Merge pull request #2204 from jkczyz/2023-04-custom-feature-bits

Support for custom feature bits

lightning-custom-message/src/lib.rs

@@ -20,6 +20,7 @@
 //! # use bitcoin::secp256k1::PublicKey;
 //! # use lightning::io;
 //! # use lightning::ln::msgs::{DecodeError, LightningError};
+//! # use lightning::ln::features::{InitFeatures, NodeFeatures};
 //! use lightning::ln::peer_handler::CustomMessageHandler;
 //! use lightning::ln::wire::{CustomMessageReader, self};
 //! use lightning::util::ser::Writeable;
@@ -66,6 +67,12 @@
 //! #     fn get_and_clear_pending_msg(&self) -> Vec<(PublicKey, Self::CustomMessage)> {
 //! #         unimplemented!()
 //! #     }
+//! #     fn provided_node_features(&self) -> NodeFeatures {
+//! #         unimplemented!()
+//! #     }
+//! #     fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
+//! #         unimplemented!()
+//! #     }
 //! }
 //!
 //! #[derive(Debug)]
@@ -106,6 +113,12 @@
 //! #     fn get_and_clear_pending_msg(&self) -> Vec<(PublicKey, Self::CustomMessage)> {
 //! #         unimplemented!()
 //! #     }
+//! #     fn provided_node_features(&self) -> NodeFeatures {
+//! #         unimplemented!()
+//! #     }
+//! #     fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
+//! #         unimplemented!()
+//! #     }
 //! }
 //!
 //! #[derive(Debug)]
@@ -146,6 +159,12 @@
 //! #     fn get_and_clear_pending_msg(&self) -> Vec<(PublicKey, Self::CustomMessage)> {
 //! #         unimplemented!()
 //! #     }
+//! #     fn provided_node_features(&self) -> NodeFeatures {
+//! #         unimplemented!()
+//! #     }
+//! #     fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
+//! #         unimplemented!()
+//! #     }
 //! }
 //!
 //! # fn main() {
@@ -268,6 +287,22 @@ macro_rules! composite_custom_message_handler {
 					)*
 					.collect()
 			}
+
+			fn provided_node_features(&self) -> $crate::lightning::ln::features::NodeFeatures {
+				$crate::lightning::ln::features::NodeFeatures::empty()
+					$(
+						| self.$field.provided_node_features()
+					)*
+			}
+
+			fn provided_init_features(
+				&self, their_node_id: &$crate::bitcoin::secp256k1::PublicKey
+			) -> $crate::lightning::ln::features::InitFeatures {
+				$crate::lightning::ln::features::InitFeatures::empty()
+					$(
+						| self.$field.provided_init_features(their_node_id)
+					)*
+			}
 		}
 
 		impl $crate::lightning::ln::wire::CustomMessageReader for $handler {

lightning/src/ln/features.rs

@@ -422,8 +422,10 @@ pub struct Features<T: sealed::Context> {
 	mark: PhantomData<T>,
 }
 
-impl <T: sealed::Context> Features<T> {
-	pub(crate) fn or(mut self, o: Self) -> Self {
+impl<T: sealed::Context> core::ops::BitOr for Features<T> {
+	type Output = Self;
+
+	fn bitor(mut self, o: Self) -> Self {
 		let total_feature_len = cmp::max(self.flags.len(), o.flags.len());
 		self.flags.resize(total_feature_len, 0u8);
 		for (byte, o_byte) in self.flags.iter_mut().zip(o.flags.iter()) {
@@ -695,6 +697,25 @@ impl<T: sealed::Context> Features<T> {
 		self.flags.iter().any(|&byte| (byte & 0b10_10_10_10) != 0)
 	}
 
