[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_dev.c b/net/decnet/dn_dev.c
index 8def682..83cb076 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -42,6 +42,7 @@
 #include <linux/notifier.h>
 #include <asm/uaccess.h>
 #include <asm/system.h>
+#include <net/net_namespace.h>
 #include <net/neighbour.h>
 #include <net/dst.h>
 #include <net/flow.h>
@@ -1462,7 +1463,7 @@
 	rtnl_register(PF_DECnet, RTM_DELADDR, dn_nl_deladdr, NULL);
 	rtnl_register(PF_DECnet, RTM_GETADDR, NULL, dn_nl_dump_ifaddr);
 
-	proc_net_fops_create("decnet_dev", S_IRUGO, &dn_dev_seq_fops);
+	proc_net_fops_create(&init_net, "decnet_dev", S_IRUGO, &dn_dev_seq_fops);
 
 #ifdef CONFIG_SYSCTL
 	{
@@ -1483,7 +1484,7 @@
 	}
 #endif /* CONFIG_SYSCTL */
 
-	proc_net_remove("decnet_dev");
+	proc_net_remove(&init_net, "decnet_dev");
 
 	dn_dev_devices_off();
 }