Add a test of gossip message buffer limiting in PeerManager

This adds a simple test that the gossip message buffer in
`PeerManager` is limited, including the new behavior of bypassing
the limit when the broadcast comes from the
`ChannelMessageHandler`.

lightning/src/ln/peer_handler.rs

@@ -2725,20 +2725,21 @@ fn is_gossip_msg(type_id: u16) -> bool {
 
 #[cfg(test)]
 mod tests {
+	use super::*;
+
 	use crate::sign::{NodeSigner, Recipient};
 	use crate::events;
 	use crate::io;
 	use crate::ln::types::ChannelId;
 	use crate::ln::features::{InitFeatures, NodeFeatures};
 	use crate::ln::peer_channel_encryptor::PeerChannelEncryptor;
-	use crate::ln::peer_handler::{CustomMessageHandler, PeerManager, MessageHandler, SocketDescriptor, IgnoringMessageHandler, filter_addresses, ErroringMessageHandler, MAX_BUFFER_DRAIN_TICK_INTERVALS_PER_PEER};
 	use crate::ln::{msgs, wire};
 	use crate::ln::msgs::{Init, LightningError, SocketAddress};
 	use crate::util::test_utils;
 
 	use bitcoin::Network;
 	use bitcoin::constants::ChainHash;
-	use bitcoin::secp256k1::{PublicKey, SecretKey};
+	use bitcoin::secp256k1::{PublicKey, SecretKey, Secp256k1};
 
 	use crate::sync::{Arc, Mutex};
 	use core::convert::Infallible;
@@ -3196,6 +3197,8 @@ mod tests {
 		let cfgs = create_peermgr_cfgs(2);
 		cfgs[0].routing_handler.request_full_sync.store(true, Ordering::Release);
 		cfgs[1].routing_handler.request_full_sync.store(true, Ordering::Release);
+		cfgs[0].routing_handler.announcement_available_for_sync.store(true, Ordering::Release);
+		cfgs[1].routing_handler.announcement_available_for_sync.store(true, Ordering::Release);
 		let peers = create_network(2, &cfgs);
 
 		// By calling establish_connect, we trigger do_attempt_write_data between
@@ -3359,6 +3362,79 @@ mod tests {
 		assert_eq!(peer_b.peers.read().unwrap().len(), 0);
 	}
 
+	#[test]
+	fn test_gossip_flood_pause() {
+		use crate::routing::test_utils::channel_announcement;
+		use lightning_types::features::ChannelFeatures;
+
+		// Simple test which connects two nodes to a PeerManager and checks that if we run out of
+		// socket buffer space we'll stop forwarding gossip but still push our own gossip.
+		let cfgs = create_peermgr_cfgs(2);
+		let peers = create_network(2, &cfgs);
+		let (mut fd_a, mut fd_b) = establish_connection(&peers[0], &peers[1]);
+
+		macro_rules! drain_queues { () => {
+			loop {
+				peers[0].process_events();
+				peers[1].process_events();
+
+				let msg = fd_a.outbound_data.lock().unwrap().split_off(0);
+				if !msg.is_empty() {
+					assert_eq!(peers[1].read_event(&mut fd_b, &msg).unwrap(), false);
+					continue;
+				}
+				let msg = fd_b.outbound_data.lock().unwrap().split_off(0);
+				if !msg.is_empty() {
+					assert_eq!(peers[0].read_event(&mut fd_a, &msg).unwrap(), false);
+					continue;
+				}
+				break;
+			}
+		} }
+
+		// First, make sure all pending messages have been processed and queues drained.
+		drain_queues!();
+
+		let secp_ctx = Secp256k1::new();
+		let key = SecretKey::from_slice(&[1; 32]).unwrap();
+		let msg = channel_announcement(&key, &key, ChannelFeatures::empty(), 42, &secp_ctx);
+		let msg_ev = MessageSendEvent::BroadcastChannelAnnouncement {
+			msg,
+			update_msg: None,
+		};
+
+		fd_a.hang_writes.store(true, Ordering::Relaxed);
+
+		// Now push an arbitrarily large number of messages and check that only
+		// `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP` messages end up in the queue.
+		for _ in 0..OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP * 2 {
+			cfgs[0].routing_handler.pending_events.lock().unwrap().push(msg_ev.clone());
+			peers[0].process_events();
+		}
+
+		assert_eq!(peers[0].peers.read().unwrap().get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len(),
+			OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP);
+
+		// Check that if a broadcast message comes in from the channel handler (i.e. it is an
+		// announcement for our own channel), it gets queued anyway.
+		cfgs[0].chan_handler.pending_events.lock().unwrap().push(msg_ev);
+		peers[0].process_events();
+		assert_eq!(peers[0].peers.read().unwrap().get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.len(),
+			OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 1);
+
+		// Finally, deliver all the messages and make sure we got the right count. Note that there
+		// was an extra message that had already moved from the broadcast queue to the encrypted
+		// message queue so we actually receive `OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2` messages.
+		fd_a.hang_writes.store(false, Ordering::Relaxed);
+		cfgs[1].routing_handler.chan_anns_recvd.store(0, Ordering::Relaxed);
+		peers[0].write_buffer_space_avail(&mut fd_a).unwrap();
+
+		drain_queues!();
+		assert!(peers[0].peers.read().unwrap().get(&fd_a).unwrap().lock().unwrap().gossip_broadcast_buffer.is_empty());
+		assert_eq!(cfgs[1].routing_handler.chan_anns_recvd.load(Ordering::Relaxed),
+			OUTBOUND_BUFFER_LIMIT_DROP_GOSSIP + 2);
+	}
+
 	#[test]
 	fn test_filter_addresses(){
 		// Tests the filter_addresses function.

