-               let feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
+               let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if context.opt_anchors() {
+                       (0, 0)
+               } else {
+                       (context.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000,
+                               context.feerate_per_kw as u64 * htlc_timeout_tx_weight(false) / 1000)
+               };
+               let real_dust_limit_success_sat = htlc_success_dust_limit + context.holder_dust_limit_satoshis;
+               let real_dust_limit_timeout_sat = htlc_timeout_dust_limit + context.holder_dust_limit_satoshis;
 
-               let value_to_self_msat = channel_value_satoshis * 1000 - push_msat;
-               let commitment_tx_fee = commit_tx_fee_msat(feerate, MIN_AFFORDABLE_HTLC_COUNT, channel_type.requires_anchors_zero_fee_htlc_tx());
-               if value_to_self_msat < commitment_tx_fee {
-                       return Err(APIError::APIMisuseError{ err: format!("Funding amount ({}) can't even pay fee for initial commitment transaction fee of {}.", value_to_self_msat / 1000, commitment_tx_fee / 1000) });
+               let mut addl_htlcs = 0;
+               if fee_spike_buffer_htlc.is_some() { addl_htlcs += 1; }
+               match htlc.origin {
+                       HTLCInitiator::LocalOffered => {
+                               if htlc.amount_msat / 1000 >= real_dust_limit_timeout_sat {
+                                       addl_htlcs += 1;
+                               }
+                       },
+                       HTLCInitiator::RemoteOffered => {
+                               if htlc.amount_msat / 1000 >= real_dust_limit_success_sat {
+                                       addl_htlcs += 1;
+                               }
+                       }
                }
 
-               let mut secp_ctx = Secp256k1::new();
-               secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
-
-               let shutdown_scriptpubkey = if config.channel_handshake_config.commit_upfront_shutdown_pubkey {
-                       match signer_provider.get_shutdown_scriptpubkey() {
-                               Ok(scriptpubkey) => Some(scriptpubkey),
-                               Err(_) => return Err(APIError::ChannelUnavailable { err: "Failed to get shutdown scriptpubkey".to_owned()}),
+               let mut included_htlcs = 0;
+               for ref htlc in context.pending_inbound_htlcs.iter() {
+                       if htlc.amount_msat / 1000 < real_dust_limit_success_sat {
+                               continue
                        }
-               } else { None };
+                       // We include LocalRemoved HTLCs here because we may still need to broadcast a commitment
+                       // transaction including this HTLC if it times out before they RAA.
+                       included_htlcs += 1;
+               }
 
-               if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
-                       if !shutdown_scriptpubkey.is_compatible(&their_features) {
-                               return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
+               for ref htlc in context.pending_outbound_htlcs.iter() {
+                       if htlc.amount_msat / 1000 < real_dust_limit_timeout_sat {
+                               continue
+                       }
+                       match htlc.state {
+                               OutboundHTLCState::LocalAnnounced {..} => included_htlcs += 1,
+                               OutboundHTLCState::Committed => included_htlcs += 1,
+                               OutboundHTLCState::RemoteRemoved {..} => included_htlcs += 1,
+                               // We don't include AwaitingRemoteRevokeToRemove HTLCs because our next commitment
+                               // transaction won't be generated until they send us their next RAA, which will mean
+                               // dropping any HTLCs in this state.
+                               _ => {},
                        }
                }
 
-               let destination_script = match signer_provider.get_destination_script() {
-                       Ok(script) => script,
-                       Err(_) => return Err(APIError::ChannelUnavailable { err: "Failed to get destination script".to_owned()}),
-               };
-
-               let temporary_channel_id = entropy_source.get_secure_random_bytes();
-
-               Ok(Channel {
-                       context: ChannelContext {
-                               user_id,
-
-                               config: LegacyChannelConfig {
-                                       options: config.channel_config.clone(),
-                                       announced_channel: config.channel_handshake_config.announced_channel,
-                                       commit_upfront_shutdown_pubkey: config.channel_handshake_config.commit_upfront_shutdown_pubkey,
+               for htlc in context.holding_cell_htlc_updates.iter() {
+                       match htlc {
+                               &HTLCUpdateAwaitingACK::AddHTLC { amount_msat, .. } => {
+                                       if amount_msat / 1000 < real_dust_limit_timeout_sat {
+                                               continue
+                                       }
+                                       included_htlcs += 1
                                },
+                               _ => {}, // Don't include claims/fails that are awaiting ack, because once we get the
+                                        // ack we're guaranteed to never include them in commitment txs anymore.
+                       }
+               }
 
-                               prev_config: None,
-
-                               inbound_handshake_limits_override: Some(config.channel_handshake_limits.clone()),
-
-                               channel_id: temporary_channel_id,
-                               temporary_channel_id: Some(temporary_channel_id),
-                               channel_state: ChannelState::OurInitSent as u32,
-                               announcement_sigs_state: AnnouncementSigsState::NotSent,
-                               secp_ctx,
-                               channel_value_satoshis,
-
-                               latest_monitor_update_id: 0,
-
-                               holder_signer,
-                               shutdown_scriptpubkey,
-                               destination_script,
+               let num_htlcs = included_htlcs + addl_htlcs;
+               let res = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs, context.opt_anchors());
+               #[cfg(any(test, fuzzing))]
+               {
+                       let mut fee = res;
+                       if fee_spike_buffer_htlc.is_some() {
+                               fee = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs - 1, context.opt_anchors());
+                       }
+                       let total_pending_htlcs = context.pending_inbound_htlcs.len() + context.pending_outbound_htlcs.len()
+                               + context.holding_cell_htlc_updates.len();
+                       let commitment_tx_info = CommitmentTxInfoCached {
+                               fee,
+                               total_pending_htlcs,
+                               next_holder_htlc_id: match htlc.origin {
+                                       HTLCInitiator::LocalOffered => context.next_holder_htlc_id + 1,
+                                       HTLCInitiator::RemoteOffered => context.next_holder_htlc_id,
+                               },
+                               next_counterparty_htlc_id: match htlc.origin {
+                                       HTLCInitiator::LocalOffered => context.next_counterparty_htlc_id,
+                                       HTLCInitiator::RemoteOffered => context.next_counterparty_htlc_id + 1,
+                               },
+                               feerate: context.feerate_per_kw,
+                       };
+                       *context.next_local_commitment_tx_fee_info_cached.lock().unwrap() = Some(commitment_tx_info);
+               }
+               res
+       }
 
-                               cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
-                               cur_counterparty_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
-                               value_to_self_msat,
+       /// Get the commitment tx fee for the remote's next commitment transaction based on the number of
+       /// pending HTLCs that are on track to be in their next commitment tx
+       ///
+       /// Optionally includes the `HTLCCandidate` given by `htlc` and an additional non-dust HTLC if
+       /// `fee_spike_buffer_htlc` is `Some`.
+       ///
+       /// The first extra HTLC is useful for determining whether we can accept a further HTLC, the
+       /// second allows for creating a buffer to ensure a further HTLC can always be accepted/added.
+       ///
+       /// Dust HTLCs are excluded.
+       fn next_remote_commit_tx_fee_msat(&self, htlc: HTLCCandidate, fee_spike_buffer_htlc: Option<()>) -> u64 {
+               let context = &self;
+               assert!(!context.is_outbound());
 
-                               pending_inbound_htlcs: Vec::new(),
-                               pending_outbound_htlcs: Vec::new(),
-                               holding_cell_htlc_updates: Vec::new(),
-                               pending_update_fee: None,
-                               holding_cell_update_fee: None,
-                               next_holder_htlc_id: 0,
-                               next_counterparty_htlc_id: 0,
-                               update_time_counter: 1,
+               let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if context.opt_anchors() {
+                       (0, 0)
+               } else {
+                       (context.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000,
+                               context.feerate_per_kw as u64 * htlc_timeout_tx_weight(false) / 1000)
+               };
+               let real_dust_limit_success_sat = htlc_success_dust_limit + context.counterparty_dust_limit_satoshis;
+               let real_dust_limit_timeout_sat = htlc_timeout_dust_limit + context.counterparty_dust_limit_satoshis;
 
-                               resend_order: RAACommitmentOrder::CommitmentFirst,
+               let mut addl_htlcs = 0;
+               if fee_spike_buffer_htlc.is_some() { addl_htlcs += 1; }
+               match htlc.origin {
+                       HTLCInitiator::LocalOffered => {
+                               if htlc.amount_msat / 1000 >= real_dust_limit_success_sat {
+                                       addl_htlcs += 1;
+                               }
+                       },
+                       HTLCInitiator::RemoteOffered => {
+                               if htlc.amount_msat / 1000 >= real_dust_limit_timeout_sat {
+                                       addl_htlcs += 1;
+                               }
+                       }
+               }
 
-                               monitor_pending_channel_ready: false,
-                               monitor_pending_revoke_and_ack: false,
-                               monitor_pending_commitment_signed: false,
-                               monitor_pending_forwards: Vec::new(),
-                               monitor_pending_failures: Vec::new(),
-                               monitor_pending_finalized_fulfills: Vec::new(),
+               // When calculating the set of HTLCs which will be included in their next commitment_signed, all
+               // non-dust inbound HTLCs are included (as all states imply it will be included) and only
+               // committed outbound HTLCs, see below.
+               let mut included_htlcs = 0;
+               for ref htlc in context.pending_inbound_htlcs.iter() {
+                       if htlc.amount_msat / 1000 <= real_dust_limit_timeout_sat {
+                               continue
+                       }
+                       included_htlcs += 1;
+               }
 
-                               #[cfg(debug_assertions)]
-                               holder_max_commitment_tx_output: Mutex::new((channel_value_satoshis * 1000 - push_msat, push_msat)),
-                               #[cfg(debug_assertions)]
-                               counterparty_max_commitment_tx_output: Mutex::new((channel_value_satoshis * 1000 - push_msat, push_msat)),
+               for ref htlc in context.pending_outbound_htlcs.iter() {
+                       if htlc.amount_msat / 1000 <= real_dust_limit_success_sat {
+                               continue
+                       }
+                       // We only include outbound HTLCs if it will not be included in their next commitment_signed,
+                       // i.e. if they've responded to us with an RAA after announcement.
+                       match htlc.state {
+                               OutboundHTLCState::Committed => included_htlcs += 1,
+                               OutboundHTLCState::RemoteRemoved {..} => included_htlcs += 1,
+                               OutboundHTLCState::LocalAnnounced { .. } => included_htlcs += 1,
+                               _ => {},
+                       }
+               }
 
-                               last_sent_closing_fee: None,
-                               pending_counterparty_closing_signed: None,
-                               closing_fee_limits: None,
-                               target_closing_feerate_sats_per_kw: None,
+               let num_htlcs = included_htlcs + addl_htlcs;
+               let res = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs, context.opt_anchors());
+               #[cfg(any(test, fuzzing))]
+               {
+                       let mut fee = res;
+                       if fee_spike_buffer_htlc.is_some() {
+                               fee = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs - 1, context.opt_anchors());
+                       }
+                       let total_pending_htlcs = context.pending_inbound_htlcs.len() + context.pending_outbound_htlcs.len();
+                       let commitment_tx_info = CommitmentTxInfoCached {
+                               fee,
+                               total_pending_htlcs,
+                               next_holder_htlc_id: match htlc.origin {
+                                       HTLCInitiator::LocalOffered => context.next_holder_htlc_id + 1,
+                                       HTLCInitiator::RemoteOffered => context.next_holder_htlc_id,
+                               },
+                               next_counterparty_htlc_id: match htlc.origin {
+                                       HTLCInitiator::LocalOffered => context.next_counterparty_htlc_id,
+                                       HTLCInitiator::RemoteOffered => context.next_counterparty_htlc_id + 1,
+                               },
+                               feerate: context.feerate_per_kw,
+                       };
+                       *context.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = Some(commitment_tx_info);
+               }
+               res
+       }
 
-                               inbound_awaiting_accept: false,
+       /// Returns transaction if there is pending funding transaction that is yet to broadcast
+       pub fn unbroadcasted_funding(&self) -> Option<Transaction> {
+               if self.channel_state & (ChannelState::FundingCreated as u32) != 0 {
+                       self.funding_transaction.clone()
+               } else {
+                       None
+               }
+       }
+}
 
-                               funding_tx_confirmed_in: None,
-                               funding_tx_confirmation_height: 0,
-                               short_channel_id: None,
-                               channel_creation_height: current_chain_height,
+// Internal utility functions for channels
 
-                               feerate_per_kw: feerate,
-                               counterparty_dust_limit_satoshis: 0,
-                               holder_dust_limit_satoshis: MIN_CHAN_DUST_LIMIT_SATOSHIS,
-                               counterparty_max_htlc_value_in_flight_msat: 0,
-                               holder_max_htlc_value_in_flight_msat: get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis, &config.channel_handshake_config),
-                               counterparty_selected_channel_reserve_satoshis: None, // Filled in in accept_channel
-                               holder_selected_channel_reserve_satoshis,
-                               counterparty_htlc_minimum_msat: 0,
-                               holder_htlc_minimum_msat: if config.channel_handshake_config.our_htlc_minimum_msat == 0 { 1 } else { config.channel_handshake_config.our_htlc_minimum_msat },
-                               counterparty_max_accepted_htlcs: 0,
-                               holder_max_accepted_htlcs: cmp::min(config.channel_handshake_config.our_max_accepted_htlcs, MAX_HTLCS),
-                               minimum_depth: None, // Filled in in accept_channel
+/// Returns the value to use for `holder_max_htlc_value_in_flight_msat` as a percentage of the
+/// `channel_value_satoshis` in msat, set through
+/// [`ChannelHandshakeConfig::max_inbound_htlc_value_in_flight_percent_of_channel`]
+///
+/// The effective percentage is lower bounded by 1% and upper bounded by 100%.
+///
+/// [`ChannelHandshakeConfig::max_inbound_htlc_value_in_flight_percent_of_channel`]: crate::util::config::ChannelHandshakeConfig::max_inbound_htlc_value_in_flight_percent_of_channel
+fn get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis: u64, config: &ChannelHandshakeConfig) -> u64 {
+       let configured_percent = if config.max_inbound_htlc_value_in_flight_percent_of_channel < 1 {
+               1
+       } else if config.max_inbound_htlc_value_in_flight_percent_of_channel > 100 {
+               100
+       } else {
+               config.max_inbound_htlc_value_in_flight_percent_of_channel as u64
+       };
+       channel_value_satoshis * 10 * configured_percent
+}
 
-                               counterparty_forwarding_info: None,
+/// Returns a minimum channel reserve value the remote needs to maintain,
+/// required by us according to the configured or default
+/// [`ChannelHandshakeConfig::their_channel_reserve_proportional_millionths`]
+///
+/// Guaranteed to return a value no larger than channel_value_satoshis
+///
+/// This is used both for outbound and inbound channels and has lower bound
+/// of `MIN_THEIR_CHAN_RESERVE_SATOSHIS`.
+pub(crate) fn get_holder_selected_channel_reserve_satoshis(channel_value_satoshis: u64, config: &UserConfig) -> u64 {
+       let calculated_reserve = channel_value_satoshis.saturating_mul(config.channel_handshake_config.their_channel_reserve_proportional_millionths as u64) / 1_000_000;
+       cmp::min(channel_value_satoshis, cmp::max(calculated_reserve, MIN_THEIR_CHAN_RESERVE_SATOSHIS))
+}
 
-                               channel_transaction_parameters: ChannelTransactionParameters {
-                                       holder_pubkeys: pubkeys,
-                                       holder_selected_contest_delay: config.channel_handshake_config.our_to_self_delay,
-                                       is_outbound_from_holder: true,
-                                       counterparty_parameters: None,
-                                       funding_outpoint: None,
-                                       opt_anchors: if channel_type.requires_anchors_zero_fee_htlc_tx() { Some(()) } else { None },
-                                       opt_non_zero_fee_anchors: None
-                               },
-                               funding_transaction: None,
+/// This is for legacy reasons, present for forward-compatibility.
+/// LDK versions older than 0.0.104 don't know how read/handle values other than default
+/// from storage. Hence, we use this function to not persist default values of
+/// `holder_selected_channel_reserve_satoshis` for channels into storage.
+pub(crate) fn get_legacy_default_holder_selected_channel_reserve_satoshis(channel_value_satoshis: u64) -> u64 {
+       let (q, _) = channel_value_satoshis.overflowing_div(100);
+       cmp::min(channel_value_satoshis, cmp::max(q, 1000))
+}
 
