Add RtcpMuxPolicy support to PeerConnection.

BUG=4611
R=juberti@google.com

Review URL: https://webrtc-codereview.appspot.com/46169004

Cr-Commit-Position: refs/heads/master@{#9251}

talk/app/webrtc/java/jni/classreferenceholder.cc

@@ -93,6 +93,7 @@ ClassReferenceHolder::ClassReferenceHolder(JNIEnv* jni) {
   LoadClass(jni, "org/webrtc/MediaStream");
   LoadClass(jni, "org/webrtc/MediaStreamTrack$State");
   LoadClass(jni, "org/webrtc/PeerConnection$BundlePolicy");
+  LoadClass(jni, "org/webrtc/PeerConnection$RtcpMuxPolicy");
   LoadClass(jni, "org/webrtc/PeerConnection$IceConnectionState");
   LoadClass(jni, "org/webrtc/PeerConnection$IceGatheringState");
   LoadClass(jni, "org/webrtc/PeerConnection$IceTransportsType");
@@ -143,4 +144,3 @@ jclass FindClass(JNIEnv* jni, const char* name) {
 }
 
 }  // namespace webrtc_jni
-

talk/app/webrtc/java/jni/peerconnection_jni.cc

@@ -1216,6 +1216,22 @@ JavaBundlePolicyToNativeType(JNIEnv* jni, jobject j_bundle_policy) {
   return PeerConnectionInterface::kBundlePolicyBalanced;
 }
 
+static PeerConnectionInterface::RtcpMuxPolicy
+JavaRtcpMuxPolicyToNativeType(JNIEnv* jni, jobject j_rtcp_mux_policy) {
+  std::string enum_name = GetJavaEnumName(
+      jni, "org/webrtc/PeerConnection$RtcpMuxPolicy",
+      j_rtcp_mux_policy);
+
+  if (enum_name == "NEGOTIATE")
+    return PeerConnectionInterface::kRtcpMuxPolicyNegotiate;
+
+  if (enum_name == "REQUIRE")
+    return PeerConnectionInterface::kRtcpMuxPolicyRequire;
+
+  CHECK(false) << "Unexpected RtcpMuxPolicy enum_name " << enum_name;
+  return PeerConnectionInterface::kRtcpMuxPolicyNegotiate;
+}
+
 static PeerConnectionInterface::TcpCandidatePolicy
 JavaTcpCandidatePolicyToNativeType(
     JNIEnv* jni, jobject j_tcp_candidate_policy) {
@@ -1292,6 +1308,12 @@ JOW(jlong, PeerConnectionFactory_nativeCreatePeerConnection)(
   jobject j_bundle_policy = GetObjectField(
       jni, j_rtc_config, j_bundle_policy_id);
 
+  jfieldID j_rtcp_mux_policy_id = GetFieldID(
+      jni, j_rtc_config_class, "rtcpMuxPolicy",
+      "Lorg/webrtc/PeerConnection$RtcpMuxPolicy;");
+  jobject j_rtcp_mux_policy = GetObjectField(
+      jni, j_rtc_config, j_rtcp_mux_policy_id);
+
   jfieldID j_tcp_candidate_policy_id = GetFieldID(
       jni, j_rtc_config_class, "tcpCandidatePolicy",
       "Lorg/webrtc/PeerConnection$TcpCandidatePolicy;");
@@ -1311,6 +1333,8 @@ JOW(jlong, PeerConnectionFactory_nativeCreatePeerConnection)(
   rtc_config.type =
       JavaIceTransportsTypeToNativeType(jni, j_ice_transports_type);
   rtc_config.bundle_policy = JavaBundlePolicyToNativeType(jni, j_bundle_policy);
+  rtc_config.rtcp_mux_policy =
+      JavaRtcpMuxPolicyToNativeType(jni, j_rtcp_mux_policy);
   rtc_config.tcp_candidate_policy =
       JavaTcpCandidatePolicyToNativeType(jni, j_tcp_candidate_policy);
   JavaIceServersToJsepIceServers(jni, j_ice_servers, &rtc_config.servers);

talk/app/webrtc/java/src/org/webrtc/PeerConnection.java

@@ -117,7 +117,11 @@ public class PeerConnection {
     BALANCED, MAXBUNDLE, MAXCOMPAT
   };
 
