netfilter: nf_conntrack: prepare namespace support for l4 protocol trackers

This patch prepares the namespace support for layer 4 protocol trackers.
Basically, this modifies the following interfaces:

* nf_ct_[un]register_sysctl
* nf_conntrack_l4proto_[un]register

to include the namespace parameter. We still use init_net in this patch
to prepare the ground for follow-up patches for each layer 4 protocol
tracker.

We add a new net_id field to struct nf_conntrack_l4proto that is used
to store the pernet_operations id for each layer 4 protocol tracker.

Note that AF_INET6's protocols do not need to do sysctl compat. Thus,
we only register compat sysctl when l4proto.l3proto != AF_INET6.

Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack_l4proto.h

@@ -12,6 +12,7 @@
 #include <linux/netlink.h>
 #include <net/netlink.h>
 #include <net/netfilter/nf_conntrack.h>
+#include <net/netns/generic.h>
 
 struct seq_file;
 
@@ -103,6 +104,10 @@ struct nf_conntrack_l4proto {
 	struct ctl_table	*ctl_compat_table;
 #endif
 #endif
+	int	*net_id;
+	/* Init l4proto pernet data */
+	int (*init_net)(struct net *net);
+
 	/* Protocol name */
 	const char *name;
 
@@ -123,8 +128,10 @@ nf_ct_l4proto_find_get(u_int16_t l3proto, u_int8_t l4proto);
 extern void nf_ct_l4proto_put(struct nf_conntrack_l4proto *p);
 
 /* Protocol registration. */
-extern int nf_conntrack_l4proto_register(struct nf_conntrack_l4proto *proto);
-extern void nf_conntrack_l4proto_unregister(struct nf_conntrack_l4proto *proto);
+extern int nf_conntrack_l4proto_register(struct net *net,
+					 struct nf_conntrack_l4proto *proto);
+extern void nf_conntrack_l4proto_unregister(struct net *net,
+					    struct nf_conntrack_l4proto *proto);
 
 /* Generic netlink helpers */
 extern int nf_ct_port_tuple_to_nlattr(struct sk_buff *skb,