bird6: "Netlink: No such process" error from kernel proto on OSPF multipath prefixes

[Gruber Gerold]

Hi list and Ondrej,

as stated earlier, we also would very much appreciate the implementation
of ecmp for bird6.

Unfortunately we cannot offer to take part in efforts to enhance bird's
capabilities due to a lack of resources.

But we are also waiting impatiently for the availability of ecmp for IPv6.

Best regards

Gerold


Am 28.07.2015 um 15:38 schrieb Israel G. Lugo:
> Hello,
> 
> On 27-07-2015 20:57, Ondrej Zajicek wrote:
>> The problem here is that Linux IPv6 multipath API is different from the
>> IPv4 multipath API and very inconvenient for our purposes.
>>
>> AFAIK people from Cumulus Networks are trying to fix this issue directly
>> in Linux kernel to have more reasonable API, which would probably make
>> BIRD work with some minimal fixes.
>>
>> For more details, see slides 15+ in:
>> https://www.netdev01.org/docs/prabhu-linux_ipv4_ipv6_inconsistencies_talk_slides.pdf
> 
> I see. Indeed there can be some nuisances, especially in cases with
> multiple concurrent insertions/deletions, where there might apparently
> be duplicate netlink messages.
> 
> I found a paper by the same author on this subject, which goes into a
> bit more detail on the suggested solutions:
> 
> http://people.netfilter.org/pablo/netdev0.1/papers/The-case-for-eliminating-inconsistencies-between-IPv4-and-IPv6-kernel-User-API.pdf
> 
> Do you happen to know what is the status of this proposal in the Linux
> kernel? I would imagine that it will take a while for these changes to
> be available in production, if they are accepted at all.
> 
> May I suggest that it might be worthwhile the effort to attempt tackling
> this problem in user space, at least for now? The multipath feature does
> help a lot, and as it is now we can't really use it (routes are
> constantly being added and deleted).
> 
> As I understand the problem, this would require some work of keeping the
> internal route table in sync with the kernel notifications: detecting
> when a notification relates to an already existing prefix and add to to
> the internal table as a multihop route, etc. I am not familiar with the
> BIRD codebase other than through a cursory glance, but I could try to
> think about it a bit. Of course, it would be much easier with your guidance.
> 
> I haven't seen how others implemented  this, for example the Quagga
> people, but they must have had to deal with it somehow.
> 
> Regards,
> 
> --
> Israel G. Lugo

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