+	/// Returns true if this `Features` object contains required features unknown by `other`.
+	pub fn requires_unknown_bits_from(&self, other: &Features<T>) -> bool {
+		// Bitwise AND-ing with all even bits set except for known features will select required
+		// unknown features.
+		self.flags.iter().enumerate().any(|(i, &byte)| {
+			const REQUIRED_FEATURES: u8 = 0b01_01_01_01;
+			const OPTIONAL_FEATURES: u8 = 0b10_10_10_10;
+			let unknown_features = if i < other.flags.len() {
+				// Form a mask similar to !T::KNOWN_FEATURE_MASK only for `other`
+				!(other.flags[i]
+					| ((other.flags[i] >> 1) & REQUIRED_FEATURES)
+					| ((other.flags[i] << 1) & OPTIONAL_FEATURES))
+			} else {
+				0b11_11_11_11
+			};
+			(byte & (REQUIRED_FEATURES & unknown_features)) != 0
+		})
+	}
+
 	/// Returns true if this `Features` object contains unknown feature flags which are set as
 	/// "required".
 	pub fn requires_unknown_bits(&self) -> bool {
@@ -743,6 +764,50 @@ impl<T: sealed::Context> Features<T> {
 		}
 		true
 	}
+
+	/// Sets a required custom feature bit. Errors if `bit` is outside the custom range as defined
+	/// by [bLIP 2] or if it is a known `T` feature.
+	///
+	/// Note: Required bits are even. If an odd bit is given, then the corresponding even bit will
+	/// be set instead (i.e., `bit - 1`).
+	///
+	/// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
+	pub fn set_required_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
+		self.set_custom_bit(bit - (bit % 2))
+	}
+
+	/// Sets an optional custom feature bit. Errors if `bit` is outside the custom range as defined
+	/// by [bLIP 2] or if it is a known `T` feature.
+	///
+	/// Note: Optional bits are odd. If an even bit is given, then the corresponding odd bit will be
+	/// set instead (i.e., `bit + 1`).
+	///
+	/// [bLIP 2]: https://github.com/lightning/blips/blob/master/blip-0002.md#feature-bits
+	pub fn set_optional_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
+		self.set_custom_bit(bit + (1 - (bit % 2)))
+	}
+
+	fn set_custom_bit(&mut self, bit: usize) -> Result<(), ()> {
+		if bit < 256 {
+			return Err(());
+		}
+
+		let byte_offset = bit / 8;
+		let mask = 1 << (bit - 8 * byte_offset);
+		if byte_offset < T::KNOWN_FEATURE_MASK.len() {
+			if (T::KNOWN_FEATURE_MASK[byte_offset] & mask) != 0 {
+				return Err(());
+			}
+		}
+
+		if self.flags.len() <= byte_offset {
+			self.flags.resize(byte_offset + 1, 0u8);
+		}
+
+		self.flags[byte_offset] |= mask;
+
+		Ok(())
+	}
 }
 
 impl<T: sealed::UpfrontShutdownScript> Features<T> {
@@ -869,6 +934,43 @@ mod tests {
 		assert!(features.supports_unknown_bits());
 	}
 
+	#[test]
+	fn requires_unknown_bits_from() {
+		let mut features1 = InitFeatures::empty();
+		let mut features2 = InitFeatures::empty();
+		assert!(!features1.requires_unknown_bits_from(&features2));
+		assert!(!features2.requires_unknown_bits_from(&features1));
+
+		features1.set_data_loss_protect_required();
+		assert!(features1.requires_unknown_bits_from(&features2));
+		assert!(!features2.requires_unknown_bits_from(&features1));
+
+		features2.set_data_loss_protect_optional();
+		assert!(!features1.requires_unknown_bits_from(&features2));
+		assert!(!features2.requires_unknown_bits_from(&features1));
+
+		features2.set_gossip_queries_required();
+		assert!(!features1.requires_unknown_bits_from(&features2));
+		assert!(features2.requires_unknown_bits_from(&features1));
+
+		features1.set_gossip_queries_optional();
+		assert!(!features1.requires_unknown_bits_from(&features2));
+		assert!(!features2.requires_unknown_bits_from(&features1));
+
+		features1.set_variable_length_onion_required();
+		assert!(features1.requires_unknown_bits_from(&features2));
+		assert!(!features2.requires_unknown_bits_from(&features1));
+
+		features2.set_variable_length_onion_optional();
+		assert!(!features1.requires_unknown_bits_from(&features2));
+		assert!(!features2.requires_unknown_bits_from(&features1));
+
+		features1.set_basic_mpp_required();
+		features2.set_wumbo_required();
+		assert!(features1.requires_unknown_bits_from(&features2));
+		assert!(features2.requires_unknown_bits_from(&features1));
+	}
+
 	#[test]
 	fn convert_to_context_with_relevant_flags() {
 		let mut init_features = InitFeatures::empty();
@@ -881,12 +983,12 @@ mod tests {
 		init_features.set_payment_secret_required();
 		init_features.set_basic_mpp_optional();
 		init_features.set_wumbo_optional();
+		init_features.set_anchors_zero_fee_htlc_tx_optional();
 		init_features.set_shutdown_any_segwit_optional();
 		init_features.set_onion_messages_optional();
 		init_features.set_channel_type_optional();
 		init_features.set_scid_privacy_optional();
 		init_features.set_zero_conf_optional();
-		init_features.set_anchors_zero_fee_htlc_tx_optional();
 
