Merge pull request #1657 from TheBlueMatt/2022-08-async-man-update
[rust-lightning] / lightning / src / ln / features.rs
index b90748aa87b7e5cd55bf0461244fd2c654feb7eb..c978c61a3a563428e38f3368e557e544a6c623b9 100644 (file)
 //! supports a feature if it advertises the feature (as either required or optional) to its peers.
 //! And the implementation can interpret a feature if the feature is known to it.
 //!
-//! [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
+//! The following features are currently required in the LDK:
+//! - `VariableLengthOnion` - requires/supports variable-length routing onion payloads
+//!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
+//! - `StaticRemoteKey` - requires/supports static key for remote output
+//!     (see [BOLT-3](https://github.com/lightning/bolts/blob/master/03-transactions.md) for more information).
+//!
+//! The following features are currently supported in the LDK:
+//! - `DataLossProtect` - requires/supports that a node which has somehow fallen behind, e.g., has been restored from an old backup,
+//!     can detect that it has fallen behind
+//!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
+//! - `InitialRoutingSync` - requires/supports that the sending node needs a complete routing information dump
+//!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#initial-sync) for more information).
+//! - `UpfrontShutdownScript` - commits to a shutdown scriptpubkey when opening a channel
+//!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message) for more information).
+//! - `GossipQueries` - requires/supports more sophisticated gossip control
+//!     (see [BOLT-7](https://github.com/lightning/bolts/blob/master/07-routing-gossip.md) for more information).
+//! - `PaymentSecret` - requires/supports that a node supports payment_secret field
+//!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md) for more information).
+//! - `BasicMPP` - requires/supports that a node can receive basic multi-part payments
+//!     (see [BOLT-4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md#basic-multi-part-payments) for more information).
+//! - `ShutdownAnySegwit` - requires/supports that future segwit versions are allowed in `shutdown`
+//!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
+//! - `ChannelType` - node supports the channel_type field in open/accept
+//!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
+//! - `SCIDPrivacy` - supply channel aliases for routing
+//!     (see [BOLT-2](https://github.com/lightning/bolts/blob/master/02-peer-protocol.md) for more information).
+//! - `Keysend` - send funds to a node without an invoice
+//!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
+//!
+//! [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
 //! [messages]: crate::ln::msgs
 
+use {io, io_extras};
 use prelude::*;
 use core::{cmp, fmt};
+use core::hash::{Hash, Hasher};
 use core::marker::PhantomData;
 
 use bitcoin::bech32;
@@ -124,6 +155,12 @@ mod sealed {
                        ,
                        // Byte 3
                        ,
+                       // Byte 4
+                       ,
+                       // Byte 5
+                       ,
+                       // Byte 6
+                       ,
                ],
                optional_features: [
                        // Byte 0
@@ -131,9 +168,15 @@ mod sealed {
                        // Byte 1
                        ,
                        // Byte 2
-                       BasicMPP,
+                       BasicMPP | Wumbo,
                        // Byte 3
                        ShutdownAnySegwit,
+                       // Byte 4
+                       ,
+                       // Byte 5
+                       ChannelType | SCIDPrivacy,
+                       // Byte 6
+                       ZeroConf,
                ],
        });
        define_context!(NodeContext {
@@ -159,15 +202,15 @@ mod sealed {
                        // Byte 1
                        ,
                        // Byte 2
-                       BasicMPP,
+                       BasicMPP | Wumbo,
                        // Byte 3
                        ShutdownAnySegwit,
                        // Byte 4
                        ,
                        // Byte 5
-                       ,
+                       ChannelType | SCIDPrivacy,
                        // Byte 6
-                       Keysend,
+                       ZeroConf | Keysend,
                ],
        });
        define_context!(ChannelContext {
@@ -192,17 +235,53 @@ mod sealed {
                        BasicMPP,
                ],
        });
+       // This isn't a "real" feature context, and is only used in the channel_type field in an
+       // `OpenChannel` message.
+       define_context!(ChannelTypeContext {
+               required_features: [
+                       // Byte 0
+                       ,
+                       // Byte 1
+                       StaticRemoteKey,
+                       // Byte 2
+                       ,
+                       // Byte 3
+                       ,
+                       // Byte 4
+                       ,
+                       // Byte 5
+                       SCIDPrivacy,
+                       // Byte 6
+                       ZeroConf,
+               ],
+               optional_features: [
+                       // Byte 0
+                       ,
+                       // Byte 1
+                       ,
+                       // Byte 2
+                       ,
+                       // Byte 3
+                       ,
+                       // Byte 4
+                       ,
+                       // Byte 5
+                       ,
+                       // Byte 6
+                       ,
+               ],
+       });
 
