net: use INET_ECN_MASK instead of hardcoded 3

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_sockglue.c

@@ -33,6 +33,7 @@
 #include <linux/netfilter.h>
 #include <linux/route.h>
 #include <linux/mroute.h>
+#include <net/inet_ecn.h>
 #include <net/route.h>
 #include <net/xfrm.h>
 #include <net/compat.h>
@@ -578,8 +579,8 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 		break;
 	case IP_TOS:	/* This sets both TOS and Precedence */
 		if (sk->sk_type == SOCK_STREAM) {
-			val &= ~3;
-			val |= inet->tos & 3;
+			val &= ~INET_ECN_MASK;
+			val |= inet->tos & INET_ECN_MASK;
 		}
 		if (inet->tos != val) {
 			inet->tos = val;