sip: redirect RTP destination on re-INVITE port change

pkg/sip/inbound.go

@@ -312,6 +312,26 @@ func (s *Server) handleInviteAuth(tid traceid.ID, log logger.Logger, req *sip.Re
 	return true, false
 }
 
+func sdpBodyFromRequest(req *sip.Request) []byte {
+	ct := req.ContentType()
+	if ct != nil && ct.Value() != "application/sdp" {
+		return nil
+	}
+	return req.Body()
+}
+
+func updateRemoteFromSDP(media *MediaPort, log logger.Logger, body []byte) {
+	if len(body) == 0 || media == nil {
+		return
+	}
+	desc, err := sdp.ParseWith(msdk.GlobalCodecs(), body)
+	if err != nil {
+		log.Warnw("failed to parse re-INVITE SDP, RTP destination not updated", err)
+		return
+	}
+	media.UpdateRemote(desc.Addr)
+}
+
 func (s *Server) onInvite(log *slog.Logger, req *sip.Request, tx sip.ServerTransaction) {
 	// Error processed in defer
 	_ = s.processInvite(req, tx)
@@ -380,19 +400,21 @@ func (s *Server) processInvite(req *sip.Request, tx sip.ServerTransaction) (retE
 	existing := s.byLocalTag[cc.ID()]
 	s.cmu.RUnlock()
 	if existing != nil && existing.cc.InviteCSeq() < cc.InviteCSeq() {
-		existing.log().Infow("reinvite", "content-type", req.ContentType(), "content-length", req.ContentLength(), "cseq", cc.InviteCSeq())
+		existing.log().Infow("reinvite", "content-length", req.ContentLength(), "cseq", cc.InviteCSeq())
+		updateRemoteFromSDP(existing.media, existing.log(), sdpBodyFromRequest(req))
 		cc.AcceptAsKeepAlive(existing.cc.OwnSDP())
 		return nil
 	}
 	if s.cli != nil { // Process reinvite for existing outbound calls
 		oc := s.cli.getActiveCall(cc.ID())
 		newCSeq := cc.InviteCSeq()
 		if oc != nil && oc.cc != nil && oc.cc.InviteCSeq() < newCSeq {
-			sdp := oc.cc.LocalSDP()
-			if len(sdp) != 0 {
-				oc.log.Infow("accepting reinvite", "content-type", req.ContentType(), "content-length", req.ContentLength(), "cseq", cc.InviteCSeq())
+			localSDP := oc.cc.LocalSDP()
+			if len(localSDP) != 0 {
+				oc.log.Infow("accepting reinvite", "content-length", req.ContentLength(), "cseq", cc.InviteCSeq())
+				updateRemoteFromSDP(oc.media, oc.log, sdpBodyFromRequest(req))
 				oc.cc.RecordInvite(newCSeq)
-				cc.AcceptAsKeepAlive(sdp)
+				cc.AcceptAsKeepAlive(localSDP)
 				return nil
 			}
 		}

pkg/sip/media_port.go

@@ -241,7 +241,7 @@ func (c *udpConn) SetDst(addr netip.AddrPort) {
 	if addr.IsValid() {
 		prev := c.dst.Swap(&addr)
 		if prev == nil || !prev.IsValid() {
-			c.log.Infow("setting media destination", "prev", prev, "addr", addr.String())
+			c.log.Infow("setting media destination", "addr", addr.String())
 		} else if *prev != addr {
 			changeCount := c.dstChangeCount.Add(1)
 			now := time.Now().UnixNano()
@@ -257,7 +257,7 @@ func (c *udpConn) Read(b []byte) (n int, err error) {
 	n, addr, err := c.ReadFromUDPAddrPort(b)
 	prev := c.src.Swap(&addr)
 	if prev == nil || !prev.IsValid() {
-		c.log.Infow("setting media source", "prev", prev, "addr", addr.String())
+		c.log.Infow("setting media source", "addr", addr.String())
 	} else if *prev != addr {
 		changeCount := c.srcChangeCount.Add(1)
 		now := time.Now().UnixNano()
@@ -630,6 +630,20 @@ func (p *MediaPort) Port() int {
 	return p.port.LocalAddr().(*net.UDPAddr).Port
 }
 
+func (p *MediaPort) RemoteAddr() netip.AddrPort {
+	dst := p.port.dst.Load()
+	if dst == nil {
+		return netip.AddrPort{}
+	}
+	return *dst
+}
+
+func (p *MediaPort) UpdateRemote(addr netip.AddrPort) {
+	if addr.IsValid() && !addr.Addr().IsUnspecified() {
+		p.port.SetDst(addr)
+	}
+}
+
 func (p *MediaPort) Received() <-chan struct{} {
 	return p.mediaReceived.Watch()
 }

