[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/drivers/net/wireless/hostap/hostap_main.c b/drivers/net/wireless/hostap/hostap_main.c
index 446de51..9a470e8 100644
--- a/drivers/net/wireless/hostap/hostap_main.c
+++ b/drivers/net/wireless/hostap/hostap_main.c
@@ -24,6 +24,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/wireless.h>
 #include <linux/etherdevice.h>
+#include <net/net_namespace.h>
 #include <net/iw_handler.h>
 #include <net/ieee80211.h>
 #include <net/ieee80211_crypt.h>
@@ -1093,8 +1094,8 @@
 
 static int __init hostap_init(void)
 {
-	if (proc_net != NULL) {
-		hostap_proc = proc_mkdir("hostap", proc_net);
+	if (init_net.proc_net != NULL) {
+		hostap_proc = proc_mkdir("hostap", init_net.proc_net);
 		if (!hostap_proc)
 			printk(KERN_WARNING "Failed to mkdir "
 			       "/proc/net/hostap\n");
@@ -1109,7 +1110,7 @@
 {
 	if (hostap_proc != NULL) {
 		hostap_proc = NULL;
-		remove_proc_entry("hostap", proc_net);
+		remove_proc_entry("hostap", init_net.proc_net);
 	}
 }