        /// Defines a feature with the given bits for the specified [`Context`]s. The generated trait is
        /// useful for manipulating feature flags.
        macro_rules! define_feature {
                ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
-                $required_setter: ident) => {
+                $required_setter: ident, $supported_getter: ident) => {
                        #[doc = $doc]
                        ///
                        /// See [BOLT #9] for details.
                        ///
-                       /// [BOLT #9]: https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
+                       /// [BOLT #9]: https://github.com/lightning/bolts/blob/master/09-features.md
                        pub trait $feature: Context {
                                /// The bit used to signify that the feature is required.
                                const EVEN_BIT: usize = $odd_bit - 1;
@@ -284,15 +363,18 @@ mod sealed {
 
                        impl <T: $feature> Features<T> {
                                /// Set this feature as optional.
-                               pub fn $optional_setter(mut self) -> Self {
+                               pub fn $optional_setter(&mut self) {
                                        <T as $feature>::set_optional_bit(&mut self.flags);
-                                       self
                                }
 
                                /// Set this feature as required.
-                               pub fn $required_setter(mut self) -> Self {
+                               pub fn $required_setter(&mut self) {
                                        <T as $feature>::set_required_bit(&mut self.flags);
-                                       self
+                               }
+
+                               /// Checks if this feature is supported.
+                               pub fn $supported_getter(&self) -> bool {
+                                       <T as $feature>::supports_feature(&self.flags)
                                }
                        }
 
@@ -305,41 +387,74 @@ mod sealed {
                                        const ASSERT_ODD_BIT_PARITY: usize = (<Self as $feature>::ODD_BIT % 2) - 1;
                                }
                        )*
-
+               };
+               ($odd_bit: expr, $feature: ident, [$($context: ty),+], $doc: expr, $optional_setter: ident,
+                $required_setter: ident, $supported_getter: ident, $required_getter: ident) => {
+                       define_feature!($odd_bit, $feature, [$($context),+], $doc, $optional_setter, $required_setter, $supported_getter);
+                       impl <T: $feature> Features<T> {
+                               /// Checks if this feature is required.
+                               pub fn $required_getter(&self) -> bool {
+                                       <T as $feature>::requires_feature(&self.flags)
+                               }
+                       }
                }
        }
 
