[Babel-users] Buggy routes exported by babeld

[Baptiste Jonglez]

On Tue, Apr 23, 2013 at 12:48:44PM +0200, Gabriel Kerneis wrote:
> Hi Denis,
> 
> I'm not sure I understand: which exact command do you use to get the above
> output?  I can see similar entries, but only if I request cache entries
> specifically:
> 
> $ ip -6 route show cache
> 2a00:1450:4007:80a::1013 via 2001:41d0:1:f1ff:ff:ff:ff:ff dev eth0  metric 0 
>     cache 
> 
> If recent kernels output such entries even when you do not request "cache", this
> might explain the issue (assuming the same feature/bug occurs at a lower level,
> in the kernel calls performed by babeld).

The kernel I'm using doesn't.

However, the routing cache seems to be the root of the issue. I'm
using the following program to monitor kernel route changes using
netlink (which is what babeld also does):

  http://paste.isomorphis.me/3SL

(adapted from [1] to work with IPv6)

In my case, the kernel indeed reports a new route each time a new host
is contacted. I've tested it on Archlinux (kernel 3.8.7) and Debian
testing (kernel 3.2.0), which both expose the same behavior.


I'm assuming that babeld also picks these routes up, which explains
why it redistributes them if they are not filtered by the configuration.

A possible fix would be to discard all routes related to the routing
cache (I haven't checked if netlink has an option for this, however).

Baptiste

[1] http://stackoverflow.com/questions/11788326/extract-current-route-from-netlink-message-code-attached 
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