fix three ways ws + WebRTC could not work in practice

Review of #15684 and hbb_common#579. Each of these left the code reading
correct while the feature did not function.

- The RelayResponse race classified P2P with `result.2 == "IPv6"`, but
  that site's futures are only ever the relay ("Relay"/"WebSocket") and
  the WebRTC branch's own "WebRTC" — so the predicate was constantly
  false. When the relay landed first the result was still right (the
  webrtc arm's `others_fut.is_none()` fallback), but when WebRTC
  connected FIRST it was parked as if it were a relay and the relay was
  committed on arrival, discarding a live direct connection. That is the
  LAN case: the better the network, the worse the outcome. Classify by
  what the label means, via is_direct_transport, and test both orderings
  — only the relay-first one was covered.

- handle_peer_info wrote "force-always-relay=Y" into the peer's saved
  config whenever force_relay was set, which now includes the WebSocket
  transport. One ws session therefore turned the peer into a permanent
  relay-by-policy peer, and relay-by-policy means Relay-only ICE, so
  WebRTC could never go direct to it again — the flagship path worked
  exactly once. Persist policy_relay, which is the user's choice; the
  transport is a property of this client, not of the peer.

- The answerer gated on this machine's enable-webrtc option, but that is
  LocalConfig: the UI process writes it and never syncs it over IPC,
  while handle_punch_hole runs in the server process, which on Windows
  resolves LocalConfig under a different profile and reads the
  private-server default of "N". The gate refused to answer in exactly
  the self-hosted deployments the transport exists for. Drop it: the
  answerer follows the request, like the udp/ipv6 legs, and the option
  still gates the feature where it can — an offer only exists because
  some controller had it enabled.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ExUfAkYbq8UC9pQCiLy8TQ

src/client.rs

@@ -225,6 +225,15 @@ impl Drop for OffererGuard {
 ///   into one error.
 ///
 /// `others` must be non-empty (`select_ok` requires it).
+/// Whether a transport label names a peer-to-peer path rather than the RustDesk relay.
+///
+/// The preference window exists to let one of these beat a relay that connects sooner, so a
+/// label misclassified here inverts the race: a direct connection is parked as if it were a
+/// relay, and the relay is then committed the moment it arrives.
+fn is_direct_transport(typ: &str) -> bool {
+    !matches!(typ, "Relay" | "WebSocket")
+}
+
 async fn race_transports_prefer_webrtc<'a, T: 'a>(
     webrtc_fut: BoxFuture<'a, ResultType<T>>,
     others: Vec<BoxFuture<'a, ResultType<T>>>,
@@ -1098,7 +1107,7 @@ impl Client {
                                     webrtc_fut,
                                     connect_futures,
                                     Self::WEBRTC_PREFER_WINDOW_MS,
-                                    |result| result.2 == "IPv6",
+                                    |result| is_direct_transport(result.2),
                                 )
                                 .await
                             }
@@ -3453,7 +3462,12 @@ impl LoginConfigHandler {
                     .insert("other-server-key".to_owned(), c.clone());
             }
         }
-        if self.force_relay {
+        // policy_relay, not force_relay: this writes the user's relay CHOICE back into the peer's
+        // saved config, and force_relay also carries the WebSocket transport, which is a property
+        // of this client's current setup rather than of the peer. Persisting that turned one ws
+        // session into a permanent relay-by-policy peer — and since relay-by-policy means
+        // Relay-only ICE, WebRTC could never go direct to it again.
+        if self.policy_relay {
             config
                 .options
                 .insert("force-always-relay".to_owned(), "Y".to_owned());
@@ -5282,7 +5296,7 @@ async fn udp_nat_connect(
 
 #[cfg(test)]
 mod webrtc_race_tests {
-    use super::{race_transports_prefer_webrtc, request_allows_tcp_punch};
+    use super::{is_direct_transport, race_transports_prefer_webrtc, request_allows_tcp_punch};
     use hbb_common::{
         anyhow::anyhow,
         futures::future::{BoxFuture, FutureExt},
@@ -5315,6 +5329,37 @@ mod webrtc_race_tests {
         assert!(!request_allows_tcp_punch("webrtc://offer"));
     }
 
+    // The transport labels the RelayResponse race actually runs on. Its predicate has to
+    // recognise the WebRTC branch's own label as direct, or a WebRTC connection that completes
+    // BEFORE the relay is parked as if it were a relay and the relay is committed on arrival —
+    // inverting the race exactly on the fast networks where ICE beats a TCP relay connect.
+    #[test]
+    fn transport_labels_are_classified_as_direct_or_relayed() {
+        for direct in ["WebRTC", "TCP", "UDP", "IPv6"] {
+            assert!(is_direct_transport(direct), "{direct} is a direct path");
+        }
+        for relayed in ["Relay", "WebSocket"] {
+            assert!(
+                !is_direct_transport(relayed),
+                "{relayed} goes via the relay"
+            );
+        }
+    }
+
+    #[tokio::test]
+    async fn direct_result_wins_even_when_it_arrives_first() {
+        // Same ordering as a LAN: the preferred branch connects before the relay does.
+        let got = race_transports_prefer_webrtc(
+            ok_after(10, "WebRTC"),
+            vec![ok_after(120, "Relay")],
+            60_000,
+            |result| is_direct_transport(result),
+        )
+        .await
+        .unwrap();
+        assert_eq!(got, "WebRTC");
+    }
+
     #[tokio::test]
     async fn webrtc_preferred_over_faster_relay_within_window() {
         let got = race_transports_prefer_webrtc(

src/rendezvous_mediator.rs

@@ -854,13 +854,16 @@ impl RendezvousMediator {
         // transport-forced (ws) and its offer carries every candidate type, so answer with
         // full ICE and let a direct pair form; without it the offer is Relay-only ICE by
         // policy, viable (and answerable) only through TURN.
-        let webrtc_relay_only = ph.force_relay
-            && !WebRTCStream::endpoint_declares_all_ice(&ph.webrtc_sdp_offer);
-        // Unlike the udp/ipv6 legs - which deliberately just follow the request - WebRTC is
-        // gated on this machine's own option too: answering builds a pc that gathers ICE
-        // from this host, so a machine with WebRTC off must not be pulled into it.
+        let webrtc_relay_only =
+            ph.force_relay && !WebRTCStream::endpoint_declares_all_ice(&ph.webrtc_sdp_offer);
+        // Like the udp/ipv6 legs, the answerer follows the request and does not consult this
+        // machine's own enable-webrtc option. That option is LocalConfig, which the UI process
+        // writes and never syncs over IPC — this code runs in the server process, which on
+        // Windows resolves LocalConfig under a different profile entirely and would read the
+        // private-server default of "N", silently refusing to answer in exactly the self-hosted
+        // deployments the transport is for. The option still gates the feature where it can:
+        // an offer only exists because a controller had it enabled.
         let webrtc_viable = !ph.webrtc_sdp_offer.is_empty()
-            && crate::get_webrtc_enabled()
             && !Config::is_proxy()
             && (!webrtc_relay_only || WebRTCStream::has_turn_server());
         let webrtc_sdp_answer = if webrtc_viable {