        define_feature!(1, DataLossProtect, [InitContext, NodeContext],
                "Feature flags for `option_data_loss_protect`.", set_data_loss_protect_optional,
-               set_data_loss_protect_required);
+               set_data_loss_protect_required, supports_data_loss_protect, requires_data_loss_protect);
        // NOTE: Per Bolt #9, initial_routing_sync has no even bit.
        define_feature!(3, InitialRoutingSync, [InitContext], "Feature flags for `initial_routing_sync`.",
-               set_initial_routing_sync_optional, set_initial_routing_sync_required);
+               set_initial_routing_sync_optional, set_initial_routing_sync_required,
+               initial_routing_sync);
        define_feature!(5, UpfrontShutdownScript, [InitContext, NodeContext],
                "Feature flags for `option_upfront_shutdown_script`.", set_upfront_shutdown_script_optional,
-               set_upfront_shutdown_script_required);
+               set_upfront_shutdown_script_required, supports_upfront_shutdown_script,
+               requires_upfront_shutdown_script);
        define_feature!(7, GossipQueries, [InitContext, NodeContext],
-               "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required);
+               "Feature flags for `gossip_queries`.", set_gossip_queries_optional, set_gossip_queries_required,
+               supports_gossip_queries, requires_gossip_queries);
        define_feature!(9, VariableLengthOnion, [InitContext, NodeContext, InvoiceContext],
                "Feature flags for `var_onion_optin`.", set_variable_length_onion_optional,
-               set_variable_length_onion_required);
-       define_feature!(13, StaticRemoteKey, [InitContext, NodeContext],
+               set_variable_length_onion_required, supports_variable_length_onion,
+               requires_variable_length_onion);
+       define_feature!(13, StaticRemoteKey, [InitContext, NodeContext, ChannelTypeContext],
                "Feature flags for `option_static_remotekey`.", set_static_remote_key_optional,
-               set_static_remote_key_required);
+               set_static_remote_key_required, supports_static_remote_key, requires_static_remote_key);
        define_feature!(15, PaymentSecret, [InitContext, NodeContext, InvoiceContext],
-               "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required);
+               "Feature flags for `payment_secret`.", set_payment_secret_optional, set_payment_secret_required,
+               supports_payment_secret, requires_payment_secret);
        define_feature!(17, BasicMPP, [InitContext, NodeContext, InvoiceContext],
-               "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required);
+               "Feature flags for `basic_mpp`.", set_basic_mpp_optional, set_basic_mpp_required,
+               supports_basic_mpp, requires_basic_mpp);
+       define_feature!(19, Wumbo, [InitContext, NodeContext],
+               "Feature flags for `option_support_large_channel` (aka wumbo channels).", set_wumbo_optional, set_wumbo_required,
+               supports_wumbo, requires_wumbo);
        define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
                "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
-               set_shutdown_any_segwit_required);
+               set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
+       // We do not yet advertise the onion messages feature bit, but we need to detect when peers
+       // support it.
+       define_feature!(39, OnionMessages, [InitContext, NodeContext],
+               "Feature flags for `option_onion_messages`.", set_onion_messages_optional,
+               set_onion_messages_required, supports_onion_messages, requires_onion_messages);
+       define_feature!(45, ChannelType, [InitContext, NodeContext],
+               "Feature flags for `option_channel_type`.", set_channel_type_optional,
+               set_channel_type_required, supports_channel_type, requires_channel_type);
+       define_feature!(47, SCIDPrivacy, [InitContext, NodeContext, ChannelTypeContext],
+               "Feature flags for only forwarding with SCID aliasing. Called `option_scid_alias` in the BOLTs",
+               set_scid_privacy_optional, set_scid_privacy_required, supports_scid_privacy, requires_scid_privacy);
+       define_feature!(51, ZeroConf, [InitContext, NodeContext, ChannelTypeContext],
+               "Feature flags for accepting channels with zero confirmations. Called `option_zeroconf` in the BOLTs",
+               set_zero_conf_optional, set_zero_conf_required, supports_zero_conf, requires_zero_conf);
        define_feature!(55, Keysend, [NodeContext],
-               "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required);
+               "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
+               supports_keysend, requires_keysend);
 
        #[cfg(test)]
        define_feature!(123456789, UnknownFeature, [NodeContext, ChannelContext, InvoiceContext],
                "Feature flags for an unknown feature used in testing.", set_unknown_feature_optional,
-               set_unknown_feature_required);
+               set_unknown_feature_required, supports_unknown_test_feature, requires_unknown_test_feature);
 }
 
 /// Tracks the set of features which a node implements, templated by the context in which it
@@ -361,6 +476,11 @@ impl<T: sealed::Context> Clone for Features<T> {
                }
        }
 }
+impl<T: sealed::Context> Hash for Features<T> {
+       fn hash<H: Hasher>(&self, hasher: &mut H) {
+               self.flags.hash(hasher);
+       }
+}
 impl<T: sealed::Context> PartialEq for Features<T> {
        fn eq(&self, o: &Self) -> bool {
                self.flags.eq(&o.flags)
@@ -381,11 +501,22 @@ pub type ChannelFeatures = Features<sealed::ChannelContext>;
 /// Features used within an invoice.
 pub type InvoiceFeatures = Features<sealed::InvoiceContext>;
 
