p2p: Add BIP434 to `NetworkMessage`

diff --git a/contrib/check-encodable-coverage.sh b/contrib/check-encodable-coverage.sh
index 8375bf53..ebac25d8 100755
--- a/contrib/check-encodable-coverage.sh
+++ b/contrib/check-encodable-coverage.sh
@@ -19,7 +19,8 @@ TRAIT_IMPL_JS="$REPO_DIR/target/doc/trait.impl/bitcoin_consensus_encoding/encode
 # - InventoryPayload has no type in 0.32 bitcoin. Vec<Inventory> fails special case consideration.
 # - FeeFilter is a FeeRate newtype. FeeRate has no old Encodable/Decodable and is just a u64 le encoding in FeeFilter.
 # - SendTxRcnCl is a new type that does not have a comparison.
-EXCLUSIONS="CommandString HeadersMessage InventoryPayload FeeFilter NetworkMessage Script Validation V2NetworkMessage V1MessageHeader SendTxRcnCl"
+# - Feature is a new type that does not have a comparison.
+EXCLUSIONS="CommandString HeadersMessage InventoryPayload FeeFilter NetworkMessage Script Validation V2NetworkMessage V1MessageHeader SendTxRcnCl Feature FeatureId FeatureData"
 
 main() {
     check_required_commands
diff --git a/fuzz/generate-encoding-roundtrip.sh b/fuzz/generate-encoding-roundtrip.sh
index 8251aadb..ff929d37 100755
--- a/fuzz/generate-encoding-roundtrip.sh
+++ b/fuzz/generate-encoding-roundtrip.sh
@@ -80,6 +80,9 @@ ROUNDTRIP_TYPES=(
     "p2p::message_network::UserAgent"
     "p2p::message_network::VersionMessage"
     "p2p::message_erlay::SendTxRcnCl"
+    "p2p::bip434::Feature"
+    "p2p::bip434::FeatureId"
+    "p2p::bip434::FeatureData"
 )
 
 # Types tested with check_script_roundtrip (Buf types that Deref to their Encodable target).
diff --git a/p2p/src/lib.rs b/p2p/src/lib.rs
index 6744952b..9ffd13ad 100644
--- a/p2p/src/lib.rs
+++ b/p2p/src/lib.rs
@@ -77,6 +77,7 @@ pub use self::error::{
 /// may lead to you incorrectly banning other peers or other peers banning you.
 ///
 /// These are the features required for each version:
+/// 70017 - Support `feature` messages between `version` and `verack` message
 /// 70016 - Support receiving `wtxidrelay` message between `version` and `verack` message
 /// 70015 - Support receiving invalid compact blocks from a peer without banning them
 /// 70014 - Support compact block messages `sendcmpct`, `cmpctblock`, `getblocktxn` and `blocktxn`
@@ -91,6 +92,8 @@ pub use self::error::{
 pub struct ProtocolVersion(u32);
 
 impl ProtocolVersion {
+    /// Support `feature` messages between `version` and `verack` message
+    pub const FEATURE_VERSION: Self = Self(70017);
     /// Support receiving `wtxidrelay` message between `version` and `verack` message
     pub const WTXID_RELAY_VERSION: Self = Self(70016);
     /// Support receiving invalid compact blocks from a peer without banning them
diff --git a/p2p/src/message.rs b/p2p/src/message.rs
index a1d9e967..e0666c95 100644
--- a/p2p/src/message.rs
+++ b/p2p/src/message.rs
@@ -23,6 +23,7 @@ use units::{Amount, FeeRate};
 
