pub outbound_capacity_msat: u64,
/// The maximum value we can assign to the next outbound HTLC
pub next_outbound_htlc_limit_msat: u64,
+ /// The minimum value we can assign to the next outbound HTLC
+ pub next_outbound_htlc_minimum_msat: u64,
}
#[derive(Debug, Clone, Copy, PartialEq)]
/// corner case properly.
pub fn get_available_balances(&self) -> AvailableBalances {
// Note that we have to handle overflow due to the above case.
+ let inbound_stats = self.get_inbound_pending_htlc_stats(None);
let outbound_stats = self.get_outbound_pending_htlc_stats(None);
let mut balance_msat = self.value_to_self_msat;
}
balance_msat -= outbound_stats.pending_htlcs_value_msat;
- let outbound_capacity_msat = cmp::max(self.value_to_self_msat as i64
- - outbound_stats.pending_htlcs_value_msat as i64
- - self.counterparty_selected_channel_reserve_satoshis.unwrap_or(0) as i64 * 1000,
- 0) as u64;
+ let outbound_capacity_msat = self.value_to_self_msat
+ .saturating_sub(outbound_stats.pending_htlcs_value_msat)
+ .saturating_sub(
+ self.counterparty_selected_channel_reserve_satoshis.unwrap_or(0) * 1000);
+
+ let mut available_capacity_msat = outbound_capacity_msat;
+
+ if self.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 = self.holder_dust_limit_satoshis;
+ if !self.opt_anchors() {
+ real_dust_limit_timeout_sat += self.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(()));
+
+ // 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 = self.counterparty_dust_limit_satoshis;
+ if !self.opt_anchors() {
+ real_dust_limit_success_sat += self.feerate_per_kw as u64 * htlc_success_tx_weight(false) / 1000;
+ }
+
+ 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 holder_selected_chan_reserve_msat = self.holder_selected_channel_reserve_satoshis * 1000;
+ let remote_balance_msat = (self.channel_value_satoshis * 1000 - self.value_to_self_msat)
+ .saturating_sub(inbound_stats.pending_htlcs_value_msat);
+
+ 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);
+ }
+ }
+
+ let mut next_outbound_htlc_minimum_msat = self.counterparty_htlc_minimum_msat;
+
+ // 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;
+
+ let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if self.opt_anchors() {
+ (self.counterparty_dust_limit_satoshis, self.holder_dust_limit_satoshis)
+ } else {
+ let dust_buffer_feerate = self.get_dust_buffer_feerate(None) as u64;
+ (self.counterparty_dust_limit_satoshis + dust_buffer_feerate * htlc_success_tx_weight(false) / 1000,
+ self.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 > self.get_max_dust_htlc_exposure_msat() as i64 {
+ remaining_msat_below_dust_exposure_limit =
+ Some(self.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);
+ }
+
+ 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 > self.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()),
+ self.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);
+ }
+
+ 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);
+ }
+ }
+
+ available_capacity_msat = cmp::min(available_capacity_msat,
+ self.counterparty_max_htlc_value_in_flight_msat - outbound_stats.pending_htlcs_value_msat);
+
+ if outbound_stats.pending_htlcs + 1 > self.counterparty_max_accepted_htlcs as u32 {
+ available_capacity_msat = 0;
+ }
+
AvailableBalances {
inbound_capacity_msat: cmp::max(self.channel_value_satoshis as i64 * 1000
- self.value_to_self_msat as i64
- self.holder_selected_channel_reserve_satoshis as i64 * 1000,
0) as u64,
outbound_capacity_msat,
- next_outbound_htlc_limit_msat: cmp::max(cmp::min(outbound_capacity_msat as i64,
- self.counterparty_max_htlc_value_in_flight_msat as i64
- - outbound_stats.pending_htlcs_value_msat as i64),
- 0) as u64,
+ next_outbound_htlc_limit_msat: available_capacity_msat,
+ next_outbound_htlc_minimum_msat,
balance_msat,
}
}
feerate_per_kw as u64 * (commitment_tx_base_weight(opt_anchors) + num_htlcs as u64 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000
}
- // 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, plus an additional
- // HTLC if `fee_spike_buffer_htlc` is Some, plus a new HTLC given by `new_htlc_amount`. Dust HTLCs
- // are excluded.
+ /// 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 {
assert!(self.is_outbound());
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, plus an additional HTLC if
- // `fee_spike_buffer_htlc` is Some, plus a new HTLC given by `new_htlc_amount`. Dust HTLCs are
- // excluded.
