netfilter: ip6t_REJECT: check for IP6T_F_PROTO

Make sure IP6T_F_PROTO is set to enforce layer 4 protocol matching from
the ip6_tables core.
Suggested-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv6/netfilter/ip6t_REJECT.c

@@ -83,7 +83,8 @@ static int reject_tg6_check(const struct xt_tgchk_param *par)
 		return -EINVAL;
 	} else if (rejinfo->with == IP6T_TCP_RESET) {
 		/* Must specify that it's a TCP packet */
-		if (e->ipv6.proto != IPPROTO_TCP ||
+		if (!(e->ipv6.flags & IP6T_F_PROTO) ||
+		    e->ipv6.proto != IPPROTO_TCP ||
 		    (e->ipv6.invflags & XT_INV_PROTO)) {
 			pr_info("TCP_RESET illegal for non-tcp\n");
 			return -EINVAL;