From bc95a1f425078f70cdcd16e370d9775f15b9a4e1 Mon Sep 17 00:00:00 2001
From: Thomas Eizinger <thomas@eizinger.io>
Date: Mon, 10 Nov 2025 12:41:23 +1100
Subject: [PATCH] chore(snownet): log connection state on failure (#10820)

When investigating, why a connection fails it is useful to know right
away, what the last connection state was, including the kind of
connection, such as `PeerToPeer`, `RelayToPeer` etc.
---
 rust/connlib/snownet/src/node.rs | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/rust/connlib/snownet/src/node.rs b/rust/connlib/snownet/src/node.rs
index ba863e4c5..b25193538 100644
--- a/rust/connlib/snownet/src/node.rs
+++ b/rust/connlib/snownet/src/node.rs
@@ -1726,6 +1726,19 @@ impl ConnectionState {
     }
 }
 
+impl fmt::Display for ConnectionState {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ConnectionState::Connecting { .. } => write!(f, "Connecting"),
+            ConnectionState::Connected { peer_socket, .. } => {
+                write!(f, "Connected({})", peer_socket.kind())
+            }
+            ConnectionState::Idle { peer_socket } => write!(f, "Idle({})", peer_socket.kind()),
+            ConnectionState::Failed => write!(f, "Failed"),
+        }
+    }
+}
+
 fn idle_at(last_activity: Instant) -> Instant {
     const MAX_IDLE: Duration = Duration::from_secs(20); // Must be longer than the ICE timeout otherwise we might not detect a failed connection early enough.
 
@@ -1775,6 +1788,15 @@ impl PeerSocket {
             }
         }
     }
+
+    fn kind(&self) -> &'static str {
+        match self {
+            PeerSocket::PeerToPeer { .. } => "PeerToPeer",
+            PeerSocket::PeerToRelay { .. } => "PeerToRelay",
+            PeerSocket::RelayToPeer { .. } => "RelayToPeer",
+            PeerSocket::RelayToRelay { .. } => "RelayToRelay",
+        }
+    }
 }
 
 impl<RId> Connection<RId>
@@ -1839,7 +1861,7 @@ where
             .candidate_timeout()
             .is_some_and(|timeout| now >= timeout)
         {
-            tracing::info!("Connection failed (no candidates received)");
+            tracing::info!(state = %self.state, "Connection failed (no candidates received)");
             self.state = ConnectionState::Failed;
             return;
         }
@@ -1848,7 +1870,7 @@ where
             .disconnect_timeout()
             .is_some_and(|timeout| now >= timeout)
         {
-            tracing::info!("Connection failed (ICE timeout)");
+            tracing::info!(state = %self.state, "Connection failed (ICE timeout)");
             self.state = ConnectionState::Failed;
             return;
         }
@@ -2080,7 +2102,7 @@ where
         match self.tunnel.update_timers_at(&mut buf, now) {
             TunnResult::Done => {}
             TunnResult::Err(WireGuardError::ConnectionExpired) => {
-                tracing::info!("Connection failed (wireguard tunnel expired)");
+                tracing::info!(state = %self.state, "Connection failed (wireguard tunnel expired)");
                 self.state = ConnectionState::Failed;
             }
             TunnResult::Err(e) => {