Added send-thresholding and fixed text packet dumping. Also a little squelch for the over-max-MTU log spam we see in there.

BUG=https://code.google.com/p/webrtc/issues/detail?id=4468
R=pthatcher@chromium.org, pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1266033005 .

Cr-Commit-Position: refs/heads/master@{#9788}

talk/media/sctp/sctpdataengine.cc

@@ -109,6 +109,8 @@ typedef rtc::ScopedMessageData<rtc::Buffer> OutboundPacketMessage;
 // take off 80 bytes for DTLS/TURN/TCP/IP overhead.
 static const size_t kSctpMtu = 1200;
 
+// The size of the SCTP association send buffer.  256kB, the usrsctp default.
+static const int kSendBufferSize = 262144;
 enum {
   MSG_SCTPINBOUNDPACKET = 1,   // MessageData is SctpInboundPacket
   MSG_SCTPOUTBOUNDPACKET = 2,  // MessageData is rtc:Buffer
@@ -177,11 +179,11 @@ static bool GetDataMediaType(
 }
 
 // Log the packet in text2pcap format, if log level is at LS_VERBOSE.
-static void VerboseLogPacket(void *addr, size_t length, int direction) {
+static void VerboseLogPacket(void *data, size_t length, int direction) {
   if (LOG_CHECK_LEVEL(LS_VERBOSE) && length > 0) {
     char *dump_buf;
     if ((dump_buf = usrsctp_dumppacket(
-             addr, length, direction)) != NULL) {
+             data, length, direction)) != NULL) {
       LOG(LS_VERBOSE) << dump_buf;
       usrsctp_freedumpbuffer(dump_buf);
     }
@@ -244,6 +246,10 @@ static int OnSctpInboundPacket(struct socket* sock, union sctp_sockstore addr,
 
 // Set the initial value of the static SCTP Data Engines reference count.
 int SctpDataEngine::usrsctp_engines_count = 0;
+// All the channels created by this engine, used for callbacks from
+// usrsctplib that only contain socket pointers.  Channels are removed when
+// SignalDestroyed is fired.
+std::vector<SctpDataMediaChannel*> SctpDataEngine::channels_;
 
 SctpDataEngine::SctpDataEngine() {
   if (usrsctp_engines_count == 0) {
@@ -258,6 +264,11 @@ SctpDataEngine::SctpDataEngine() {
     // TODO(ldixon): Consider turning this on/off.
     usrsctp_sysctl_set_sctp_ecn_enable(0);
 
+    int send_size = usrsctp_sysctl_get_sctp_sendspace();
+    if (send_size != kSendBufferSize) {
+      LOG(LS_ERROR) << "Got different send size than expected: " << send_size;
+    }
+
     // TODO(ldixon): Consider turning this on/off.
     // This is not needed right now (we don't do dynamic address changes):
     // If SCTP Auto-ASCONF is enabled, the peer is informed automatically
@@ -312,9 +323,48 @@ DataMediaChannel* SctpDataEngine::CreateChannel(
   if (data_channel_type != DCT_SCTP) {
     return NULL;
   }
-  return new SctpDataMediaChannel(rtc::Thread::Current());
+  SctpDataMediaChannel *channel = new SctpDataMediaChannel(
+      rtc::Thread::Current());
+  channels_.push_back(channel);
+  channel->SignalDestroyed.connect(this, &SctpDataEngine::OnChannelDestroyed);
+  return channel;
 }
 
+// static
+SctpDataMediaChannel* SctpDataEngine::GetChannelFromSocket(
+    struct socket* sock) {
+  for (auto p:channels_) {
+    if (p->socket() == sock) {
+      return p;
+    }
+  }
+  return 0;
+}
+
+
+void SctpDataEngine::OnChannelDestroyed(SctpDataMediaChannel* channel) {
+  auto it = std::find(channels_.begin(), channels_.end(), channel);
+  if (it == channels_.end()) {
+    LOG(LS_ERROR) << "OnChannelDestroyed: the channel wasn't registered.";
+    return;
+  }
+  channels_.erase(it);
+}
+
+// static
+int SctpDataEngine::SendThresholdCallback(struct socket* sock,
+                                          uint32_t sb_free) {
+  SctpDataMediaChannel *channel = GetChannelFromSocket(sock);
+  if (!channel) {
+    LOG(LS_ERROR) << "SendThresholdCallback: Failed to get channel for socket "
+                  << sock;
+    return 0;
+  }
+  channel->SignalReadyToSend(true);
+  return 0;
+}
+
+
 SctpDataMediaChannel::SctpDataMediaChannel(rtc::Thread* thread)
     : worker_thread_(thread),
       local_port_(kSctpDefaultPort),
@@ -327,6 +377,7 @@ SctpDataMediaChannel::SctpDataMediaChannel(rtc::Thread* thread)
 
