Setting ONLINK flag for arbitrary routes

[Ondrej Zajicek]

On Sun, Apr 29, 2018 at 10:54:06PM +0200, Toke Høiland-Jørgensen wrote:
> Hi
> 
> Is it possible to set the ONLINK flag for arbitrary routes?
> 
> The use case is a common setup in mesh networks: All devices have a /32
> assigned to the interface and advertise this as the nexthop for v4
> routes. The routing protocol then installs all kernel routes as onlink,
> allowing routes to be installed even though the nexthop is not in the
> same subnet as the local link address.
> 
> Is this possible to configure in Bird currently?

Hi

Onlink flag cannot be set in filters, it can be set by protocol code
(currently done by Static and Kernel). Generally protocols are expected
to validate next hop address by neigh_find2() before a route is
propagated to nest. Babel does not do that, probably because of its
beginning as IPv6-only implementation (which uses link-local addresses).

It cannot be done currently, but it could be done by a simple patch, as
most of infrastructure is here. See proto/static/static.c file for onlink
handling.

-- 
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."