Allow p2p UDP packages to set DSCP

net/udp/udp_socket_libevent.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/udp/udp_socket_libevent.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <sys/socket.h>
@@ skipping 633 matching lines @@
   DCHECK(CalledOnValidThread());
   if (is_connected())
     return ERR_SOCKET_IS_CONNECTED;
 
   if (loopback)
     socket_options_ |= SOCKET_OPTION_MULTICAST_LOOP;
   else
     socket_options_ &= ~SOCKET_OPTION_MULTICAST_LOOP;
   return OK;
 }
+
+int UDPSocketLibevent::SetTos(DiffServCodePoint dscp) {
+  if (dscp == DSCP_NO_CHANGE) {
+    return OK;
+  }
+  int rv;
+  int dscp_and_ecn = dscp << 2;
+  if (addr_family_ == AF_INET) {
+    rv = setsockopt(socket_, IPPROTO_IP, IP_TOS,
+                    &dscp_and_ecn, sizeof(dscp_and_ecn));
+  } else {
+    rv = setsockopt(socket_, IPPROTO_IPV6, IPV6_TCLASS,
+                    &dscp_and_ecn, sizeof(dscp_and_ecn));
+  }
+  if (rv < 0)
+    return MapSystemError(errno);
+
+  return OK;
+}
+
 }  // namespace net