Allow p2p UDP packages to set DSCP

net/udp/udp_socket_libevent.cc

Index: net/udp/udp_socket_libevent.cc
diff --git a/net/udp/udp_socket_libevent.cc b/net/udp/udp_socket_libevent.cc
index 90c7da6504103dead9150b5cf28adde33b598f5f..cc9756de87fa9190ab284bd6a394b68018a58914 100644
--- a/net/udp/udp_socket_libevent.cc
+++ b/net/udp/udp_socket_libevent.cc
@@ -42,6 +42,7 @@ UDPSocketLibevent::UDPSocketLibevent(
           addr_family_(0),
           socket_options_(SOCKET_OPTION_MULTICAST_LOOP),
           multicast_time_to_live_(1),
+          dscp_(DSCP_CS0),
           bind_type_(bind_type),
           rand_int_cb_(rand_int_cb),
           read_watcher_(this),
@@ -531,6 +532,21 @@ int UDPSocketLibevent::SetSocketOptions() {
     if (rv < 0)
       return MapSystemError(errno);
   }
+
+  if (dscp_) {
+    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) {
+      LOG(INFO) << "Failed to set dscp, errno=" << errno;
+    }
+  }
   return OK;
 }
 
@@ -651,4 +667,15 @@ int UDPSocketLibevent::SetMulticastLoopbackMode(bool loopback) {
     socket_options_ &= ~SOCKET_OPTION_MULTICAST_LOOP;
   return OK;
 }
+
+int UDPSocketLibevent::SetToS(DiffServCodePoint dscp) {
+  DCHECK_GE(dscp, 0);
+  DCHECK_LT(dscp, 64);
+  if (is_connected())
+    return ERR_SOCKET_IS_CONNECTED;
+
+  dscp_ = dscp;
+  return OK;
+}
+
 }  // namespace net