Added send-thresholding and fixed text packet dumping.

talk/media/sctp/sctpdataengine.cc

Index: talk/media/sctp/sctpdataengine.cc
diff --git a/talk/media/sctp/sctpdataengine.cc b/talk/media/sctp/sctpdataengine.cc
index 8c8a6a192fa25833c3de66c0587b9ed7ed3bccb3..4274012245a62a9e80d00f8b7a9aa0860d97469e 100644
--- a/talk/media/sctp/sctpdataengine.cc
+++ b/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 +246,8 @@ 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;
+// Our registrar of sockets to their channels.  Used for callbacks.

[pthatcher1, 2015/08/24 19:09:31]

This might be more clear as "All the channels created by this engine, used for
callbacks from usrsctplib that only contain socket pointers.  Channels are
removed when SignalDestroyed is fired."

[lally1, 2015/08/25 16:01:56]

Done.

+std::vector<SctpDataMediaChannel*> SctpDataEngine::channels_;
 
 SctpDataEngine::SctpDataEngine() {
   if (usrsctp_engines_count == 0) {
@@ -258,6 +262,11 @@ 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 +321,37 @@ 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;
 }
 
+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

[pthatcher1, 2015/08/24 19:09:31]

Is it really static?

[lally1, 2015/08/25 16:01:56]

Yup.

+int SctpDataEngine::SendThresholdCallback(struct socket* sock,
+                                          uint32_t sb_free) {
+  for (auto p:channels_) {
+    if (p->socket() == sock) {
+      p->SignalReadyToSend(true);
+      return 0;
+    }

[pthatcher1, 2015/08/24 19:09:31]

Would a GetChannelFromSocket method make sense?

[lally1, 2015/08/25 16:01:56]

I added it in.  Whether it makes sense: it feels like better practice, even
though it adds no utility here.

+  }
+  LOG(LS_ERROR) << "SendThresholdCallback: Failed to get channel for socket "
+                << sock;
+  return 0;
+}
+
+
 SctpDataMediaChannel::SctpDataMediaChannel(rtc::Thread* thread)
     : worker_thread_(thread),
       local_port_(kSctpDefaultPort),
@@ -327,6 +364,7 @@ SctpDataMediaChannel::SctpDataMediaChannel(rtc::Thread* thread)
 
 SctpDataMediaChannel::~SctpDataMediaChannel() {
   CloseSctpSocket();
+  SignalDestroyed(this);
 }
 
 sockaddr_conn SctpDataMediaChannel::GetSctpSockAddr(int port) {
@@ -347,8 +385,16 @@ bool SctpDataMediaChannel::OpenSctpSocket() {
                     << "->Ignoring attempt to re-create existing socket.";
     return false;
   }
+
+  // If kSendBufferSize isn't reflective of reality, we log an error, still

[pthatcher1, 2015/08/24 19:09:31]

still => but we still

?

[lally1, 2015/08/25 16:01:56]

Done.

+  // 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 +439,8 @@ 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 +951,17 @@ 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);
 }