 SctpDataMediaChannel::~SctpDataMediaChannel() {
   CloseSctpSocket();
+  SignalDestroyed(this);
 }
 
 sockaddr_conn SctpDataMediaChannel::GetSctpSockAddr(int port) {
@@ -347,8 +398,16 @@ bool SctpDataMediaChannel::OpenSctpSocket() {
                     << "->Ignoring attempt to re-create existing socket.";
     return false;
   }
+
+  // If kSendBufferSize isn't reflective of reality, we log an error, but we
+  // still have to do something reasonable here.  Look up what the buffer's
+  // real size is and set our threshold to something reasonable.
+  const static int send_threshold = usrsctp_sysctl_get_sctp_sendspace() / 2;
+
   sock_ = usrsctp_socket(AF_CONN, SOCK_STREAM, IPPROTO_SCTP,
-                         cricket::OnSctpInboundPacket, NULL, 0, this);
+                         cricket::OnSctpInboundPacket,
+                         &SctpDataEngine::SendThresholdCallback,
+                         send_threshold, this);
   if (!sock_) {
     LOG_ERRNO(LS_ERROR) << debug_name_ << "Failed to create SCTP socket.";
     return false;
@@ -393,7 +452,8 @@ bool SctpDataMediaChannel::OpenSctpSocket() {
   }
 
   // Disable MTU discovery
-  struct sctp_paddrparams params = {{0}};
+  struct sctp_paddrparams params;
+  memset(&params, 0, sizeof(params));
   params.spp_assoc_id = 0;
   params.spp_flags = SPP_PMTUD_DISABLE;
   params.spp_pathmtu = kSctpMtu;
@@ -904,10 +964,17 @@ bool SctpDataMediaChannel::SetRecvCodecs(const std::vector<DataCodec>& codecs) {
 
 void SctpDataMediaChannel::OnPacketFromSctpToNetwork(
     rtc::Buffer* buffer) {
-  if (buffer->size() > kSctpMtu) {
+  // usrsctp seems to interpret the MTU we give it strangely -- it seems to
+  // give us back packets bigger than that MTU, if only by a fixed amount.
+  // This is that amount that we've observed.
+  const int kSctpOverhead = 76;
+  if (buffer->size() > (kSctpOverhead + kSctpMtu)) {
     LOG(LS_ERROR) << debug_name_ << "->OnPacketFromSctpToNetwork(...): "
                   << "SCTP seems to have made a packet that is bigger "
-                     "than its official MTU.";
+                  << "than its official MTU: " << buffer->size()
+                  << " vs max of " << kSctpMtu
+                  << " even after adding " << kSctpOverhead
+                  << " extra SCTP overhead";
   }
   MediaChannel::SendPacket(buffer);
 }

talk/media/sctp/sctpdataengine.h

@@ -64,6 +64,8 @@ const uint32 kMaxSctpSid = 1023;
 // usrsctp.h)
 const int kSctpDefaultPort = 5000;
 
+class SctpDataMediaChannel;
+
 // A DataEngine that interacts with usrsctp.
 //
 // From channel calls, data flows like this:
@@ -88,7 +90,7 @@ const int kSctpDefaultPort = 5000;
 //  14. SctpDataMediaChannel::SignalDataReceived(data)
 // [from the same thread, methods registered/connected to
 //  SctpDataMediaChannel are called with the recieved data]
-class SctpDataEngine : public DataEngineInterface {
+class SctpDataEngine : public DataEngineInterface, public sigslot::has_slots<> {
  public:
   SctpDataEngine();
   virtual ~SctpDataEngine();
@@ -97,9 +99,15 @@ class SctpDataEngine : public DataEngineInterface {
 
   virtual const std::vector<DataCodec>& data_codecs() { return codecs_; }
 
+  static int SendThresholdCallback(struct socket* sock, uint32_t sb_free);
+
  private:
+  static std::vector<SctpDataMediaChannel*> channels_;
   static int usrsctp_engines_count;
   std::vector<DataCodec> codecs_;
+
+  static SctpDataMediaChannel* GetChannelFromSocket(struct socket* sock);
+  void OnChannelDestroyed(SctpDataMediaChannel *channel);
 };
 