+/// Features used within the channel_type field in an OpenChannel message.
+///
+/// A channel is always of some known "type", describing the transaction formats used and the exact
+/// semantics of our interaction with our peer.
+///
+/// Note that because a channel is a specific type which is proposed by the opener and accepted by
+/// the counterparty, only required features are allowed here.
+///
+/// This is serialized differently from other feature types - it is not prefixed by a length, and
+/// thus must only appear inside a TLV where its length is known in advance.
+pub type ChannelTypeFeatures = Features<sealed::ChannelTypeContext>;
+
 impl InitFeatures {
        /// Writes all features present up to, and including, 13.
-       pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
+       pub(crate) fn write_up_to_13<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
                let len = cmp::min(2, self.flags.len());
-               w.size_hint(len + 2);
                (len as u16).write(w)?;
                for i in (0..len).rev() {
                        if i == 0 {
@@ -426,13 +557,37 @@ impl InvoiceFeatures {
        /// Getting a route for a keysend payment to a private node requires providing the payee's
        /// features (since they were not announced in a node announcement). However, keysend payments
        /// don't have an invoice to pull the payee's features from, so this method is provided for use in
-       /// [`get_keysend_route`], thus omitting the need for payers to manually construct an
-       /// `InvoiceFeatures` for [`get_route`].
+       /// [`PaymentParameters::for_keysend`], thus omitting the need for payers to manually construct an
+       /// `InvoiceFeatures` for [`find_route`].
        ///
-       /// [`get_keysend_route`]: crate::routing::router::get_keysend_route
-       /// [`get_route`]: crate::routing::router::get_route
+       /// [`PaymentParameters::for_keysend`]: crate::routing::router::PaymentParameters::for_keysend
+       /// [`find_route`]: crate::routing::router::find_route
        pub(crate) fn for_keysend() -> InvoiceFeatures {
-               InvoiceFeatures::empty().set_variable_length_onion_optional()
+               let mut res = InvoiceFeatures::empty();
+               res.set_variable_length_onion_optional();
+               res
+       }
+}
+
+impl ChannelTypeFeatures {
+       /// Constructs the implicit channel type based on the common supported types between us and our
+       /// counterparty
+       pub(crate) fn from_counterparty_init(counterparty_init: &InitFeatures) -> Self {
+               let mut ret = counterparty_init.to_context_internal();
+               // ChannelTypeFeatures must only contain required bits, so we OR the required forms of all
+               // optional bits and then AND out the optional ones.
+               for byte in ret.flags.iter_mut() {
+                       *byte |= (*byte & 0b10_10_10_10) >> 1;
+                       *byte &= 0b01_01_01_01;
+               }
+               ret
+       }
+
+       /// Constructs a ChannelTypeFeatures with only static_remotekey set
+       pub(crate) fn only_static_remote_key() -> Self {
+               let mut ret = Self::empty();
+               <sealed::ChannelTypeContext as sealed::StaticRemoteKey>::set_required_bit(&mut ret.flags);
+               ret
        }
 }
 
@@ -547,7 +702,28 @@ impl<T: sealed::Context> Features<T> {
                &self.flags
        }
 
-       pub(crate) fn requires_unknown_bits(&self) -> bool {
+       fn write_be<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+               for f in self.flags.iter().rev() { // Swap back to big-endian
+                       f.write(w)?;
+               }
+               Ok(())
+       }
+
+       fn from_be_bytes(mut flags: Vec<u8>) -> Features<T> {
+               flags.reverse(); // Swap to little-endian
+               Self {
+                       flags,
+                       mark: PhantomData,
+               }
+       }
+
+       pub(crate) fn supports_any_optional_bits(&self) -> bool {
+               self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
+       }
+
+       /// Returns true if this `Features` object contains unknown feature flags which are set as
+       /// "required".
+       pub fn requires_unknown_bits(&self) -> bool {
                // Bitwise AND-ing with all even bits set except for known features will select required
                // unknown features.
                let byte_count = T::KNOWN_FEATURE_MASK.len();
@@ -575,33 +751,9 @@ impl<T: sealed::Context> Features<T> {
                        (byte & unknown_features) != 0
                })
        }
-
-       /// The number of bytes required to represent the feature flags present. This does not include
-       /// the length bytes which are included in the serialized form.
-       pub(crate) fn byte_count(&self) -> usize {
-               self.flags.len()
-       }
-}
-
-impl<T: sealed::DataLossProtect> Features<T> {
-       #[cfg(test)]
-       pub(crate) fn requires_data_loss_protect(&self) -> bool {
-               <T as sealed::DataLossProtect>::requires_feature(&self.flags)
-       }
-       #[cfg(test)]
-       pub(crate) fn supports_data_loss_protect(&self) -> bool {
-               <T as sealed::DataLossProtect>::supports_feature(&self.flags)
-       }
 }
 