 		assert!(init_features.initial_routing_sync());
 		assert!(!init_features.supports_upfront_shutdown_script());
@@ -897,7 +999,7 @@ mod tests {
 			// Check that the flags are as expected:
 			// - option_data_loss_protect (req)
 			// - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
-			// - basic_mpp | wumbo
+			// - basic_mpp | wumbo | anchors_zero_fee_htlc_tx
 			// - opt_shutdown_anysegwit
 			// - onion_messages
 			// - option_channel_type | option_scid_alias
@@ -945,6 +1047,36 @@ mod tests {
 		assert!(features.supports_payment_secret());
 	}
 
+	#[test]
+	fn set_custom_bits() {
+		let mut features = InvoiceFeatures::empty();
+		features.set_variable_length_onion_optional();
+		assert_eq!(features.flags[1], 0b00000010);
+
+		assert!(features.set_optional_custom_bit(255).is_err());
+		assert!(features.set_required_custom_bit(256).is_ok());
+		assert!(features.set_required_custom_bit(258).is_ok());
+		assert_eq!(features.flags[31], 0b00000000);
+		assert_eq!(features.flags[32], 0b00000101);
+
+		let known_bit = <sealed::InvoiceContext as sealed::PaymentSecret>::EVEN_BIT;
+		let byte_offset = <sealed::InvoiceContext as sealed::PaymentSecret>::BYTE_OFFSET;
+		assert_eq!(byte_offset, 1);
+		assert_eq!(features.flags[byte_offset], 0b00000010);
+		assert!(features.set_required_custom_bit(known_bit).is_err());
+		assert_eq!(features.flags[byte_offset], 0b00000010);
+
+		let mut features = InvoiceFeatures::empty();
+		assert!(features.set_optional_custom_bit(256).is_ok());
+		assert!(features.set_optional_custom_bit(259).is_ok());
+		assert_eq!(features.flags[32], 0b00001010);
+
+		let mut features = InvoiceFeatures::empty();
+		assert!(features.set_required_custom_bit(257).is_ok());
+		assert!(features.set_required_custom_bit(258).is_ok());
+		assert_eq!(features.flags[32], 0b00000101);
+	}
+
 	#[test]
 	fn encodes_features_without_length() {
 		let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);

lightning/src/ln/msgs.rs

@@ -1738,7 +1738,7 @@ impl Readable for Init {
 			(3, remote_network_address, option)
 		});
 		Ok(Init {
-			features: features.or(global_features),
+			features: features | global_features,
 			remote_network_address,
 		})
 	}

lightning/src/ln/peer_handler.rs

@@ -64,6 +64,20 @@ pub trait CustomMessageHandler: wire::CustomMessageReader {
 	/// in the process. Each message is paired with the node id of the intended recipient. If no
 	/// connection to the node exists, then the message is simply not sent.
 	fn get_and_clear_pending_msg(&self) -> Vec<(PublicKey, Self::CustomMessage)>;
+
+	/// Gets the node feature flags which this handler itself supports. All available handlers are
+	/// queried similarly and their feature flags are OR'd together to form the [`NodeFeatures`]
+	/// which are broadcasted in our [`NodeAnnouncement`] message.
+	///
+	/// [`NodeAnnouncement`]: crate::ln::msgs::NodeAnnouncement
+	fn provided_node_features(&self) -> NodeFeatures;
+
+	/// Gets the init feature flags which should be sent to the given peer. All available handlers
+	/// are queried similarly and their feature flags are OR'd together to form the [`InitFeatures`]
+	/// which are sent in our [`Init`] message.
+	///
+	/// [`Init`]: crate::ln::msgs::Init
+	fn provided_init_features(&self, their_node_id: &PublicKey) -> InitFeatures;
 }
 
 /// A dummy struct which implements `RoutingMessageHandler` without storing any routing information
@@ -149,6 +163,12 @@ impl CustomMessageHandler for IgnoringMessageHandler {
 	}
 
 	fn get_and_clear_pending_msg(&self) -> Vec<(PublicKey, Self::CustomMessage)> { Vec::new() }
+
+	fn provided_node_features(&self) -> NodeFeatures { NodeFeatures::empty() }
+
+	fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
+		InitFeatures::empty()
+	}
 }
 
