How to make BIRD use the kernel routing metric?

[Ondrej Zajicek]

On Wed, Nov 14, 2018 at 08:21:12AM +0100, Lukas Liebig wrote:
> Hello,
> 
> I use BIRD 2.0.2 and want the OSPF daemon to announce the Linux kernel
> routing metric. For instance, if I run "ip route add table 44 to 10.2.3.0/24
> metric 1234 dev eth0", I want this route to propagate into BIRD. Therefore
> I use the kernel protocol configured like this:
> 
> protocol kernel {
>     ipv4 {
>         export all;
>         import all;
>     };
>     learn;
>     kernel table 44;
>     scan time 10;
> }
> 
> My OSPF instance reads data from table master4. "show ospf state" displays
> my kernel route as "external", but with "metric2 10000". According to the
> documentation https://bird.network.cz/?get_doc&v=20&f=bird-6.html#ss6.6 I
> tried to use metric 0; but without any effect. Do I overlook something
> essential?

Hi

Kernel metric is stored in attribute krt_metric, OSPF metric is set by
attribute ospf_metric1 or ospf_metric2.

Therefore the required behavior could be achieved by:

  ospf_metric2 = krt_metric;

in either kernel import filter or OSPF export filter.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."