bird 2.0.3 does not install multipath route in kernel

[Ondrej Zajicek]

On Fri, Mar 01, 2019 at 08:57:28AM +0000, Kenth Eriksson wrote:
> > 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.

BIRD does not detect that. I don't know if there is a reasonable way
how to detect it. Just disable ECMP in OSPF if your kernel does not
support ECMP routes.

> 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. 

-- 
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."