[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>
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index c5b2470..5ae4849 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -55,6 +55,7 @@
 #include <linux/root_dev.h>
 #include <linux/delay.h>
 #include <linux/nfs_fs.h>
+#include <net/net_namespace.h>
 #include <net/arp.h>
 #include <net/ip.h>
 #include <net/ipconfig.h>
@@ -1253,7 +1254,7 @@
 	__be32 addr;
 
 #ifdef CONFIG_PROC_FS
-	proc_net_fops_create("pnp", S_IRUGO, &pnp_seq_fops);
+	proc_net_fops_create(&init_net, "pnp", S_IRUGO, &pnp_seq_fops);
 #endif /* CONFIG_PROC_FS */
 
 	if (!ic_enable)