+ /// 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 {
assert!(!self.is_outbound());
return Err(ChannelError::Ignore("Cannot send 0-msat HTLC".to_owned()));
}
- if amount_msat < self.counterparty_htlc_minimum_msat {
- return Err(ChannelError::Ignore(format!("Cannot send less than their minimum HTLC value ({})", self.counterparty_htlc_minimum_msat)));
+ let available_balances = self.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)));
+ }
+
+ if amount_msat > available_balances.next_outbound_htlc_limit_msat {
+ return Err(ChannelError::Ignore(format!("Cannot send more than our next-HTLC maximum - {} msat",
+ available_balances.next_outbound_htlc_limit_msat)));
}
if (self.channel_state & (ChannelState::PeerDisconnected as u32)) != 0 {
return Err(ChannelError::Ignore("Cannot send an HTLC while disconnected from channel counterparty".to_owned()));
}
- let inbound_stats = self.get_inbound_pending_htlc_stats(None);
- let outbound_stats = self.get_outbound_pending_htlc_stats(None);
- if outbound_stats.pending_htlcs + 1 > self.counterparty_max_accepted_htlcs as u32 {
- return Err(ChannelError::Ignore(format!("Cannot push more than their max accepted HTLCs ({})", self.counterparty_max_accepted_htlcs)));
- }
- // Check their_max_htlc_value_in_flight_msat
- if outbound_stats.pending_htlcs_value_msat + amount_msat > self.counterparty_max_htlc_value_in_flight_msat {
- return Err(ChannelError::Ignore(format!("Cannot send value that would put us over the max HTLC value in flight our peer will accept ({})", self.counterparty_max_htlc_value_in_flight_msat)));
- }
+ let need_holding_cell = (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::MonitorUpdateInProgress as u32)) != 0;
+ log_debug!(logger, "Pushing new outbound HTLC for {} msat {}", amount_msat,
+ if force_holding_cell { "into holding cell" }
+ else if need_holding_cell { "into holding cell as we're awaiting an RAA or monitor" }
+ else { "to peer" });
- let keys = self.build_holder_transaction_keys(self.cur_holder_commitment_transaction_number);
- let commitment_stats = self.build_commitment_transaction(self.cur_holder_commitment_transaction_number, &keys, true, true, logger);
- if !self.is_outbound() {
- // Check that we won't violate the remote channel reserve by adding this HTLC.
- let htlc_candidate = HTLCCandidate::new(amount_msat, HTLCInitiator::LocalOffered);
- let counterparty_commit_tx_fee_msat = self.next_remote_commit_tx_fee_msat(htlc_candidate, None);
- let holder_selected_chan_reserve_msat = self.holder_selected_channel_reserve_satoshis * 1000;
- if commitment_stats.remote_balance_msat < counterparty_commit_tx_fee_msat + holder_selected_chan_reserve_msat {
- return Err(ChannelError::Ignore("Cannot send value that would put counterparty balance under holder-announced channel reserve value".to_owned()));
- }
- }
-
- let (htlc_success_dust_limit, htlc_timeout_dust_limit) = if self.opt_anchors() {
- (0, 0)
- } else {
- let dust_buffer_feerate = self.get_dust_buffer_feerate(None) as u64;
- (dust_buffer_feerate * htlc_success_tx_weight(false) / 1000,
- dust_buffer_feerate * htlc_timeout_tx_weight(false) / 1000)
- };
- let exposure_dust_limit_success_sats = htlc_success_dust_limit + self.counterparty_dust_limit_satoshis;
- if amount_msat / 1000 < exposure_dust_limit_success_sats {
- let on_counterparty_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat + amount_msat;
- if on_counterparty_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
- return Err(ChannelError::Ignore(format!("Cannot send value that would put our exposure to dust HTLCs at {} over the limit {} on counterparty commitment tx",
- on_counterparty_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat())));
- }
- }
-
- let exposure_dust_limit_timeout_sats = htlc_timeout_dust_limit + self.holder_dust_limit_satoshis;
- if amount_msat / 1000 < exposure_dust_limit_timeout_sats {
- let on_holder_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat + amount_msat;
- if on_holder_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
- return Err(ChannelError::Ignore(format!("Cannot send value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
- on_holder_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat())));
- }
- }
-
- let holder_balance_msat = commitment_stats.local_balance_msat - outbound_stats.holding_cell_msat;
- if holder_balance_msat < amount_msat {
- return Err(ChannelError::Ignore(format!("Cannot send value that would overdraw remaining funds. Amount: {}, pending value to self {}", amount_msat, holder_balance_msat)));
- }
-
- // `2 *` and extra HTLC are for the fee spike buffer.
- let commit_tx_fee_msat = if self.is_outbound() {
- let htlc_candidate = HTLCCandidate::new(amount_msat, HTLCInitiator::LocalOffered);
- FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE * self.next_local_commit_tx_fee_msat(htlc_candidate, Some(()))
- } else { 0 };
- if holder_balance_msat - amount_msat < commit_tx_fee_msat {
- return Err(ChannelError::Ignore(format!("Cannot send value that would not leave enough to pay for fees. Pending value to self: {}. local_commit_tx_fee {}", holder_balance_msat, commit_tx_fee_msat)));
- }
-
- // Check self.counterparty_selected_channel_reserve_satoshis (the amount we must keep as
- // reserve for the remote to have something to claim if we misbehave)
- let chan_reserve_msat = self.counterparty_selected_channel_reserve_satoshis.unwrap() * 1000;
- if holder_balance_msat - amount_msat - commit_tx_fee_msat < chan_reserve_msat {
- return Err(ChannelError::Ignore(format!("Cannot send value that would put our balance under counterparty-announced channel reserve value ({})", chan_reserve_msat)));
- }
-
- if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::MonitorUpdateInProgress as u32)) != 0 {
+ if need_holding_cell {
force_holding_cell = true;
}
projects / rust-lightning / blobdiff