[NETNS]: Provide correct namespace for fibnl netlink socket.

This patch makes the netlink socket to be per namespace. That allows
to have each namespace its own socket for routing queries.

Acked-by: Benjamin Thery <benjamin.thery@bull.net>
Acked-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netns/ipv4.h

@@ -9,6 +9,7 @@ struct ctl_table_header;
 struct ipv4_devconf;
 struct fib_rules_ops;
 struct hlist_head;
+struct sock;
 
 struct netns_ipv4 {
 #ifdef CONFIG_SYSCTL
@@ -20,5 +21,6 @@ struct netns_ipv4 {
 	struct fib_rules_ops	*rules_ops;
 #endif
 	struct hlist_head	*fib_table_hash;
+	struct sock		*fibnl;
 };
 #endif