bird 2.0.3 does not install multipath route in kernel

[Kenth Eriksson]

On Thu, 2019-02-28 at 17:59 +0100, Ondrej Zajicek wrote:
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> On Thu, Feb 28, 2019 at 01:15:02PM +0000, Kenth Eriksson wrote:
> > We have some multi-path routes that fails to get pushed into the
> > kernel. We are running bird 2.0.3 and kernel 4.14.92+.
> > 
> > 
> > bird> show route
> > ...
> > Table master4:
> > 
> > 10.210.138.3/32      unicast [ospf1 13:24:23.022] E1 (145/1020)
> > [10.210.138.3]
> >       via 10.210.138.2 on p1-1-1-1-2 weight 1
> >       via 10.210.138.2 on p1-1-5-1-6 weight 1
> > ...
> > bird>
> 
> It is possible that it is related to the same IP address on different
> interfaces? Are these two interfaces to the same network?
> 
These are two unnumbered point-to-point interfaces.

We don't have multipath enabled in our kernel
(CONFIG_IP_ROUTE_MULTIPATH). How does bird tell whether the kernel
supports multipath? Probing run time via netlink? Didn't find any
configure.ac option.

If disable multipath in the bird config like this;

protocol ospf v2 ospf1 {
    ecmp no;
    ...

then I could get bird to push one of the ospf multipath routes to the
kernel again. 


> 
> > The bird log has the following warning messages (unclear if it is
> > related):
> > 
> > 2019-02-28 13:30:38.343 <WARN> Netlink: Invalid argument
> > 
> > What is the expected behaviour for bird here? Install both routes
> > or
> > just one of them?
> > 
> > Thanks,
> > Kenth
> 
> --
> Elen sila lumenn' omentielvo
> 
> Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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