Fix port zero when tranceiver stopping

lib/ex_webrtc/peer_connection.ex

@@ -844,7 +844,7 @@
       |> ExSDP.add_attributes([
         %ExSDP.Attribute.Group{semantics: "BUNDLE", mids: mids},
         # always allow for mixing one- and two-byte RTP header extensions
         # TODO ensure this was also offered
         "extmap-allow-mixed",
         {"msid-semantic", "WMS *"}
       ])
@@ -2417,6 +2417,9 @@
   # https://www.w3.org/TR/webrtc/#dfn-check-if-negotiation-is-needed
   defp tr_negotiation_needed?([], _), do: false
 
+  defp tr_negotiation_needed?([tr | _transceivers], _state) when tr.stopping and not tr.stopped,
+    do: true
+
   defp tr_negotiation_needed?([tr | _transceivers], _state) when tr.mid == nil, do: true
 
   defp tr_negotiation_needed?([tr | transceivers], state) do

lib/ex_webrtc/rtp_transceiver.ex

@@ -434,7 +434,11 @@ defmodule ExWebRTC.RTPTransceiver do
         mline = to_mline(transceiver, opts)
         %ExSDP.Media{mline | port: 0}
 
-      transceiver.stopping == true or transceiver.stopped == true ->
+      transceiver.stopping == true ->
+        opts = Keyword.put(opts, :direction, :inactive)
+        to_mline(transceiver, opts)
+
+      transceiver.stopped == true ->
         opts = Keyword.put(opts, :direction, :inactive)
         mline = to_mline(transceiver, opts)
         %ExSDP.Media{mline | port: 0}

test/ex_webrtc/peer_connection_test.exs

@@ -651,6 +651,59 @@ defmodule ExWebRTC.PeerConnectionTest do
       assert sdp.media == []
     end
 
+    test "after remote offer" do
+      {:ok, pc1} = PeerConnection.start_link()
+      {:ok, pc2} = PeerConnection.start_link()
+
+      PeerConnection.add_transceiver(pc1, :video)
+      {:ok, offer} = PeerConnection.create_offer(pc1)
+      :ok = PeerConnection.set_local_description(pc1, offer)
+
+      :ok = PeerConnection.set_remote_description(pc2, offer)
+      [tr] = PeerConnection.get_transceivers(pc2)
+      :ok = PeerConnection.stop_transceiver(pc2, tr.id)
+
+      assert [
+               %RTPTransceiver{
+                 current_direction: nil,
+                 direction: :inactive,
+                 stopping: true,
+                 stopped: false
+               }
+             ] = PeerConnection.get_transceivers(pc2)
+
+      {:ok, answer} = PeerConnection.create_answer(pc2)
+      [video] = ExSDP.parse!(answer.sdp).media
+      assert video.port == 9
+
+      :ok = PeerConnection.set_local_description(pc2, answer)
+      :ok = PeerConnection.set_remote_description(pc1, answer)
+
+      assert_receive {:ex_webrtc, ^pc2, :negotiation_needed}
+
+      # Ensure transceiver is removed after renegotiation
+
+      {:ok, offer2} = PeerConnection.create_offer(pc2)
+      :ok = PeerConnection.set_local_description(pc2, offer2)
+      [new_video] = ExSDP.parse!(offer2.sdp).media
+      assert new_video.port == 0
+
+      assert [
+               %RTPTransceiver{
+                 current_direction: :inactive,
+                 direction: :inactive,
+                 stopping: true,
+                 stopped: false
+               }
+             ] = PeerConnection.get_transceivers(pc2)
+
+      :ok = PeerConnection.set_remote_description(pc1, offer2)
+      {:ok, answer2} = PeerConnection.create_answer(pc1)
+
+      :ok = PeerConnection.set_remote_description(pc2, answer2)
+      assert [] = PeerConnection.get_transceivers(pc2)
+    end
+
     test "with renegotiation" do
       {:ok, pc1} = PeerConnection.start_link()
       {:ok, pc2} = PeerConnection.start_link()