Enable QOS prioritization on macOS

host.c

@@ -64,6 +64,7 @@ enet_host_create (int addressFamily, const ENetAddress * address, size_t peerCou
     enet_socket_set_option (host -> socket, ENET_SOCKOPT_NONBLOCK, 1);
     enet_socket_set_option (host -> socket, ENET_SOCKOPT_RCVBUF, ENET_HOST_RECEIVE_BUFFER_SIZE);
     enet_socket_set_option (host -> socket, ENET_SOCKOPT_SNDBUF, ENET_HOST_SEND_BUFFER_SIZE);
+    enet_socket_set_option (host -> socket, ENET_SOCKOPT_QOS, 1);
 
     if (address != NULL && enet_socket_get_address (host -> socket, & host -> address) < 0)   
       host -> address = * address;

include/enet/enet.h

@@ -62,6 +62,7 @@ typedef enum _ENetSocketOption
    ENET_SOCKOPT_SNDTIMEO,
    ENET_SOCKOPT_ERROR,
    ENET_SOCKOPT_NODELAY,
+   ENET_SOCKOPT_QOS,
 } ENetSocketOption;
 
 typedef enum _ENetSocketShutdown

unix.c

@@ -319,6 +319,14 @@ enet_socket_set_option (ENetSocket socket, ENetSocketOption option, int value)
             result = setsockopt (socket, IPPROTO_TCP, TCP_NODELAY, (char *) & value, sizeof (int));
             break;
 
+        case ENET_SOCKOPT_QOS:
+#if defined(SO_NET_SERVICE_TYPE)
+            // iOS/macOS
+            value = value ? NET_SERVICE_TYPE_VO : NET_SERVICE_TYPE_BE;
+            result = setsockopt (socket, SOL_SOCKET, SO_NET_SERVICE_TYPE, (char *) & value, sizeof (int));
+#endif
+            break;
+
         default:
             break;
     }