[NET]: Make /proc/net per network namespace

This patch makes /proc/net per network namespace.  It modifies the global
variables proc_net and proc_net_stat to be per network namespace.
The proc_net file helpers are modified to take a network namespace argument,
and all of their callers are fixed to pass &init_net for that argument.
This ensures that all of the /proc/net files are only visible and
usable in the initial network namespace until the code behind them
has been updated to be handle multiple network namespaces.

Making /proc/net per namespace is necessary as at least some files
in /proc/net depend upon the set of network devices which is per
network namespace, and even more files in /proc/net have contents
that are relevant to a single network namespace.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -57,6 +57,7 @@
 #include <linux/selinux.h>
 #include <linux/mutex.h>
 
+#include <net/net_namespace.h>
 #include <net/sock.h>
 #include <net/scm.h>
 #include <net/netlink.h>
@@ -1927,7 +1928,7 @@ static int __init netlink_proto_init(void)
 
 	sock_register(&netlink_family_ops);
 #ifdef CONFIG_PROC_FS
-	proc_net_fops_create("netlink", 0, &netlink_seq_fops);
+	proc_net_fops_create(&init_net, "netlink", 0, &netlink_seq_fops);
 #endif
 	/* The netlink device handler may be needed early. */
 	rtnetlink_init();