From 9fb07a119f2422d472a58d189b72af83bcc69ef8 Mon Sep 17 00:00:00 2001
From: Jon Kinney <jonkinney@gmail.com>
Date: Tue, 5 May 2026 01:18:32 -0500
Subject: [PATCH] fix(version-exchange): also store peer commit on the listen
 side
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Previously the Hello handler in `ListenTask` echoed our local commit
back but deliberately threw away the peer's, on the assumption that
the outgoing connect-side path (`connect.rs:278-279` →
`set_peer_commit`) would always populate the visible state for any
bidirectionally-configured peer.

That assumption breaks any time the *outgoing* TCP/DTLS direction is
broken even though the inbound direction is fine — happened just now
when the peer Mac's daemon stopped listening on 4242 (DHCP-renewed
IP, daemon crashed, asymmetric NAT, …). Mac was still happily
connecting in the other direction and sending events, including the
initial Hello, but Linux silently displayed "peer version unknown"
because the listen side dropped Mac's commit on the floor.

Add a `PeerHello { addr, commit }` EmulationEvent variant fired from
the listen-side Hello handler. The service maps `addr → ClientHandle`
via `client_manager.get_client(addr)` and calls `set_peer_commit` +
`broadcast_client` exactly like the connect path does. The connect
path remains the primary source for symmetric setups; this is the
defensive fallback so version visibility doesn't depend on outbound
reachability.

Skips silently when no outgoing client is configured for the peer's
addr (incoming-only setup) — there's no UI row to update in that
case anyway.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 src/emulation.rs | 36 ++++++++++++++++++++++++++----------
 src/service.rs   | 11 +++++++++++
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/src/emulation.rs b/src/emulation.rs
index d2ff60f..923bf99 100644
--- a/src/emulation.rs
+++ b/src/emulation.rs
@@ -53,6 +53,17 @@ pub(crate) enum EmulationEvent {
     EmulationEnabled,
     /// capture should be released
     ReleaseNotify,
+    /// peer sent us a Hello with its build commit hash. Used to
+    /// populate `client_manager.peer_commit` from the listen side
+    /// too — without this, peer-version visibility silently fails
+    /// whenever the outgoing connection in the *other* direction is
+    /// broken (one-way setups, asymmetric NAT, peer's TCP listener
+    /// down). The connect-side path stays as the primary source;
+    /// this is the defensive fallback.
+    PeerHello {
+        addr: SocketAddr,
+        commit: [u8; 8],
+    },
 }
 
 enum EmulationRequest {
@@ -151,16 +162,21 @@ impl ListenTask {
                             }
                             ProtoEvent::Input(event) => self.emulation_proxy.consume(event, addr),
                             ProtoEvent::Ping => self.listener.reply(addr, ProtoEvent::Pong(self.emulation_proxy.emulation_active.get())).await,
-                            // Mirror the peer's version handshake. The
-                            // outgoing connect side initiated this with
-                            // its own Hello; we echo ours back so the
-                            // peer's connect-side receive_loop can
-                            // populate `peer_commit`. We don't store
-                            // the peer's commit on the listen side —
-                            // the user-visible state lives on outgoing
-                            // connections, where the same peer is also
-                            // configured as a `[[clients]]` entry.
-                            ProtoEvent::Hello { .. } => self.listener.reply(addr, ProtoEvent::Hello { commit: local_commit() }).await,
+                            // Peer's version handshake. Echo our own
+                            // commit back so the peer's connect-side
+                            // receive_loop populates its `peer_commit`,
+                            // AND publish a PeerHello upward so our
+                            // service can populate ours from the listen
+                            // side too — the connect side is the primary
+                            // path, but if the outbound direction is
+                            // broken (one-way setup, NAT, peer's TCP
+                            // listener down) the version display would
+                            // otherwise silently say "unknown" while
+                            // the peer is in fact happily talking to us.
+                            ProtoEvent::Hello { commit } => {
+                                self.listener.reply(addr, ProtoEvent::Hello { commit: local_commit() }).await;
+                                self.event_tx.send(EmulationEvent::PeerHello { addr, commit }).expect("channel closed");
+                            }
                             _ => {}
                         }
                     }
diff --git a/src/service.rs b/src/service.rs
index d0772f6..46f3693 100644
--- a/src/service.rs
+++ b/src/service.rs
@@ -319,6 +319,17 @@ impl Service {
             EmulationEvent::Connected { addr, fingerprint } => {
                 self.notify_frontend(FrontendEvent::DeviceConnected { addr, fingerprint });
             }
+            EmulationEvent::PeerHello { addr, commit } => {
+                // Map the peer's source addr back to its client handle
+                // and stamp the commit. Skip if we don't have an
+                // outgoing client configured for this peer (incoming-
+                // only setup) — there's nowhere to display the version
+                // in that case anyway.
+                if let Some(handle) = self.client_manager.get_client(addr) {
+                    self.client_manager.set_peer_commit(handle, Some(commit));
+                    self.broadcast_client(handle);
+                }
+            }
         }
     }