 impl<T: sealed::UpfrontShutdownScript> Features<T> {
-       #[cfg(test)]
-       pub(crate) fn requires_upfront_shutdown_script(&self) -> bool {
-               <T as sealed::UpfrontShutdownScript>::requires_feature(&self.flags)
-       }
-       pub(crate) fn supports_upfront_shutdown_script(&self) -> bool {
-               <T as sealed::UpfrontShutdownScript>::supports_feature(&self.flags)
-       }
        #[cfg(test)]
        pub(crate) fn clear_upfront_shutdown_script(mut self) -> Self {
                <T as sealed::UpfrontShutdownScript>::clear_bits(&mut self.flags);
@@ -611,13 +763,6 @@ impl<T: sealed::UpfrontShutdownScript> Features<T> {
 
 
 impl<T: sealed::GossipQueries> Features<T> {
-       #[cfg(test)]
-       pub(crate) fn requires_gossip_queries(&self) -> bool {
-               <T as sealed::GossipQueries>::requires_feature(&self.flags)
-       }
-       pub(crate) fn supports_gossip_queries(&self) -> bool {
-               <T as sealed::GossipQueries>::supports_feature(&self.flags)
-       }
        #[cfg(test)]
        pub(crate) fn clear_gossip_queries(mut self) -> Self {
                <T as sealed::GossipQueries>::clear_bits(&mut self.flags);
@@ -625,32 +770,9 @@ impl<T: sealed::GossipQueries> Features<T> {
        }
 }
 
-impl<T: sealed::VariableLengthOnion> Features<T> {
-       #[cfg(test)]
-       pub(crate) fn requires_variable_length_onion(&self) -> bool {
-               <T as sealed::VariableLengthOnion>::requires_feature(&self.flags)
-       }
-       pub(crate) fn supports_variable_length_onion(&self) -> bool {
-               <T as sealed::VariableLengthOnion>::supports_feature(&self.flags)
-       }
-}
-
-impl<T: sealed::StaticRemoteKey> Features<T> {
-       pub(crate) fn supports_static_remote_key(&self) -> bool {
-               <T as sealed::StaticRemoteKey>::supports_feature(&self.flags)
-       }
-       #[cfg(test)]
-       pub(crate) fn requires_static_remote_key(&self) -> bool {
-               <T as sealed::StaticRemoteKey>::requires_feature(&self.flags)
-       }
-}
-
 impl<T: sealed::InitialRoutingSync> Features<T> {
-       pub(crate) fn initial_routing_sync(&self) -> bool {
-               <T as sealed::InitialRoutingSync>::supports_feature(&self.flags)
-       }
        // We are no longer setting initial_routing_sync now that gossip_queries
-       // is enabled. This feature is ignored by a peer when gossip_queries has 
+       // is enabled. This feature is ignored by a peer when gossip_queries has
        // been negotiated.
        #[cfg(test)]
        pub(crate) fn clear_initial_routing_sync(&mut self) {
@@ -658,64 +780,60 @@ impl<T: sealed::InitialRoutingSync> Features<T> {
        }
 }
 
-impl<T: sealed::PaymentSecret> Features<T> {
-       #[cfg(test)]
-       pub(crate) fn requires_payment_secret(&self) -> bool {
-               <T as sealed::PaymentSecret>::requires_feature(&self.flags)
-       }
-       /// Returns whether the `payment_secret` feature is supported.
-       pub fn supports_payment_secret(&self) -> bool {
-               <T as sealed::PaymentSecret>::supports_feature(&self.flags)
-       }
-}
-
-impl<T: sealed::BasicMPP> Features<T> {
+impl<T: sealed::ShutdownAnySegwit> Features<T> {
        #[cfg(test)]
-       pub(crate) fn requires_basic_mpp(&self) -> bool {
-               <T as sealed::BasicMPP>::requires_feature(&self.flags)
-       }
-       // We currently never test for this since we don't actually *generate* multipath routes.
-       pub(crate) fn supports_basic_mpp(&self) -> bool {
-               <T as sealed::BasicMPP>::supports_feature(&self.flags)
+       pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
+               <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
+               self
        }
 }
 
