Re: [PATCH 2.6.11.7] x25: Call accept with call request CUD

[Andrew Hendry <ahendry@tusc.com.au>]

Hi Michael,

We have noticed the same issue.
Im not sure blocking the cud on call accept outright covers all cases. 
It looks like there is one case (fast select) where a call accept may
contain call user data, but it is not an exact copy of the received cud.
Shaun here is working on a patch to better control this call accept
packet and its contents.

Not much life on this linux-x25 list, ive found its best to CC patches
to the main kernel list for someone to pickup.

Andrew.

On Sun, 2005-04-10 at 16:52, Michael Flower wrote:
> I believe that I have found a bug in the X25 code in the kernel and have
> attached a simple patch.
> 
> An incoming x25 connecton request with call user data (CUD) generates  a
> call accept with a copy of the user data in the packet.
> 
> I do not believe that the X25 spec allows such a call accept
> packet.
> 
> The problem arose using XOT from a linux box, through a cisco router
> (doing the de-encapsulation) and forwarding to a telecom switch via X25.
> 
> When switch tried to connect to the Linux box the router encapsulated
> the connection request into an XOT packet and sent it to the linux box.
> 
> The connection request had CUD.
> 
> The linux box (running xotd), de-encapsulated the packet, and routed it
> to X25.
> 
> The X25 system sent a call accept packet back to the router
> (XOT encapsulated) which had the original CUD inside the packet.
> 
> The router immediately barfed, and sent a clear request back
> to the linux box and the switch.  The Cisco router complained
> that the X25 call acknowledgement packet was too long in its debug log.
> 
> It seems reasonable that it did barf. I am not sure that sending the CUD
> back with the connect accept packet makes sense, and the
> only reference I can find on the X25 protocol doesn't allow for
> CUD in call accept packets.
> 
> The fix is to remove the offending four lines of code in X25_utilities.c
> that append the CUD to the call acknowledgement packet. It certainly
> fixes the problems described above with cisco routers.
> 
> The XOT stuff, lately ported to 2.6 by Andrew Hendry
> (ahendry@tusc.com.au) appears to be very useful in a telecoms arena.
> There are some issues with x25 module useage counting, that I will 
> fix ASAP. I hope that all this can then be integrated into future
> kernels.
> 
> The patch
> 
> --- linux-2.6.11.7/net/x25/x25_subr.c	2005-04-08 04:57:26.000000000
> +1000
> +++ linux-2.6.11.7_new/net/x25/x25_subr.c	2005-04-08 17:46:32.591950835
> +1000
> @@ -203,10 +203,6 @@
>  							x25->vc_facil_mask);
>  			dptr    = skb_put(skb, len);
>  			memcpy(dptr, facilities, len);
> -			dptr = skb_put(skb,x25->calluserdata.cudlength);
> -			memcpy(dptr, x25->calluserdata.cuddata,
> -			       x25->calluserdata.cudlength);
> -			x25->calluserdata.cudlength = 0;
>  			break;
>  
>  		case X25_CLEAR_REQUEST:
> 
> Michael Flower
> 
> mcf-tech@windsurfwa.com
> 
> 
> -
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