netdev - Re: [PATCH] Fix routing tables with id

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Date:	Tue, 3 Jun 2008 17:15:04 +0200 (CEST)
From:	Krzysztof Oledzki <olel@....pl>
To:	Patrick McHardy <kaber@...sh.net>
cc:	Jarek Poplawski <jarkao2@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH]  Fix routing tables with id > 255 for legacy software



On Tue, 3 Jun 2008, Patrick McHardy wrote:

> Krzysztof Oledzki wrote:
>> On Tue, 3 Jun 2008, Patrick McHardy wrote:
>> 
>>> Well, if people already use table 253, I guess they might care.
>> 
>> Not really as if pople use a FRA_TABLE aware application they should not 
>> notice any difference.
>
> In that case not of course.
>
>>> I'm not convinced this is any better than overflowing.
>> 
>> But if they use FRA_TABLE unaware application than overflowing means 
>> mismatching all:
>>  - N*256 table as RT_TABLE_UNSPEC
>>  - N*256+253 tables as RT_TABLE_DEFAULT
>>  - N*256+254 tables as RT_TABLE_MAIN
>>  - N*256+255 tables as RT_TABLE_LOCAL
>> 
>> And as I just find out, when it happens is quite unexpected and can really 
>> hurt. :(
>> 
>>> And I still don't see any other way to handle this properly.
>> 
>> Exactly. So that's why I came with above solution, similar to AS_TRANSIT 
>> idea used in BGP to handle 16bit -> 32bit ASN transformation.
>
> I think the proper solution is what I wrote in the changelog
> entry: fix userspace applications when using extended table
> IDs.

It is unquestionably true, however it may take some time and people may 
still use old version of such applications for whatsoever reasons.

> Your patch makes it more predictable, so I'm not completely
> opposed, but still its just a workaround.

Indeed - it is a workaround but I believe we need it.

Best regards,

 				Krzysztof Olędzki