inet: Register fragmentation some ctls at read-only root.

Parts of fragments-related sysctls are read-only, but this is
done by cloning all the tables and dropping write-bits from
mode. Do the same but with read-only root.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 7f102ee..be1cb89 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -624,6 +624,10 @@
 		.proc_handler	= &proc_dointvec_jiffies,
 		.strategy	= &sysctl_jiffies
 	},
+	{ }
+};
+
+static struct ctl_table ip4_frags_ctl_table[] = {
 	{
 		.ctl_name	= NET_IPV4_IPFRAG_SECRET_INTERVAL,
 		.procname	= "ipfrag_secret_interval",
@@ -658,8 +662,6 @@
 		table[0].data = &net->ipv4.frags.high_thresh;
 		table[1].data = &net->ipv4.frags.low_thresh;
 		table[2].data = &net->ipv4.frags.timeout;
-		table[3].mode &= ~0222;
-		table[4].mode &= ~0222;
 	}
 
 	hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table);
@@ -684,6 +686,11 @@
 	unregister_net_sysctl_table(net->ipv4.frags_hdr);
 	kfree(table);
 }
+
+static void ip4_frags_ctl_register(void)
+{
+	register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table);
+}
 #else
 static inline int ip4_frags_ns_ctl_register(struct net *net)
 {
@@ -693,6 +700,10 @@
 static inline void ip4_frags_ns_ctl_unregister(struct net *net)
 {
 }
+
+static inline void ip4_frags_ctl_register(void)
+{
+}
 #endif
 
 static int ipv4_frags_init_net(struct net *net)
@@ -730,6 +741,7 @@
 
 void __init ipfrag_init(void)
 {
+	ip4_frags_ctl_register();
 	register_pernet_subsys(&ip4_frags_ops);
 	ip4_frags.hashfn = ip4_hashfn;
 	ip4_frags.constructor = ip4_frag_init;