 // TODO(ldixon): Make into a special type of TypedMessageData.
@@ -188,6 +196,9 @@ class SctpDataMediaChannel : public DataMediaChannel,
     debug_name_ = debug_name;
   }
   const std::string& debug_name() const { return debug_name_; }
+  const struct socket* socket() { return sock_; }
+
+  sigslot::signal1<SctpDataMediaChannel*> SignalDestroyed;
 
  private:
   sockaddr_conn GetSctpSockAddr(int port);

talk/media/sctp/sctpdataengine_unittest.cc

@@ -240,10 +240,16 @@ class SctpDataMediaChannelTest : public testing::Test,
     net2_.reset(new SctpFakeNetworkInterface(rtc::Thread::Current()));
     recv1_.reset(new SctpFakeDataReceiver());
     recv2_.reset(new SctpFakeDataReceiver());
+    chan1_ready_to_send_count_ = 0;
+    chan2_ready_to_send_count_ = 0;
     chan1_.reset(CreateChannel(net1_.get(), recv1_.get()));
     chan1_->set_debug_name("chan1/connector");
+    chan1_->SignalReadyToSend.connect(
+        this, &SctpDataMediaChannelTest::OnChan1ReadyToSend);
     chan2_.reset(CreateChannel(net2_.get(), recv2_.get()));
     chan2_->set_debug_name("chan2/listener");
+    chan2_->SignalReadyToSend.connect(
+        this, &SctpDataMediaChannelTest::OnChan2ReadyToSend);
     // Setup two connected channels ready to send and receive.
     net1_->SetDestination(chan2_.get());
     net2_->SetDestination(chan1_.get());
@@ -330,6 +336,8 @@ class SctpDataMediaChannelTest : public testing::Test,
   SctpFakeDataReceiver* receiver1() { return recv1_.get(); }
   SctpFakeDataReceiver* receiver2() { return recv2_.get(); }
 
+  int channel1_ready_to_send_count() { return chan1_ready_to_send_count_; }
+  int channel2_ready_to_send_count() { return chan2_ready_to_send_count_; }
  private:
   rtc::scoped_ptr<cricket::SctpDataEngine> engine_;
   rtc::scoped_ptr<SctpFakeNetworkInterface> net1_;
@@ -338,6 +346,12 @@ class SctpDataMediaChannelTest : public testing::Test,
   rtc::scoped_ptr<SctpFakeDataReceiver> recv2_;
   rtc::scoped_ptr<cricket::SctpDataMediaChannel> chan1_;
   rtc::scoped_ptr<cricket::SctpDataMediaChannel> chan2_;
+
+  int chan1_ready_to_send_count_;
+  int chan2_ready_to_send_count_;
+
+  void OnChan1ReadyToSend(bool send) { if (send) chan1_ready_to_send_count_++; }
+  void OnChan2ReadyToSend(bool send) { if (send) chan2_ready_to_send_count_++; }
 };
 
 // Verifies that SignalReadyToSend is fired.
@@ -486,6 +500,15 @@ TEST_F(SctpDataMediaChannelTest, ClosesStreamsOnBothSides) {
   EXPECT_TRUE_WAIT(chan_1_sig_receiver.WasStreamClosed(4), 1000);
 }
 
+TEST_F(SctpDataMediaChannelTest, EngineSignalsRightChannel) {
+  SetupConnectedChannels();
+  EXPECT_TRUE_WAIT(channel1()->socket() != NULL, 1000);
+  struct socket *sock = const_cast<struct socket*>(channel1()->socket());
+  int prior_count = channel1_ready_to_send_count();
+  cricket::SctpDataEngine::SendThresholdCallback(sock, 0);
+  EXPECT_GT(channel1_ready_to_send_count(), prior_count);
+}
+
 // Flaky on Linux and Windows. See webrtc:4453.
 #if defined(WEBRTC_WIN) || defined(WEBRTC_LINUX)
 #define MAYBE_ReusesAStream DISABLED_ReusesAStream