Problem with OSPF NBMA and MikroTik

[Ondrej Zajicek]

On Thu, May 19, 2011 at 12:36:38AM +0200, Adrian Czapek wrote:
> W dniu 2011-05-19 00:41, Ondrej Zajicek pisze:
>> On Wed, May 18, 2011 at 09:41:14PM +0200, Marek Wajdzik wrote:
>>> Hi.
>>>
>>> 172.30.0.1 - compiled from fresh sources: bird 1.3.1 running debian
>>> with kernel 2.6.38.6 x64
>>> 172.30.0.120 - It is a mikrotik routeros version 5.2 node with configured ospf.
>>>
>>> When I restart the ospf in bird (birdc restrart OSPF) :P Mikrotik says:
>>
>> Hello
>>
>> Could you try BIRD with this (attached) patch?
>>
> Just applied this one and looks the issue is gone.
> However, I had more ways to trigger 'wrong checksum' on MTs so I will  
> try them all now and report.

Hello

There is authentication data field in OSPF packet, which should be
ignored if authentication is not used. Mikrotik OSPF, contrary to the
RFC, checked the value of this field (or used the value when computed
checksums) in that case. Because BIRD sent some random values in that,
Mikrotik rejected that packets, that caused incompatibility.
This patch fixed that.

So the problem was triggered essentially by some unpredictable changes
in memory and i would expect all the ways to trigger that problem
caused that.

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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