[Babel-users] Investigating kernel's cache

[Dave Taht]

I am curious if you've got anywhere with this?

I just saw kernel commit e0056593b61253f1a8a9941dacda22e73b963cdc
 ip_tunnel: fix ip_tunnel_lookup

and thought that might have been an issue somewhat related.


On Wed, Jul 16, 2014 at 6:00 PM, Matthieu Boutier <
boutier at pps.univ-paris-diderot.fr> wrote:

> Hi,
>
> we are investigating some strange behaviour with "native" source specific
> routes (i.e. not with multiple routing tables): it seems cached routes may
> make things go wrong.  Here are the details.
>
> I have two default routes:
>
>     default from 2001:41d0:1:f100::/56 via fe80::4e72:b9ff:fe43:7608 dev
> tun-ariane  proto 42  metric 1024
>     default via fe80::8618:8803:5474:9b01 dev eth1  proto zebra  metric 3
>
> and I try to use mtr with two different addresses:
>
> (1) mtr 2a00:1450:4007:804::1006 --address
> 2001:660:3301:9208:e246:9aff:fe4e:912e
> (2) mtr 2a00:1450:4007:804::1006 --address
> 2001:41d0:1:f19f:e246:9aff:fe4e:912e
>
> When 1 is run first, the following route is added to the cache, and then,
> when 2 is launched, the wrong path is taken since the cache match.
>
>     2a00:1450:4007:804::1006 via fe80::8618:8803:5474:9b01 dev eth1
>  metric 0
>
> When 2 is run first, the following two entries are in the cache, and
> things goes right (at least while the cache keeps the specific route).
>
>     2a00:1450:4007:804::1006 from 2001:41d0:1:f100::/56 via
> fe80::4e72:b9ff:fe43:7608 dev tun-ariane  metric 0
>     2a00:1450:4007:804::1006 via fe80::8618:8803:5474:9b01 dev eth1
>  metric 0
>
>
> This has been done on an openwrt 3.10.36 and on a Debian 3.13.7.  This
> behaviour was not observed with the same route entries added by hand with a
> /128 destination, i.e.
>
>     2a00:1450:4007:804::1006 from 2001:41d0:1:f100::/56 via
> fe80::4e72:b9ff:fe43:7608 dev tun-ariane
>     2a00:1450:4007:804::1006 via fe80::8618:8803:5474:9b01 dev eth1
>
> The packets are well routed when multiple routing tables are used.
>
> Does anyone has some feedback about this ?
>
> Matthieu
>
>


-- 
Dave Täht

NSFW:
https://w2.eff.org/Censorship/Internet_censorship_bills/russell_0296_indecent.article
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