ipv4: Disallow non-namespace aware protocols to register.

All in-tree ipv4 protocol implementations are now namespace
aware. Therefore all the run-time checks are superfluous.

Reject registry of any non-namespace aware ipv4 protocol.
Eventually we'll remove prot->netns_ok and this registry
time check as well.

Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/af_inet.c

···
 }
 EXPORT_SYMBOL(build_ehash_secret);
 
-static inline int inet_netns_ok(struct net *net, __u8 protocol)
-{
-	const struct net_protocol *ipprot;
-
-	if (net_eq(net, &init_net))
-		return 1;
-
-	ipprot = rcu_dereference(inet_protos[protocol]);
-	if (ipprot == NULL) {
-		/* raw IP is OK */
-		return 1;
-	}
-	return ipprot->netns_ok;
-}
-
 /*
  *	Create an inet socket.
  */
···
 	err = -EPERM;
 	if (sock->type == SOCK_RAW && !kern &&
 	    !ns_capable(net->user_ns, CAP_NET_RAW))
-		goto out_rcu_unlock;
-
-	err = -EAFNOSUPPORT;
-	if (!inet_netns_ok(net, protocol))
 		goto out_rcu_unlock;
 
 	sock->ops = answer->ops;

net/ipv4/ip_input.c

···
 		if (ipprot != NULL) {
 			int ret;
 
-			if (!net_eq(net, &init_net) && !ipprot->netns_ok) {
-				net_info_ratelimited("%s: proto %d isn't netns-ready\n",
-						     __func__, protocol);
-				kfree_skb(skb);
-				goto out;
-			}
-
 			if (!ipprot->no_policy) {
 				if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 					kfree_skb(skb);

net/ipv4/protocol.c

···
 
 int inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
 {
+	if (!prot->netns_ok) {
+		pr_err("Protocol %u is not namespace aware, cannot register.\n",
+			protocol);
+		return -EINVAL;
+	}
+
 	return !cmpxchg((const struct net_protocol **)&inet_protos[protocol],
 			NULL, prot) ? 0 : -1;
 }