Getting rid of "benign blocking error" log spam.

webrtc/base/physicalsocketserver.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #include "webrtc/base/physicalsocketserver.h"
@@ skipping 671 matching lines @@
 
 int SocketDispatcher::next_id_ = 0;
 
 #elif defined(WEBRTC_POSIX)
 
 int SocketDispatcher::GetDescriptor() {
   return s_;
 }
 
 bool SocketDispatcher::IsDescriptorClosed() {
+  if (udp_) {
+    // The MSG_PEEK trick doesn't work for UDP, since (at least in some
+    // circumstances) it requires reading an entire UDP packet, which would be
+    // bad for performance here. So, just check whether |s_| has been closed,
+    // which should be sufficient.
+    return s_ == INVALID_SOCKET;
+  }
   // We don't have a reliable way of distinguishing end-of-stream
   // from readability.  So test on each readable call.  Is this
   // inefficient?  Probably.
   char ch;
   ssize_t res = ::recv(s_, &ch, 1, MSG_PEEK);
   if (res > 0) {
     // Data available, so not closed.
     return false;
   } else if (res == 0) {
     // EOF, so closed.
     return true;
   } else {  // error
     switch (errno) {
       // Returned if we've already closed s_.
       case EBADF:
       // Returned during ungraceful peer shutdown.
       case ECONNRESET:
         return true;
+      // The normal blocking error; don't log anything.
+      case EWOULDBLOCK:
+      // Interrupted system call.
+      case EINTR:
+        return false;
       default:
         // Assume that all other errors are just blocking errors, meaning the
         // connection is still good but we just can't read from it right now.
         // This should only happen when connecting (and at most once), because
         // in all other cases this function is only called if the file
         // descriptor is already known to be in the readable state. However,
         // it's not necessary a problem if we spuriously interpret a
         // "connection lost"-type error as a blocking error, because typically
         // the next recv() will get EOF, so we'll still eventually notice that
         // the socket is closed.
@@ skipping 879 matching lines @@
        break;
     }
   }
 
   // Done
   return true;
 }
 #endif  // WEBRTC_WIN
 
 }  // namespace rtc