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..2cbaf6233d65ea89357424ce465a2b99ee81b6de 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.
+static const int kSendBufferSize = 262144;

[pthatcher1, 2015/08/18 21:51:52]

Can you comment on how this number was chosen?

[lally1, 2015/08/24 15:46:39]

Done.

 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);
     }
@@ -258,6 +260,11 @@ 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
@@ -315,6 +322,9 @@ DataMediaChannel* SctpDataEngine::CreateChannel(
   return new SctpDataMediaChannel(rtc::Thread::Current());
 }
 
+// Our registrar of sockets to their channels.  Used for callbacks.
+std::vector<SctpDataMediaChannel*> SctpDataMediaChannel::sock_channel_map_;

[pthatcher1, 2015/08/18 21:51:52]

Since it's not a map anymore, perhaps channels_ would make more sense as a name?

[lally1, 2015/08/24 15:46:39]

Done.

+
 SctpDataMediaChannel::SctpDataMediaChannel(rtc::Thread* thread)
     : worker_thread_(thread),
       local_port_(kSctpDefaultPort),
@@ -323,10 +333,19 @@ SctpDataMediaChannel::SctpDataMediaChannel(rtc::Thread* thread)
       sending_(false),
       receiving_(false),
       debug_name_("SctpDataMediaChannel") {
+  sock_channel_map_.push_back(this);
 }
 
 SctpDataMediaChannel::~SctpDataMediaChannel() {
   CloseSctpSocket();
+  auto it = std::find(sock_channel_map_.begin(),
+                      sock_channel_map_.end(),
+                      this);
+  if (it != sock_channel_map_.end()) {
+    sock_channel_map_.erase(it);
+  } else {
+    LOG(LS_ERROR) << "~SctpDataMediaChannel: the channel wasn't registered.";
+  }

[pthatcher1, 2015/08/18 21:51:53]

An early return might look a little better:

if (it == end()) {
  LOG(LS_ERROR) << "~SctpDataMediaChannel: the channel wasn't registered.";
  return;
}
erase(it);

[lally1, 2015/08/24 15:46:39]

Done, in OnChannelDestroyed(), where this code was moved.

 }
 
 sockaddr_conn SctpDataMediaChannel::GetSctpSockAddr(int port) {
@@ -341,14 +360,36 @@ sockaddr_conn SctpDataMediaChannel::GetSctpSockAddr(int port) {
   return sconn;
 }
 
+// static
+int SctpDataMediaChannel::SendThresholdCallback(struct socket* sock,
+                                                uint32_t sb_free) {
+  for (auto p:sock_channel_map_) {
+    if (p->socket() == sock) {

[pthatcher1, 2015/08/18 21:51:52]

Did you mean to put this in GetSctpChannel?

[lally1, 2015/08/24 15:46:39]

I took that method out.  Did you want it back in?

+      p->SignalReadyToSend(true);
+      return 0;
+    }
+  }
+  LOG(LS_ERROR) << "SendThresholdCallback: Failed to get channel for socket "
+                << sock;
+  return 0;
+}
+
 bool SctpDataMediaChannel::OpenSctpSocket() {
   if (sock_) {
     LOG(LS_VERBOSE) << debug_name_
                     << "->Ignoring attempt to re-create existing socket.";
     return false;
   }
+
+  // kSendBufferSize is our expected default buffer size.  If it isn't
+  // reflective of reality we'll log an error, but we still have to do
+  // something reasonable here.

[pthatcher1, 2015/08/18 21:51:52]

This comment looks like it belongs up by where kSendBufferSize is used.  Did you
mean to put it there?

[lally1, 2015/08/24 15:46:39]

No I just wrote it poorly.  Rewritten.

+  const 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,
+                         &SctpDataMediaChannel::SendThresholdCallback,
+                         send_threshold, this);
   if (!sock_) {
     LOG_ERRNO(LS_ERROR) << debug_name_ << "Failed to create SCTP socket.";
     return false;
@@ -393,7 +434,8 @@ 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 +946,17 @@ 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);
 }