RTP out: improve soft-error handling

When the socket is congested, we should simply skip sending.
When there is a soft-error, we should resend and simply ignore.

Instead, we were dropping the socket if the failure remained on the
second try, which was always the case in the congestion scenario.
This should fix the socket dropping problem described at:
http://forum.videolan.org/viewtopic.php?f=4&t=56493

modules/stream_out/rtp.c

@@ -1468,6 +1468,17 @@ static int  HttpCallback( httpd_file_sys_t *p_args,
  ****************************************************************************/
 static void* ThreadSend( vlc_object_t *p_this )
 {
+#ifdef WIN32
+# define ECONNREFUSED WSAECONNREFUSED
+# define ENOPROTOOPT  WSAENOPROTOOPT
+# define EPROTO       WSAEPROTO
+# define EHOSTUNREACH WSAEHOSTUNREACH
+# define ENETUNREACH  WSAEHOSTUNREACH
+# define ENETDOWN     WSAENETDOWN
+# define ENOBUFS      WSAENOBUFS
+# define EAGAIN       WSAEGAIN
+# define EWOULDBLOCK  WSAEWOULDBLOCK
+#endif
     sout_stream_id_t *id = (sout_stream_id_t *)p_this;
     unsigned i_caching = id->i_caching;
 
@@ -1516,9 +1527,25 @@ static void* ThreadSend( vlc_object_t *p_this )
 
             if( send( id->sinkv[i].rtp_fd, out->p_buffer, len, 0 ) >= 0 )
                 continue;
-            /* Retry sending to root out soft-errors */
-            if( send( id->sinkv[i].rtp_fd, out->p_buffer, len, 0 ) >= 0 )
-                continue;
+            switch( net_errno )
+            {
+                /* Soft errors (e.g. ICMP): */
+                case ECONNREFUSED: /* Port unreachable */
+                case ENOPROTOOPT:
+                case EPROTO:       /* Protocol unreachable */
+                case EHOSTUNREACH: /* Host unreachable */
+                case ENETUNREACH:  /* Network unreachable */
+                case ENETDOWN:     /* Entire network down */
+                    send( id->sinkv[i].rtp_fd, out->p_buffer, len, 0 );
+                /* Transient congestion: */
+                case ENOMEM: /* out of socket buffers */
+                case ENOBUFS:
+                case EAGAIN:
+#if (EAGAIN != EWOULDBLOCK)
+                case EWOULDBLOCK:
+#endif
+                    continue;
+            }
 
             deadv[deadc++] = id->sinkv[i].rtp_fd;
         }