netfilter: conntrack: do not enable connection tracking unless needed

Discussion during NFWS 2017 in Faro has shown that the current
conntrack behaviour is unreasonable.

Even if conntrack module is loaded on behalf of a single net namespace,
its turned on for all namespaces, which is expensive.  Commit
481fa373476 ("netfilter: conntrack: add nf_conntrack_default_on sysctl")
attempted to provide an alternative to the 'default on' behaviour by
adding a sysctl to change it.

However, as Eric points out, the sysctl only becomes available
once the module is loaded, and then its too late.

So we either have to move the sysctl to the core, or, alternatively,
change conntrack to become active only once the rule set requires this.

This does the latter, conntrack is only enabled when a rule needs it.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 0 insertions, 15 deletions

diff --git a/include/net/netfilter/nf_conntrack_l3proto.h b/include/net/netfilter/nf_conntrack_l3proto.h
index 6d14b36..1b8de16 100644
--- a/include/net/netfilter/nf_conntrack_l3proto.h
+++ b/include/net/netfilter/nf_conntrack_l3proto.h
@@ -73,21 +73,6 @@ struct nf_conntrack_l3proto {
 
 extern struct nf_conntrack_l3proto __rcu *nf_ct_l3protos[NFPROTO_NUMPROTO];
 
-#ifdef CONFIG_SYSCTL
-/* Protocol pernet registration. */
-int nf_ct_l3proto_pernet_register(struct net *net,
-				  struct nf_conntrack_l3proto *proto);
-#else
-static inline int nf_ct_l3proto_pernet_register(struct net *n,
-						struct nf_conntrack_l3proto *p)
-{
-	return 0;
-}
-#endif
-
-void nf_ct_l3proto_pernet_unregister(struct net *net,
-				     struct nf_conntrack_l3proto *proto);
-
 /* Protocol global registration. */
 int nf_ct_l3proto_register(struct nf_conntrack_l3proto *proto);
 void nf_ct_l3proto_unregister(struct nf_conntrack_l3proto *proto);