Some handers and strategies of devinet sysctl tables need
to know the net to propagate the ctl change to all the
net devices.

I use the (currently unused) extra2 pointer on the tables
to get it.

Holding the reference on the struct net is not possible,
because otherwise we'll get a net->ctl_table->net circular
dependency. But since the ctl tables are unregistered during 
the net destruction, this is safe to get it w/o additional 
protection.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 872883e..bfb0fb0 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1237,12 +1237,12 @@ errout:
 
 #ifdef CONFIG_SYSCTL
 
-static void devinet_copy_dflt_conf(int i)
+static void devinet_copy_dflt_conf(struct net *net, int i)
 {
 	struct net_device *dev;
 
 	read_lock(&dev_base_lock);
-	for_each_netdev(&init_net, dev) {
+	for_each_netdev(net, dev) {
 		struct in_device *in_dev;
 		rcu_read_lock();
 		in_dev = __in_dev_get_rcu(dev);
@@ -1253,7 +1253,7 @@ static void devinet_copy_dflt_conf(int i)
 	read_unlock(&dev_base_lock);
 }
 
-static void inet_forward_change(void)
+static void inet_forward_change(struct net *net)
 {
 	struct net_device *dev;
 	int on = IPV4_DEVCONF_ALL(FORWARDING);
@@ -1262,7 +1262,7 @@ static void inet_forward_change(void)
 	IPV4_DEVCONF_DFLT(FORWARDING) = on;
 
 	read_lock(&dev_base_lock);
-	for_each_netdev(&init_net, dev) {
+	for_each_netdev(net, dev) {
 		struct in_device *in_dev;
 		rcu_read_lock();
 		in_dev = __in_dev_get_rcu(dev);
@@ -1283,12 +1283,13 @@ static int devinet_conf_proc(ctl_table *ctl, int write,
 
 	if (write) {
 		struct ipv4_devconf *cnf = ctl->extra1;
+		struct net *net = ctl->extra2;
 		int i = (int *)ctl->data - cnf->data;
 
 		set_bit(i, cnf->state);
 
 		if (cnf == &ipv4_devconf_dflt)
-			devinet_copy_dflt_conf(i);
+			devinet_copy_dflt_conf(net, i);
 	}
 
 	return ret;
@@ -1299,6 +1300,7 @@ static int devinet_conf_sysctl(ctl_table *table, int __user *name, int nlen,
 			       void __user *newval, size_t newlen)
 {
 	struct ipv4_devconf *cnf;
+	struct net *net;
 	int *valp = table->data;
 	int new;
 	int i;
@@ -1334,12 +1336,13 @@ static int devinet_conf_sysctl(ctl_table *table, int __user *name, int nlen,
 	*valp = new;
 
 	cnf = table->extra1;
+	net = table->extra2;
 	i = (int *)table->data - cnf->data;
 
 	set_bit(i, cnf->state);
 
 	if (cnf == &ipv4_devconf_dflt)
-		devinet_copy_dflt_conf(i);
+		devinet_copy_dflt_conf(net, i);
 
 	return 1;
 }
@@ -1353,8 +1356,10 @@ static int devinet_sysctl_forward(ctl_table *ctl, int write,
 	int ret = proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
 
 	if (write && *valp != val) {
+		struct net *net = ctl->extra2;
+
 		if (valp == &IPV4_DEVCONF_ALL(FORWARDING))
-			inet_forward_change();
+			inet_forward_change(net);
 		else if (valp != &IPV4_DEVCONF_DFLT(FORWARDING))
 			rt_cache_flush(0);
 	}
@@ -1478,6 +1483,7 @@ static void __devinet_sysctl_register(char *dev_name, int ctl_name,
 	for (i = 0; i < ARRAY_SIZE(t->devinet_vars) - 1; i++) {
 		t->devinet_vars[i].data += (char *)p - (char *)&ipv4_devconf;
 		t->devinet_vars[i].extra1 = p;
+		t->devinet_vars[i].extra2 = net;
 	}
 
 	/*
@@ -1525,8 +1531,8 @@ static void devinet_sysctl_register(struct in_device *idev)
 {
 	neigh_sysctl_register(idev->dev, idev->arp_parms, NET_IPV4,
 			NET_IPV4_NEIGH, "ipv4", NULL, NULL);
-	__devinet_sysctl_register(idev->dev->name, idev->dev->ifindex,
-			&idev->cnf);
+	__devinet_sysctl_register(idev->dev->nd_net, idev->dev->name,
+			idev->dev->ifindex, &idev->cnf);
 }
 
 static void devinet_sysctl_unregister(struct in_device *idev)
@@ -1547,6 +1553,7 @@ static struct ctl_table ctl_forward_entry[] = {
 		.proc_handler	= devinet_sysctl_forward,
 		.strategy	= devinet_conf_sysctl,
 		.extra1		= &ipv4_devconf,
+		.extra2		= &init_net,
 	},
 	{ },
 };
@@ -1566,9 +1573,9 @@ void __init devinet_init(void)
 	rtnl_register(PF_INET, RTM_DELADDR, inet_rtm_deladdr, NULL);
 	rtnl_register(PF_INET, RTM_GETADDR, NULL, inet_dump_ifaddr);
 #ifdef CONFIG_SYSCTL
-	__devinet_sysctl_register("all", NET_PROTO_CONF_ALL,
+	__devinet_sysctl_register(&init_net, "all", NET_PROTO_CONF_ALL,
 			&ipv4_devconf);
-	__devinet_sysctl_register("default", NET_PROTO_CONF_DEFAULT,
+	__devinet_sysctl_register(&init_net, "default", NET_PROTO_CONF_DEFAULT,
 			&ipv4_devconf_dflt);
 	register_sysctl_paths(net_ipv4_path, ctl_forward_entry);
 #endif
-- 
1.5.3.4