Allow p2p UDP packages to set DSCP

net/udp/udp_socket_win.cc

Index: net/udp/udp_socket_win.cc
diff --git a/net/udp/udp_socket_win.cc b/net/udp/udp_socket_win.cc
index 1f0c337fd4a609fcb783bb0382345a88ab4ecd34..66570fe2c2fbf70332f1ddc6f001f9caf707285c 100644
--- a/net/udp/udp_socket_win.cc
+++ b/net/udp/udp_socket_win.cc
@@ -752,4 +752,26 @@ int UDPSocketWin::SetMulticastLoopbackMode(bool loopback) {
   return OK;
 }
 
+int UDPSocketLibevent::SetTos(DiffServCodePoint dscp) {
+  if (dscp == DSCP_NO_CHANGE) {
+    return OK;
+  }
+  int rv;
+  DWORD dscp_and_ecn = dscp << 2;
+  if (addr_family_ == AF_INET) {
+    rv = setsockopt(socket_, IPPROTO_IP, IP_TOS,
+                    reinterpret_cast<const char*>(&dscp_and_ecn),
+                    sizeof(dscp_and_ecn));
+  } else {
+    rv = setsockopt(socket_, IPPROTO_IPV6, IPV6_TCLASS,
+                    reinterpret_cast<const char*>(&dscp_and_ecn),
+                    sizeof(dscp_and_ecn));
+  }
+  if (rv < 0)
+    return MapSystemError(errno);
+
+  return OK;
+}
+
+
 }  // namespace net