-impl<T: sealed::ShutdownAnySegwit> Features<T> {
-       pub(crate) fn supports_shutdown_anysegwit(&self) -> bool {
-               <T as sealed::ShutdownAnySegwit>::supports_feature(&self.flags)
-       }
+impl<T: sealed::Wumbo> Features<T> {
        #[cfg(test)]
-       pub(crate) fn clear_shutdown_anysegwit(mut self) -> Self {
-               <T as sealed::ShutdownAnySegwit>::clear_bits(&mut self.flags);
+       pub(crate) fn clear_wumbo(mut self) -> Self {
+               <T as sealed::Wumbo>::clear_bits(&mut self.flags);
                self
        }
 }
 
-impl<T: sealed::Context> Writeable for Features<T> {
-       fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
-               w.size_hint(self.flags.len() + 2);
-               (self.flags.len() as u16).write(w)?;
-               for f in self.flags.iter().rev() { // Swap back to big-endian
-                       f.write(w)?;
+macro_rules! impl_feature_len_prefixed_write {
+       ($features: ident) => {
+               impl Writeable for $features {
+                       fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+                               (self.flags.len() as u16).write(w)?;
+                               self.write_be(w)
+                       }
+               }
+               impl Readable for $features {
+                       fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
+                               Ok(Self::from_be_bytes(Vec::<u8>::read(r)?))
+                       }
                }
-               Ok(())
        }
 }
-
-impl<T: sealed::Context> Readable for Features<T> {
-       fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
-               let mut flags: Vec<u8> = Readable::read(r)?;
-               flags.reverse(); // Swap to little-endian
-               Ok(Self {
-                       flags,
-                       mark: PhantomData,
-               })
+impl_feature_len_prefixed_write!(InitFeatures);
+impl_feature_len_prefixed_write!(ChannelFeatures);
+impl_feature_len_prefixed_write!(NodeFeatures);
+impl_feature_len_prefixed_write!(InvoiceFeatures);
+
+// Because ChannelTypeFeatures only appears inside of TLVs, it doesn't have a length prefix when
+// serialized. Thus, we can't use `impl_feature_len_prefixed_write`, above, and have to write our
+// own serialization.
+impl Writeable for ChannelTypeFeatures {
+       fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+               self.write_be(w)
+       }
+}
+impl Readable for ChannelTypeFeatures {
+       fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
+               let v = io_extras::read_to_end(r)?;
+               Ok(Self::from_be_bytes(v))
        }
 }
 
 #[cfg(test)]
 mod tests {
-       use super::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
+       use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
        use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
 
        #[test]
@@ -768,9 +886,33 @@ mod tests {
                assert!(!NodeFeatures::known().requires_basic_mpp());
                assert!(!InvoiceFeatures::known().requires_basic_mpp());
 
+               assert!(InitFeatures::known().supports_channel_type());
+               assert!(NodeFeatures::known().supports_channel_type());
+               assert!(!InitFeatures::known().requires_channel_type());
+               assert!(!NodeFeatures::known().requires_channel_type());
+
                assert!(InitFeatures::known().supports_shutdown_anysegwit());
                assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 
+               assert!(InitFeatures::known().supports_scid_privacy());
+               assert!(NodeFeatures::known().supports_scid_privacy());
+               assert!(ChannelTypeFeatures::known().supports_scid_privacy());
+               assert!(!InitFeatures::known().requires_scid_privacy());
+               assert!(!NodeFeatures::known().requires_scid_privacy());
+               assert!(ChannelTypeFeatures::known().requires_scid_privacy());
+
+               assert!(InitFeatures::known().supports_wumbo());
+               assert!(NodeFeatures::known().supports_wumbo());
+               assert!(!InitFeatures::known().requires_wumbo());
+               assert!(!NodeFeatures::known().requires_wumbo());
+
+               assert!(InitFeatures::known().supports_zero_conf());
+               assert!(!InitFeatures::known().requires_zero_conf());
+               assert!(NodeFeatures::known().supports_zero_conf());
+               assert!(!NodeFeatures::known().requires_zero_conf());
+               assert!(ChannelTypeFeatures::known().supports_zero_conf());
+               assert!(ChannelTypeFeatures::known().requires_zero_conf());
+
                let mut init_features = InitFeatures::known();
                assert!(init_features.initial_routing_sync());
                init_features.clear_initial_routing_sync();
@@ -783,11 +925,13 @@ mod tests {
                assert!(!features.requires_unknown_bits());
                assert!(!features.supports_unknown_bits());
 