 /// A dummy struct which implements `ChannelMessageHandler` without having any channels.
@@ -895,6 +915,13 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 		SecretKey::from_slice(&Sha256::from_engine(ephemeral_hash).into_inner()).expect("You broke SHA-256!")
 	}
 
+	fn init_features(&self, their_node_id: &PublicKey) -> InitFeatures {
+		self.message_handler.chan_handler.provided_init_features(their_node_id)
+			| self.message_handler.route_handler.provided_init_features(their_node_id)
+			| self.message_handler.onion_message_handler.provided_init_features(their_node_id)
+			| self.message_handler.custom_message_handler.provided_init_features(their_node_id)
+	}
+
 	/// Indicates a new outbound connection has been established to a node with the given `node_id`
 	/// and an optional remote network address.
 	///
@@ -1290,9 +1317,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 
 								peer.set_their_node_id(their_node_id);
 								insert_node_id!();
-								let features = self.message_handler.chan_handler.provided_init_features(&their_node_id)
-									.or(self.message_handler.route_handler.provided_init_features(&their_node_id))
-									.or(self.message_handler.onion_message_handler.provided_init_features(&their_node_id));
+								let features = self.init_features(&their_node_id);
 								let resp = msgs::Init { features, remote_network_address: filter_addresses(peer.their_net_address.clone()) };
 								self.enqueue_message(peer, &resp);
 								peer.awaiting_pong_timer_tick_intervals = 0;
@@ -1304,9 +1329,7 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 								peer.pending_read_is_header = true;
 								peer.set_their_node_id(their_node_id);
 								insert_node_id!();
-								let features = self.message_handler.chan_handler.provided_init_features(&their_node_id)
-									.or(self.message_handler.route_handler.provided_init_features(&their_node_id))
-									.or(self.message_handler.onion_message_handler.provided_init_features(&their_node_id));
+								let features = self.init_features(&their_node_id);
 								let resp = msgs::Init { features, remote_network_address: filter_addresses(peer.their_net_address.clone()) };
 								self.enqueue_message(peer, &resp);
 								peer.awaiting_pong_timer_tick_intervals = 0;
@@ -1423,10 +1446,17 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 
 		// Need an Init as first message
 		if let wire::Message::Init(msg) = message {
-			if msg.features.requires_unknown_bits() {
-				log_debug!(self.logger, "Peer features required unknown version bits");
+			let our_features = self.init_features(&their_node_id);
+			if msg.features.requires_unknown_bits_from(&our_features) {
+				log_debug!(self.logger, "Peer requires features unknown to us");
 				return Err(PeerHandleError { }.into());
 			}
+
+			if our_features.requires_unknown_bits_from(&msg.features) {
+				log_debug!(self.logger, "We require features unknown to our peer");
+				return Err(PeerHandleError { }.into());
+			}
+
 			if peer_lock.their_features.is_some() {
 				return Err(PeerHandleError { }.into());
 			}
@@ -2348,8 +2378,9 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 		addresses.sort_by_key(|addr| addr.get_id());
 
 		let features = self.message_handler.chan_handler.provided_node_features()
-			.or(self.message_handler.route_handler.provided_node_features())
-			.or(self.message_handler.onion_message_handler.provided_node_features());
+			| self.message_handler.route_handler.provided_node_features()
+			| self.message_handler.onion_message_handler.provided_node_features()
+			| self.message_handler.custom_message_handler.provided_node_features();
 		let announcement = msgs::UnsignedNodeAnnouncement {
 			features,
 			timestamp: self.last_node_announcement_serial.fetch_add(1, Ordering::AcqRel),
@@ -2398,16 +2429,19 @@ fn is_gossip_msg(type_id: u16) -> bool {
 mod tests {
 	use crate::sign::{NodeSigner, Recipient};
 	use crate::events;
+	use crate::io;
+	use crate::ln::features::{InitFeatures, NodeFeatures};
 	use crate::ln::peer_channel_encryptor::PeerChannelEncryptor;
-	use crate::ln::peer_handler::{PeerManager, MessageHandler, SocketDescriptor, IgnoringMessageHandler, filter_addresses};
+	use crate::ln::peer_handler::{CustomMessageHandler, PeerManager, MessageHandler, SocketDescriptor, IgnoringMessageHandler, filter_addresses};
 	use crate::ln::{msgs, wire};
-	use crate::ln::msgs::NetAddress;
+	use crate::ln::msgs::{LightningError, NetAddress};
 	use crate::util::test_utils;
 
