netfilter: ctnetlink: reject new conntrack request with different l4proto

Currently, user can add a conntrack with different l4proto via nfnetlink.
For example, original tuple is TCP while reply tuple is SCTP. This is
invalid combination, we should report EINVAL to userspace.
Signed-off-by: Liping Zhang <liping.zhang@spreadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_netlink.c

@@ -1894,6 +1894,8 @@ static int ctnetlink_new_conntrack(struct net *net, struct sock *ctnl,
 
 			if (!cda[CTA_TUPLE_ORIG] || !cda[CTA_TUPLE_REPLY])
 				return -EINVAL;
+			if (otuple.dst.protonum != rtuple.dst.protonum)
+				return -EINVAL;
 
 			ct = ctnetlink_create_conntrack(net, &zone, cda, &otuple,
 							&rtuple, u3);