OSPF on OpenBSD

[Ondrej Zajicek]

On Wed, Sep 29, 2021 at 09:35:13AM +0200, Bastien Durel wrote:
> Hello,
> 
> I'm trying to use bird to replace ospfd on OpenBSD, but it seems to
> have a strange effect on the networking stack :(
> 
> I've tried multiple times, from OpenBSD 6.6 to 6.9, with bird2 (2.0.8
> now)
> 
> ...
> 
> On OpenBSD mailing list, someone said the problem may be bird
> overwriting the 10.42.42/24 route (which was directly connected) by
> another (the flags changed from UCn to U1h)

Hello

It is true, basic OSPF configuration rewrites direct routes. That is OK
on Linux, as it allows multiple routes for same network, so kernel
ones are also kept, but on BSD there is only one so they are removed.

During our testing, it works on FreeBSD / NetBSD / OpenBSD at least while
BIRD is running, but likely we have some old versions for testing that
might behave differently.

One thing that should work as a workaround is to have protocol direct,
which generates direct routes more preferred than ones from OSPF, and
then filter them out in kernel protocol, so they are not pused to kernel:

protocol direct {
    ipv4;
    ipv6;
}

protocol kernel kernel4 {
    ipv4 {
        export where source != RTS_DEVICE;
    };
}


But this is something we should improve in BIRD.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."