-  /** Java version of PeerConnectionInterface.BundlePolicy */
+  /** Java version of PeerConnectionInterface.RtcpMuxPolicy */
+  public enum RtcpMuxPolicy {
+    NEGOTIATE, REQUIRE
+  };
+  /** Java version of PeerConnectionInterface.TcpCandidatePolicy */
   public enum TcpCandidatePolicy {
     ENABLED, DISABLED
   };
@@ -127,12 +131,14 @@ public class PeerConnection {
     public IceTransportsType iceTransportsType;
     public List<IceServer> iceServers;
     public BundlePolicy bundlePolicy;
+    public RtcpMuxPolicy rtcpMuxPolicy;
     public TcpCandidatePolicy tcpCandidatePolicy;
     public int audioJitterBufferMaxPackets;
 
     public RTCConfiguration(List<IceServer> iceServers) {
       iceTransportsType = IceTransportsType.ALL;
       bundlePolicy = BundlePolicy.BALANCED;
+      rtcpMuxPolicy = RtcpMuxPolicy.NEGOTIATE;
       tcpCandidatePolicy = TcpCandidatePolicy.ENABLED;
       this.iceServers = iceServers;
       audioJitterBufferMaxPackets = 50;

talk/app/webrtc/peerconnectioninterface.h

@@ -197,6 +197,12 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
     kBundlePolicyMaxCompat
   };
 
+  // https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-09#section-4.1.1
+  enum RtcpMuxPolicy {
+    kRtcpMuxPolicyNegotiate,
+    kRtcpMuxPolicyRequire,
+  };
+
   enum TcpCandidatePolicy {
     kTcpCandidatePolicyEnabled,
     kTcpCandidatePolicyDisabled
@@ -210,12 +216,14 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
     // at the same time.
     IceServers servers;
     BundlePolicy bundle_policy;
+    RtcpMuxPolicy rtcp_mux_policy;
     TcpCandidatePolicy tcp_candidate_policy;
     int audio_jitter_buffer_max_packets;
 
     RTCConfiguration()
         : type(kAll),
           bundle_policy(kBundlePolicyBalanced),
+          rtcp_mux_policy(kRtcpMuxPolicyNegotiate),
           tcp_candidate_policy(kTcpCandidatePolicyEnabled),
           audio_jitter_buffer_max_packets(50) {}
   };

talk/app/webrtc/webrtcsession.cc

@@ -523,6 +523,7 @@ bool WebRtcSession::Initialize(
     DTLSIdentityServiceInterface* dtls_identity_service,
     const PeerConnectionInterface::RTCConfiguration& rtc_configuration) {
   bundle_policy_ = rtc_configuration.bundle_policy;
+  rtcp_mux_policy_ = rtc_configuration.rtcp_mux_policy;
 
   // TODO(perkj): Take |constraints| into consideration. Return false if not all
   // mandatory constraints can be fulfilled. Note that |constraints|
@@ -1600,6 +1601,18 @@ bool WebRtcSession::CreateChannels(const SessionDescription* desc) {
     }
   }
 
+  if (rtcp_mux_policy_ == PeerConnectionInterface::kRtcpMuxPolicyRequire) {
+    if (voice_channel()) {
+      voice_channel()->ActivateRtcpMux();
+    }
+    if (video_channel()) {
+      video_channel()->ActivateRtcpMux();
+    }
+    if (data_channel()) {
+      data_channel()->ActivateRtcpMux();
+    }
+  }
+
   // Enable bundle before when kMaxBundle policy is in effect.
   if (bundle_policy_ == PeerConnectionInterface::kBundlePolicyMaxBundle) {
     const cricket::ContentGroup* bundle_group = desc->GetGroupByName(

talk/app/webrtc/webrtcsession.h

@@ -413,6 +413,9 @@ class WebRtcSession : public cricket::BaseSession,
   // Declares the bundle policy for the WebRTCSession.
   PeerConnectionInterface::BundlePolicy bundle_policy_;
 