-                               counterparty_cur_commitment_point: None,
-                               counterparty_prev_commitment_point: None,
-                               counterparty_node_id,
+// Get the fee cost in SATS of a commitment tx with a given number of HTLC outputs.
+// Note that num_htlcs should not include dust HTLCs.
+#[inline]
+fn commit_tx_fee_sat(feerate_per_kw: u32, num_htlcs: usize, opt_anchors: bool) -> u64 {
+       feerate_per_kw as u64 * (commitment_tx_base_weight(opt_anchors) + num_htlcs as u64 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000
+}
 
-                               counterparty_shutdown_scriptpubkey: None,
+// Get the fee cost in MSATS of a commitment tx with a given number of HTLC outputs.
+// Note that num_htlcs should not include dust HTLCs.
+fn commit_tx_fee_msat(feerate_per_kw: u32, num_htlcs: usize, opt_anchors: bool) -> u64 {
+       // Note that we need to divide before multiplying to round properly,
+       // since the lowest denomination of bitcoin on-chain is the satoshi.
+       (commitment_tx_base_weight(opt_anchors) + num_htlcs as u64 * COMMITMENT_TX_WEIGHT_PER_HTLC) * feerate_per_kw as u64 / 1000 * 1000
+}
 
-                               commitment_secrets: CounterpartyCommitmentSecrets::new(),
+// TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
+// has been completed, and then turn into a Channel to get compiler-time enforcement of things like
+// calling channel_id() before we're set up or things like get_outbound_funding_signed on an
+// inbound channel.
+//
+// Holder designates channel data owned for the benefit of the user client.
+// Counterparty designates channel data owned by the another channel participant entity.
+pub(super) struct Channel<Signer: ChannelSigner> {
+       pub context: ChannelContext<Signer>,
+}
 
-                               channel_update_status: ChannelUpdateStatus::Enabled,
-                               closing_signed_in_flight: false,
-
-                               announcement_sigs: None,
-
-                               #[cfg(any(test, fuzzing))]
-                               next_local_commitment_tx_fee_info_cached: Mutex::new(None),
-                               #[cfg(any(test, fuzzing))]
-                               next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
-
-                               workaround_lnd_bug_4006: None,
-                               sent_message_awaiting_response: None,
-
-                               latest_inbound_scid_alias: None,
-                               outbound_scid_alias,
-
-                               channel_pending_event_emitted: false,
-                               channel_ready_event_emitted: false,
-
-                               #[cfg(any(test, fuzzing))]
-                               historical_inbound_htlc_fulfills: HashSet::new(),
-
-                               channel_type,
-                               channel_keys_id,
+#[cfg(any(test, fuzzing))]
+struct CommitmentTxInfoCached {
+       fee: u64,
+       total_pending_htlcs: usize,
+       next_holder_htlc_id: u64,
+       next_counterparty_htlc_id: u64,
+       feerate: u32,
+}
 
-                               pending_monitor_updates: Vec::new(),
-                       }
-               })
+impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
+       /// If we receive an error message, it may only be a rejection of the channel type we tried,
+       /// not of our ability to open any channel at all. Thus, on error, we should first call this
+       /// and see if we get a new `OpenChannel` message, otherwise the channel is failed.
+       pub(crate) fn maybe_handle_error_without_close(&mut self, chain_hash: BlockHash) -> Result<msgs::OpenChannel, ()> {
+               if !self.context.is_outbound() || self.context.channel_state != ChannelState::OurInitSent as u32 { return Err(()); }
+               if self.context.channel_type == ChannelTypeFeatures::only_static_remote_key() {
+                       // We've exhausted our options
+                       return Err(());
+               }
+               // We support opening a few different types of channels. Try removing our additional
+               // features one by one until we've either arrived at our default or the counterparty has
+               // accepted one.
+               //
+               // Due to the order below, we may not negotiate `option_anchors_zero_fee_htlc_tx` if the
+               // counterparty doesn't support `option_scid_privacy`. Since `get_initial_channel_type`
+               // checks whether the counterparty supports every feature, this would only happen if the
+               // counterparty is advertising the feature, but rejecting channels proposing the feature for
+               // whatever reason.
+               if self.context.channel_type.supports_anchors_zero_fee_htlc_tx() {
+                       self.context.channel_type.clear_anchors_zero_fee_htlc_tx();
+                       assert!(self.context.channel_transaction_parameters.opt_non_zero_fee_anchors.is_none());
+                       self.context.channel_transaction_parameters.opt_anchors = None;
+               } else if self.context.channel_type.supports_scid_privacy() {
+                       self.context.channel_type.clear_scid_privacy();
+               } else {
+                       self.context.channel_type = ChannelTypeFeatures::only_static_remote_key();
+               }
+               Ok(self.get_open_channel(chain_hash))
        }
 