pkg/sip/media_port_test.go

@@ -165,6 +165,35 @@ func newIP(v string) netip.Addr {
 	return ip
 }
 
+func TestMediaPortUpdateRemote(t *testing.T) {
+	log := logger.GetLogger()
+	mon := newTestCallMonitor(t)
+
+	// newUDPPipe wires two in-memory testUDPConn together.
+	c1, _ := newUDPPipe()
+	mp, err := NewMediaPortWith(1, log, mon, c1, &MediaOptions{
+		IP: netip.MustParseAddr("127.0.0.1"),
+	}, 8000)
+	require.NoError(t, err)
+	defer mp.Close()
+
+	// Initially no destination is set.
+	require.False(t, mp.RemoteAddr().IsValid(), "RemoteAddr should be invalid before any update")
+
+	// Update to a valid address.
+	addr := netip.MustParseAddrPort("9.8.7.6:12345")
+	mp.UpdateRemote(addr)
+	require.Equal(t, addr, mp.RemoteAddr(), "RemoteAddr should reflect the updated address")
+
+	// UpdateRemote with invalid addr should be a no-op.
+	mp.UpdateRemote(netip.AddrPort{})
+	require.Equal(t, addr, mp.RemoteAddr(), "UpdateRemote with invalid addr should not change RemoteAddr")
+
+	// UpdateRemote with unspecified address (c=0.0.0.0 hold form) should be a no-op.
+	mp.UpdateRemote(netip.MustParseAddrPort("0.0.0.0:12345"))
+	require.Equal(t, addr, mp.RemoteAddr(), "UpdateRemote with unspecified addr should not change RemoteAddr")
+}
+
 func TestMediaPort(t *testing.T) {
 	// Main resampler has unpredictable (although tiny) output delay
 	// and other randomness in the generated samples.

pkg/sip/signaling_test.go

@@ -641,7 +641,7 @@ func TestReinvite(t *testing.T) {
 	t.Run("inbound", func(t *testing.T) {
 		t.Run("normal", func(t *testing.T) {
 			st := NewServiceTest(t, nil)
-			call, _ := st.CreateInboundCall(t)
+			call, ic := st.CreateInboundCall(t)
 			serverLocalSDP := call.remoteSDP
 
 			// Re-INVITE
@@ -661,6 +661,9 @@ func TestReinvite(t *testing.T) {
 			resp = st.TestUA.TransactionRequest(t, req, true)
 			require.Equal(t, sip.StatusCode(200), resp.StatusCode, "reinvite for outbound call should get 200 OK")
 			require.Equal(t, serverLocalSDP, resp.Body(), "reinvite 200 OK should return server local SDP")
+
+			// After the re-INVITE with new offer, the media port destination must be updated.
+			require.Equal(t, newOffer.Addr, ic.media.RemoteAddr(), "re-INVITE should redirect RTP to the new remote address")
 		})
 
 		t.Run("miss", func(t *testing.T) {
@@ -683,6 +686,20 @@ func TestReinvite(t *testing.T) {
 			require.Equal(t, sip.StatusCode(200), resp.StatusCode, "reinvite for outbound call should get 200 OK")
 			require.NotEqual(t, serverLocalSDP, resp.Body(), "reinvite for new call should return new server local SDP")
 		})
+
+		t.Run("no_body", func(t *testing.T) {
+			st := NewServiceTest(t, nil)
+			call, ic := st.CreateInboundCall(t)
+			serverLocalSDP := call.remoteSDP
+			initialRemote := ic.media.RemoteAddr()
+
+			// Re-INVITE with no SDP body — destination must not change.
+			req := call.NewRequest(sip.INVITE) // no body, no Content-Type
+			resp := st.TestUA.TransactionRequest(t, req, true)
+			require.Equal(t, sip.StatusCode(200), resp.StatusCode, "body-less re-INVITE should still get 200 OK")
+			require.Equal(t, serverLocalSDP, resp.Body(), "body-less re-INVITE should return server local SDP")
+			require.Equal(t, initialRemote, ic.media.RemoteAddr(), "body-less re-INVITE must not change RTP destination")
+		})
 	})
 	t.Run("outbound", func(t *testing.T) {
 		t.Run("normal", func(t *testing.T) {
@@ -708,6 +725,23 @@ func TestReinvite(t *testing.T) {
 			resp = st.TestUA.TransactionRequest(t, req, false)
 			require.Equal(t, sip.StatusCode(200), resp.StatusCode, "reinvite for outbound call should get 200 OK")
 			require.Equal(t, serverLocalSDP, resp.Body(), "reinvite 200 OK should return server local SDP")
+
+			// After the re-INVITE with new offer, the media port destination must be updated.
+			require.Equal(t, newOffer.Addr, oc.media.RemoteAddr(), "re-INVITE should redirect outbound call RTP to the new remote address")
+		})
+
+		t.Run("no_body", func(t *testing.T) {
+			st := NewServiceTest(t, nil)
+			call, oc, _ := st.CreateOutboundCall(t)
+			serverLocalSDP := oc.cc.LocalSDP()
+			initialRemote := oc.media.RemoteAddr()
+
+			// Re-INVITE with no SDP body — destination must not change.
+			req := call.NewRequest(sip.INVITE) // no body, no Content-Type
+			resp := st.TestUA.TransactionRequest(t, req, false)
+			require.Equal(t, sip.StatusCode(200), resp.StatusCode, "body-less re-INVITE should still get 200 OK")
+			require.Equal(t, serverLocalSDP, resp.Body(), "body-less re-INVITE should return server local SDP")
+			require.Equal(t, initialRemote, oc.media.RemoteAddr(), "body-less re-INVITE must not change RTP destination")
 		})
 
 		t.Run("miss", func(t *testing.T) {