[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/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 69bd362..50fc9e0 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -25,6 +25,7 @@
 #include <linux/netfilter_ipv4/ip_tables.h>
 #include <linux/netfilter_ipv4/ipt_CLUSTERIP.h>
 #include <net/netfilter/nf_conntrack.h>
+#include <net/net_namespace.h>
 #include <net/checksum.h>
 
 #define CLUSTERIP_VERSION "0.8"
@@ -726,7 +727,7 @@
 		goto cleanup_target;
 
 #ifdef CONFIG_PROC_FS
-	clusterip_procdir = proc_mkdir("ipt_CLUSTERIP", proc_net);
+	clusterip_procdir = proc_mkdir("ipt_CLUSTERIP", init_net.proc_net);
 	if (!clusterip_procdir) {
 		printk(KERN_ERR "CLUSTERIP: Unable to proc dir entry\n");
 		ret = -ENOMEM;