[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/decnet/dn_neigh.c b/net/decnet/dn_neigh.c
index 174d8a7..a424a8d 100644
--- a/net/decnet/dn_neigh.c
+++ b/net/decnet/dn_neigh.c
@@ -38,6 +38,7 @@
 #include <linux/rcupdate.h>
 #include <linux/jhash.h>
 #include <asm/atomic.h>
+#include <net/net_namespace.h>
 #include <net/neighbour.h>
 #include <net/dst.h>
 #include <net/flow.h>
@@ -611,11 +612,11 @@
 void __init dn_neigh_init(void)
 {
 	neigh_table_init(&dn_neigh_table);
-	proc_net_fops_create("decnet_neigh", S_IRUGO, &dn_neigh_seq_fops);
+	proc_net_fops_create(&init_net, "decnet_neigh", S_IRUGO, &dn_neigh_seq_fops);
 }
 
 void __exit dn_neigh_cleanup(void)
 {
-	proc_net_remove("decnet_neigh");
+	proc_net_remove(&init_net, "decnet_neigh");
 	neigh_table_clear(&dn_neigh_table);
 }