netfilter: nf_log: prepare net namespace support for loggers

This patch adds netns support to nf_log and it prepares netns
support for existing loggers. It is composed of four major
changes.

1) nf_log_register has been split to two functions: nf_log_register
   and nf_log_set. The new nf_log_register is used to globally
   register the nf_logger and nf_log_set is used for enabling
   pernet support from nf_loggers.

   Per netns is not yet complete after this patch, it comes in
   separate follow up patches.

2) Add net as a parameter of nf_log_bind_pf. Per netns is not
   yet complete after this patch, it only allows to bind the
   nf_logger to the protocol family from init_net and it skips
   other cases.

3) Adapt all nf_log_packet callers to pass netns as parameter.
   After this patch, this function only works for init_net.

4) Make the sysctl net/netfilter/nf_log pernet.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index f248db5..b593fd1 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -767,6 +767,7 @@
 	u_int16_t group_num = ntohs(nfmsg->res_id);
 	struct nfulnl_instance *inst;
 	struct nfulnl_msg_config_cmd *cmd = NULL;
+	struct net *net = sock_net(ctnl);
 	int ret = 0;
 
 	if (nfula[NFULA_CFG_CMD]) {
@@ -776,9 +777,9 @@
 		/* Commands without queue context */
 		switch (cmd->command) {
 		case NFULNL_CFG_CMD_PF_BIND:
-			return nf_log_bind_pf(pf, &nfulnl_logger);
+			return nf_log_bind_pf(net, pf, &nfulnl_logger);
 		case NFULNL_CFG_CMD_PF_UNBIND:
-			nf_log_unbind_pf(pf);
+			nf_log_unbind_pf(net, pf);
 			return 0;
 		}
 	}