[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, 163 insertions, 0 deletions

diff --git a/net/x25/x25_forward.c b/net/x25/x25_forward.c
new file mode 100644
index 00000000000..d339e0c810a
--- /dev/null
+++ b/net/x25/x25_forward.c
@@ -0,0 +1,163 @@
+/*
+ *	This module:
+ *		This module is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ *	History
+ *	03-01-2007	Added forwarding for x.25	Andrew Hendry
+ */
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <net/x25.h>
+
+struct list_head x25_forward_list = LIST_HEAD_INIT(x25_forward_list);
+DEFINE_RWLOCK(x25_forward_list_lock);
+
+int x25_forward_call(struct x25_address *dest_addr, struct x25_neigh *from,
+			struct sk_buff *skb, int lci)
+{
+	struct x25_route *rt;
+	struct x25_neigh *neigh_new = NULL;
+	struct list_head *entry;
+	struct x25_forward *x25_frwd, *new_frwd;
+	struct sk_buff *skbn;
+	short same_lci = 0;
+	int rc = 0;
+
+	if ((rt = x25_get_route(dest_addr)) != NULL) {
+
+		if ((neigh_new = x25_get_neigh(rt->dev)) == NULL) {
+			/* This shouldnt happen, if it occurs somehow
+			 * do something sensible
+			 */
+			goto out_put_route;
+		}
+
+		/* Avoid a loop. This is the normal exit path for a
+		 * system with only one x.25 iface and default route
+		 */
+		if (rt->dev == from->dev) {
+			goto out_put_nb;
+		}
+
+		/* Remote end sending a call request on an already
+		 * established LCI? It shouldnt happen, just in case..
+		 */
+		read_lock_bh(&x25_forward_list_lock);
+		list_for_each(entry, &x25_forward_list) {
+			x25_frwd = list_entry(entry, struct x25_forward, node);
+			if (x25_frwd->lci == lci) {
+				printk(KERN_WARNING "X.25: call request for lci which is already registered!, transmitting but not registering new pair\n");
+				same_lci = 1;
+			}
+		}
+		read_unlock_bh(&x25_forward_list_lock);
+
+		/* Save the forwarding details for future traffic */
+		if (!same_lci){
+			if ((new_frwd = kmalloc(sizeof(struct x25_forward),
+							GFP_ATOMIC)) == NULL){
+				rc = -ENOMEM;
+				goto out_put_nb;
+			}
+			new_frwd->lci = lci;
+			new_frwd->dev1 = rt->dev;
+			new_frwd->dev2 = from->dev;
+			write_lock_bh(&x25_forward_list_lock);
+			list_add(&new_frwd->node, &x25_forward_list);
+			write_unlock_bh(&x25_forward_list_lock);
+		}
+
+		/* Forward the call request */
+		if ( (skbn = skb_clone(skb, GFP_ATOMIC)) == NULL){
+			goto out_put_nb;
+		}
+		x25_transmit_link(skbn, neigh_new);
+		rc = 1;
+	}
+
+
+out_put_nb:
+	x25_neigh_put(neigh_new);
+
+out_put_route:
+	x25_route_put(rt);
+	return rc;
+}
+
+
+int x25_forward_data(int lci, struct x25_neigh *from, struct sk_buff *skb) {
+
+	struct x25_forward *frwd;
+	struct list_head *entry;
+	struct net_device *peer = NULL;
+	struct x25_neigh *nb;
+	struct sk_buff *skbn;
+	int rc = 0;
+
+	read_lock_bh(&x25_forward_list_lock);
+	list_for_each(entry, &x25_forward_list) {
+		frwd = list_entry(entry, struct x25_forward, node);
+		if (frwd->lci == lci) {
+			/* The call is established, either side can send */
+			if (from->dev == frwd->dev1) {
+				peer = frwd->dev2;
+			} else {
+				peer = frwd->dev1;
+			}
+			break;
+		}
+	}
+	read_unlock_bh(&x25_forward_list_lock);
+
+	if ( (nb = x25_get_neigh(peer)) == NULL)
+		goto out;
+
+	if ( (skbn = pskb_copy(skb, GFP_ATOMIC)) == NULL){
+		goto out;
+
+	}
+	x25_transmit_link(skbn, nb);
+
+	x25_neigh_put(nb);
+	rc = 1;
+out:
+	return rc;
+}
+
+void x25_clear_forward_by_lci(unsigned int lci)
+{
+	struct x25_forward *fwd;
+	struct list_head *entry, *tmp;
+
+	write_lock_bh(&x25_forward_list_lock);
+
+	list_for_each_safe(entry, tmp, &x25_forward_list) {
+		fwd = list_entry(entry, struct x25_forward, node);
+		if (fwd->lci == lci) {
+			list_del(&fwd->node);
+			kfree(fwd);
+		}
+	}
+	write_unlock_bh(&x25_forward_list_lock);
+}
+
+
+void x25_clear_forward_by_dev(struct net_device *dev)
+{
+	struct x25_forward *fwd;
+	struct list_head *entry, *tmp;
+
+	write_lock_bh(&x25_forward_list_lock);
+
+	list_for_each_safe(entry, tmp, &x25_forward_list) {
+		fwd = list_entry(entry, struct x25_forward, node);
+		if ((fwd->dev1 == dev) || (fwd->dev2 == dev)){
+			list_del(&fwd->node);
+			kfree(fwd);
+		}
+	}
+	write_unlock_bh(&x25_forward_list_lock);
+}