lightning/src/routing/test_utils.rs

@@ -27,13 +27,11 @@ use crate::sync::{self, Arc};
 
 use crate::routing::gossip::NodeId;
 
-// Using the same keys for LN and BTC ids
-pub(crate) fn add_channel(
-	gossip_sync: &P2PGossipSync<Arc<NetworkGraph<Arc<test_utils::TestLogger>>>, Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
-	secp_ctx: &Secp256k1<All>, node_1_privkey: &SecretKey, node_2_privkey: &SecretKey, features: ChannelFeatures, short_channel_id: u64
-) {
-	let node_1_pubkey = PublicKey::from_secret_key(&secp_ctx, node_1_privkey);
-	let node_id_1 = NodeId::from_pubkey(&node_1_pubkey);
+pub(crate) fn channel_announcement(
+	node_1_privkey: &SecretKey, node_2_privkey: &SecretKey, features: ChannelFeatures,
+	short_channel_id: u64, secp_ctx: &Secp256k1<All>,
+) -> ChannelAnnouncement {
+	let node_id_1 = NodeId::from_pubkey(&PublicKey::from_secret_key(&secp_ctx, node_1_privkey));
 	let node_id_2 = NodeId::from_pubkey(&PublicKey::from_secret_key(&secp_ctx, node_2_privkey));
 
 	let unsigned_announcement = UnsignedChannelAnnouncement {
@@ -48,13 +46,23 @@ pub(crate) fn add_channel(
 	};
 
 	let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_announcement.encode()[..])[..]);
-	let valid_announcement = ChannelAnnouncement {
+	ChannelAnnouncement {
 		node_signature_1: secp_ctx.sign_ecdsa(&msghash, node_1_privkey),
 		node_signature_2: secp_ctx.sign_ecdsa(&msghash, node_2_privkey),
 		bitcoin_signature_1: secp_ctx.sign_ecdsa(&msghash, node_1_privkey),
 		bitcoin_signature_2: secp_ctx.sign_ecdsa(&msghash, node_2_privkey),
 		contents: unsigned_announcement.clone(),
-	};
+	}
+}
+
+// Using the same keys for LN and BTC ids
+pub(crate) fn add_channel(
+	gossip_sync: &P2PGossipSync<Arc<NetworkGraph<Arc<test_utils::TestLogger>>>, Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
+	secp_ctx: &Secp256k1<All>, node_1_privkey: &SecretKey, node_2_privkey: &SecretKey, features: ChannelFeatures, short_channel_id: u64
+) {
+	let valid_announcement =
+		channel_announcement(node_1_privkey, node_2_privkey, features, short_channel_id, secp_ctx);
+	let node_1_pubkey = PublicKey::from_secret_key(&secp_ctx, node_1_privkey);
 	match gossip_sync.handle_channel_announcement(Some(node_1_pubkey), &valid_announcement) {
 		Ok(res) => assert!(res),
 		_ => panic!()
@@ -108,7 +116,7 @@ pub(crate) fn update_channel(
 