-	use bitcoin::secp256k1::SecretKey;
+	use bitcoin::secp256k1::{PublicKey, SecretKey};
 
 	use crate::prelude::*;
 	use crate::sync::{Arc, Mutex};
+	use core::convert::Infallible;
 	use core::sync::atomic::{AtomicBool, Ordering};
 
 	#[derive(Clone)]
@@ -2440,19 +2474,51 @@ mod tests {
 	struct PeerManagerCfg {
 		chan_handler: test_utils::TestChannelMessageHandler,
 		routing_handler: test_utils::TestRoutingMessageHandler,
+		custom_handler: TestCustomMessageHandler,
 		logger: test_utils::TestLogger,
 		node_signer: test_utils::TestNodeSigner,
 	}
 
+	struct TestCustomMessageHandler {
+		features: InitFeatures,
+	}
+
+	impl wire::CustomMessageReader for TestCustomMessageHandler {
+		type CustomMessage = Infallible;
+		fn read<R: io::Read>(&self, _: u16, _: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError> {
+			Ok(None)
+		}
+	}
+
+	impl CustomMessageHandler for TestCustomMessageHandler {
+		fn handle_custom_message(&self, _: Infallible, _: &PublicKey) -> Result<(), LightningError> {
+			unreachable!();
+		}
+
+		fn get_and_clear_pending_msg(&self) -> Vec<(PublicKey, Self::CustomMessage)> { Vec::new() }
+
+		fn provided_node_features(&self) -> NodeFeatures { NodeFeatures::empty() }
+
+		fn provided_init_features(&self, _: &PublicKey) -> InitFeatures {
+			self.features.clone()
+		}
+	}
+
 	fn create_peermgr_cfgs(peer_count: usize) -> Vec<PeerManagerCfg> {
 		let mut cfgs = Vec::new();
 		for i in 0..peer_count {
 			let node_secret = SecretKey::from_slice(&[42 + i as u8; 32]).unwrap();
+			let features = {
+				let mut feature_bits = vec![0u8; 33];
+				feature_bits[32] = 0b00000001;
+				InitFeatures::from_le_bytes(feature_bits)
+			};
 			cfgs.push(
 				PeerManagerCfg{
 					chan_handler: test_utils::TestChannelMessageHandler::new(),
 					logger: test_utils::TestLogger::new(),
 					routing_handler: test_utils::TestRoutingMessageHandler::new(),
+					custom_handler: TestCustomMessageHandler { features },
 					node_signer: test_utils::TestNodeSigner::new(node_secret),
 				}
 			);
@@ -2461,13 +2527,36 @@ mod tests {
 		cfgs
 	}
 
-	fn create_network<'a>(peer_count: usize, cfgs: &'a Vec<PeerManagerCfg>) -> Vec<PeerManager<FileDescriptor, &'a test_utils::TestChannelMessageHandler, &'a test_utils::TestRoutingMessageHandler, IgnoringMessageHandler, &'a test_utils::TestLogger, IgnoringMessageHandler, &'a test_utils::TestNodeSigner>> {
+	fn create_incompatible_peermgr_cfgs(peer_count: usize) -> Vec<PeerManagerCfg> {
+		let mut cfgs = Vec::new();
+		for i in 0..peer_count {
+			let node_secret = SecretKey::from_slice(&[42 + i as u8; 32]).unwrap();
+			let features = {
+				let mut feature_bits = vec![0u8; 33 + i + 1];
+				feature_bits[33 + i] = 0b00000001;
+				InitFeatures::from_le_bytes(feature_bits)
+			};
+			cfgs.push(
+				PeerManagerCfg{
+					chan_handler: test_utils::TestChannelMessageHandler::new(),
+					logger: test_utils::TestLogger::new(),
+					routing_handler: test_utils::TestRoutingMessageHandler::new(),
+					custom_handler: TestCustomMessageHandler { features },
+					node_signer: test_utils::TestNodeSigner::new(node_secret),
+				}
+			);
+		}
+
+		cfgs
+	}
+
+	fn create_network<'a>(peer_count: usize, cfgs: &'a Vec<PeerManagerCfg>) -> Vec<PeerManager<FileDescriptor, &'a test_utils::TestChannelMessageHandler, &'a test_utils::TestRoutingMessageHandler, IgnoringMessageHandler, &'a test_utils::TestLogger, &'a TestCustomMessageHandler, &'a test_utils::TestNodeSigner>> {
 		let mut peers = Vec::new();
 		for i in 0..peer_count {
 			let ephemeral_bytes = [i as u8; 32];
 			let msg_handler = MessageHandler {
 				chan_handler: &cfgs[i].chan_handler, route_handler: &cfgs[i].routing_handler,
-				onion_message_handler: IgnoringMessageHandler {}, custom_message_handler: IgnoringMessageHandler {}
+				onion_message_handler: IgnoringMessageHandler {}, custom_message_handler: &cfgs[i].custom_handler
 			};
 			let peer = PeerManager::new(msg_handler, 0, &ephemeral_bytes, &cfgs[i].logger, &cfgs[i].node_signer);
 			peers.push(peer);
@@ -2476,7 +2565,7 @@ mod tests {
 		peers
 	}
 
