Date:	Thu, 04 Jan 2007 14:37:02 +1100
From:	ahendry <ahendry@...c.com.au>
To:	linux-x25@...r.kernel.org, eis@...y.hanse.de
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH 2.6.19 1/2] X.25: Adds call forwarding to X.25

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.

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

Signed-off-by: Andrew Hendry <andrew.hendry@...il.com>

diff -uprN -X linux-2.6.19/Documentation/dontdiff linux-2.6.19-vanilla/include/net/x25.h linux-2.6.19/include/net/x25.h
--- linux-2.6.19-vanilla/include/net/x25.h	2006-12-31 22:31:06.000000000 +1100
+++ linux-2.6.19/include/net/x25.h	2007-01-01 17:06:13.000000000 +1100
@@ -161,6 +161,14 @@ struct x25_sock {
 	unsigned long 		vc_facil_mask;	/* inc_call facilities mask */
 };
 
+struct x25_forward {
+	struct list_head	node;
+	unsigned int		lci;
+	struct net_device	*dev1;
+	struct net_device	*dev2;
+	atomic_t		refcnt;
+};
+
 static inline struct x25_sock *x25_sk(const struct sock *sk)
 {
 	return (struct x25_sock *)sk;
@@ -198,6 +206,12 @@ extern int x25_negotiate_facilities(stru
 				struct x25_dte_facilities *);
 extern void x25_limit_facilities(struct x25_facilities *, struct x25_neigh *);
 
+/* x25_forward.c */
+extern void x25_clear_forwards(struct net_device *);
+extern struct x25_neigh *x25_find_forward(int, struct x25_neigh *);
+extern int x25_forward_call(struct x25_address *, struct x25_neigh *,
+				struct sk_buff *, int);
+
 /* x25_in.c */
 extern int  x25_process_rx_frame(struct sock *, struct sk_buff *);
 extern int  x25_backlog_rcv(struct sock *, struct sk_buff *);
@@ -281,6 +295,8 @@ extern struct hlist_head x25_list;
 extern rwlock_t x25_list_lock;
 extern struct list_head x25_route_list;
 extern rwlock_t x25_route_list_lock;
+extern struct list_head x25_forward_list;
+extern rwlock_t x25_forward_list_lock;
 
 extern int x25_proc_init(void);
 extern void x25_proc_exit(void);
diff -uprN -X linux-2.6.19/Documentation/dontdiff linux-2.6.19-vanilla/net/x25/af_x25.c linux-2.6.19/net/x25/af_x25.c
--- linux-2.6.19-vanilla/net/x25/af_x25.c	2006-12-31 22:31:07.000000000 +1100
+++ linux-2.6.19/net/x25/af_x25.c	2007-01-01 00:32:48.000000000 +1100
@@ -850,6 +850,9 @@ int x25_rx_call_request(struct sk_buff *
 	struct x25_dte_facilities dte_facilities;
 	int len, rc;
 
+	struct sk_buff *skbn;
+	skbn = skb_clone(skb, GFP_ATOMIC);
+
 	/*
 	 *	Remove the LCI and frame type.
 	 */
@@ -875,11 +878,23 @@ int x25_rx_call_request(struct sk_buff *
 	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) {
+		if (x25_forward_call(&dest_addr, nb, skbn, lci) == 0) {
+			/* Call was fowarded, dont process it any more */
+			return 0;
+		} else {
+			/* No listeners, can't forward, clear the call */
+			goto out_clear_request;
+		}
+	}
 
 	/*
 	 *	Try to reach a compromise on the requested facilities.
@@ -1600,6 +1615,9 @@ void x25_kill_by_neigh(struct x25_neigh 
 			x25_disconnect(s, ENETUNREACH, 0, 0);
 
 	write_unlock_bh(&x25_list_lock);
+
+	/* Remove any related forwards */
+	x25_clear_forwards(nb->dev);
 }
 
 static int __init x25_init(void)
diff -uprN -X linux-2.6.19/Documentation/dontdiff linux-2.6.19-vanilla/net/x25/Makefile linux-2.6.19/net/x25/Makefile
--- linux-2.6.19-vanilla/net/x25/Makefile	2006-12-31 22:31:07.000000000 +1100
+++ linux-2.6.19/net/x25/Makefile	2006-12-31 23:25:38.000000000 +1100
@@ -6,5 +6,5 @@ obj-$(CONFIG_X25) += x25.o
 