+  // Declares the RTCP mux policy for the WebRTCSession.
+  PeerConnectionInterface::RtcpMuxPolicy rtcp_mux_policy_;
+
   DISALLOW_COPY_AND_ASSIGN(WebRtcSession);
 };
 }  // namespace webrtc

talk/app/webrtc/webrtcsession_unittest.cc

@@ -156,8 +156,6 @@ static const char kSdpWithRtx[] =
     "a=rtpmap:96 rtx/90000\r\n"
     "a=fmtp:96 apt=0\r\n";
 
-static const int kAudioJitterBufferMaxPackets = 50;
-
 // Add some extra |newlines| to the |message| after |line|.
 static void InjectAfter(const std::string& line,
                         const std::string& newlines,
@@ -405,11 +403,6 @@ class WebRtcSessionTest : public testing::Test {
 
   void Init() {
     PeerConnectionInterface::RTCConfiguration configuration;
-    configuration.type = PeerConnectionInterface::kAll;
-    configuration.bundle_policy =
-        PeerConnectionInterface::kBundlePolicyBalanced;
-    configuration.audio_jitter_buffer_max_packets =
-        kAudioJitterBufferMaxPackets;
     Init(NULL, configuration);
   }
 
@@ -417,20 +410,20 @@ class WebRtcSessionTest : public testing::Test {
       PeerConnectionInterface::IceTransportsType ice_transport_type) {
     PeerConnectionInterface::RTCConfiguration configuration;
     configuration.type = ice_transport_type;
-    configuration.bundle_policy =
-        PeerConnectionInterface::kBundlePolicyBalanced;
-    configuration.audio_jitter_buffer_max_packets =
-        kAudioJitterBufferMaxPackets;
     Init(NULL, configuration);
   }
 
   void InitWithBundlePolicy(
       PeerConnectionInterface::BundlePolicy bundle_policy) {
     PeerConnectionInterface::RTCConfiguration configuration;
-    configuration.type = PeerConnectionInterface::kAll;
     configuration.bundle_policy = bundle_policy;
-    configuration.audio_jitter_buffer_max_packets =
-        kAudioJitterBufferMaxPackets;
+    Init(NULL, configuration);
+  }
+
+  void InitWithRtcpMuxPolicy(
+      PeerConnectionInterface::RtcpMuxPolicy rtcp_mux_policy) {
+    PeerConnectionInterface::RTCConfiguration configuration;
+    configuration.rtcp_mux_policy = rtcp_mux_policy;
     Init(NULL, configuration);
   }
 
@@ -438,11 +431,6 @@ class WebRtcSessionTest : public testing::Test {
     FakeIdentityService* identity_service = new FakeIdentityService();
     identity_service->set_should_fail(identity_request_should_fail);
     PeerConnectionInterface::RTCConfiguration configuration;
-    configuration.type = PeerConnectionInterface::kAll;
-    configuration.bundle_policy =
-        PeerConnectionInterface::kBundlePolicyBalanced;
-    configuration.audio_jitter_buffer_max_packets =
-        kAudioJitterBufferMaxPackets;
     Init(identity_service, configuration);
   }
 
@@ -2789,6 +2777,46 @@ TEST_F(WebRtcSessionTest, TestMaxBundleWithSetRemoteDescriptionFirst) {
             session_->GetTransportProxy("video")->impl());
 }
 