 use self::error::V1NetworkMessageDecoderErrorInner;
 use crate::address::{AddrV1Message, AddrV2Message, AddrV2MessageDecoderError};
+use crate::bip434::{Feature, FeatureDecoder};
 use crate::merkle_tree::MerkleBlock;
 use crate::message_erlay::{SendTxRcnCl, SendTxRcnClDecoder};
 use crate::{
@@ -662,6 +663,8 @@ pub enum NetworkMessage {
     SendAddrV2,
     /// `sendtxrcncl`
     SendTxRcnCl(SendTxRcnCl),
+    /// `feature`
+    Feature(Feature),
     /// Any other message.
     Unknown {
         /// The command of this message.
@@ -716,6 +719,7 @@ impl NetworkMessage {
             Self::AddrV2(_) => "addrv2",
             Self::SendAddrV2 => "sendaddrv2",
             Self::SendTxRcnCl(_) => "sendtxrcncl",
+            Self::Feature(_) => "feature",
             Self::Unknown { .. } => "unknown",
         }
     }
@@ -863,6 +867,8 @@ pub enum NetworkMessageEncoder<'e> {
     AddrV2(<AddrV2Payload as encoding::Encode>::Encoder<'e>),
     /// Encodes [`NetworkMessage::SendTxRcnCl`].
     SendTxRcnCl(<SendTxRcnCl as encoding::Encode>::Encoder<'e>),
+    /// Encodes [`NetworkMessage::Feature`].
+    Feature(<Feature as encoding::Encode>::Encoder<'e>),
     /// Encodes zero-payload messages: verack, mempool, sendheaders, getaddr, wtxidrelay,
     /// filterclear, sendaddrv2.
     Empty,
@@ -904,6 +910,7 @@ impl<'e> NetworkMessageEncoder<'e> {
             NetworkMessage::FeeFilter(dat) => Self::FeeFilter(dat.encoder()),
             NetworkMessage::AddrV2(dat) => Self::AddrV2(dat.encoder()),
             NetworkMessage::SendTxRcnCl(dat) => Self::SendTxRcnCl(dat.encoder()),
+            NetworkMessage::Feature(dat) => Self::Feature(dat.encoder()),
             NetworkMessage::Verack
             | NetworkMessage::SendHeaders
             | NetworkMessage::MemPool
@@ -949,6 +956,7 @@ impl encoding::Encoder for NetworkMessageEncoder<'_> {
             Self::FeeFilter(e) => e.current_chunk(),
             Self::AddrV2(e) => e.current_chunk(),
             Self::SendTxRcnCl(e) => e.current_chunk(),
+            Self::Feature(e) => e.current_chunk(),
             Self::Empty => &[],
             Self::Unknown(e) => e.current_chunk(),
         }
@@ -984,6 +992,7 @@ impl encoding::Encoder for NetworkMessageEncoder<'_> {
             Self::FeeFilter(e) => e.advance(),
             Self::AddrV2(e) => e.advance(),
             Self::SendTxRcnCl(e) => e.advance(),
+            Self::Feature(e) => e.advance(),
             Self::Empty => EncoderStatus::Finished,
             Self::Unknown(e) => e.advance(),
         }
@@ -1044,6 +1053,7 @@ enum NetworkMessageDecoderInner {
     FeeFilter(FeeFilterDecoder),
     AddrV2(AddrV2PayloadDecoder),
     SendTxRcnCl(SendTxRcnClDecoder),
+    Feature(FeatureDecoder),
     /// Zero-payload messages: verack, mempool, sendheaders, getaddr, wtxidrelay,
     /// filterclear, sendaddrv2.
     Empty(CommandString),
@@ -1091,6 +1101,7 @@ impl NetworkMessageDecoderInner {
             "feefilter" => Self::FeeFilter(FeeFilter::decoder()),
             "sendtxrcncl" => Self::SendTxRcnCl(SendTxRcnCl::decoder()),
             "addrv2" => Self::AddrV2(AddrV2Payload::decoder()),
+            "feature" => Self::Feature(Feature::decoder()),
             _ => Self::Unknown {
                 command,
                 remaining: payload_len,
