From 677c47154817857c806ec755bae6cf1b83023cc3 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Mon, 9 May 2022 11:54:34 +0200
Subject: Handle the possibility of several alternative IP addresses for peers

---
 src/peering/fullmesh.rs | 77 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 68 insertions(+), 9 deletions(-)

(limited to 'src/peering')

diff --git a/src/peering/fullmesh.rs b/src/peering/fullmesh.rs
index 52d7fda..bb0c9dc 100644
--- a/src/peering/fullmesh.rs
+++ b/src/peering/fullmesh.rs
@@ -52,7 +52,13 @@ impl Message for PeerListMessage {
 
 #[derive(Debug)]
 struct PeerInfoInternal {
+	// addr is the currently connected address,
+	// or the last address we were connected to,
+	// or an arbitrary address some other peer gave us
 	addr: SocketAddr,
+	// all_addrs contains all of the addresses everyone gave us
+	all_addrs: Vec<SocketAddr>,
+
 	state: PeerConnState,
 	last_seen: Option<Instant>,
 	ping: VecDeque<Duration>,
@@ -180,6 +186,7 @@ impl FullMeshPeeringStrategy {
 					id,
 					PeerInfoInternal {
 						addr,
+						all_addrs: vec![addr],
 						state: PeerConnState::Waiting(0, Instant::now()),
 						last_seen: None,
 						ping: VecDeque::new(),
@@ -194,6 +201,7 @@ impl FullMeshPeeringStrategy {
 				netapp.id,
 				PeerInfoInternal {
 					addr,
+					all_addrs: vec![addr],
 					state: PeerConnState::Ourself,
 					last_seen: None,
 					ping: VecDeque::new(),
@@ -281,11 +289,22 @@ impl FullMeshPeeringStrategy {
 							info!(
 								"Retrying connection to {} at {} ({})",
 								hex::encode(&id[..8]),
-								h.addr,
+								h.all_addrs
+									.iter()
+									.map(|x| format!("{}", x))
+									.collect::<Vec<_>>()
+									.join(", "),
 								i + 1
 							);
 							h.state = PeerConnState::Trying(i);
-							tokio::spawn(self.clone().try_connect(id, h.addr));
+
+							let alternate_addrs = h
+								.all_addrs
+								.iter()
+								.filter(|x| **x != h.addr)
+								.cloned()
+								.collect::<Vec<_>>();
+							tokio::spawn(self.clone().try_connect(id, h.addr, alternate_addrs));
 						}
 					}
 				}
@@ -422,7 +441,12 @@ impl FullMeshPeeringStrategy {
 
 		let mut changed = false;
 		for (id, addr) in list.iter() {
-			if !known_hosts.list.contains_key(id) {
+			if let Some(kh) = known_hosts.list.get_mut(id) {
+				if !kh.all_addrs.contains(addr) {
+					kh.all_addrs.push(*addr);
+					changed = true;
+				}
+			} else {
 				known_hosts.list.insert(*id, self.new_peer(id, *addr));
 				changed = true;
 			}
@@ -434,10 +458,42 @@ impl FullMeshPeeringStrategy {
 		}
 	}
 
-	async fn try_connect(self: Arc<Self>, id: NodeID, addr: SocketAddr) {
-		let conn_result = self.netapp.clone().try_connect(addr, id).await;
-		if let Err(e) = conn_result {
-			warn!("Error connecting to {}: {}", hex::encode(&id[..8]), e);
+	async fn try_connect(
+		self: Arc<Self>,
+		id: NodeID,
+		default_addr: SocketAddr,
+		alternate_addrs: Vec<SocketAddr>,
+	) {
+		let conn_addr = {
+			let mut ret = None;
+			for addr in [default_addr].iter().chain(alternate_addrs.iter()) {
+				debug!("Trying address {} for peer {}", addr, hex::encode(&id[..8]));
+				match self.netapp.clone().try_connect(*addr, id).await {
+					Ok(()) => {
+						ret = Some(*addr);
+						break;
+					}
+					Err(e) => {
+						debug!(
+							"Error connecting to {} at {}: {}",
+							hex::encode(&id[..8]),
+							addr,
+							e
+						);
+					}
+				}
+			}
+			ret
+		};
+
+		if let Some(ok_addr) = conn_addr {
+			self.on_connected(id, ok_addr, false);
+		} else {
+			warn!(
+				"Could not connect to peer {} ({} addresses tried)",
+				hex::encode(&id[..8]),
+				1 + alternate_addrs.len()
+			);
 			let mut known_hosts = self.known_hosts.write().unwrap();
 			if let Some(host) = known_hosts.list.get_mut(&id) {
 				host.state = match host.state {
@@ -452,8 +508,6 @@ impl FullMeshPeeringStrategy {
 				};
 				self.update_public_peer_list(&known_hosts);
 			}
-		} else {
-			self.on_connected(id, addr, false);
 		}
 	}
 
@@ -475,12 +529,16 @@ impl FullMeshPeeringStrategy {
 			if let Some(host) = known_hosts.list.get_mut(&id) {
 				host.state = PeerConnState::Connected;
 				host.addr = addr;
+				if !host.all_addrs.contains(&addr) {
+					host.all_addrs.push(addr);
+				}
 			} else {
 				known_hosts.list.insert(
 					id,
 					PeerInfoInternal {
 						state: PeerConnState::Connected,
 						addr,
+						all_addrs: vec![addr],
 						last_seen: None,
 						ping: VecDeque::new(),
 						failed_pings: 0,
@@ -512,6 +570,7 @@ impl FullMeshPeeringStrategy {
 		};
 		PeerInfoInternal {
 			addr,
+			all_addrs: vec![addr],
 			state,
 			last_seen: None,
 			ping: VecDeque::new(),
-- 
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