+TEST_F(WebRtcSessionTest, TestRequireRtcpMux) {
+  InitWithRtcpMuxPolicy(PeerConnectionInterface::kRtcpMuxPolicyRequire);
+  mediastream_signaling_.SendAudioVideoStream1();
+
+  PeerConnectionInterface::RTCOfferAnswerOptions options;
+  SessionDescriptionInterface* offer = CreateOffer(options);
+  SetLocalDescriptionWithoutError(offer);
+
+  EXPECT_FALSE(session_->GetTransportProxy("audio")->impl()->HasChannel(2));
+  EXPECT_FALSE(session_->GetTransportProxy("video")->impl()->HasChannel(2));
+
+  mediastream_signaling_.SendAudioVideoStream2();
+  SessionDescriptionInterface* answer =
+      CreateRemoteAnswer(session_->local_description());
+  SetRemoteDescriptionWithoutError(answer);
+
+  EXPECT_FALSE(session_->GetTransportProxy("audio")->impl()->HasChannel(2));
+  EXPECT_FALSE(session_->GetTransportProxy("video")->impl()->HasChannel(2));
+}
+
+TEST_F(WebRtcSessionTest, TestNegotiateRtcpMux) {
+  InitWithRtcpMuxPolicy(PeerConnectionInterface::kRtcpMuxPolicyNegotiate);
+  mediastream_signaling_.SendAudioVideoStream1();
+
+  PeerConnectionInterface::RTCOfferAnswerOptions options;
+  SessionDescriptionInterface* offer = CreateOffer(options);
+  SetLocalDescriptionWithoutError(offer);
+
+  EXPECT_TRUE(session_->GetTransportProxy("audio")->impl()->HasChannel(2));
+  EXPECT_TRUE(session_->GetTransportProxy("video")->impl()->HasChannel(2));
+
+  mediastream_signaling_.SendAudioVideoStream2();
+  SessionDescriptionInterface* answer =
+      CreateRemoteAnswer(session_->local_description());
+  SetRemoteDescriptionWithoutError(answer);
+
+  EXPECT_FALSE(session_->GetTransportProxy("audio")->impl()->HasChannel(2));
+  EXPECT_FALSE(session_->GetTransportProxy("video")->impl()->HasChannel(2));
+}
+
 // This test verifies that SetLocalDescription and SetRemoteDescription fails
 // if BUNDLE is enabled but rtcp-mux is disabled in m-lines.
 TEST_F(WebRtcSessionTest, TestDisabledRtcpMuxWithBundleEnabled) {

talk/session/media/channel.cc

@@ -1042,6 +1042,18 @@ bool BaseChannel::SetSrtp_w(const std::vector<CryptoParams>& cryptos,
   return true;
 }
 
+void BaseChannel::ActivateRtcpMux() {
+  worker_thread_->Invoke<void>(Bind(
+      &BaseChannel::ActivateRtcpMux_w, this));
+}
+
+void BaseChannel::ActivateRtcpMux_w() {
+  if (!rtcp_mux_filter_.IsActive()) {
+    rtcp_mux_filter_.SetActive();
+    set_rtcp_transport_channel(NULL);
+  }
+}
+
 bool BaseChannel::SetRtcpMux_w(bool enable, ContentAction action,
                                ContentSource src,
                                std::string* error_desc) {

talk/session/media/channel.h

@@ -108,6 +108,11 @@ class BaseChannel
   bool writable() const { return writable_; }
   bool IsStreamMuted(uint32 ssrc);
 
+  // Activate RTCP mux, regardless of the state so far.  Once
+  // activated, it can not be deactivated, and if the remote
+  // description doesn't support RTCP mux, setting the remote
+  // description will fail.
+  void ActivateRtcpMux();
   bool PushdownLocalDescription(const SessionDescription* local_desc,
                                 ContentAction action,
                                 std::string* error_desc);
@@ -350,6 +355,7 @@ class BaseChannel
                  ContentAction action,
                  ContentSource src,
                  std::string* error_desc);
+  void ActivateRtcpMux_w();
   bool SetRtcpMux_w(bool enable,
                     ContentAction action,
                     ContentSource src,

talk/session/media/channel_unittest.cc

@@ -1140,6 +1140,89 @@ class ChannelTest : public testing::Test, public sigslot::has_slots<> {
     EXPECT_TRUE(CheckNoRtcp2());
   }
 