 x25-y			:= af_x25.o x25_dev.o x25_facilities.o x25_in.o \
 			   x25_link.o x25_out.o x25_route.o x25_subr.o \
-			   x25_timer.o x25_proc.o
+			   x25_timer.o x25_proc.o x25_forward.o
 x25-$(CONFIG_SYSCTL)	+= sysctl_net_x25.o
diff -uprN -X linux-2.6.19/Documentation/dontdiff linux-2.6.19-vanilla/net/x25/x25_dev.c linux-2.6.19/net/x25/x25_dev.c
--- linux-2.6.19-vanilla/net/x25/x25_dev.c	2006-12-31 22:31:07.000000000 +1100
+++ linux-2.6.19/net/x25/x25_dev.c	2007-01-01 17:07:30.000000000 +1100
@@ -29,6 +29,7 @@ static int x25_receive_data(struct sk_bu
 	struct sock *sk;
 	unsigned short frametype;
 	unsigned int lci;
+	struct x25_neigh *to_neigh;
 
 	frametype = skb->data[2];
         lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
@@ -66,9 +67,19 @@ static int x25_receive_data(struct sk_bu
 		return x25_rx_call_request(skb, nb, lci);
 
 	/*
-	 *	Its not a Call Request, nor is it a control frame.
-	 *      Let caller throw it away.
+	 * 	Its not a Call Request, nor is it a control frame.
+	 *	Can we forward it?
 	 */
+
+	if (( to_neigh = x25_find_forward(lci, nb)) != NULL) {
+		struct sk_buff *skbn = pskb_copy (skb, GFP_ATOMIC);
+		x25_transmit_link(skbn, to_neigh);
+		if (frametype == X25_CLEAR_CONFIRMATION) {
+			x25_clear_forwards(nb->dev);
+		}
+		return 1;
+	}
+
 /*
 	x25_transmit_clear_request(nb, lci, 0x0D);
 */
diff -uprN -X linux-2.6.19/Documentation/dontdiff linux-2.6.19-vanilla/net/x25/x25_forward.c linux-2.6.19/net/x25/x25_forward.c
--- linux-2.6.19-vanilla/net/x25/x25_forward.c	1970-01-01 10:00:00.000000000 +1000
+++ linux-2.6.19/net/x25/x25_forward.c	2007-01-01 17:07:24.000000000 +1100
@@ -0,0 +1,115 @@
+/*
+ *	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 *skbn, int lci)
+{
+	struct x25_route *rt;
+	struct x25_neigh *neigh_new;
+	struct list_head *entry;
+	struct x25_forward *x25_frwd, *new_frwd;
+	short same_lci = 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
+			 */
+			return 1;
+		}
+
+		/* 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) {
+			return 1;
+		}
+
+		/* 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)
+				return -ENOMEM;
+			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 */
+		x25_transmit_link(skbn, neigh_new);
+		return 0;
+	} else
+		return 1;
+}
+
+
+struct x25_neigh *x25_find_forward(int lci, struct x25_neigh *from) {
+
+	struct x25_forward *frwd;
+	struct list_head *entry;
+	struct net_device *peer = NULL;
+
+	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);
+	return x25_get_neigh(peer);
+}
+
+
+void x25_clear_forwards(struct net_device *dev)
+{
+	struct x25_forward *fwd;
+	struct list_head *entry, *tmp;
+
+        /* Remove any related forwards */
+	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);
+		}
+	}
+	write_unlock_bh(&x25_forward_list_lock);
+}
diff -uprN -X linux-2.6.19/Documentation/dontdiff linux-2.6.19-vanilla/net/x25/x25_route.c linux-2.6.19/net/x25/x25_route.c
--- linux-2.6.19-vanilla/net/x25/x25_route.c	2006-12-31 22:31:07.000000000 +1100
+++ linux-2.6.19/net/x25/x25_route.c	2006-12-31 23:23:17.000000000 +1100
@@ -119,6 +119,9 @@ void x25_route_device_down(struct net_de
 			__x25_remove_route(rt);
 	}
 	write_unlock_bh(&x25_route_list_lock);
+
+	/* Remove any related forwarding */
+	x25_clear_forwards(dev);
 }
 
 /*

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