netfilter: move reroute indirection to struct nf_ipv6_ops

We cannot make a direct call to nf_ip6_reroute() because that would result
in autoloading the 'ipv6' module because of symbol dependencies.
Therefore, define reroute indirection in nf_ipv6_ops where this really
belongs to.

For IPv4, we can indeed make a direct function call, which is faster,
given IPv4 is built-in in the networking code by default. Still,
CONFIG_INET=n and CONFIG_NETFILTER=y is possible, so define empty inline
stub for IPv4 in such case.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_queue.c b/net/netfilter/nf_queue.c
index dfa35bd..15382ff 100644
--- a/net/netfilter/nf_queue.c
+++ b/net/netfilter/nf_queue.c
@@ -266,7 +266,6 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 	const struct nf_hook_entry *hook_entry;
 	const struct nf_hook_entries *hooks;
 	struct sk_buff *skb = entry->skb;
-	const struct nf_afinfo *afinfo;
 	const struct net *net;
 	unsigned int i;
 	int err;
@@ -293,8 +292,7 @@ void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict)
 		verdict = nf_hook_entry_hookfn(hook_entry, skb, &entry->state);
 
 	if (verdict == NF_ACCEPT) {
-		afinfo = nf_get_afinfo(entry->state.pf);
-		if (!afinfo || afinfo->reroute(entry->state.net, skb, entry) < 0)
+		if (nf_reroute(skb, entry) < 0)
 			verdict = NF_DROP;
 	}