-	fn establish_connection<'a>(peer_a: &PeerManager<FileDescriptor, &'a test_utils::TestChannelMessageHandler, &'a test_utils::TestRoutingMessageHandler, IgnoringMessageHandler, &'a test_utils::TestLogger, IgnoringMessageHandler, &'a test_utils::TestNodeSigner>, peer_b: &PeerManager<FileDescriptor, &'a test_utils::TestChannelMessageHandler, &'a test_utils::TestRoutingMessageHandler, IgnoringMessageHandler, &'a test_utils::TestLogger, IgnoringMessageHandler, &'a test_utils::TestNodeSigner>) -> (FileDescriptor, FileDescriptor) {
+	fn establish_connection<'a>(peer_a: &PeerManager<FileDescriptor, &'a test_utils::TestChannelMessageHandler, &'a test_utils::TestRoutingMessageHandler, IgnoringMessageHandler, &'a test_utils::TestLogger, &'a TestCustomMessageHandler, &'a test_utils::TestNodeSigner>, peer_b: &PeerManager<FileDescriptor, &'a test_utils::TestChannelMessageHandler, &'a test_utils::TestRoutingMessageHandler, IgnoringMessageHandler, &'a test_utils::TestLogger, &'a TestCustomMessageHandler, &'a test_utils::TestNodeSigner>) -> (FileDescriptor, FileDescriptor) {
 		let id_a = peer_a.node_signer.get_node_id(Recipient::Node).unwrap();
 		let mut fd_a = FileDescriptor {
 			fd: 1, outbound_data: Arc::new(Mutex::new(Vec::new())),
@@ -2591,6 +2680,42 @@ mod tests {
 		thrd_b.join().unwrap();
 	}
 
+	#[test]
+	fn test_incompatible_peers() {
+		let cfgs = create_peermgr_cfgs(2);
+		let incompatible_cfgs = create_incompatible_peermgr_cfgs(2);
+
+		let peers = create_network(2, &cfgs);
+		let incompatible_peers = create_network(2, &incompatible_cfgs);
+		let peer_pairs = [(&peers[0], &incompatible_peers[0]), (&incompatible_peers[1], &peers[1])];
+		for (peer_a, peer_b) in peer_pairs.iter() {
+			let id_a = peer_a.node_signer.get_node_id(Recipient::Node).unwrap();
+			let mut fd_a = FileDescriptor {
+				fd: 1, outbound_data: Arc::new(Mutex::new(Vec::new())),
+				disconnect: Arc::new(AtomicBool::new(false)),
+			};
+			let addr_a = NetAddress::IPv4{addr: [127, 0, 0, 1], port: 1000};
+			let mut fd_b = FileDescriptor {
+				fd: 1, outbound_data: Arc::new(Mutex::new(Vec::new())),
+				disconnect: Arc::new(AtomicBool::new(false)),
+			};
+			let addr_b = NetAddress::IPv4{addr: [127, 0, 0, 1], port: 1001};
+			let initial_data = peer_b.new_outbound_connection(id_a, fd_b.clone(), Some(addr_a.clone())).unwrap();
+			peer_a.new_inbound_connection(fd_a.clone(), Some(addr_b.clone())).unwrap();
+			assert_eq!(peer_a.read_event(&mut fd_a, &initial_data).unwrap(), false);
+			peer_a.process_events();
+
+			let a_data = fd_a.outbound_data.lock().unwrap().split_off(0);
+			assert_eq!(peer_b.read_event(&mut fd_b, &a_data).unwrap(), false);
+
+			peer_b.process_events();
+			let b_data = fd_b.outbound_data.lock().unwrap().split_off(0);
+
+			// Should fail because of unknown required features
+			assert!(peer_a.read_event(&mut fd_a, &b_data).is_err());
+		}
+	}
+
 	#[test]
 	fn test_disconnect_peer() {
 		// Simple test which builds a network of PeerManager, connects and brings them to NoiseState::Finished and