+       // Constructors:
+
        fn check_remote_fee<F: Deref, L: Deref>(fee_estimator: &LowerBoundedFeeEstimator<F>,
                feerate_per_kw: u32, cur_feerate_per_kw: Option<u32>, logger: &L)
                -> Result<(), ChannelError> where F::Target: FeeEstimator, L::Target: Logger,
@@ -2504,859 +2626,514 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
        ///
        /// If we do fail twice, we `debug_assert!(false)` and return `Ok(None)`. Thus, this will always
        /// return `Ok(_)` if preconditions are met. In any case, `Err`s will only be
-       /// [`ChannelError::Ignore`].
-       pub fn queue_fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, logger: &L)
-       -> Result<(), ChannelError> where L::Target: Logger {
-               self.fail_htlc(htlc_id_arg, err_packet, true, logger)
-                       .map(|msg_opt| assert!(msg_opt.is_none(), "We forced holding cell?"))
-       }
-
-       /// We can only have one resolution per HTLC. In some cases around reconnect, we may fulfill
-       /// an HTLC more than once or fulfill once and then attempt to fail after reconnect. We cannot,
-       /// however, fail more than once as we wait for an upstream failure to be irrevocably committed
-       /// before we fail backwards.
-       ///
-       /// If we do fail twice, we `debug_assert!(false)` and return `Ok(None)`. Thus, this will always
-       /// return `Ok(_)` if preconditions are met. In any case, `Err`s will only be
-       /// [`ChannelError::Ignore`].
-       fn fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, mut force_holding_cell: bool, logger: &L)
-       -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> where L::Target: Logger {
-               if (self.context.channel_state & (ChannelState::ChannelReady as u32)) != (ChannelState::ChannelReady as u32) {
-                       panic!("Was asked to fail an HTLC when channel was not in an operational state");
-               }
-               assert_eq!(self.context.channel_state & ChannelState::ShutdownComplete as u32, 0);
-
-               // ChannelManager may generate duplicate claims/fails due to HTLC update events from
-               // on-chain ChannelsMonitors during block rescan. Ideally we'd figure out a way to drop
-               // these, but for now we just have to treat them as normal.
-
-               let mut pending_idx = core::usize::MAX;
-               for (idx, htlc) in self.context.pending_inbound_htlcs.iter().enumerate() {
-                       if htlc.htlc_id == htlc_id_arg {
-                               match htlc.state {
-                                       InboundHTLCState::Committed => {},
-                                       InboundHTLCState::LocalRemoved(ref reason) => {
-                                               if let &InboundHTLCRemovalReason::Fulfill(_) = reason {
-                                               } else {
-                                                       debug_assert!(false, "Tried to fail an HTLC that was already failed");
-                                               }
-                                               return Ok(None);
-                                       },
-                                       _ => {
-                                               debug_assert!(false, "Have an inbound HTLC we tried to claim before it was fully committed to");
-                                               return Err(ChannelError::Ignore(format!("Unable to find a pending HTLC which matched the given HTLC ID ({})", htlc.htlc_id)));
-                                       }
-                               }
-                               pending_idx = idx;
-                       }
-               }
-               if pending_idx == core::usize::MAX {
-                       #[cfg(any(test, fuzzing))]
-                       // If we failed to find an HTLC to fail, make sure it was previously fulfilled and this
-                       // is simply a duplicate fail, not previously failed and we failed-back too early.
-                       debug_assert!(self.context.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
-                       return Ok(None);
-               }
-
-               if (self.context.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateInProgress as u32)) != 0 {
-                       debug_assert!(force_holding_cell, "!force_holding_cell is only called when emptying the holding cell, so we shouldn't end up back in it!");
-                       force_holding_cell = true;
-               }
-
-               // Now update local state:
-               if force_holding_cell {
-                       for pending_update in self.context.holding_cell_htlc_updates.iter() {
-                               match pending_update {
-                                       &HTLCUpdateAwaitingACK::ClaimHTLC { htlc_id, .. } => {
-                                               if htlc_id_arg == htlc_id {
-                                                       #[cfg(any(test, fuzzing))]
-                                                       debug_assert!(self.context.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
-                                                       return Ok(None);
-                                               }
-                                       },
-                                       &HTLCUpdateAwaitingACK::FailHTLC { htlc_id, .. } => {
-                                               if htlc_id_arg == htlc_id {
-                                                       debug_assert!(false, "Tried to fail an HTLC that was already failed");
-                                                       return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
-                                               }
-                                       },
-                                       _ => {}
-                               }
-                       }
-                       log_trace!(logger, "Placing failure for HTLC ID {} in holding cell in channel {}.", htlc_id_arg, log_bytes!(self.context.channel_id()));
-                       self.context.holding_cell_htlc_updates.push(HTLCUpdateAwaitingACK::FailHTLC {
-                               htlc_id: htlc_id_arg,
-                               err_packet,
-                       });
-                       return Ok(None);
-               }
-
-               log_trace!(logger, "Failing HTLC ID {} back with a update_fail_htlc message in channel {}.", htlc_id_arg, log_bytes!(self.context.channel_id()));
-               {
-                       let htlc = &mut self.context.pending_inbound_htlcs[pending_idx];
-                       htlc.state = InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::FailRelay(err_packet.clone()));
-               }
-
-               Ok(Some(msgs::UpdateFailHTLC {
-                       channel_id: self.context.channel_id(),
-                       htlc_id: htlc_id_arg,
-                       reason: err_packet
-               }))
-       }
-
-       // Message handlers:
-
-       pub fn accept_channel(&mut self, msg: &msgs::AcceptChannel, default_limits: &ChannelHandshakeLimits, their_features: &InitFeatures) -> Result<(), ChannelError> {
-               let peer_limits = if let Some(ref limits) = self.context.inbound_handshake_limits_override { limits } else { default_limits };
-
-               // Check sanity of message fields:
-               if !self.context.is_outbound() {
-                       return Err(ChannelError::Close("Got an accept_channel message from an inbound peer".to_owned()));
-               }
-               if self.context.channel_state != ChannelState::OurInitSent as u32 {
-                       return Err(ChannelError::Close("Got an accept_channel message at a strange time".to_owned()));
-               }
-               if msg.dust_limit_satoshis > 21000000 * 100000000 {
-                       return Err(ChannelError::Close(format!("Peer never wants payout outputs? dust_limit_satoshis was {}", msg.dust_limit_satoshis)));
-               }
-               if msg.channel_reserve_satoshis > self.context.channel_value_satoshis {
-                       return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than ({})", msg.channel_reserve_satoshis, self.context.channel_value_satoshis)));
-               }
-               if msg.dust_limit_satoshis > self.context.holder_selected_channel_reserve_satoshis {
-                       return Err(ChannelError::Close(format!("Dust limit ({}) is bigger than our channel reserve ({})", msg.dust_limit_satoshis, self.context.holder_selected_channel_reserve_satoshis)));
-               }
-               if msg.channel_reserve_satoshis > self.context.channel_value_satoshis - self.context.holder_selected_channel_reserve_satoshis {
-                       return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than channel value minus our reserve ({})",
-                               msg.channel_reserve_satoshis, self.context.channel_value_satoshis - self.context.holder_selected_channel_reserve_satoshis)));
-               }
-               let full_channel_value_msat = (self.context.channel_value_satoshis - msg.channel_reserve_satoshis) * 1000;
-               if msg.htlc_minimum_msat >= full_channel_value_msat {
-                       return Err(ChannelError::Close(format!("Minimum htlc value ({}) is full channel value ({})", msg.htlc_minimum_msat, full_channel_value_msat)));
-               }
-               let max_delay_acceptable = u16::min(peer_limits.their_to_self_delay, MAX_LOCAL_BREAKDOWN_TIMEOUT);
-               if msg.to_self_delay > max_delay_acceptable {
-                       return Err(ChannelError::Close(format!("They wanted our payments to be delayed by a needlessly long period. Upper limit: {}. Actual: {}", max_delay_acceptable, msg.to_self_delay)));
-               }
-               if msg.max_accepted_htlcs < 1 {
-                       return Err(ChannelError::Close("0 max_accepted_htlcs makes for a useless channel".to_owned()));
-               }
-               if msg.max_accepted_htlcs > MAX_HTLCS {
-                       return Err(ChannelError::Close(format!("max_accepted_htlcs was {}. It must not be larger than {}", msg.max_accepted_htlcs, MAX_HTLCS)));
-               }
-
-               // Now check against optional parameters as set by config...
-               if msg.htlc_minimum_msat > peer_limits.max_htlc_minimum_msat {
-                       return Err(ChannelError::Close(format!("htlc_minimum_msat ({}) is higher than the user specified limit ({})", msg.htlc_minimum_msat, peer_limits.max_htlc_minimum_msat)));
-               }
-               if msg.max_htlc_value_in_flight_msat < peer_limits.min_max_htlc_value_in_flight_msat {
-                       return Err(ChannelError::Close(format!("max_htlc_value_in_flight_msat ({}) is less than the user specified limit ({})", msg.max_htlc_value_in_flight_msat, peer_limits.min_max_htlc_value_in_flight_msat)));
-               }
-               if msg.channel_reserve_satoshis > peer_limits.max_channel_reserve_satoshis {
-                       return Err(ChannelError::Close(format!("channel_reserve_satoshis ({}) is higher than the user specified limit ({})", msg.channel_reserve_satoshis, peer_limits.max_channel_reserve_satoshis)));
-               }
-               if msg.max_accepted_htlcs < peer_limits.min_max_accepted_htlcs {
-                       return Err(ChannelError::Close(format!("max_accepted_htlcs ({}) is less than the user specified limit ({})", msg.max_accepted_htlcs, peer_limits.min_max_accepted_htlcs)));
-               }
-               if msg.dust_limit_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
-                       return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is less than the implementation limit ({})", msg.dust_limit_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS)));
-               }
-               if msg.dust_limit_satoshis > MAX_CHAN_DUST_LIMIT_SATOSHIS {
-                       return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is greater than the implementation limit ({})", msg.dust_limit_satoshis, MAX_CHAN_DUST_LIMIT_SATOSHIS)));
-               }
-               if msg.minimum_depth > peer_limits.max_minimum_depth {
-                       return Err(ChannelError::Close(format!("We consider the minimum depth to be unreasonably large. Expected minimum: ({}). Actual: ({})", peer_limits.max_minimum_depth, msg.minimum_depth)));
-               }
-
-               if let Some(ty) = &msg.channel_type {
-                       if *ty != self.context.channel_type {
-                               return Err(ChannelError::Close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
-                       }
-               } else if their_features.supports_channel_type() {
-                       // Assume they've accepted the channel type as they said they understand it.
-               } else {
-                       let channel_type = ChannelTypeFeatures::from_init(&their_features);
-                       if channel_type != ChannelTypeFeatures::only_static_remote_key() {
-                               return Err(ChannelError::Close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
-                       }
-                       self.context.channel_type = channel_type;
-               }
-
-               let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
-                       match &msg.shutdown_scriptpubkey {
-                               &Some(ref script) => {
-                                       // Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
-                                       if script.len() == 0 {
-                                               None
-                                       } else {
-                                               if !script::is_bolt2_compliant(&script, their_features) {
-                                                       return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script)));
-                                               }
-                                               Some(script.clone())
-                                       }
-                               },
-                               // Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
-                               &None => {
-                                       return Err(ChannelError::Close("Peer is signaling upfront_shutdown but we don't get any script. Use 0-length script to opt-out".to_owned()));
-                               }
-                       }
-               } else { None };
-
-               self.context.counterparty_dust_limit_satoshis = msg.dust_limit_satoshis;
-               self.context.counterparty_max_htlc_value_in_flight_msat = cmp::min(msg.max_htlc_value_in_flight_msat, self.context.channel_value_satoshis * 1000);
-               self.context.counterparty_selected_channel_reserve_satoshis = Some(msg.channel_reserve_satoshis);
-               self.context.counterparty_htlc_minimum_msat = msg.htlc_minimum_msat;
-               self.context.counterparty_max_accepted_htlcs = msg.max_accepted_htlcs;
-
-               if peer_limits.trust_own_funding_0conf {
-                       self.context.minimum_depth = Some(msg.minimum_depth);
-               } else {
-                       self.context.minimum_depth = Some(cmp::max(1, msg.minimum_depth));
-               }
-
-               let counterparty_pubkeys = ChannelPublicKeys {
-                       funding_pubkey: msg.funding_pubkey,
-                       revocation_basepoint: msg.revocation_basepoint,
-                       payment_point: msg.payment_point,
-                       delayed_payment_basepoint: msg.delayed_payment_basepoint,
-                       htlc_basepoint: msg.htlc_basepoint
-               };
-
-               self.context.channel_transaction_parameters.counterparty_parameters = Some(CounterpartyChannelTransactionParameters {
-                       selected_contest_delay: msg.to_self_delay,
-                       pubkeys: counterparty_pubkeys,
-               });
-
-               self.context.counterparty_cur_commitment_point = Some(msg.first_per_commitment_point);
-               self.context.counterparty_shutdown_scriptpubkey = counterparty_shutdown_scriptpubkey;
-
-               self.context.channel_state = ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32;
-               self.context.inbound_handshake_limits_override = None; // We're done enforcing limits on our peer's handshake now.
-
-               Ok(())
-       }
-
-       fn funding_created_signature<L: Deref>(&mut self, sig: &Signature, logger: &L) -> Result<(Txid, CommitmentTransaction, Signature), ChannelError> where L::Target: Logger {
-               let funding_script = self.context.get_funding_redeemscript();
-
-               let keys = self.context.build_holder_transaction_keys(self.context.cur_holder_commitment_transaction_number);
-               let initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_holder_commitment_transaction_number, &keys, true, false, logger).tx;
-               {
-                       let trusted_tx = initial_commitment_tx.trust();
-                       let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
-                       let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.context.channel_value_satoshis);
-                       // They sign the holder commitment transaction...
-                       log_trace!(logger, "Checking funding_created tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
-                               log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.context.counterparty_funding_pubkey().serialize()),
-                               encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
-                               encode::serialize_hex(&funding_script), log_bytes!(self.context.channel_id()));
-                       secp_check!(self.context.secp_ctx.verify_ecdsa(&sighash, &sig, self.context.counterparty_funding_pubkey()), "Invalid funding_created signature from peer".to_owned());
-               }
-
-               let counterparty_keys = self.context.build_remote_transaction_keys();
-               let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
-
-               let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
-               let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
-               log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
-                       log_bytes!(self.context.channel_id()), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));
-
-               let counterparty_signature = self.context.holder_signer.sign_counterparty_commitment(&counterparty_initial_commitment_tx, Vec::new(), &self.context.secp_ctx)
-                               .map_err(|_| ChannelError::Close("Failed to get signatures for new commitment_signed".to_owned()))?.0;
-
-               // We sign "counterparty" commitment transaction, allowing them to broadcast the tx if they wish.
-               Ok((counterparty_initial_bitcoin_tx.txid, initial_commitment_tx, counterparty_signature))
-       }
-
-       pub fn funding_created<SP: Deref, L: Deref>(
-               &mut self, msg: &msgs::FundingCreated, best_block: BestBlock, signer_provider: &SP, logger: &L
-       ) -> Result<(msgs::FundingSigned, ChannelMonitor<Signer>), ChannelError>
-       where
-               SP::Target: SignerProvider<Signer = Signer>,
-               L::Target: Logger
-       {
-               if self.context.is_outbound() {
-                       return Err(ChannelError::Close("Received funding_created for an outbound channel?".to_owned()));
-               }
-               if self.context.channel_state != (ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32) {
-                       // BOLT 2 says that if we disconnect before we send funding_signed we SHOULD NOT
-                       // remember the channel, so it's safe to just send an error_message here and drop the
-                       // channel.
-                       return Err(ChannelError::Close("Received funding_created after we got the channel!".to_owned()));
-               }
-               if self.context.inbound_awaiting_accept {
-                       return Err(ChannelError::Close("FundingCreated message received before the channel was accepted".to_owned()));
-               }
-               if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
-                               self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
-                               self.context.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
-                       panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
-               }
-
-               let funding_txo = OutPoint { txid: msg.funding_txid, index: msg.funding_output_index };
-               self.context.channel_transaction_parameters.funding_outpoint = Some(funding_txo);
-               // This is an externally observable change before we finish all our checks.  In particular
-               // funding_created_signature may fail.
-               self.context.holder_signer.provide_channel_parameters(&self.context.channel_transaction_parameters);
-
-               let (counterparty_initial_commitment_txid, initial_commitment_tx, signature) = match self.funding_created_signature(&msg.signature, logger) {
-                       Ok(res) => res,
-                       Err(ChannelError::Close(e)) => {
-                               self.context.channel_transaction_parameters.funding_outpoint = None;
-                               return Err(ChannelError::Close(e));
-                       },
-                       Err(e) => {
-                               // The only error we know how to handle is ChannelError::Close, so we fall over here
-                               // to make sure we don't continue with an inconsistent state.
-                               panic!("unexpected error type from funding_created_signature {:?}", e);
-                       }
-               };
-
-               let holder_commitment_tx = HolderCommitmentTransaction::new(
-                       initial_commitment_tx,
-                       msg.signature,
-                       Vec::new(),
-                       &self.context.get_holder_pubkeys().funding_pubkey,
-                       self.context.counterparty_funding_pubkey()
-               );
-
-               self.context.holder_signer.validate_holder_commitment(&holder_commitment_tx, Vec::new())
-                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
-
-                       // Now that we're past error-generating stuff, update our local state:
-
-               let funding_redeemscript = self.context.get_funding_redeemscript();
-               let funding_txo_script = funding_redeemscript.to_v0_p2wsh();
-               let obscure_factor = get_commitment_transaction_number_obscure_factor(&self.context.get_holder_pubkeys().payment_point, &self.context.get_counterparty_pubkeys().payment_point, self.context.is_outbound());
-               let shutdown_script = self.context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
-               let mut monitor_signer = signer_provider.derive_channel_signer(self.context.channel_value_satoshis, self.context.channel_keys_id);
-               monitor_signer.provide_channel_parameters(&self.context.channel_transaction_parameters);
-               let channel_monitor = ChannelMonitor::new(self.context.secp_ctx.clone(), monitor_signer,
-                                                         shutdown_script, self.context.get_holder_selected_contest_delay(),
-                                                         &self.context.destination_script, (funding_txo, funding_txo_script.clone()),
-                                                         &self.context.channel_transaction_parameters,
-                                                         funding_redeemscript.clone(), self.context.channel_value_satoshis,
-                                                         obscure_factor,
-                                                         holder_commitment_tx, best_block, self.context.counterparty_node_id);
-
-               channel_monitor.provide_latest_counterparty_commitment_tx(counterparty_initial_commitment_txid, Vec::new(), self.context.cur_counterparty_commitment_transaction_number, self.context.counterparty_cur_commitment_point.unwrap(), logger);
-
-               self.context.channel_state = ChannelState::FundingSent as u32;
-               self.context.channel_id = funding_txo.to_channel_id();
-               self.context.cur_counterparty_commitment_transaction_number -= 1;
-               self.context.cur_holder_commitment_transaction_number -= 1;
-
-               log_info!(logger, "Generated funding_signed for peer for channel {}", log_bytes!(self.context.channel_id()));
-
-               let need_channel_ready = self.check_get_channel_ready(0).is_some();
-               self.monitor_updating_paused(false, false, need_channel_ready, Vec::new(), Vec::new(), Vec::new());
-
-               Ok((msgs::FundingSigned {
-                       channel_id: self.context.channel_id,
-                       signature,
-                       #[cfg(taproot)]
-                       partial_signature_with_nonce: None,
-               }, channel_monitor))
-       }
-
-       /// Handles a funding_signed message from the remote end.
-       /// If this call is successful, broadcast the funding transaction (and not before!)
-       pub fn funding_signed<SP: Deref, L: Deref>(
-               &mut self, msg: &msgs::FundingSigned, best_block: BestBlock, signer_provider: &SP, logger: &L
-       ) -> Result<ChannelMonitor<Signer>, ChannelError>
-       where
-               SP::Target: SignerProvider<Signer = Signer>,
-               L::Target: Logger
-       {
-               if !self.context.is_outbound() {
-                       return Err(ChannelError::Close("Received funding_signed for an inbound channel?".to_owned()));
-               }
-               if self.context.channel_state & !(ChannelState::MonitorUpdateInProgress as u32) != ChannelState::FundingCreated as u32 {
-                       return Err(ChannelError::Close("Received funding_signed in strange state!".to_owned()));
-               }
-               if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
-                               self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
-                               self.context.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
-                       panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
-               }
-
-               let funding_script = self.context.get_funding_redeemscript();
-
-               let counterparty_keys = self.context.build_remote_transaction_keys();
-               let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
-               let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
-               let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
-
-               log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
-                       log_bytes!(self.context.channel_id()), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));
-
-               let holder_signer = self.context.build_holder_transaction_keys(self.context.cur_holder_commitment_transaction_number);
-               let initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_holder_commitment_transaction_number, &holder_signer, true, false, logger).tx;
-               {
-                       let trusted_tx = initial_commitment_tx.trust();
-                       let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
-                       let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.context.channel_value_satoshis);
-                       // They sign our commitment transaction, allowing us to broadcast the tx if we wish.
-                       if let Err(_) = self.context.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &self.context.get_counterparty_pubkeys().funding_pubkey) {
-                               return Err(ChannelError::Close("Invalid funding_signed signature from peer".to_owned()));
-                       }
-               }
-
-               let holder_commitment_tx = HolderCommitmentTransaction::new(
-                       initial_commitment_tx,
-                       msg.signature,
-                       Vec::new(),
-                       &self.context.get_holder_pubkeys().funding_pubkey,
-                       self.context.counterparty_funding_pubkey()
-               );
-
-               self.context.holder_signer.validate_holder_commitment(&holder_commitment_tx, Vec::new())
-                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
-
-
-               let funding_redeemscript = self.context.get_funding_redeemscript();
-               let funding_txo = self.context.get_funding_txo().unwrap();
-               let funding_txo_script = funding_redeemscript.to_v0_p2wsh();
-               let obscure_factor = get_commitment_transaction_number_obscure_factor(&self.context.get_holder_pubkeys().payment_point, &self.context.get_counterparty_pubkeys().payment_point, self.context.is_outbound());
-               let shutdown_script = self.context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
-               let mut monitor_signer = signer_provider.derive_channel_signer(self.context.channel_value_satoshis, self.context.channel_keys_id);
-               monitor_signer.provide_channel_parameters(&self.context.channel_transaction_parameters);
-               let channel_monitor = ChannelMonitor::new(self.context.secp_ctx.clone(), monitor_signer,
-                                                         shutdown_script, self.context.get_holder_selected_contest_delay(),
-                                                         &self.context.destination_script, (funding_txo, funding_txo_script),
-                                                         &self.context.channel_transaction_parameters,
-                                                         funding_redeemscript.clone(), self.context.channel_value_satoshis,
-                                                         obscure_factor,
-                                                         holder_commitment_tx, best_block, self.context.counterparty_node_id);
-
-               channel_monitor.provide_latest_counterparty_commitment_tx(counterparty_initial_bitcoin_tx.txid, Vec::new(), self.context.cur_counterparty_commitment_transaction_number, self.context.counterparty_cur_commitment_point.unwrap(), logger);
-
-               assert_eq!(self.context.channel_state & (ChannelState::MonitorUpdateInProgress as u32), 0); // We have no had any monitor(s) yet to fail update!
-               self.context.channel_state = ChannelState::FundingSent as u32;
-               self.context.cur_holder_commitment_transaction_number -= 1;
-               self.context.cur_counterparty_commitment_transaction_number -= 1;
-
-               log_info!(logger, "Received funding_signed from peer for channel {}", log_bytes!(self.context.channel_id()));
-
-               let need_channel_ready = self.check_get_channel_ready(0).is_some();
-               self.monitor_updating_paused(false, false, need_channel_ready, Vec::new(), Vec::new(), Vec::new());
-               Ok(channel_monitor)
+       /// [`ChannelError::Ignore`].
+       pub fn queue_fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, logger: &L)
+       -> Result<(), ChannelError> where L::Target: Logger {
+               self.fail_htlc(htlc_id_arg, err_packet, true, logger)
+                       .map(|msg_opt| assert!(msg_opt.is_none(), "We forced holding cell?"))
        }
 
-       /// Handles a channel_ready message from our peer. If we've already sent our channel_ready
-       /// and the channel is now usable (and public), this may generate an announcement_signatures to
-       /// reply with.
-       pub fn channel_ready<NS: Deref, L: Deref>(
-               &mut self, msg: &msgs::ChannelReady, node_signer: &NS, genesis_block_hash: BlockHash,
-               user_config: &UserConfig, best_block: &BestBlock, logger: &L
-       ) -> Result<Option<msgs::AnnouncementSignatures>, ChannelError>
-       where
-               NS::Target: NodeSigner,
-               L::Target: Logger
-       {
-               if self.context.channel_state & (ChannelState::PeerDisconnected as u32) == ChannelState::PeerDisconnected as u32 {
-                       self.context.workaround_lnd_bug_4006 = Some(msg.clone());
-                       return Err(ChannelError::Ignore("Peer sent channel_ready when we needed a channel_reestablish. The peer is likely lnd, see https://github.com/lightningnetwork/lnd/issues/4006".to_owned()));
+       /// We can only have one resolution per HTLC. In some cases around reconnect, we may fulfill
+       /// an HTLC more than once or fulfill once and then attempt to fail after reconnect. We cannot,
+       /// however, fail more than once as we wait for an upstream failure to be irrevocably committed
+       /// before we fail backwards.
+       ///
+       /// If we do fail twice, we `debug_assert!(false)` and return `Ok(None)`. Thus, this will always
+       /// return `Ok(_)` if preconditions are met. In any case, `Err`s will only be
+       /// [`ChannelError::Ignore`].
+       fn fail_htlc<L: Deref>(&mut self, htlc_id_arg: u64, err_packet: msgs::OnionErrorPacket, mut force_holding_cell: bool, logger: &L)
+       -> Result<Option<msgs::UpdateFailHTLC>, ChannelError> where L::Target: Logger {
+               if (self.context.channel_state & (ChannelState::ChannelReady as u32)) != (ChannelState::ChannelReady as u32) {
+                       panic!("Was asked to fail an HTLC when channel was not in an operational state");
                }
+               assert_eq!(self.context.channel_state & ChannelState::ShutdownComplete as u32, 0);
 
