Expose relay transport in status and label relay peer metrics by transport

shared/relay/client/client.go

@@ -182,6 +182,23 @@ type Client struct {
 	// datagramFallbackTriggered guards a single fallback per connection so a
 	// burst of oversized datagrams triggers one reconnect, not many.
 	datagramFallbackTriggered atomic.Bool
+
+	// transport is the negotiated relay transport (e.g. "quic", "ws") of the
+	// current connection, guarded by mu.
+	transport string
+}
+
+// transportConn is implemented by relay connections that know their transport.
+type transportConn interface {
+	Protocol() string
+}
+
+// Transport returns the negotiated relay transport of the current connection,
+// or an empty string when not connected.
+func (c *Client) Transport() string {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.transport
 }
 
 // SetTransportFallback wires the shared datagram-transport fallback tracker.
@@ -402,6 +419,9 @@ func (c *Client) connect(ctx context.Context) (*RelayAddr, error) {
 	}
 	c.relayConn = conn
 	c.datagramFallbackTriggered.Store(false)
+	if tc, ok := conn.(transportConn); ok {
+		c.transport = tc.Protocol()
+	}
 
 	instanceURL, err := c.handShake(ctx)
 	if err != nil {

shared/relay/client/dialer/quic/conn.go

@@ -57,6 +57,11 @@ func (c *Conn) Write(b []byte) (int, error) {
 	return len(b), nil
 }
 
+// Protocol returns the transport name for this connection.
+func (c *Conn) Protocol() string {
+	return Network
+}
+
 func (c *Conn) RemoteAddr() net.Addr {
 	return c.session.RemoteAddr()
 }

shared/relay/client/dialer/ws/conn.go

@@ -33,6 +33,11 @@ func NewConn(wsConn *websocket.Conn, serverAddress string, underlying net.Conn)
 	}
 }
 
+// Protocol returns the transport name for this connection.
+func (c *Conn) Protocol() string {
+	return Network
+}
+
 func (c *Conn) Read(b []byte) (n int, err error) {
 	t, ioReader, err := c.Conn.Reader(c.ctx)
 	if err != nil {

shared/relay/client/manager.go

@@ -242,6 +242,54 @@ func (m *Manager) ServerURLs() []string {
 	return m.serverPicker.ServerURLs.Load().([]string)
 }
 
+// RelayConnState is the connection state of a single relay server.
+type RelayConnState struct {
+	// URL is the server's instance address when connected, otherwise the
+	// configured server URL.
+	URL string
+	// Transport is the negotiated transport ("quic", "ws"), empty if not connected.
+	Transport string
+	// Err is set when the relay is not connected.
+	Err error
+}
+
+// RelayStates returns the connection state of the home relay and every foreign
+// relay the manager currently tracks.
+func (m *Manager) RelayStates() []RelayConnState {
+	var states []RelayConnState
+
+	m.relayClientMu.RLock()
+	home := m.relayClient
+	m.relayClientMu.RUnlock()
+	if home != nil {
+		states = append(states, relayConnState(home))
+	}
+
+	m.relayClientsMutex.RLock()
+	for _, rt := range m.relayClients {
+		rt.RLock()
+		rc, rtErr := rt.relayClient, rt.err
+		rt.RUnlock()
+		switch {
+		case rc != nil:
+			states = append(states, relayConnState(rc))
+		case rtErr != nil:
+			states = append(states, RelayConnState{Err: rtErr})
+		}
+	}
+	m.relayClientsMutex.RUnlock()
+
+	return states
+}
+
+func relayConnState(c *Client) RelayConnState {
+	addr, err := c.ServerInstanceURL()
+	if err != nil {
+		return RelayConnState{URL: c.connectionURL, Err: err}
+	}
+	return RelayConnState{URL: addr, Transport: c.Transport()}
+}
+
 // HasRelayAddress returns true if the manager is serving. With this method can check if the peer can communicate with
 // Relay service.
 func (m *Manager) HasRelayAddress() bool {