[X.25]: Adds /proc/sys/net/x25/x25_forward to control forwarding.

echo "1" > /proc/sys/net/x25/x25_forward 
To turn on x25_forwarding, defaults to off
Requires the previous patch.

Signed-off-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/x25/af_x25.c

@@ -63,6 +63,7 @@ int sysctl_x25_call_request_timeout    = X25_DEFAULT_T21;
 int sysctl_x25_reset_request_timeout   = X25_DEFAULT_T22;
 int sysctl_x25_clear_request_timeout   = X25_DEFAULT_T23;
 int sysctl_x25_ack_holdback_timeout    = X25_DEFAULT_T2;
+int sysctl_x25_forward                 = 0;
 
 HLIST_HEAD(x25_list);
 DEFINE_RWLOCK(x25_list_lock);
@@ -884,7 +885,8 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
 	 */
 	if (sk == NULL) {
 		skb_push(skb, addr_len + X25_STD_MIN_LEN);
-		if (x25_forward_call(&dest_addr, nb, skb, lci) > 0)
+		if (sysctl_x25_forward &&
+				x25_forward_call(&dest_addr, nb, skb, lci) > 0)
 		{
 			/* Call was forwarded, dont process it any more */
 			kfree_skb(skb);

net/x25/sysctl_net_x25.c

@@ -73,6 +73,14 @@ static struct ctl_table x25_table[] = {
 		.extra1 =	&min_timer,
 		.extra2 =	&max_timer,
 	},
+	{
+		.ctl_name =	NET_X25_FORWARD,
+		.procname =	"x25_forward",
+		.data = 	&sysctl_x25_forward,
+		.maxlen = 	sizeof(int),
+		.mode = 	0644,
+		.proc_handler = &proc_dointvec,
+	},
 	{ 0, },
 };