-               if let Some(scid_alias) = msg.short_channel_id_alias {
-                       if Some(scid_alias) != self.context.short_channel_id {
-                               // The scid alias provided can be used to route payments *from* our counterparty,
-                               // i.e. can be used for inbound payments and provided in invoices, but is not used
-                               // when routing outbound payments.
-                               self.context.latest_inbound_scid_alias = Some(scid_alias);
+               // ChannelManager may generate duplicate claims/fails due to HTLC update events from
+               // on-chain ChannelsMonitors during block rescan. Ideally we'd figure out a way to drop
+               // these, but for now we just have to treat them as normal.
+
+               let mut pending_idx = core::usize::MAX;
+               for (idx, htlc) in self.context.pending_inbound_htlcs.iter().enumerate() {
+                       if htlc.htlc_id == htlc_id_arg {
+                               match htlc.state {
+                                       InboundHTLCState::Committed => {},
+                                       InboundHTLCState::LocalRemoved(ref reason) => {
+                                               if let &InboundHTLCRemovalReason::Fulfill(_) = reason {
+                                               } else {
+                                                       debug_assert!(false, "Tried to fail an HTLC that was already failed");
+                                               }
+                                               return Ok(None);
+                                       },
+                                       _ => {
+                                               debug_assert!(false, "Have an inbound HTLC we tried to claim before it was fully committed to");
+                                               return Err(ChannelError::Ignore(format!("Unable to find a pending HTLC which matched the given HTLC ID ({})", htlc.htlc_id)));
+                                       }
+                               }
+                               pending_idx = idx;
                        }
                }
+               if pending_idx == core::usize::MAX {
+                       #[cfg(any(test, fuzzing))]
+                       // If we failed to find an HTLC to fail, make sure it was previously fulfilled and this
+                       // is simply a duplicate fail, not previously failed and we failed-back too early.
+                       debug_assert!(self.context.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
+                       return Ok(None);
+               }
 
-               let non_shutdown_state = self.context.channel_state & (!MULTI_STATE_FLAGS);
+               if (self.context.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::PeerDisconnected as u32 | ChannelState::MonitorUpdateInProgress as u32)) != 0 {
+                       debug_assert!(force_holding_cell, "!force_holding_cell is only called when emptying the holding cell, so we shouldn't end up back in it!");
+                       force_holding_cell = true;
+               }
 
-               if non_shutdown_state == ChannelState::FundingSent as u32 {
-                       self.context.channel_state |= ChannelState::TheirChannelReady as u32;
-               } else if non_shutdown_state == (ChannelState::FundingSent as u32 | ChannelState::OurChannelReady as u32) {
-                       self.context.channel_state = ChannelState::ChannelReady as u32 | (self.context.channel_state & MULTI_STATE_FLAGS);
-                       self.context.update_time_counter += 1;
-               } else if self.context.channel_state & (ChannelState::ChannelReady as u32) != 0 ||
-                       // If we reconnected before sending our `channel_ready` they may still resend theirs:
-                       (self.context.channel_state & (ChannelState::FundingSent as u32 | ChannelState::TheirChannelReady as u32) ==
-                                             (ChannelState::FundingSent as u32 | ChannelState::TheirChannelReady as u32))
-               {
-                       // They probably disconnected/reconnected and re-sent the channel_ready, which is
-                       // required, or they're sending a fresh SCID alias.
-                       let expected_point =
-                               if self.context.cur_counterparty_commitment_transaction_number == INITIAL_COMMITMENT_NUMBER - 1 {
-                                       // If they haven't ever sent an updated point, the point they send should match
-                                       // the current one.
-                                       self.context.counterparty_cur_commitment_point
-                               } else if self.context.cur_counterparty_commitment_transaction_number == INITIAL_COMMITMENT_NUMBER - 2 {
-                                       // If we've advanced the commitment number once, the second commitment point is
-                                       // at `counterparty_prev_commitment_point`, which is not yet revoked.
-                                       debug_assert!(self.context.counterparty_prev_commitment_point.is_some());
-                                       self.context.counterparty_prev_commitment_point
-                               } else {
-                                       // If they have sent updated points, channel_ready is always supposed to match
-                                       // their "first" point, which we re-derive here.
-                                       Some(PublicKey::from_secret_key(&self.context.secp_ctx, &SecretKey::from_slice(
-                                                       &self.context.commitment_secrets.get_secret(INITIAL_COMMITMENT_NUMBER - 1).expect("We should have all prev secrets available")
-                                               ).expect("We already advanced, so previous secret keys should have been validated already")))
-                               };
-                       if expected_point != Some(msg.next_per_commitment_point) {
-                               return Err(ChannelError::Close("Peer sent a reconnect channel_ready with a different point".to_owned()));
+               // Now update local state:
+               if force_holding_cell {
+                       for pending_update in self.context.holding_cell_htlc_updates.iter() {
+                               match pending_update {
+                                       &HTLCUpdateAwaitingACK::ClaimHTLC { htlc_id, .. } => {
+                                               if htlc_id_arg == htlc_id {
+                                                       #[cfg(any(test, fuzzing))]
+                                                       debug_assert!(self.context.historical_inbound_htlc_fulfills.contains(&htlc_id_arg));
+                                                       return Ok(None);
+                                               }
+                                       },
+                                       &HTLCUpdateAwaitingACK::FailHTLC { htlc_id, .. } => {
+                                               if htlc_id_arg == htlc_id {
+                                                       debug_assert!(false, "Tried to fail an HTLC that was already failed");
+                                                       return Err(ChannelError::Ignore("Unable to find a pending HTLC which matched the given HTLC ID".to_owned()));
+                                               }
+                                       },
+                                       _ => {}
+                               }
                        }
+                       log_trace!(logger, "Placing failure for HTLC ID {} in holding cell in channel {}.", htlc_id_arg, log_bytes!(self.context.channel_id()));
+                       self.context.holding_cell_htlc_updates.push(HTLCUpdateAwaitingACK::FailHTLC {
+                               htlc_id: htlc_id_arg,
+                               err_packet,
+                       });
                        return Ok(None);
-               } else {
-                       return Err(ChannelError::Close("Peer sent a channel_ready at a strange time".to_owned()));
                }
 
-               self.context.counterparty_prev_commitment_point = self.context.counterparty_cur_commitment_point;
-               self.context.counterparty_cur_commitment_point = Some(msg.next_per_commitment_point);
-
-               log_info!(logger, "Received channel_ready from peer for channel {}", log_bytes!(self.context.channel_id()));
+               log_trace!(logger, "Failing HTLC ID {} back with a update_fail_htlc message in channel {}.", htlc_id_arg, log_bytes!(self.context.channel_id()));
+               {
+                       let htlc = &mut self.context.pending_inbound_htlcs[pending_idx];
+                       htlc.state = InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::FailRelay(err_packet.clone()));
+               }
 
-               Ok(self.get_announcement_sigs(node_signer, genesis_block_hash, user_config, best_block.height(), logger))
+               Ok(Some(msgs::UpdateFailHTLC {
+                       channel_id: self.context.channel_id(),
+                       htlc_id: htlc_id_arg,
+                       reason: err_packet
+               }))
        }
 
-       /// Returns transaction if there is pending funding transaction that is yet to broadcast
-       pub fn unbroadcasted_funding(&self) -> Option<Transaction> {
-               if self.context.channel_state & (ChannelState::FundingCreated as u32) != 0 {
-                       self.context.funding_transaction.clone()
-               } else {
-                       None
-               }
-       }
+       // Message handlers:
 
-       /// Get the available balances, see [`AvailableBalances`]'s fields for more info.
-       /// Doesn't bother handling the
-       /// if-we-removed-it-already-but-haven't-fully-resolved-they-can-still-send-an-inbound-HTLC
-       /// corner case properly.
-       pub fn get_available_balances(&self) -> AvailableBalances {
-               let context = &self.context;
-               // Note that we have to handle overflow due to the above case.
-               let inbound_stats = context.get_inbound_pending_htlc_stats(None);
-               let outbound_stats = context.get_outbound_pending_htlc_stats(None);
+       pub fn accept_channel(&mut self, msg: &msgs::AcceptChannel, default_limits: &ChannelHandshakeLimits, their_features: &InitFeatures) -> Result<(), ChannelError> {
+               let peer_limits = if let Some(ref limits) = self.context.inbound_handshake_limits_override { limits } else { default_limits };
 
-               let mut balance_msat = context.value_to_self_msat;
-               for ref htlc in context.pending_inbound_htlcs.iter() {
-                       if let InboundHTLCState::LocalRemoved(InboundHTLCRemovalReason::Fulfill(_)) = htlc.state {
-                               balance_msat += htlc.amount_msat;
-                       }
+               // Check sanity of message fields:
+               if !self.context.is_outbound() {
+                       return Err(ChannelError::Close("Got an accept_channel message from an inbound peer".to_owned()));
+               }
+               if self.context.channel_state != ChannelState::OurInitSent as u32 {
+                       return Err(ChannelError::Close("Got an accept_channel message at a strange time".to_owned()));
+               }
+               if msg.dust_limit_satoshis > 21000000 * 100000000 {
+                       return Err(ChannelError::Close(format!("Peer never wants payout outputs? dust_limit_satoshis was {}", msg.dust_limit_satoshis)));
+               }
+               if msg.channel_reserve_satoshis > self.context.channel_value_satoshis {
+                       return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than ({})", msg.channel_reserve_satoshis, self.context.channel_value_satoshis)));
+               }
+               if msg.dust_limit_satoshis > self.context.holder_selected_channel_reserve_satoshis {
+                       return Err(ChannelError::Close(format!("Dust limit ({}) is bigger than our channel reserve ({})", msg.dust_limit_satoshis, self.context.holder_selected_channel_reserve_satoshis)));
+               }
+               if msg.channel_reserve_satoshis > self.context.channel_value_satoshis - self.context.holder_selected_channel_reserve_satoshis {
+                       return Err(ChannelError::Close(format!("Bogus channel_reserve_satoshis ({}). Must not be greater than channel value minus our reserve ({})",
+                               msg.channel_reserve_satoshis, self.context.channel_value_satoshis - self.context.holder_selected_channel_reserve_satoshis)));
+               }
+               let full_channel_value_msat = (self.context.channel_value_satoshis - msg.channel_reserve_satoshis) * 1000;
+               if msg.htlc_minimum_msat >= full_channel_value_msat {
+                       return Err(ChannelError::Close(format!("Minimum htlc value ({}) is full channel value ({})", msg.htlc_minimum_msat, full_channel_value_msat)));
+               }
+               let max_delay_acceptable = u16::min(peer_limits.their_to_self_delay, MAX_LOCAL_BREAKDOWN_TIMEOUT);
+               if msg.to_self_delay > max_delay_acceptable {
+                       return Err(ChannelError::Close(format!("They wanted our payments to be delayed by a needlessly long period. Upper limit: {}. Actual: {}", max_delay_acceptable, msg.to_self_delay)));
+               }
+               if msg.max_accepted_htlcs < 1 {
+                       return Err(ChannelError::Close("0 max_accepted_htlcs makes for a useless channel".to_owned()));
+               }
+               if msg.max_accepted_htlcs > MAX_HTLCS {
+                       return Err(ChannelError::Close(format!("max_accepted_htlcs was {}. It must not be larger than {}", msg.max_accepted_htlcs, MAX_HTLCS)));
                }
-               balance_msat -= outbound_stats.pending_htlcs_value_msat;
-
-               let outbound_capacity_msat = context.value_to_self_msat
-                               .saturating_sub(outbound_stats.pending_htlcs_value_msat)
-                               .saturating_sub(
-                                       context.counterparty_selected_channel_reserve_satoshis.unwrap_or(0) * 1000);
-
-               let mut available_capacity_msat = outbound_capacity_msat;
-
-               if context.is_outbound() {
-                       // We should mind channel commit tx fee when computing how much of the available capacity
-                       // can be used in the next htlc. Mirrors the logic in send_htlc.
-                       //
-                       // The fee depends on whether the amount we will be sending is above dust or not,
-                       // and the answer will in turn change the amount itself — making it a circular
-                       // dependency.
-                       // This complicates the computation around dust-values, up to the one-htlc-value.
-                       let mut real_dust_limit_timeout_sat = context.holder_dust_limit_satoshis;
-                       if !context.opt_anchors() {
-                               real_dust_limit_timeout_sat += context.feerate_per_kw as u64 * htlc_timeout_tx_weight(false) / 1000;
-                       }
 
-                       let htlc_above_dust = HTLCCandidate::new(real_dust_limit_timeout_sat * 1000, HTLCInitiator::LocalOffered);
-                       let max_reserved_commit_tx_fee_msat = FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE * self.next_local_commit_tx_fee_msat(htlc_above_dust, Some(()));
-                       let htlc_dust = HTLCCandidate::new(real_dust_limit_timeout_sat * 1000 - 1, HTLCInitiator::LocalOffered);
-                       let min_reserved_commit_tx_fee_msat = FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE * self.next_local_commit_tx_fee_msat(htlc_dust, Some(()));
+               // Now check against optional parameters as set by config...
+               if msg.htlc_minimum_msat > peer_limits.max_htlc_minimum_msat {
+                       return Err(ChannelError::Close(format!("htlc_minimum_msat ({}) is higher than the user specified limit ({})", msg.htlc_minimum_msat, peer_limits.max_htlc_minimum_msat)));
+               }
+               if msg.max_htlc_value_in_flight_msat < peer_limits.min_max_htlc_value_in_flight_msat {
+                       return Err(ChannelError::Close(format!("max_htlc_value_in_flight_msat ({}) is less than the user specified limit ({})", msg.max_htlc_value_in_flight_msat, peer_limits.min_max_htlc_value_in_flight_msat)));
+               }
+               if msg.channel_reserve_satoshis > peer_limits.max_channel_reserve_satoshis {
+                       return Err(ChannelError::Close(format!("channel_reserve_satoshis ({}) is higher than the user specified limit ({})", msg.channel_reserve_satoshis, peer_limits.max_channel_reserve_satoshis)));
+               }
+               if msg.max_accepted_htlcs < peer_limits.min_max_accepted_htlcs {
+                       return Err(ChannelError::Close(format!("max_accepted_htlcs ({}) is less than the user specified limit ({})", msg.max_accepted_htlcs, peer_limits.min_max_accepted_htlcs)));
+               }
+               if msg.dust_limit_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
+                       return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is less than the implementation limit ({})", msg.dust_limit_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS)));
+               }
+               if msg.dust_limit_satoshis > MAX_CHAN_DUST_LIMIT_SATOSHIS {
+                       return Err(ChannelError::Close(format!("dust_limit_satoshis ({}) is greater than the implementation limit ({})", msg.dust_limit_satoshis, MAX_CHAN_DUST_LIMIT_SATOSHIS)));
+               }
+               if msg.minimum_depth > peer_limits.max_minimum_depth {
+                       return Err(ChannelError::Close(format!("We consider the minimum depth to be unreasonably large. Expected minimum: ({}). Actual: ({})", peer_limits.max_minimum_depth, msg.minimum_depth)));
+               }
 
-                       // We will first subtract the fee as if we were above-dust. Then, if the resulting
-                       // value ends up being below dust, we have this fee available again. In that case,
-                       // match the value to right-below-dust.
-                       let mut capacity_minus_commitment_fee_msat: i64 = (available_capacity_msat as i64) - (max_reserved_commit_tx_fee_msat as i64);
-                       if capacity_minus_commitment_fee_msat < (real_dust_limit_timeout_sat as i64) * 1000 {
-                               let one_htlc_difference_msat = max_reserved_commit_tx_fee_msat - min_reserved_commit_tx_fee_msat;
-                               debug_assert!(one_htlc_difference_msat != 0);
-                               capacity_minus_commitment_fee_msat += one_htlc_difference_msat as i64;
-                               capacity_minus_commitment_fee_msat = cmp::min(real_dust_limit_timeout_sat as i64 * 1000 - 1, capacity_minus_commitment_fee_msat);
-                               available_capacity_msat = cmp::max(0, cmp::min(capacity_minus_commitment_fee_msat, available_capacity_msat as i64)) as u64;
-                       } else {
-                               available_capacity_msat = capacity_minus_commitment_fee_msat as u64;
+               if let Some(ty) = &msg.channel_type {
+                       if *ty != self.context.channel_type {
+                               return Err(ChannelError::Close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
                        }
+               } else if their_features.supports_channel_type() {
+                       // Assume they've accepted the channel type as they said they understand it.
                } else {
-                       // If the channel is inbound (i.e. counterparty pays the fee), we need to make sure
-                       // sending a new HTLC won't reduce their balance below our reserve threshold.
-                       let mut real_dust_limit_success_sat = context.counterparty_dust_limit_satoshis;
-                       if !context.opt_anchors() {
-                               real_dust_limit_success_sat += context.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000;
+                       let channel_type = ChannelTypeFeatures::from_init(&their_features);
+                       if channel_type != ChannelTypeFeatures::only_static_remote_key() {
+                               return Err(ChannelError::Close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
                        }
+                       self.context.channel_type = channel_type;
+               }
 