-               let features = ChannelFeatures::empty().set_unknown_feature_required();
+               let mut features = ChannelFeatures::empty();
+               features.set_unknown_feature_required();
                assert!(features.requires_unknown_bits());
                assert!(features.supports_unknown_bits());
 
-               let features = ChannelFeatures::empty().set_unknown_feature_optional();
+               let mut features = ChannelFeatures::empty();
+               features.set_unknown_feature_optional();
                assert!(!features.requires_unknown_bits());
                assert!(features.supports_unknown_bits());
        }
@@ -804,13 +948,19 @@ mod tests {
                        // Check that the flags are as expected:
                        // - option_data_loss_protect
                        // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
-                       // - basic_mpp
+                       // - basic_mpp | wumbo
                        // - opt_shutdown_anysegwit
-                       assert_eq!(node_features.flags.len(), 4);
+                       // -
+                       // - option_channel_type | option_scid_alias
+                       // - option_zeroconf
+                       assert_eq!(node_features.flags.len(), 7);
                        assert_eq!(node_features.flags[0], 0b00000010);
                        assert_eq!(node_features.flags[1], 0b01010001);
-                       assert_eq!(node_features.flags[2], 0b00000010);
+                       assert_eq!(node_features.flags[2], 0b00001010);
                        assert_eq!(node_features.flags[3], 0b00001000);
+                       assert_eq!(node_features.flags[4], 0b00000000);
+                       assert_eq!(node_features.flags[5], 0b10100000);
+                       assert_eq!(node_features.flags[6], 0b00001000);
                }
 
                // Check that cleared flags are kept blank when converting back:
@@ -826,8 +976,9 @@ mod tests {
        #[test]
        fn convert_to_context_with_unknown_flags() {
                // Ensure the `from` context has fewer known feature bytes than the `to` context.
-               assert!(InvoiceFeatures::known().byte_count() < NodeFeatures::known().byte_count());
-               let invoice_features = InvoiceFeatures::known().set_unknown_feature_optional();
+               assert!(InvoiceFeatures::known().flags.len() < NodeFeatures::known().flags.len());
+               let mut invoice_features = InvoiceFeatures::known();
+               invoice_features.set_unknown_feature_optional();
                assert!(invoice_features.supports_unknown_bits());
                let node_features: NodeFeatures = invoice_features.to_context();
                assert!(!node_features.supports_unknown_bits());
@@ -835,9 +986,9 @@ mod tests {
 
        #[test]
        fn set_feature_bits() {
-               let features = InvoiceFeatures::empty()
-                       .set_basic_mpp_optional()
-                       .set_payment_secret_required();
+               let mut features = InvoiceFeatures::empty();
+               features.set_basic_mpp_optional();
+               features.set_payment_secret_required();
                assert!(features.supports_basic_mpp());
                assert!(!features.requires_basic_mpp());
                assert!(features.requires_payment_secret());
@@ -874,4 +1025,16 @@ mod tests {
                let features_deserialized = InvoiceFeatures::from_base32(&features_as_u5s).unwrap();
                assert_eq!(features, features_deserialized);
        }
+
+       #[test]
+       fn test_channel_type_mapping() {
+               // If we map an InvoiceFeatures with StaticRemoteKey optional, it should map into a
+               // required-StaticRemoteKey ChannelTypeFeatures.
+               let mut init_features = InitFeatures::empty();
+               init_features.set_static_remote_key_optional();
+               let converted_features = ChannelTypeFeatures::from_counterparty_init(&init_features);
+               assert_eq!(converted_features, ChannelTypeFeatures::only_static_remote_key());
+               assert!(!converted_features.supports_any_optional_bits());
+               assert!(converted_features.requires_static_remote_key());
+       }
 }