+  // Check that RTP and RTCP are transmitted ok when both sides
+  // support mux and one the offerer requires mux.
+  void SendRequireRtcpMuxToRtcpMux() {
+    CreateChannels(RTCP | RTCP_MUX, RTCP | RTCP_MUX);
+    channel1_->ActivateRtcpMux();
+    EXPECT_TRUE(SendInitiate());
+    EXPECT_EQ(1U, GetTransport1()->channels().size());
+    EXPECT_EQ(1U, GetTransport2()->channels().size());
+    EXPECT_TRUE(SendAccept());
+    EXPECT_TRUE(SendRtp1());
+    EXPECT_TRUE(SendRtp2());
+    EXPECT_TRUE(SendRtcp1());
+    EXPECT_TRUE(SendRtcp2());
+    EXPECT_TRUE(CheckRtp1());
+    EXPECT_TRUE(CheckRtp2());
+    EXPECT_TRUE(CheckNoRtp1());
+    EXPECT_TRUE(CheckNoRtp2());
+    EXPECT_TRUE(CheckRtcp1());
+    EXPECT_TRUE(CheckRtcp2());
+    EXPECT_TRUE(CheckNoRtcp1());
+    EXPECT_TRUE(CheckNoRtcp2());
+  }
+
+  // Check that RTP and RTCP are transmitted ok when both sides
+  // support mux and one the answerer requires rtcp mux.
+  void SendRtcpMuxToRequireRtcpMux() {
+    CreateChannels(RTCP | RTCP_MUX, RTCP | RTCP_MUX);
+    channel2_->ActivateRtcpMux();
+    EXPECT_TRUE(SendInitiate());
+    EXPECT_EQ(2U, GetTransport1()->channels().size());
+    EXPECT_EQ(1U, GetTransport2()->channels().size());
+    EXPECT_TRUE(SendAccept());
+    EXPECT_EQ(1U, GetTransport1()->channels().size());
+    EXPECT_TRUE(SendRtp1());
+    EXPECT_TRUE(SendRtp2());
+    EXPECT_TRUE(SendRtcp1());
+    EXPECT_TRUE(SendRtcp2());
+    EXPECT_TRUE(CheckRtp1());
+    EXPECT_TRUE(CheckRtp2());
+    EXPECT_TRUE(CheckNoRtp1());
+    EXPECT_TRUE(CheckNoRtp2());
+    EXPECT_TRUE(CheckRtcp1());
+    EXPECT_TRUE(CheckRtcp2());
+    EXPECT_TRUE(CheckNoRtcp1());
+    EXPECT_TRUE(CheckNoRtcp2());
+  }
+
+  // Check that RTP and RTCP are transmitted ok when both sides
+  // require mux.
+  void SendRequireRtcpMuxToRequireRtcpMux() {
+    CreateChannels(RTCP | RTCP_MUX, RTCP | RTCP_MUX);
+    channel1_->ActivateRtcpMux();
+    channel2_->ActivateRtcpMux();
+    EXPECT_TRUE(SendInitiate());
+    EXPECT_EQ(1U, GetTransport1()->channels().size());
+    EXPECT_EQ(1U, GetTransport2()->channels().size());
+    EXPECT_TRUE(SendAccept());
+    EXPECT_EQ(1U, GetTransport1()->channels().size());
+    EXPECT_TRUE(SendRtp1());
+    EXPECT_TRUE(SendRtp2());
+    EXPECT_TRUE(SendRtcp1());
+    EXPECT_TRUE(SendRtcp2());
+    EXPECT_TRUE(CheckRtp1());
+    EXPECT_TRUE(CheckRtp2());
+    EXPECT_TRUE(CheckNoRtp1());
+    EXPECT_TRUE(CheckNoRtp2());
+    EXPECT_TRUE(CheckRtcp1());
+    EXPECT_TRUE(CheckRtcp2());
+    EXPECT_TRUE(CheckNoRtcp1());
+    EXPECT_TRUE(CheckNoRtcp2());
+  }
+
+  // Check that SendAccept fails if the answerer doesn't support mux
+  // and the offerer requires it.
+  void SendRequireRtcpMuxToNoRtcpMux() {
+    CreateChannels(RTCP | RTCP_MUX, RTCP);
+    channel1_->ActivateRtcpMux();
+    EXPECT_TRUE(SendInitiate());
+    EXPECT_EQ(1U, GetTransport1()->channels().size());
+    EXPECT_EQ(2U, GetTransport2()->channels().size());
+    EXPECT_FALSE(SendAccept());
+  }
+
   // Check that RTCP data sent by the initiator before the accept is not muxed.
   void SendEarlyRtcpMuxToRtcp() {
     CreateChannels(RTCP | RTCP_MUX, RTCP);
@@ -2085,6 +2168,22 @@ TEST_F(VoiceChannelTest, SendRtcpMuxToRtcpMux) {
   Base::SendRtcpMuxToRtcpMux();
 }
 