-                       let htlc_above_dust = HTLCCandidate::new(real_dust_limit_success_sat * 1000, HTLCInitiator::LocalOffered);
-                       let max_reserved_commit_tx_fee_msat = self.next_remote_commit_tx_fee_msat(htlc_above_dust, None);
+               let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
+                       match &msg.shutdown_scriptpubkey {
+                               &Some(ref script) => {
+                                       // Peer is signaling upfront_shutdown and has opt-out with a 0-length script. We don't enforce anything
+                                       if script.len() == 0 {
+                                               None
+                                       } else {
+                                               if !script::is_bolt2_compliant(&script, their_features) {
+                                                       return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script)));
+                                               }
+                                               Some(script.clone())
+                                       }
+                               },
+                               // Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
+                               &None => {
+                                       return Err(ChannelError::Close("Peer is signaling upfront_shutdown but we don't get any script. Use 0-length script to opt-out".to_owned()));
+                               }
+                       }
+               } else { None };
 
-                       let holder_selected_chan_reserve_msat = context.holder_selected_channel_reserve_satoshis * 1000;
-                       let remote_balance_msat = (context.channel_value_satoshis * 1000 - context.value_to_self_msat)
-                               .saturating_sub(inbound_stats.pending_htlcs_value_msat);
+               self.context.counterparty_dust_limit_satoshis = msg.dust_limit_satoshis;
+               self.context.counterparty_max_htlc_value_in_flight_msat = cmp::min(msg.max_htlc_value_in_flight_msat, self.context.channel_value_satoshis * 1000);
+               self.context.counterparty_selected_channel_reserve_satoshis = Some(msg.channel_reserve_satoshis);
+               self.context.counterparty_htlc_minimum_msat = msg.htlc_minimum_msat;
+               self.context.counterparty_max_accepted_htlcs = msg.max_accepted_htlcs;
 
-                       if remote_balance_msat < max_reserved_commit_tx_fee_msat + holder_selected_chan_reserve_msat {
-                               // If another HTLC's fee would reduce the remote's balance below the reserve limit
-                               // we've selected for them, we can only send dust HTLCs.
-                               available_capacity_msat = cmp::min(available_capacity_msat, real_dust_limit_success_sat * 1000 - 1);
-                       }
+               if peer_limits.trust_own_funding_0conf {
+                       self.context.minimum_depth = Some(msg.minimum_depth);
+               } else {
+                       self.context.minimum_depth = Some(cmp::max(1, msg.minimum_depth));
                }
 
-               let mut next_outbound_htlc_minimum_msat = context.counterparty_htlc_minimum_msat;
+               let counterparty_pubkeys = ChannelPublicKeys {
+                       funding_pubkey: msg.funding_pubkey,
+                       revocation_basepoint: msg.revocation_basepoint,
+                       payment_point: msg.payment_point,
+                       delayed_payment_basepoint: msg.delayed_payment_basepoint,
+                       htlc_basepoint: msg.htlc_basepoint
+               };
 
-               // If we get close to our maximum dust exposure, we end up in a situation where we can send
-               // between zero and the remaining dust exposure limit remaining OR above the dust limit.
-               // Because we cannot express this as a simple min/max, we prefer to tell the user they can
-               // send above the dust limit (as the router can always overpay to meet the dust limit).
-               let mut remaining_msat_below_dust_exposure_limit = None;
-               let mut dust_exposure_dust_limit_msat = 0;
+               self.context.channel_transaction_parameters.counterparty_parameters = Some(CounterpartyChannelTransactionParameters {
+                       selected_contest_delay: msg.to_self_delay,
+                       pubkeys: counterparty_pubkeys,
+               });
 
-               let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if context.opt_anchors() {
-                       (context.counterparty_dust_limit_satoshis, context.holder_dust_limit_satoshis)
-               } else {
-                       let dust_buffer_feerate = context.get_dust_buffer_feerate(None) as u64;
-                       (context.counterparty_dust_limit_satoshis + dust_buffer_feerate * htlc_success_tx_weight(false) / 1000,
-                        context.holder_dust_limit_satoshis       + dust_buffer_feerate * htlc_timeout_tx_weight(false) / 1000)
-               };
-               let on_counterparty_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat;
-               if on_counterparty_dust_htlc_exposure_msat as i64 + htlc_success_dust_limit as i64 * 1000 - 1 > context.get_max_dust_htlc_exposure_msat() as i64 {
-                       remaining_msat_below_dust_exposure_limit =
-                               Some(context.get_max_dust_htlc_exposure_msat().saturating_sub(on_counterparty_dust_htlc_exposure_msat));
-                       dust_exposure_dust_limit_msat = cmp::max(dust_exposure_dust_limit_msat, htlc_success_dust_limit * 1000);
-               }
+               self.context.counterparty_cur_commitment_point = Some(msg.first_per_commitment_point);
+               self.context.counterparty_shutdown_scriptpubkey = counterparty_shutdown_scriptpubkey;
 
-               let on_holder_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat;
-               if on_holder_dust_htlc_exposure_msat as i64 + htlc_timeout_dust_limit as i64 * 1000 - 1 > context.get_max_dust_htlc_exposure_msat() as i64 {
-                       remaining_msat_below_dust_exposure_limit = Some(cmp::min(
-                               remaining_msat_below_dust_exposure_limit.unwrap_or(u64::max_value()),
-                               context.get_max_dust_htlc_exposure_msat().saturating_sub(on_holder_dust_htlc_exposure_msat)));
-                       dust_exposure_dust_limit_msat = cmp::max(dust_exposure_dust_limit_msat, htlc_timeout_dust_limit * 1000);
-               }
+               self.context.channel_state = ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32;
+               self.context.inbound_handshake_limits_override = None; // We're done enforcing limits on our peer's handshake now.
 
-               if let Some(remaining_limit_msat) = remaining_msat_below_dust_exposure_limit {
-                       if available_capacity_msat < dust_exposure_dust_limit_msat {
-                               available_capacity_msat = cmp::min(available_capacity_msat, remaining_limit_msat);
-                       } else {
-                               next_outbound_htlc_minimum_msat = cmp::max(next_outbound_htlc_minimum_msat, dust_exposure_dust_limit_msat);
-                       }
-               }
+               Ok(())
+       }
 
-               available_capacity_msat = cmp::min(available_capacity_msat,
-                       context.counterparty_max_htlc_value_in_flight_msat - outbound_stats.pending_htlcs_value_msat);
+       fn funding_created_signature<L: Deref>(&mut self, sig: &Signature, logger: &L) -> Result<(Txid, CommitmentTransaction, Signature), ChannelError> where L::Target: Logger {
+               let funding_script = self.context.get_funding_redeemscript();
 
-               if outbound_stats.pending_htlcs + 1 > context.counterparty_max_accepted_htlcs as u32 {
-                       available_capacity_msat = 0;
+               let keys = self.context.build_holder_transaction_keys(self.context.cur_holder_commitment_transaction_number);
+               let initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_holder_commitment_transaction_number, &keys, true, false, logger).tx;
+               {
+                       let trusted_tx = initial_commitment_tx.trust();
+                       let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
+                       let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.context.channel_value_satoshis);
+                       // They sign the holder commitment transaction...
+                       log_trace!(logger, "Checking funding_created tx signature {} by key {} against tx {} (sighash {}) with redeemscript {} for channel {}.",
+                               log_bytes!(sig.serialize_compact()[..]), log_bytes!(self.context.counterparty_funding_pubkey().serialize()),
+                               encode::serialize_hex(&initial_commitment_bitcoin_tx.transaction), log_bytes!(sighash[..]),
+                               encode::serialize_hex(&funding_script), log_bytes!(self.context.channel_id()));
+                       secp_check!(self.context.secp_ctx.verify_ecdsa(&sighash, &sig, self.context.counterparty_funding_pubkey()), "Invalid funding_created signature from peer".to_owned());
                }
 
-               AvailableBalances {
-                       inbound_capacity_msat: cmp::max(context.channel_value_satoshis as i64 * 1000
-                                       - context.value_to_self_msat as i64
-                                       - context.get_inbound_pending_htlc_stats(None).pending_htlcs_value_msat as i64
-                                       - context.holder_selected_channel_reserve_satoshis as i64 * 1000,
-                               0) as u64,
-                       outbound_capacity_msat,
-                       next_outbound_htlc_limit_msat: available_capacity_msat,
-                       next_outbound_htlc_minimum_msat,
-                       balance_msat,
-               }
-       }
+               let counterparty_keys = self.context.build_remote_transaction_keys();
+               let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
 
-       pub fn get_holder_counterparty_selected_channel_reserve_satoshis(&self) -> (u64, Option<u64>) {
-               let context = &self.context;
-               (context.holder_selected_channel_reserve_satoshis, context.counterparty_selected_channel_reserve_satoshis)
+               let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
+               let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
+               log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
+                       log_bytes!(self.context.channel_id()), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));
+
+               let counterparty_signature = self.context.holder_signer.sign_counterparty_commitment(&counterparty_initial_commitment_tx, Vec::new(), &self.context.secp_ctx)
+                               .map_err(|_| ChannelError::Close("Failed to get signatures for new commitment_signed".to_owned()))?.0;
+
+               // We sign "counterparty" commitment transaction, allowing them to broadcast the tx if they wish.
+               Ok((counterparty_initial_bitcoin_tx.txid, initial_commitment_tx, counterparty_signature))
        }
 
-       /// Get the commitment tx fee for the local's (i.e. our) next commitment transaction based on the
-       /// number of pending HTLCs that are on track to be in our next commitment tx.
-       ///
-       /// Optionally includes the `HTLCCandidate` given by `htlc` and an additional non-dust HTLC if
-       /// `fee_spike_buffer_htlc` is `Some`.
-       ///
-       /// The first extra HTLC is useful for determining whether we can accept a further HTLC, the
-       /// second allows for creating a buffer to ensure a further HTLC can always be accepted/added.
-       ///
-       /// Dust HTLCs are excluded.
-       fn next_local_commit_tx_fee_msat(&self, htlc: HTLCCandidate, fee_spike_buffer_htlc: Option<()>) -> u64 {
-               let context = &self.context;
-               assert!(context.is_outbound());
+       pub fn funding_created<SP: Deref, L: Deref>(
+               &mut self, msg: &msgs::FundingCreated, best_block: BestBlock, signer_provider: &SP, logger: &L
+       ) -> Result<(msgs::FundingSigned, ChannelMonitor<Signer>), ChannelError>
+       where
+               SP::Target: SignerProvider<Signer = Signer>,
+               L::Target: Logger
+       {
+               if self.context.is_outbound() {
+                       return Err(ChannelError::Close("Received funding_created for an outbound channel?".to_owned()));
+               }
+               if self.context.channel_state != (ChannelState::OurInitSent as u32 | ChannelState::TheirInitSent as u32) {
+                       // BOLT 2 says that if we disconnect before we send funding_signed we SHOULD NOT
+                       // remember the channel, so it's safe to just send an error_message here and drop the
+                       // channel.
+                       return Err(ChannelError::Close("Received funding_created after we got the channel!".to_owned()));
+               }
+               if self.context.inbound_awaiting_accept {
+                       return Err(ChannelError::Close("FundingCreated message received before the channel was accepted".to_owned()));
+               }
+               if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
+                               self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
+                               self.context.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
+                       panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
+               }
 
-               let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if context.opt_anchors() {
-                       (0, 0)
-               } else {
-                       (context.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000,
-                               context.feerate_per_kw as u64 * htlc_timeout_tx_weight(false) / 1000)
-               };
-               let real_dust_limit_success_sat = htlc_success_dust_limit + context.holder_dust_limit_satoshis;
-               let real_dust_limit_timeout_sat = htlc_timeout_dust_limit + context.holder_dust_limit_satoshis;
+               let funding_txo = OutPoint { txid: msg.funding_txid, index: msg.funding_output_index };
+               self.context.channel_transaction_parameters.funding_outpoint = Some(funding_txo);
+               // This is an externally observable change before we finish all our checks.  In particular
+               // funding_created_signature may fail.
+               self.context.holder_signer.provide_channel_parameters(&self.context.channel_transaction_parameters);
 
-               let mut addl_htlcs = 0;
-               if fee_spike_buffer_htlc.is_some() { addl_htlcs += 1; }
-               match htlc.origin {
-                       HTLCInitiator::LocalOffered => {
-                               if htlc.amount_msat / 1000 >= real_dust_limit_timeout_sat {
-                                       addl_htlcs += 1;
-                               }
+               let (counterparty_initial_commitment_txid, initial_commitment_tx, signature) = match self.funding_created_signature(&msg.signature, logger) {
+                       Ok(res) => res,
+                       Err(ChannelError::Close(e)) => {
+                               self.context.channel_transaction_parameters.funding_outpoint = None;
+                               return Err(ChannelError::Close(e));
                        },
-                       HTLCInitiator::RemoteOffered => {
-                               if htlc.amount_msat / 1000 >= real_dust_limit_success_sat {
-                                       addl_htlcs += 1;
-                               }
+                       Err(e) => {
+                               // The only error we know how to handle is ChannelError::Close, so we fall over here
+                               // to make sure we don't continue with an inconsistent state.
+                               panic!("unexpected error type from funding_created_signature {:?}", e);
                        }
-               }
+               };
+
+               let holder_commitment_tx = HolderCommitmentTransaction::new(
+                       initial_commitment_tx,
+                       msg.signature,
+                       Vec::new(),
+                       &self.context.get_holder_pubkeys().funding_pubkey,
+                       self.context.counterparty_funding_pubkey()
+               );
+
+               self.context.holder_signer.validate_holder_commitment(&holder_commitment_tx, Vec::new())
+                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
+
+                       // Now that we're past error-generating stuff, update our local state:
+
+               let funding_redeemscript = self.context.get_funding_redeemscript();
+               let funding_txo_script = funding_redeemscript.to_v0_p2wsh();
+               let obscure_factor = get_commitment_transaction_number_obscure_factor(&self.context.get_holder_pubkeys().payment_point, &self.context.get_counterparty_pubkeys().payment_point, self.context.is_outbound());
+               let shutdown_script = self.context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
+               let mut monitor_signer = signer_provider.derive_channel_signer(self.context.channel_value_satoshis, self.context.channel_keys_id);
+               monitor_signer.provide_channel_parameters(&self.context.channel_transaction_parameters);
+               let channel_monitor = ChannelMonitor::new(self.context.secp_ctx.clone(), monitor_signer,
+                                                         shutdown_script, self.context.get_holder_selected_contest_delay(),
+                                                         &self.context.destination_script, (funding_txo, funding_txo_script.clone()),
+                                                         &self.context.channel_transaction_parameters,
+                                                         funding_redeemscript.clone(), self.context.channel_value_satoshis,
+                                                         obscure_factor,
+                                                         holder_commitment_tx, best_block, self.context.counterparty_node_id);
+
+               channel_monitor.provide_latest_counterparty_commitment_tx(counterparty_initial_commitment_txid, Vec::new(), self.context.cur_counterparty_commitment_transaction_number, self.context.counterparty_cur_commitment_point.unwrap(), logger);
+
+               self.context.channel_state = ChannelState::FundingSent as u32;
+               self.context.channel_id = funding_txo.to_channel_id();
+               self.context.cur_counterparty_commitment_transaction_number -= 1;
+               self.context.cur_holder_commitment_transaction_number -= 1;
+
+               log_info!(logger, "Generated funding_signed for peer for channel {}", log_bytes!(self.context.channel_id()));
+
+               let need_channel_ready = self.check_get_channel_ready(0).is_some();
+               self.monitor_updating_paused(false, false, need_channel_ready, Vec::new(), Vec::new(), Vec::new());
 
