[X.25]: Add call forwarding

Adds call forwarding to X.25, allowing it to operate like an X.25 router.
Useful if one needs to manipulate X.25 traffic with tools like tc.
This is an update/cleanup based off a patch submitted by Daniel Ferenci a few years ago.

Thanks Alan for the feedback.
Added the null check to the clones.
Moved the skb_clone's into the forwarding functions.

Worked ok with Cisco XoT, linux X.25 back to back, and some old NTUs/PADs.

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

1 files changed, 25 insertions, 5 deletions

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index b5c80b1..0872025 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -846,7 +846,7 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
 	struct x25_address source_addr, dest_addr;
 	struct x25_facilities facilities;
 	struct x25_dte_facilities dte_facilities;
-	int len, rc;
+	int len, addr_len, rc;
 
 	/*
 	 *	Remove the LCI and frame type.
@@ -857,7 +857,8 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
 	 *	Extract the X.25 addresses and convert them to ASCII strings,
 	 *	and remove them.
 	 */
-	skb_pull(skb, x25_addr_ntoa(skb->data, &source_addr, &dest_addr));
+	addr_len = x25_addr_ntoa(skb->data, &source_addr, &dest_addr);
+	skb_pull(skb, addr_len);
 
 	/*
 	 *	Get the length of the facilities, skip past them for the moment
@@ -873,11 +874,27 @@ int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
 	sk = x25_find_listener(&source_addr,skb);
 	skb_push(skb,len);
 
+	if (sk != NULL && sk_acceptq_is_full(sk)) {
+		goto out_sock_put;
+	}
+
 	/*
-	 *	We can't accept the Call Request.
+	 *	We dont have any listeners for this incoming call.
+	 *	Try forwarding it.
 	 */
-	if (sk == NULL || sk_acceptq_is_full(sk))
-		goto out_clear_request;
+	if (sk == NULL) {
+		skb_push(skb, addr_len + X25_STD_MIN_LEN);
+		if (x25_forward_call(&dest_addr, nb, skb, lci) > 0)
+		{
+			/* Call was forwarded, dont process it any more */
+			kfree_skb(skb);
+			rc = 1;
+			goto out;
+		} else {
+			/* No listeners, can't forward, clear the call */
+			goto out_clear_request;
+		}
+	}
 
 	/*
 	 *	Try to reach a compromise on the requested facilities.
@@ -1598,6 +1615,9 @@ void x25_kill_by_neigh(struct x25_neigh *nb)
 			x25_disconnect(s, ENETUNREACH, 0, 0);
 
 	write_unlock_bh(&x25_list_lock);
+
+	/* Remove any related forwards */
+	x25_clear_forward_by_dev(nb->dev);
 }
 
 static int __init x25_init(void)