+TEST_F(VoiceChannelTest, SendRequireRtcpMuxToRtcpMux) {
+  Base::SendRequireRtcpMuxToRtcpMux();
+}
+
+TEST_F(VoiceChannelTest, SendRtcpMuxToRequireRtcpMux) {
+  Base::SendRtcpMuxToRequireRtcpMux();
+}
+
+TEST_F(VoiceChannelTest, SendRequireRtcpMuxToRequireRtcpMux) {
+  Base::SendRequireRtcpMuxToRequireRtcpMux();
+}
+
+TEST_F(VoiceChannelTest, SendRequireRtcpMuxToNoRtcpMux) {
+  Base::SendRequireRtcpMuxToNoRtcpMux();
+}
+
 TEST_F(VoiceChannelTest, SendEarlyRtcpMuxToRtcp) {
   Base::SendEarlyRtcpMuxToRtcp();
 }
@@ -2507,6 +2606,22 @@ TEST_F(VideoChannelTest, SendRtcpMuxToRtcpMux) {
   Base::SendRtcpMuxToRtcpMux();
 }
 
+TEST_F(VideoChannelTest, SendRequireRtcpMuxToRtcpMux) {
+  Base::SendRequireRtcpMuxToRtcpMux();
+}
+
+TEST_F(VideoChannelTest, SendRtcpMuxToRequireRtcpMux) {
+  Base::SendRtcpMuxToRequireRtcpMux();
+}
+
+TEST_F(VideoChannelTest, SendRequireRtcpMuxToRequireRtcpMux) {
+  Base::SendRequireRtcpMuxToRequireRtcpMux();
+}
+
+TEST_F(VideoChannelTest, SendRequireRtcpMuxToNoRtcpMux) {
+  Base::SendRequireRtcpMuxToNoRtcpMux();
+}
+
 TEST_F(VideoChannelTest, SendEarlyRtcpMuxToRtcp) {
   Base::SendEarlyRtcpMuxToRtcp();
 }

talk/session/media/rtcpmuxfilter.cc

@@ -40,7 +40,16 @@ bool RtcpMuxFilter::IsActive() const {
          state_ == ST_ACTIVE;
 }
 
+void RtcpMuxFilter::SetActive() {
+  state_ = ST_ACTIVE;
+}
+
 bool RtcpMuxFilter::SetOffer(bool offer_enable, ContentSource src) {
+  if (state_ == ST_ACTIVE) {
+    // Fail if we try to deactivate and no-op if we try and activate.
+    return offer_enable;
+  }
+
   if (!ExpectOffer(offer_enable, src)) {
     LOG(LS_ERROR) << "Invalid state for change of RTCP mux offer";
     return false;
@@ -53,6 +62,11 @@ bool RtcpMuxFilter::SetOffer(bool offer_enable, ContentSource src) {
 
 bool RtcpMuxFilter::SetProvisionalAnswer(bool answer_enable,
                                          ContentSource src) {
+  if (state_ == ST_ACTIVE) {
+    // Fail if we try to deactivate and no-op if we try and activate.
+    return answer_enable;
+  }
+
   if (!ExpectAnswer(src)) {
     LOG(LS_ERROR) << "Invalid state for RTCP mux provisional answer";
     return false;
@@ -83,6 +97,11 @@ bool RtcpMuxFilter::SetProvisionalAnswer(bool answer_enable,
 }
 
 bool RtcpMuxFilter::SetAnswer(bool answer_enable, ContentSource src) {
+  if (state_ == ST_ACTIVE) {
+    // Fail if we try to deactivate and no-op if we try and activate.
+    return answer_enable;
+  }
+
   if (!ExpectAnswer(src)) {
     LOG(LS_ERROR) << "Invalid state for RTCP mux answer";
     return false;
@@ -100,19 +119,24 @@ bool RtcpMuxFilter::SetAnswer(bool answer_enable, ContentSource src) {
   return true;
 }
 