-               let mut included_htlcs = 0;
-               for ref htlc in context.pending_inbound_htlcs.iter() {
-                       if htlc.amount_msat / 1000 < real_dust_limit_success_sat {
-                               continue
-                       }
-                       // We include LocalRemoved HTLCs here because we may still need to broadcast a commitment
-                       // transaction including this HTLC if it times out before they RAA.
-                       included_htlcs += 1;
-               }
+               Ok((msgs::FundingSigned {
+                       channel_id: self.context.channel_id,
+                       signature,
+                       #[cfg(taproot)]
+                       partial_signature_with_nonce: None,
+               }, channel_monitor))
+       }
 
-               for ref htlc in context.pending_outbound_htlcs.iter() {
-                       if htlc.amount_msat / 1000 < real_dust_limit_timeout_sat {
-                               continue
-                       }
-                       match htlc.state {
-                               OutboundHTLCState::LocalAnnounced {..} => included_htlcs += 1,
-                               OutboundHTLCState::Committed => included_htlcs += 1,
-                               OutboundHTLCState::RemoteRemoved {..} => included_htlcs += 1,
-                               // We don't include AwaitingRemoteRevokeToRemove HTLCs because our next commitment
-                               // transaction won't be generated until they send us their next RAA, which will mean
-                               // dropping any HTLCs in this state.
-                               _ => {},
-                       }
+       /// Handles a funding_signed message from the remote end.
+       /// If this call is successful, broadcast the funding transaction (and not before!)
+       pub fn funding_signed<SP: Deref, L: Deref>(
+               &mut self, msg: &msgs::FundingSigned, best_block: BestBlock, signer_provider: &SP, logger: &L
+       ) -> Result<ChannelMonitor<Signer>, ChannelError>
+       where
+               SP::Target: SignerProvider<Signer = Signer>,
+               L::Target: Logger
+       {
+               if !self.context.is_outbound() {
+                       return Err(ChannelError::Close("Received funding_signed for an inbound channel?".to_owned()));
                }
-
-               for htlc in context.holding_cell_htlc_updates.iter() {
-                       match htlc {
-                               &HTLCUpdateAwaitingACK::AddHTLC { amount_msat, .. } => {
-                                       if amount_msat / 1000 < real_dust_limit_timeout_sat {
-                                               continue
-                                       }
-                                       included_htlcs += 1
-                               },
-                               _ => {}, // Don't include claims/fails that are awaiting ack, because once we get the
-                                        // ack we're guaranteed to never include them in commitment txs anymore.
-                       }
+               if self.context.channel_state & !(ChannelState::MonitorUpdateInProgress as u32) != ChannelState::FundingCreated as u32 {
+                       return Err(ChannelError::Close("Received funding_signed in strange state!".to_owned()));
+               }
+               if self.context.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
+                               self.context.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
+                               self.context.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
+                       panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
                }
 
-               let num_htlcs = included_htlcs + addl_htlcs;
-               let res = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs, context.opt_anchors());
-               #[cfg(any(test, fuzzing))]
+               let funding_script = self.context.get_funding_redeemscript();
+
+               let counterparty_keys = self.context.build_remote_transaction_keys();
+               let counterparty_initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_counterparty_commitment_transaction_number, &counterparty_keys, false, false, logger).tx;
+               let counterparty_trusted_tx = counterparty_initial_commitment_tx.trust();
+               let counterparty_initial_bitcoin_tx = counterparty_trusted_tx.built_transaction();
+
+               log_trace!(logger, "Initial counterparty tx for channel {} is: txid {} tx {}",
+                       log_bytes!(self.context.channel_id()), counterparty_initial_bitcoin_tx.txid, encode::serialize_hex(&counterparty_initial_bitcoin_tx.transaction));
+
+               let holder_signer = self.context.build_holder_transaction_keys(self.context.cur_holder_commitment_transaction_number);
+               let initial_commitment_tx = self.context.build_commitment_transaction(self.context.cur_holder_commitment_transaction_number, &holder_signer, true, false, logger).tx;
                {
-                       let mut fee = res;
-                       if fee_spike_buffer_htlc.is_some() {
-                               fee = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs - 1, context.opt_anchors());
+                       let trusted_tx = initial_commitment_tx.trust();
+                       let initial_commitment_bitcoin_tx = trusted_tx.built_transaction();
+                       let sighash = initial_commitment_bitcoin_tx.get_sighash_all(&funding_script, self.context.channel_value_satoshis);
+                       // They sign our commitment transaction, allowing us to broadcast the tx if we wish.
+                       if let Err(_) = self.context.secp_ctx.verify_ecdsa(&sighash, &msg.signature, &self.context.get_counterparty_pubkeys().funding_pubkey) {
+                               return Err(ChannelError::Close("Invalid funding_signed signature from peer".to_owned()));
                        }
-                       let total_pending_htlcs = context.pending_inbound_htlcs.len() + context.pending_outbound_htlcs.len()
-                               + context.holding_cell_htlc_updates.len();
-                       let commitment_tx_info = CommitmentTxInfoCached {
-                               fee,
-                               total_pending_htlcs,
-                               next_holder_htlc_id: match htlc.origin {
-                                       HTLCInitiator::LocalOffered => context.next_holder_htlc_id + 1,
-                                       HTLCInitiator::RemoteOffered => context.next_holder_htlc_id,
-                               },
-                               next_counterparty_htlc_id: match htlc.origin {
-                                       HTLCInitiator::LocalOffered => context.next_counterparty_htlc_id,
-                                       HTLCInitiator::RemoteOffered => context.next_counterparty_htlc_id + 1,
-                               },
-                               feerate: context.feerate_per_kw,
-                       };
-                       *context.next_local_commitment_tx_fee_info_cached.lock().unwrap() = Some(commitment_tx_info);
                }
-               res
-       }
 
-       /// Get the commitment tx fee for the remote's next commitment transaction based on the number of
-       /// pending HTLCs that are on track to be in their next commitment tx
-       ///
-       /// Optionally includes the `HTLCCandidate` given by `htlc` and an additional non-dust HTLC if
-       /// `fee_spike_buffer_htlc` is `Some`.
-       ///
-       /// The first extra HTLC is useful for determining whether we can accept a further HTLC, the
-       /// second allows for creating a buffer to ensure a further HTLC can always be accepted/added.
-       ///
-       /// Dust HTLCs are excluded.
-       fn next_remote_commit_tx_fee_msat(&self, htlc: HTLCCandidate, fee_spike_buffer_htlc: Option<()>) -> u64 {
-               let context = &self.context;
-               assert!(!context.is_outbound());
+               let holder_commitment_tx = HolderCommitmentTransaction::new(
+                       initial_commitment_tx,
+                       msg.signature,
+                       Vec::new(),
+                       &self.context.get_holder_pubkeys().funding_pubkey,
+                       self.context.counterparty_funding_pubkey()
+               );
 
-               let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if context.opt_anchors() {
-                       (0, 0)
-               } else {
-                       (context.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000,
-                               context.feerate_per_kw as u64 * htlc_timeout_tx_weight(false) / 1000)
-               };
-               let real_dust_limit_success_sat = htlc_success_dust_limit + context.counterparty_dust_limit_satoshis;
-               let real_dust_limit_timeout_sat = htlc_timeout_dust_limit + context.counterparty_dust_limit_satoshis;
+               self.context.holder_signer.validate_holder_commitment(&holder_commitment_tx, Vec::new())
+                       .map_err(|_| ChannelError::Close("Failed to validate our commitment".to_owned()))?;
 
-               let mut addl_htlcs = 0;
-               if fee_spike_buffer_htlc.is_some() { addl_htlcs += 1; }
-               match htlc.origin {
-                       HTLCInitiator::LocalOffered => {
-                               if htlc.amount_msat / 1000 >= real_dust_limit_success_sat {
-                                       addl_htlcs += 1;
-                               }
-                       },
-                       HTLCInitiator::RemoteOffered => {
-                               if htlc.amount_msat / 1000 >= real_dust_limit_timeout_sat {
-                                       addl_htlcs += 1;
-                               }
-                       }
-               }
 
-               // When calculating the set of HTLCs which will be included in their next commitment_signed, all
-               // non-dust inbound HTLCs are included (as all states imply it will be included) and only
-               // committed outbound HTLCs, see below.
-               let mut included_htlcs = 0;
-               for ref htlc in context.pending_inbound_htlcs.iter() {
-                       if htlc.amount_msat / 1000 <= real_dust_limit_timeout_sat {
-                               continue
-                       }
-                       included_htlcs += 1;
+               let funding_redeemscript = self.context.get_funding_redeemscript();
+               let funding_txo = self.context.get_funding_txo().unwrap();
+               let funding_txo_script = funding_redeemscript.to_v0_p2wsh();
+               let obscure_factor = get_commitment_transaction_number_obscure_factor(&self.context.get_holder_pubkeys().payment_point, &self.context.get_counterparty_pubkeys().payment_point, self.context.is_outbound());
+               let shutdown_script = self.context.shutdown_scriptpubkey.clone().map(|script| script.into_inner());
+               let mut monitor_signer = signer_provider.derive_channel_signer(self.context.channel_value_satoshis, self.context.channel_keys_id);
+               monitor_signer.provide_channel_parameters(&self.context.channel_transaction_parameters);
+               let channel_monitor = ChannelMonitor::new(self.context.secp_ctx.clone(), monitor_signer,
+                                                         shutdown_script, self.context.get_holder_selected_contest_delay(),
+                                                         &self.context.destination_script, (funding_txo, funding_txo_script),
+                                                         &self.context.channel_transaction_parameters,
+                                                         funding_redeemscript.clone(), self.context.channel_value_satoshis,
+                                                         obscure_factor,
+                                                         holder_commitment_tx, best_block, self.context.counterparty_node_id);
+
+               channel_monitor.provide_latest_counterparty_commitment_tx(counterparty_initial_bitcoin_tx.txid, Vec::new(), self.context.cur_counterparty_commitment_transaction_number, self.context.counterparty_cur_commitment_point.unwrap(), logger);
+
+               assert_eq!(self.context.channel_state & (ChannelState::MonitorUpdateInProgress as u32), 0); // We have no had any monitor(s) yet to fail update!
+               self.context.channel_state = ChannelState::FundingSent as u32;
+               self.context.cur_holder_commitment_transaction_number -= 1;
+               self.context.cur_counterparty_commitment_transaction_number -= 1;
+
+               log_info!(logger, "Received funding_signed from peer for channel {}", log_bytes!(self.context.channel_id()));
+
+               let need_channel_ready = self.check_get_channel_ready(0).is_some();
+               self.monitor_updating_paused(false, false, need_channel_ready, Vec::new(), Vec::new(), Vec::new());
+               Ok(channel_monitor)
+       }
+
+       /// Handles a channel_ready message from our peer. If we've already sent our channel_ready
+       /// and the channel is now usable (and public), this may generate an announcement_signatures to
+       /// reply with.
+       pub fn channel_ready<NS: Deref, L: Deref>(
+               &mut self, msg: &msgs::ChannelReady, node_signer: &NS, genesis_block_hash: BlockHash,
+               user_config: &UserConfig, best_block: &BestBlock, logger: &L
+       ) -> Result<Option<msgs::AnnouncementSignatures>, ChannelError>
+       where
+               NS::Target: NodeSigner,
+               L::Target: Logger
+       {
+               if self.context.channel_state & (ChannelState::PeerDisconnected as u32) == ChannelState::PeerDisconnected as u32 {
+                       self.context.workaround_lnd_bug_4006 = Some(msg.clone());
+                       return Err(ChannelError::Ignore("Peer sent channel_ready when we needed a channel_reestablish. The peer is likely lnd, see https://github.com/lightningnetwork/lnd/issues/4006".to_owned()));
                }
 
-               for ref htlc in context.pending_outbound_htlcs.iter() {
-                       if htlc.amount_msat / 1000 <= real_dust_limit_success_sat {
-                               continue
-                       }
-                       // We only include outbound HTLCs if it will not be included in their next commitment_signed,
-                       // i.e. if they've responded to us with an RAA after announcement.
-                       match htlc.state {
-                               OutboundHTLCState::Committed => included_htlcs += 1,
-                               OutboundHTLCState::RemoteRemoved {..} => included_htlcs += 1,
-                               OutboundHTLCState::LocalAnnounced { .. } => included_htlcs += 1,
-                               _ => {},
+               if let Some(scid_alias) = msg.short_channel_id_alias {
+                       if Some(scid_alias) != self.context.short_channel_id {
+                               // The scid alias provided can be used to route payments *from* our counterparty,
+                               // i.e. can be used for inbound payments and provided in invoices, but is not used
+                               // when routing outbound payments.
+                               self.context.latest_inbound_scid_alias = Some(scid_alias);
                        }
                }
 
-               let num_htlcs = included_htlcs + addl_htlcs;
-               let res = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs, context.opt_anchors());
-               #[cfg(any(test, fuzzing))]
+               let non_shutdown_state = self.context.channel_state & (!MULTI_STATE_FLAGS);
+
+               if non_shutdown_state == ChannelState::FundingSent as u32 {
+                       self.context.channel_state |= ChannelState::TheirChannelReady as u32;
+               } else if non_shutdown_state == (ChannelState::FundingSent as u32 | ChannelState::OurChannelReady as u32) {
+                       self.context.channel_state = ChannelState::ChannelReady as u32 | (self.context.channel_state & MULTI_STATE_FLAGS);
+                       self.context.update_time_counter += 1;
+               } else if self.context.channel_state & (ChannelState::ChannelReady as u32) != 0 ||
+                       // If we reconnected before sending our `channel_ready` they may still resend theirs:
+                       (self.context.channel_state & (ChannelState::FundingSent as u32 | ChannelState::TheirChannelReady as u32) ==
+                                             (ChannelState::FundingSent as u32 | ChannelState::TheirChannelReady as u32))
                {
-                       let mut fee = res;
-                       if fee_spike_buffer_htlc.is_some() {
-                               fee = commit_tx_fee_msat(context.feerate_per_kw, num_htlcs - 1, context.opt_anchors());
-                       }
-                       let total_pending_htlcs = context.pending_inbound_htlcs.len() + context.pending_outbound_htlcs.len();
-                       let commitment_tx_info = CommitmentTxInfoCached {
-                               fee,
-                               total_pending_htlcs,
-                               next_holder_htlc_id: match htlc.origin {
-                                       HTLCInitiator::LocalOffered => context.next_holder_htlc_id + 1,
-                                       HTLCInitiator::RemoteOffered => context.next_holder_htlc_id,
-                               },
-                               next_counterparty_htlc_id: match htlc.origin {
-                                       HTLCInitiator::LocalOffered => context.next_counterparty_htlc_id,
-                                       HTLCInitiator::RemoteOffered => context.next_counterparty_htlc_id + 1,
-                               },
-                               feerate: context.feerate_per_kw,
-                       };
-                       *context.next_remote_commitment_tx_fee_info_cached.lock().unwrap() = Some(commitment_tx_info);
+                       // They probably disconnected/reconnected and re-sent the channel_ready, which is
+                       // required, or they're sending a fresh SCID alias.
+                       let expected_point =
+                               if self.context.cur_counterparty_commitment_transaction_number == INITIAL_COMMITMENT_NUMBER - 1 {
+                                       // If they haven't ever sent an updated point, the point they send should match
+                                       // the current one.
+                                       self.context.counterparty_cur_commitment_point
+                               } else if self.context.cur_counterparty_commitment_transaction_number == INITIAL_COMMITMENT_NUMBER - 2 {
+                                       // If we've advanced the commitment number once, the second commitment point is
+                                       // at `counterparty_prev_commitment_point`, which is not yet revoked.
+                                       debug_assert!(self.context.counterparty_prev_commitment_point.is_some());
+                                       self.context.counterparty_prev_commitment_point
+                               } else {
+                                       // If they have sent updated points, channel_ready is always supposed to match
+                                       // their "first" point, which we re-derive here.
+                                       Some(PublicKey::from_secret_key(&self.context.secp_ctx, &SecretKey::from_slice(
+                                                       &self.context.commitment_secrets.get_secret(INITIAL_COMMITMENT_NUMBER - 1).expect("We should have all prev secrets available")
+                                               ).expect("We already advanced, so previous secret keys should have been validated already")))
+                               };
+                       if expected_point != Some(msg.next_per_commitment_point) {
+                               return Err(ChannelError::Close("Peer sent a reconnect channel_ready with a different point".to_owned()));
+                       }
+                       return Ok(None);
+               } else {
+                       return Err(ChannelError::Close("Peer sent a channel_ready at a strange time".to_owned()));
                }
-               res
+
+               self.context.counterparty_prev_commitment_point = self.context.counterparty_cur_commitment_point;
+               self.context.counterparty_cur_commitment_point = Some(msg.next_per_commitment_point);
+
+               log_info!(logger, "Received channel_ready from peer for channel {}", log_bytes!(self.context.channel_id()));
+
+               Ok(self.get_announcement_sigs(node_signer, genesis_block_hash, user_config, best_block.height(), logger))
        }
 