 pub(super) fn get_nodes(secp_ctx: &Secp256k1<All>) -> (SecretKey, PublicKey, Vec<SecretKey>, Vec<PublicKey>) {
 	let privkeys: Vec<SecretKey> = (2..22).map(|i| {
-		SecretKey::from_slice(&<Vec<u8>>::from_hex(&format!("{:02x}", i).repeat(32)).unwrap()[..]).unwrap()
+		SecretKey::from_slice(&[i; 32]).unwrap()
 	}).collect();
 
 	let pubkeys = privkeys.iter().map(|secret| PublicKey::from_secret_key(&secp_ctx, secret)).collect();

lightning/src/util/test_utils.rs

@@ -986,6 +986,7 @@ pub struct TestRoutingMessageHandler {
 	pub chan_anns_recvd: AtomicUsize,
 	pub pending_events: Mutex<Vec<events::MessageSendEvent>>,
 	pub request_full_sync: AtomicBool,
+	pub announcement_available_for_sync: AtomicBool,
 }
 
 impl TestRoutingMessageHandler {
@@ -995,27 +996,32 @@ impl TestRoutingMessageHandler {
 			chan_anns_recvd: AtomicUsize::new(0),
 			pending_events: Mutex::new(vec![]),
 			request_full_sync: AtomicBool::new(false),
+			announcement_available_for_sync: AtomicBool::new(false),
 		}
 	}
 }
 impl msgs::RoutingMessageHandler for TestRoutingMessageHandler {
 	fn handle_node_announcement(&self, _their_node_id: Option<PublicKey>, _msg: &msgs::NodeAnnouncement) -> Result<bool, msgs::LightningError> {
-		Err(msgs::LightningError { err: "".to_owned(), action: msgs::ErrorAction::IgnoreError })
+		Ok(true)
 	}
 	fn handle_channel_announcement(&self, _their_node_id: Option<PublicKey>, _msg: &msgs::ChannelAnnouncement) -> Result<bool, msgs::LightningError> {
 		self.chan_anns_recvd.fetch_add(1, Ordering::AcqRel);
-		Err(msgs::LightningError { err: "".to_owned(), action: msgs::ErrorAction::IgnoreError })
+		Ok(true)
 	}
 	fn handle_channel_update(&self, _their_node_id: Option<PublicKey>, _msg: &msgs::ChannelUpdate) -> Result<bool, msgs::LightningError> {
 		self.chan_upds_recvd.fetch_add(1, Ordering::AcqRel);
-		Err(msgs::LightningError { err: "".to_owned(), action: msgs::ErrorAction::IgnoreError })
+		Ok(true)
 	}
 	fn get_next_channel_announcement(&self, starting_point: u64) -> Option<(msgs::ChannelAnnouncement, Option<msgs::ChannelUpdate>, Option<msgs::ChannelUpdate>)> {
-		let chan_upd_1 = get_dummy_channel_update(starting_point);
-		let chan_upd_2 = get_dummy_channel_update(starting_point);
-		let chan_ann = get_dummy_channel_announcement(starting_point);
+		if self.announcement_available_for_sync.load(Ordering::Acquire) {
+			let chan_upd_1 = get_dummy_channel_update(starting_point);
+			let chan_upd_2 = get_dummy_channel_update(starting_point);
+			let chan_ann = get_dummy_channel_announcement(starting_point);
 
-		Some((chan_ann, Some(chan_upd_1), Some(chan_upd_2)))
+			Some((chan_ann, Some(chan_upd_1), Some(chan_upd_2)))
+		} else {
+			None
+		}
 	}
 
 	fn get_next_node_announcement(&self, _starting_point: Option<&NodeId>) -> Option<msgs::NodeAnnouncement> {