@@ -1137,6 +1148,7 @@ impl encoding::Decoder for NetworkMessageDecoderInner {
             Self::FeeFilter(d) => d.push_bytes(bytes).map_err(|_| err),
             Self::AddrV2(d) => d.push_bytes(bytes).map_err(|_| err),
             Self::SendTxRcnCl(d) => d.push_bytes(bytes).map_err(|_| err),
+            Self::Feature(d) => d.push_bytes(bytes).map_err(|_| err),
             Self::Empty(_) => Ok(encoding::DecoderStatus::Ready),
             Self::Unknown { remaining, buffer, .. } => {
                 let copy_len = bytes.len().min(*remaining);
@@ -1187,6 +1199,7 @@ impl encoding::Decoder for NetworkMessageDecoderInner {
             Self::FeeFilter(d) => Ok(NetworkMessage::FeeFilter(d.end().map_err(|_| err)?)),
             Self::AddrV2(d) => Ok(NetworkMessage::AddrV2(d.end().map_err(|_| err)?)),
             Self::SendTxRcnCl(d) => Ok(NetworkMessage::SendTxRcnCl(d.end().map_err(|_| err)?)),
+            Self::Feature(d) => Ok(NetworkMessage::Feature(d.end().map_err(|_| err)?)),
             Self::Empty(cmd) => match cmd.as_ref() {
                 "verack" => Ok(NetworkMessage::Verack),
                 "mempool" => Ok(NetworkMessage::MemPool),
@@ -1237,6 +1250,7 @@ impl encoding::Decoder for NetworkMessageDecoderInner {
             Self::FeeFilter(d) => d.read_limit(),
             Self::AddrV2(d) => d.read_limit(),
             Self::SendTxRcnCl(d) => d.read_limit(),
+            Self::Feature(d) => d.read_limit(),
             Self::Empty(_) => 0,
             Self::Unknown { remaining, .. } => *remaining,
         }
@@ -1508,6 +1522,7 @@ fn v2_command_byte(payload: &NetworkMessage) -> (u8, Option<CommandString>) {
         NetworkMessage::GetCFCheckpt(_) => (26u8, None),
         NetworkMessage::CFCheckpt(_) => (27u8, None),
         NetworkMessage::AddrV2(_) => (28u8, None),
+        NetworkMessage::Feature(_) => (37u8, None),
         NetworkMessage::Version(_)
         | NetworkMessage::Verack
         | NetworkMessage::SendHeaders
@@ -1695,6 +1710,7 @@ impl V2NetworkMessageDecoder {
             26u8 => Ok(E::GetCFCheckpt(message_filter::GetCFCheckpt::decoder())),
             27u8 => Ok(E::CFCheckpt(message_filter::CFCheckpt::decoder())),
             28u8 => Ok(E::AddrV2(AddrV2Payload::decoder())),
+            37u8 => Ok(E::Feature(Feature::decoder())),
             id => Err(V2NetworkMessageDecoderError::UnknownShortId(id)),
         })
         .map(NetworkMessageDecoder::from_inner)
@@ -2329,6 +2345,7 @@ mod test {
     use super::*;
     use crate::address::{AddrV2, Address};
     use crate::bip152::BlockTransactionsRequest;
+    use crate::bip434::FeatureData;
     use crate::message_blockdata::{BlockLocator, GetBlocksMessage, GetHeadersMessage, Inventory};
     use crate::message_bloom::{BloomFlags, FilterAdd, FilterLoad};
     use crate::message_compact_blocks::SendCmpct;
@@ -2482,6 +2499,10 @@ mod test {
             NetworkMessage::BlockTxn(blocktxn),
             NetworkMessage::SendCmpct(SendCmpct { send_compact: true, version: 8333 }),
             NetworkMessage::SendTxRcnCl(SendTxRcnCl::from_salt(224)),
+            NetworkMessage::Feature(Feature {
+                feature_id: "featureid".parse().unwrap(),
+                feature_data: FeatureData::new(Vec::new()).unwrap(),
+            }),
         ];
 
         for msg in &msgs {