        pub fn update_add_htlc<F, L: Deref>(&mut self, msg: &msgs::UpdateAddHTLC, mut pending_forward_status: PendingHTLCStatus, create_pending_htlc_status: F, logger: &L) -> Result<(), ChannelError>
@@ -3452,7 +3229,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                // feerate_per_kw, while maintaining their channel reserve (as required by the spec).
                let remote_commit_tx_fee_msat = if self.context.is_outbound() { 0 } else {
                        let htlc_candidate = HTLCCandidate::new(msg.amount_msat, HTLCInitiator::RemoteOffered);
-                       self.next_remote_commit_tx_fee_msat(htlc_candidate, None) // Don't include the extra fee spike buffer HTLC in calculations
+                       self.context.next_remote_commit_tx_fee_msat(htlc_candidate, None) // Don't include the extra fee spike buffer HTLC in calculations
                };
                if pending_remote_value_msat - msg.amount_msat < remote_commit_tx_fee_msat {
                        return Err(ChannelError::Close("Remote HTLC add would not leave enough to pay for fees".to_owned()));
@@ -3472,7 +3249,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        // still be able to afford adding this HTLC plus one more future HTLC, regardless of being
                        // sensitive to fee spikes.
                        let htlc_candidate = HTLCCandidate::new(msg.amount_msat, HTLCInitiator::RemoteOffered);
-                       let remote_fee_cost_incl_stuck_buffer_msat = 2 * self.next_remote_commit_tx_fee_msat(htlc_candidate, Some(()));
+                       let remote_fee_cost_incl_stuck_buffer_msat = 2 * self.context.next_remote_commit_tx_fee_msat(htlc_candidate, Some(()));
                        if pending_remote_value_msat - msg.amount_msat - self.context.holder_selected_channel_reserve_satoshis * 1000 < remote_fee_cost_incl_stuck_buffer_msat {
                                // Note that if the pending_forward_status is not updated here, then it's because we're already failing
                                // the HTLC, i.e. its status is already set to failing.
@@ -3482,7 +3259,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                } else {
                        // Check that they won't violate our local required channel reserve by adding this HTLC.
                        let htlc_candidate = HTLCCandidate::new(msg.amount_msat, HTLCInitiator::RemoteOffered);
-                       let local_commit_tx_fee_msat = self.next_local_commit_tx_fee_msat(htlc_candidate, None);
+                       let local_commit_tx_fee_msat = self.context.next_local_commit_tx_fee_msat(htlc_candidate, None);
                        if self.context.value_to_self_msat < self.context.counterparty_selected_channel_reserve_satoshis.unwrap() * 1000 + local_commit_tx_fee_msat {
                                return Err(ChannelError::Close("Cannot accept HTLC that would put our balance under counterparty-announced channel reserve value".to_owned()));
                        }
@@ -6048,7 +5825,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                        return Err(ChannelError::Ignore("Cannot send 0-msat HTLC".to_owned()));
                }
 
-               let available_balances = self.get_available_balances();
+               let available_balances = self.context.get_available_balances();
                if amount_msat < available_balances.next_outbound_htlc_minimum_msat {
                        return Err(ChannelError::Ignore(format!("Cannot send less than our next-HTLC minimum - {} msat",
                                available_balances.next_outbound_htlc_minimum_msat)));
@@ -6437,6 +6214,244 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
        }
 }
 
+/// A not-yet-funded outbound (from holder) channel using V1 channel establishment.
+pub(super) struct OutboundV1Channel<Signer: ChannelSigner> {
+       pub context: ChannelContext<Signer>,
+}
+
+impl<Signer: WriteableEcdsaChannelSigner> OutboundV1Channel<Signer> {
+       fn get_initial_channel_type(config: &UserConfig, their_features: &InitFeatures) -> ChannelTypeFeatures {
+               // The default channel type (ie the first one we try) depends on whether the channel is
+               // public - if it is, we just go with `only_static_remotekey` as it's the only option
+               // available. If it's private, we first try `scid_privacy` as it provides better privacy
+               // with no other changes, and fall back to `only_static_remotekey`.
+               let mut ret = ChannelTypeFeatures::only_static_remote_key();
+               if !config.channel_handshake_config.announced_channel &&
+                       config.channel_handshake_config.negotiate_scid_privacy &&
+                       their_features.supports_scid_privacy() {
+                       ret.set_scid_privacy_required();
+               }
+
+               // Optionally, if the user would like to negotiate the `anchors_zero_fee_htlc_tx` option, we
+               // set it now. If they don't understand it, we'll fall back to our default of
+               // `only_static_remotekey`.
+               #[cfg(anchors)]
+               { // Attributes are not allowed on if expressions on our current MSRV of 1.41.
+                       if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx &&
+                               their_features.supports_anchors_zero_fee_htlc_tx() {
+                               ret.set_anchors_zero_fee_htlc_tx_required();
+                       }
+               }
+
+               ret
+       }
+
+       pub fn new_outbound<ES: Deref, SP: Deref, F: Deref>(
+               fee_estimator: &LowerBoundedFeeEstimator<F>, entropy_source: &ES, signer_provider: &SP, counterparty_node_id: PublicKey, their_features: &InitFeatures,
+               channel_value_satoshis: u64, push_msat: u64, user_id: u128, config: &UserConfig, current_chain_height: u32,
+               outbound_scid_alias: u64
+       ) -> Result<Channel<Signer>, APIError>
+       where ES::Target: EntropySource,
+             SP::Target: SignerProvider<Signer = Signer>,
+             F::Target: FeeEstimator,
+       {
+               let holder_selected_contest_delay = config.channel_handshake_config.our_to_self_delay;
+               let channel_keys_id = signer_provider.generate_channel_keys_id(false, channel_value_satoshis, user_id);
+               let holder_signer = signer_provider.derive_channel_signer(channel_value_satoshis, channel_keys_id);
+               let pubkeys = holder_signer.pubkeys().clone();
+
+               if !their_features.supports_wumbo() && channel_value_satoshis > MAX_FUNDING_SATOSHIS_NO_WUMBO {
+                       return Err(APIError::APIMisuseError{err: format!("funding_value must not exceed {}, it was {}", MAX_FUNDING_SATOSHIS_NO_WUMBO, channel_value_satoshis)});
+               }
+               if channel_value_satoshis >= TOTAL_BITCOIN_SUPPLY_SATOSHIS {
+                       return Err(APIError::APIMisuseError{err: format!("funding_value must be smaller than the total bitcoin supply, it was {}", channel_value_satoshis)});
+               }
+               let channel_value_msat = channel_value_satoshis * 1000;
+               if push_msat > channel_value_msat {
+                       return Err(APIError::APIMisuseError { err: format!("Push value ({}) was larger than channel_value ({})", push_msat, channel_value_msat) });
+               }
+               if holder_selected_contest_delay < BREAKDOWN_TIMEOUT {
+                       return Err(APIError::APIMisuseError {err: format!("Configured with an unreasonable our_to_self_delay ({}) putting user funds at risks", holder_selected_contest_delay)});
+               }
+               let holder_selected_channel_reserve_satoshis = get_holder_selected_channel_reserve_satoshis(channel_value_satoshis, config);
+               if holder_selected_channel_reserve_satoshis < MIN_CHAN_DUST_LIMIT_SATOSHIS {
+                       // Protocol level safety check in place, although it should never happen because
+                       // of `MIN_THEIR_CHAN_RESERVE_SATOSHIS`
+                       return Err(APIError::APIMisuseError { err: format!("Holder selected channel  reserve below implemention limit dust_limit_satoshis {}", holder_selected_channel_reserve_satoshis) });
+               }
+
+               let channel_type = Self::get_initial_channel_type(&config, their_features);
+               debug_assert!(channel_type.is_subset(&channelmanager::provided_channel_type_features(&config)));
+
+               let feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
+
+               let value_to_self_msat = channel_value_satoshis * 1000 - push_msat;
+               let commitment_tx_fee = commit_tx_fee_msat(feerate, MIN_AFFORDABLE_HTLC_COUNT, channel_type.requires_anchors_zero_fee_htlc_tx());
+               if value_to_self_msat < commitment_tx_fee {
+                       return Err(APIError::APIMisuseError{ err: format!("Funding amount ({}) can't even pay fee for initial commitment transaction fee of {}.", value_to_self_msat / 1000, commitment_tx_fee / 1000) });
+               }
+
+               let mut secp_ctx = Secp256k1::new();
+               secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
+
+               let shutdown_scriptpubkey = if config.channel_handshake_config.commit_upfront_shutdown_pubkey {
+                       match signer_provider.get_shutdown_scriptpubkey() {
+                               Ok(scriptpubkey) => Some(scriptpubkey),
+                               Err(_) => return Err(APIError::ChannelUnavailable { err: "Failed to get shutdown scriptpubkey".to_owned()}),
+                       }
+               } else { None };
+
+               if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
+                       if !shutdown_scriptpubkey.is_compatible(&their_features) {
+                               return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
+                       }
+               }
+
+               let destination_script = match signer_provider.get_destination_script() {
+                       Ok(script) => script,
+                       Err(_) => return Err(APIError::ChannelUnavailable { err: "Failed to get destination script".to_owned()}),
+               };
+
+               let temporary_channel_id = entropy_source.get_secure_random_bytes();
+
+               Ok(Channel {
+                       context: ChannelContext {
+                               user_id,
+
+                               config: LegacyChannelConfig {
+                                       options: config.channel_config.clone(),
+                                       announced_channel: config.channel_handshake_config.announced_channel,
+                                       commit_upfront_shutdown_pubkey: config.channel_handshake_config.commit_upfront_shutdown_pubkey,
+                               },
+
+                               prev_config: None,
+
+                               inbound_handshake_limits_override: Some(config.channel_handshake_limits.clone()),
+
+                               channel_id: temporary_channel_id,
+                               temporary_channel_id: Some(temporary_channel_id),
+                               channel_state: ChannelState::OurInitSent as u32,
+                               announcement_sigs_state: AnnouncementSigsState::NotSent,
+                               secp_ctx,
+                               channel_value_satoshis,
+
+                               latest_monitor_update_id: 0,
+
+                               holder_signer,
+                               shutdown_scriptpubkey,
+                               destination_script,
+
+                               cur_holder_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
+                               cur_counterparty_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
+                               value_to_self_msat,
+
+                               pending_inbound_htlcs: Vec::new(),
+                               pending_outbound_htlcs: Vec::new(),
+                               holding_cell_htlc_updates: Vec::new(),
+                               pending_update_fee: None,
+                               holding_cell_update_fee: None,
+                               next_holder_htlc_id: 0,
+                               next_counterparty_htlc_id: 0,
+                               update_time_counter: 1,
+
+                               resend_order: RAACommitmentOrder::CommitmentFirst,
+
+                               monitor_pending_channel_ready: false,
+                               monitor_pending_revoke_and_ack: false,
+                               monitor_pending_commitment_signed: false,
+                               monitor_pending_forwards: Vec::new(),
+                               monitor_pending_failures: Vec::new(),
+                               monitor_pending_finalized_fulfills: Vec::new(),
+
+                               #[cfg(debug_assertions)]
+                               holder_max_commitment_tx_output: Mutex::new((channel_value_satoshis * 1000 - push_msat, push_msat)),
+                               #[cfg(debug_assertions)]
+                               counterparty_max_commitment_tx_output: Mutex::new((channel_value_satoshis * 1000 - push_msat, push_msat)),
+
+                               last_sent_closing_fee: None,
+                               pending_counterparty_closing_signed: None,
+                               closing_fee_limits: None,
+                               target_closing_feerate_sats_per_kw: None,
+
+                               inbound_awaiting_accept: false,
+
+                               funding_tx_confirmed_in: None,
+                               funding_tx_confirmation_height: 0,
+                               short_channel_id: None,
+                               channel_creation_height: current_chain_height,
+
+                               feerate_per_kw: feerate,
+                               counterparty_dust_limit_satoshis: 0,
+                               holder_dust_limit_satoshis: MIN_CHAN_DUST_LIMIT_SATOSHIS,
+                               counterparty_max_htlc_value_in_flight_msat: 0,
+                               holder_max_htlc_value_in_flight_msat: get_holder_max_htlc_value_in_flight_msat(channel_value_satoshis, &config.channel_handshake_config),
+                               counterparty_selected_channel_reserve_satoshis: None, // Filled in in accept_channel
+                               holder_selected_channel_reserve_satoshis,
+                               counterparty_htlc_minimum_msat: 0,
+                               holder_htlc_minimum_msat: if config.channel_handshake_config.our_htlc_minimum_msat == 0 { 1 } else { config.channel_handshake_config.our_htlc_minimum_msat },
+                               counterparty_max_accepted_htlcs: 0,
+                               holder_max_accepted_htlcs: cmp::min(config.channel_handshake_config.our_max_accepted_htlcs, MAX_HTLCS),
+                               minimum_depth: None, // Filled in in accept_channel
+
+                               counterparty_forwarding_info: None,
+
+                               channel_transaction_parameters: ChannelTransactionParameters {
+                                       holder_pubkeys: pubkeys,
+                                       holder_selected_contest_delay: config.channel_handshake_config.our_to_self_delay,
+                                       is_outbound_from_holder: true,
+                                       counterparty_parameters: None,
+                                       funding_outpoint: None,
+                                       opt_anchors: if channel_type.requires_anchors_zero_fee_htlc_tx() { Some(()) } else { None },
+                                       opt_non_zero_fee_anchors: None
+                               },
+                               funding_transaction: None,
+
+                               counterparty_cur_commitment_point: None,
+                               counterparty_prev_commitment_point: None,
+                               counterparty_node_id,
+
+                               counterparty_shutdown_scriptpubkey: None,
+
+                               commitment_secrets: CounterpartyCommitmentSecrets::new(),
+
+                               channel_update_status: ChannelUpdateStatus::Enabled,
+                               closing_signed_in_flight: false,
+
+                               announcement_sigs: None,
+
+                               #[cfg(any(test, fuzzing))]
+                               next_local_commitment_tx_fee_info_cached: Mutex::new(None),
+                               #[cfg(any(test, fuzzing))]
+                               next_remote_commitment_tx_fee_info_cached: Mutex::new(None),
+
+                               workaround_lnd_bug_4006: None,
+                               sent_message_awaiting_response: None,
+
+                               latest_inbound_scid_alias: None,
+                               outbound_scid_alias,
+
+                               channel_pending_event_emitted: false,
+                               channel_ready_event_emitted: false,
+
+                               #[cfg(any(test, fuzzing))]
+                               historical_inbound_htlc_fulfills: HashSet::new(),
+
+                               channel_type,
+                               channel_keys_id,
+
+                               pending_monitor_updates: Vec::new(),
+                       }
+               })
+       }
+}
+
+/// A not-yet-funded inbound (from counterparty) channel using V1 channel establishment.
+pub(super) struct InboundV1Channel<Signer: ChannelSigner> {
+       pub context: ChannelContext<Signer>,
+}
+
+impl<Signer: WriteableEcdsaChannelSigner> InboundV1Channel<Signer> {}
+
 const SERIALIZATION_VERSION: u8 = 3;
 const MIN_SERIALIZATION_VERSION: u8 = 2;
 
