Added send-thresholding and fixed text packet dumping.

talk/media/sctp/sctpdataengine.h

Index: talk/media/sctp/sctpdataengine.h
diff --git a/talk/media/sctp/sctpdataengine.h b/talk/media/sctp/sctpdataengine.h
index 86bfa37a48c10dca4c3f5b0cad9a330d27aea10e..d72a1003f405d927bb8d043b80fb996e1347416a 100644
--- a/talk/media/sctp/sctpdataengine.h
+++ b/talk/media/sctp/sctpdataengine.h
@@ -29,6 +29,7 @@
 #define TALK_MEDIA_SCTP_SCTPDATAENGINE_H_
 
 #include <errno.h>
+#include <map>
 #include <string>
 #include <vector>
 
@@ -190,6 +191,13 @@ class SctpDataMediaChannel : public DataMediaChannel,
   const std::string& debug_name() const { return debug_name_; }
 
  private:
+  // Maps sockets back to their SctpDataMediaChannels.  For usrsctp
+  // send-threshold callbacks, we only get the socket* on invocation, but
+  // need to find the SctpDataMediaChannels.  We can get that through the
+  // library, but would cost us an allocation/free each time the callback is
+  // invoked.
+  typedef std::map<struct socket*, SctpDataMediaChannel*> SocketChannelMap;
+  static SocketChannelMap sock_channel_map_;

[pthatcher1, 2015/08/05 21:42:55]

Instead of being a static member of the SctpDataMediaChannel, I think it would
be cleaner to make this a member of SctpDataMediaEngine.  

[lally1, 2015/08/18 20:38:56]

That makes a lot of sense, but the SctpDataMediaChannel doesn't have an instance
pointer back to the SctpDataMediaEngine.  I think we'd need it to notify
SctpDataMediaEngine when the Channel's being destroyed.  We could certainly pass
one in construction.  Is it worth it?

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

We could add SctpDataMediaChannel::SignalDestroyed that fires in the destructor,
and the MediaEngine could listen to that and remove it from the collection.  We
use a this pattern in other places in our code.  Down underneath, that is a
pointer back, but in a cleaner way.

   sockaddr_conn GetSctpSockAddr(int port);
 
   // Creates the socket and connects. Sets sending_ to true.
@@ -222,6 +230,8 @@ class SctpDataMediaChannel : public DataMediaChannel,
 
   void OnStreamResetEvent(const struct sctp_stream_reset_event* evt);
 
+  static int SendThresholdCallback(struct socket* sock, uint32_t sb_free);
+
   // Responsible for marshalling incoming data to the channels listeners, and
   // outgoing data to the network interface.
   rtc::Thread* worker_thread_;