North American Network Operators Group
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Re: That pesky AS path corruption bug...

  • From: Peter T. Whiting
  • Date: Tue May 23 13:06:22 2000 
When you say the router crashes I assume you are talking the whole box 
crashing and not just the BGP session.

As I understand the current spec, a router, upon receiving a malformed 
as_path is supposed to respond with a notification message (3.11) and
drop the BGP connection.  Your suggestion to maintain the connection
and drop the announcement is a practical one, but doesn't put as much
pressure on vendors to fix the bug.


pete

 


On Tue, May 23, 2000 at 12:40:00PM -0400, Blaine Christian wrote:
> 
> Hello all,
> 
> After observing a recent issue regarding a router that sent corrupted AS
> path (all names are witheld to protect the guilty).  I took a look at the
> path information that was being received and have a possible solution.
> Since the corrupted AS-path does not include the AS that the route is
> coming from (at least in the corruption that I saw) it seems to me that a
> simple solution for all is to filter on AS i.e. only allow routes that
> have the AS of your EBGP neighbor prepended to them.  I realize this does
> not cover all cases of wacky AS corruption problems but it may fix some of
> them.  I would suggest that those of you running mixed vendor EBGP (again
> names witheld) should implement a version of this strategy for your own
> self protection.  It can certainly be implemented as part of an overall
> customer access functionality.  This may be obvious to some of you but I
> do not believe that everyone is at this level yet.
> 
> Of course the tirade part of this email is for all vendors involved in
> this travesty.  If you do not understand or dislike a route that you have
> received don't just CRASH.  Anyone ever thought of checking the route and
> throwing it out with an error message if you don't like it?  I, of course,
> have heard and seen that several vendors have fixed this in the more
> recent releases.  This type of bug is something that everyone who writes
> software has to deal with.  If you raise an exception for bad input it is
> bad form to crash or reset your application.
> 
> BTW, I am sure all have heard this argument before.  I just wanted to get
> this topic renewed.
> 
> Regards,
> 
> Blaine
> 
>