@@ -7280,7 +7295,7 @@ mod tests {
        use crate::ln::channelmanager::{self, HTLCSource, PaymentId};
        #[cfg(anchors)]
        use crate::ln::channel::InitFeatures;
-       use crate::ln::channel::{Channel, InboundHTLCOutput, OutboundHTLCOutput, InboundHTLCState, OutboundHTLCState, HTLCCandidate, HTLCInitiator, commit_tx_fee_msat};
+       use crate::ln::channel::{Channel, InboundHTLCOutput, OutboundV1Channel, OutboundHTLCOutput, InboundHTLCState, OutboundHTLCState, HTLCCandidate, HTLCInitiator, commit_tx_fee_msat};
        use crate::ln::channel::{MAX_FUNDING_SATOSHIS_NO_WUMBO, TOTAL_BITCOIN_SUPPLY_SATOSHIS, MIN_THEIR_CHAN_RESERVE_SATOSHIS};
        use crate::ln::features::ChannelTypeFeatures;
        use crate::ln::msgs::{ChannelUpdate, DecodeError, UnsignedChannelUpdate, MAX_VALUE_MSAT};
@@ -7389,7 +7404,7 @@ mod tests {
                let secp_ctx = Secp256k1::new();
                let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               match Channel::<EnforcingSigner>::new_outbound(&LowerBoundedFeeEstimator::new(&TestFeeEstimator { fee_est: 253 }), &&keys_provider, &&keys_provider, node_id, &features, 10000000, 100000, 42, &config, 0, 42) {
+               match OutboundV1Channel::<EnforcingSigner>::new_outbound(&LowerBoundedFeeEstimator::new(&TestFeeEstimator { fee_est: 253 }), &&keys_provider, &&keys_provider, node_id, &features, 10000000, 100000, 42, &config, 0, 42) {
                        Err(APIError::IncompatibleShutdownScript { script }) => {
                                assert_eq!(script.into_inner(), non_v0_segwit_shutdown_script.into_inner());
                        },
@@ -7412,7 +7427,7 @@ mod tests {
 
                let node_a_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let node_a_chan = Channel::<EnforcingSigner>::new_outbound(&bounded_fee_estimator, &&keys_provider, &&keys_provider, node_a_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
+               let node_a_chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&bounded_fee_estimator, &&keys_provider, &&keys_provider, node_a_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
 
                // Now change the fee so we can check that the fee in the open_channel message is the
                // same as the old fee.
@@ -7438,7 +7453,7 @@ mod tests {
                // Create Node A's channel pointing to Node B's pubkey
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
+               let mut node_a_chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
 
                // Create Node B's channel by receiving Node A's open_channel message
                // Make sure A's dust limit is as we expect.
@@ -7479,7 +7494,7 @@ mod tests {
                // Make sure when Node A calculates their local commitment transaction, none of the HTLCs pass
                // the dust limit check.
                let htlc_candidate = HTLCCandidate::new(htlc_amount_msat, HTLCInitiator::LocalOffered);
-               let local_commit_tx_fee = node_a_chan.next_local_commit_tx_fee_msat(htlc_candidate, None);
+               let local_commit_tx_fee = node_a_chan.context.next_local_commit_tx_fee_msat(htlc_candidate, None);
                let local_commit_fee_0_htlcs = commit_tx_fee_msat(node_a_chan.context.feerate_per_kw, 0, node_a_chan.context.opt_anchors());
                assert_eq!(local_commit_tx_fee, local_commit_fee_0_htlcs);
 
@@ -7488,7 +7503,7 @@ mod tests {
                node_a_chan.context.channel_transaction_parameters.is_outbound_from_holder = false;
                let remote_commit_fee_3_htlcs = commit_tx_fee_msat(node_a_chan.context.feerate_per_kw, 3, node_a_chan.context.opt_anchors());
                let htlc_candidate = HTLCCandidate::new(htlc_amount_msat, HTLCInitiator::LocalOffered);
-               let remote_commit_tx_fee = node_a_chan.next_remote_commit_tx_fee_msat(htlc_candidate, None);
+               let remote_commit_tx_fee = node_a_chan.context.next_remote_commit_tx_fee_msat(htlc_candidate, None);
                assert_eq!(remote_commit_tx_fee, remote_commit_fee_3_htlcs);
        }
 
@@ -7506,7 +7521,7 @@ mod tests {
 
                let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut chan = Channel::<EnforcingSigner>::new_outbound(&fee_est, &&keys_provider, &&keys_provider, node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
+               let mut chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&fee_est, &&keys_provider, &&keys_provider, node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
 
                let commitment_tx_fee_0_htlcs = commit_tx_fee_msat(chan.context.feerate_per_kw, 0, chan.context.opt_anchors());
                let commitment_tx_fee_1_htlc = commit_tx_fee_msat(chan.context.feerate_per_kw, 1, chan.context.opt_anchors());
@@ -7515,13 +7530,13 @@ mod tests {
                // counted as dust when it shouldn't be.
                let htlc_amt_above_timeout = ((253 * htlc_timeout_tx_weight(chan.context.opt_anchors()) / 1000) + chan.context.holder_dust_limit_satoshis + 1) * 1000;
                let htlc_candidate = HTLCCandidate::new(htlc_amt_above_timeout, HTLCInitiator::LocalOffered);
-               let commitment_tx_fee = chan.next_local_commit_tx_fee_msat(htlc_candidate, None);
+               let commitment_tx_fee = chan.context.next_local_commit_tx_fee_msat(htlc_candidate, None);
                assert_eq!(commitment_tx_fee, commitment_tx_fee_1_htlc);
 
                // If swapped: this HTLC would be counted as non-dust when it shouldn't be.
                let dust_htlc_amt_below_success = ((253 * htlc_success_tx_weight(chan.context.opt_anchors()) / 1000) + chan.context.holder_dust_limit_satoshis - 1) * 1000;
                let htlc_candidate = HTLCCandidate::new(dust_htlc_amt_below_success, HTLCInitiator::RemoteOffered);
-               let commitment_tx_fee = chan.next_local_commit_tx_fee_msat(htlc_candidate, None);
+               let commitment_tx_fee = chan.context.next_local_commit_tx_fee_msat(htlc_candidate, None);
                assert_eq!(commitment_tx_fee, commitment_tx_fee_0_htlcs);
 
                chan.context.channel_transaction_parameters.is_outbound_from_holder = false;
@@ -7529,13 +7544,13 @@ mod tests {
                // If swapped: this HTLC would be counted as non-dust when it shouldn't be.
                let dust_htlc_amt_above_timeout = ((253 * htlc_timeout_tx_weight(chan.context.opt_anchors()) / 1000) + chan.context.counterparty_dust_limit_satoshis + 1) * 1000;
                let htlc_candidate = HTLCCandidate::new(dust_htlc_amt_above_timeout, HTLCInitiator::LocalOffered);
-               let commitment_tx_fee = chan.next_remote_commit_tx_fee_msat(htlc_candidate, None);
+               let commitment_tx_fee = chan.context.next_remote_commit_tx_fee_msat(htlc_candidate, None);
                assert_eq!(commitment_tx_fee, commitment_tx_fee_0_htlcs);
 
                // If swapped: this HTLC would be counted as dust when it shouldn't be.
                let htlc_amt_below_success = ((253 * htlc_success_tx_weight(chan.context.opt_anchors()) / 1000) + chan.context.counterparty_dust_limit_satoshis - 1) * 1000;
                let htlc_candidate = HTLCCandidate::new(htlc_amt_below_success, HTLCInitiator::RemoteOffered);
-               let commitment_tx_fee = chan.next_remote_commit_tx_fee_msat(htlc_candidate, None);
+               let commitment_tx_fee = chan.context.next_remote_commit_tx_fee_msat(htlc_candidate, None);
                assert_eq!(commitment_tx_fee, commitment_tx_fee_1_htlc);
        }
 
@@ -7555,7 +7570,7 @@ mod tests {
                // Create Node A's channel pointing to Node B's pubkey
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
+               let mut node_a_chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
 
                // Create Node B's channel by receiving Node A's open_channel message
                let open_channel_msg = node_a_chan.get_open_channel(chain_hash);
@@ -7618,12 +7633,12 @@ mod tests {
                // Test that `new_outbound` creates a channel with the correct value for
                // `holder_max_htlc_value_in_flight_msat`, when configured with a valid percentage value,
                // which is set to the lower bound + 1 (2%) of the `channel_value`.
-               let chan_1 = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_2_percent), 10000000, 100000, 42, &config_2_percent, 0, 42).unwrap();
+               let chan_1 = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_2_percent), 10000000, 100000, 42, &config_2_percent, 0, 42).unwrap();
                let chan_1_value_msat = chan_1.context.channel_value_satoshis * 1000;
                assert_eq!(chan_1.context.holder_max_htlc_value_in_flight_msat, (chan_1_value_msat as f64 * 0.02) as u64);
 
                // Test with the upper bound - 1 of valid values (99%).
-               let chan_2 = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_99_percent), 10000000, 100000, 42, &config_99_percent, 0, 42).unwrap();
+               let chan_2 = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_99_percent), 10000000, 100000, 42, &config_99_percent, 0, 42).unwrap();
                let chan_2_value_msat = chan_2.context.channel_value_satoshis * 1000;
                assert_eq!(chan_2.context.holder_max_htlc_value_in_flight_msat, (chan_2_value_msat as f64 * 0.99) as u64);
 
@@ -7643,14 +7658,14 @@ mod tests {
 
                // Test that `new_outbound` uses the lower bound of the configurable percentage values (1%)
                // if `max_inbound_htlc_value_in_flight_percent_of_channel` is set to a value less than 1.
-               let chan_5 = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_0_percent), 10000000, 100000, 42, &config_0_percent, 0, 42).unwrap();
+               let chan_5 = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_0_percent), 10000000, 100000, 42, &config_0_percent, 0, 42).unwrap();
                let chan_5_value_msat = chan_5.context.channel_value_satoshis * 1000;
                assert_eq!(chan_5.context.holder_max_htlc_value_in_flight_msat, (chan_5_value_msat as f64 * 0.01) as u64);
 
                // Test that `new_outbound` uses the upper bound of the configurable percentage values
                // (100%) if `max_inbound_htlc_value_in_flight_percent_of_channel` is set to a larger value
                // than 100.
-               let chan_6 = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_101_percent), 10000000, 100000, 42, &config_101_percent, 0, 42).unwrap();
+               let chan_6 = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&config_101_percent), 10000000, 100000, 42, &config_101_percent, 0, 42).unwrap();
                let chan_6_value_msat = chan_6.context.channel_value_satoshis * 1000;
                assert_eq!(chan_6.context.holder_max_htlc_value_in_flight_msat, chan_6_value_msat);
 
@@ -7703,7 +7718,7 @@ mod tests {
 
                let mut outbound_node_config = UserConfig::default();
                outbound_node_config.channel_handshake_config.their_channel_reserve_proportional_millionths = (outbound_selected_channel_reserve_perc * 1_000_000.0) as u32;
-               let chan = Channel::<EnforcingSigner>::new_outbound(&&fee_est, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&outbound_node_config), channel_value_satoshis, 100_000, 42, &outbound_node_config, 0, 42).unwrap();
+               let chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&&fee_est, &&keys_provider, &&keys_provider, outbound_node_id, &channelmanager::provided_init_features(&outbound_node_config), channel_value_satoshis, 100_000, 42, &outbound_node_config, 0, 42).unwrap();
 
                let expected_outbound_selected_chan_reserve = cmp::max(MIN_THEIR_CHAN_RESERVE_SATOSHIS, (chan.context.channel_value_satoshis as f64 * outbound_selected_channel_reserve_perc) as u64);
                assert_eq!(chan.context.holder_selected_channel_reserve_satoshis, expected_outbound_selected_chan_reserve);
@@ -7738,7 +7753,7 @@ mod tests {
                // Create a channel.
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let mut node_a_chan = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
+               let mut node_a_chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
                assert!(node_a_chan.context.counterparty_forwarding_info.is_none());
                assert_eq!(node_a_chan.context.holder_htlc_minimum_msat, 1); // the default
                assert!(node_a_chan.context.counterparty_forwarding_info().is_none());
@@ -8536,7 +8551,7 @@ mod tests {
 
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
-               let node_a_chan = Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider,
+               let node_a_chan = OutboundV1Channel::<EnforcingSigner>::new_outbound(&feeest, &&keys_provider, &&keys_provider,
                        node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42).unwrap();
 
                let mut channel_type_features = ChannelTypeFeatures::only_static_remote_key();
@@ -8570,7 +8585,7 @@ mod tests {
 
                // It is not enough for just the initiator to signal `option_anchors_zero_fee_htlc_tx`, both
                // need to signal it.
-               let channel_a = Channel::<EnforcingSigner>::new_outbound(
+               let channel_a = OutboundV1Channel::<EnforcingSigner>::new_outbound(
                        &fee_estimator, &&keys_provider, &&keys_provider, node_id_b,
                        &channelmanager::provided_init_features(&UserConfig::default()), 10000000, 100000, 42,
                        &config, 0, 42
@@ -8581,7 +8596,7 @@ mod tests {
                expected_channel_type.set_static_remote_key_required();
                expected_channel_type.set_anchors_zero_fee_htlc_tx_required();
 
-               let channel_a = Channel::<EnforcingSigner>::new_outbound(
+               let channel_a = OutboundV1Channel::<EnforcingSigner>::new_outbound(
                        &fee_estimator, &&keys_provider, &&keys_provider, node_id_b,
                        &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42
                ).unwrap();
@@ -8619,7 +8634,7 @@ mod tests {
                let raw_init_features = static_remote_key_required | simple_anchors_required;
                let init_features_with_simple_anchors = InitFeatures::from_le_bytes(raw_init_features.to_le_bytes().to_vec());
 
-               let channel_a = Channel::<EnforcingSigner>::new_outbound(
+               let channel_a = OutboundV1Channel::<EnforcingSigner>::new_outbound(
                        &fee_estimator, &&keys_provider, &&keys_provider, node_id_b,
                        &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42
                ).unwrap();
@@ -8666,7 +8681,7 @@ mod tests {
                // First, we'll try to open a channel between A and B where A requests a channel type for
                // the original `option_anchors` feature (non zero fee htlc tx). This should be rejected by
                // B as it's not supported by LDK.
-               let channel_a = Channel::<EnforcingSigner>::new_outbound(
+               let channel_a = OutboundV1Channel::<EnforcingSigner>::new_outbound(
                        &fee_estimator, &&keys_provider, &&keys_provider, node_id_b,
                        &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42
                ).unwrap();
@@ -8685,7 +8700,7 @@ mod tests {
                // `anchors_zero_fee_htlc_tx`. B is malicious and tries to downgrade the channel type to the
                // original `option_anchors` feature, which should be rejected by A as it's not supported by
                // LDK.
-               let mut channel_a = Channel::<EnforcingSigner>::new_outbound(
+               let mut channel_a = OutboundV1Channel::<EnforcingSigner>::new_outbound(
                        &fee_estimator, &&keys_provider, &&keys_provider, node_id_b, &simple_anchors_init,
                        10000000, 100000, 42, &config, 0, 42
                ).unwrap();