-bool RtcpMuxFilter::DemuxRtcp(const char* data, int len) {
-  // If we're muxing RTP/RTCP, we must inspect each packet delivered and
-  // determine whether it is RTP or RTCP. We do so by checking the packet type,
-  // and assuming RTP if type is 0-63 or 96-127. For additional details, see
-  // http://tools.ietf.org/html/rfc5761.
-  // Note that if we offer RTCP mux, we may receive muxed RTCP before we
-  // receive the answer, so we operate in that state too.
-  if (!offer_enable_ || state_ < ST_SENTOFFER) {
+// Check the RTP payload type.  If 63 < payload type < 96, it's RTCP.
+// For additional details, see http://tools.ietf.org/html/rfc5761.
+bool IsRtcp(const char* data, int len) {
+  if (len < 2) {
     return false;
   }
+  char pt = data[1] & 0x7F;
+  return (63 < pt) && (pt < 96);
+}
 
-  int type = (len >= 2) ? (static_cast<uint8>(data[1]) & 0x7F) : 0;
-  return (type >= 64 && type < 96);
+bool RtcpMuxFilter::DemuxRtcp(const char* data, int len) {
+  // If we're muxing RTP/RTCP, we must inspect each packet delivered
+  // and determine whether it is RTP or RTCP. We do so by looking at
+  // the RTP payload type (see IsRtcp).  Note that if we offer RTCP
+  // mux, we may receive muxed RTCP before we receive the answer, so
+  // we operate in that state too.
+  bool offered_mux = ((state_ == ST_SENTOFFER) && offer_enable_);
+  return (IsActive() || offered_mux) && IsRtcp(data, len);
 }
 
 bool RtcpMuxFilter::ExpectOffer(bool offer_enable, ContentSource source) {

talk/session/media/rtcpmuxfilter.h

@@ -41,6 +41,9 @@ class RtcpMuxFilter {
   // Whether the filter is active, i.e. has RTCP mux been properly negotiated.
   bool IsActive() const;
 
+  // Make the filter active, regardless of the current state.
+  void SetActive();
+
   // Specifies whether the offer indicates the use of RTCP mux.
   bool SetOffer(bool offer_enable, ContentSource src);
 

talk/session/media/rtcpmuxfilter_unittest.cc

@@ -212,3 +212,44 @@ TEST(RtcpMuxFilterTest, KeepFilterDisabledDuringUpdate) {
   EXPECT_TRUE(filter.SetAnswer(false, cricket::CS_LOCAL));
   EXPECT_FALSE(filter.IsActive());
 }
+
+// Test that we can SetActive and then can't deactivate.
+TEST(RtcpMuxFilterTest, SetActiveCantDeactivate) {
+  cricket::RtcpMuxFilter filter;
+  const char data[] = { 0, 73, 0, 0 };
+  const int len = 4;
+
+  filter.SetActive();
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.DemuxRtcp(data, len));
+
+  EXPECT_FALSE(filter.SetOffer(false, cricket::CS_LOCAL));
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.SetOffer(true, cricket::CS_LOCAL));
+  EXPECT_TRUE(filter.IsActive());
+
+  EXPECT_FALSE(filter.SetProvisionalAnswer(false, cricket::CS_REMOTE));
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.SetProvisionalAnswer(true, cricket::CS_REMOTE));
+  EXPECT_TRUE(filter.IsActive());
+
+  EXPECT_FALSE(filter.SetAnswer(false, cricket::CS_REMOTE));
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.SetAnswer(true, cricket::CS_REMOTE));
+  EXPECT_TRUE(filter.IsActive());
+
+  EXPECT_FALSE(filter.SetOffer(false, cricket::CS_REMOTE));
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.SetOffer(true, cricket::CS_REMOTE));
+  EXPECT_TRUE(filter.IsActive());
+
+  EXPECT_FALSE(filter.SetProvisionalAnswer(false, cricket::CS_LOCAL));
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.SetProvisionalAnswer(true, cricket::CS_LOCAL));
+  EXPECT_TRUE(filter.IsActive());
+
+  EXPECT_FALSE(filter.SetAnswer(false, cricket::CS_LOCAL));
+  EXPECT_TRUE(filter.IsActive());
+  EXPECT_TRUE(filter.SetAnswer(true, cricket::CS_LOCAL));
+  EXPECT_TRUE(filter.IsActive());
+}