bird's not forwarding point-to-point routes via OSPF

[Ondrej Zajicek]

On Wed, Oct 15, 2014 at 11:00:03AM -0700, Noel Burton-Krahn wrote:
> Is there something about point to point addresses that could keep bird
> from forwarding them?  I'm assigning a point-to-point address to a
> veth pair like so:
> 
>     ip link add veth1 type veth peer name veth2
>     ip addr add 10.0.0.1/32 peer 10.0.0.2/32 dev veth1
>     ip addr add 10.0.0.2/32 peer 10.0.0.1/32 dev veth2
> 
> Neither of those addresses get forwarded via OSPF to other hosts.
> They *do* get forwarded if I add the addresses without a peer like
> this:
> 
>     ip addr add 10.0.0.1/32 dev veth1
> 
> Now I've added the same address (10.0.0.1/32) to veth twice, and bird
> is forwarding a route for that address to OSPF peers.
> 
> Is there a way for bird to accept the "peer" address?  I tried "learn"
> in the kernel but that didn't help.

.. also ..

On Fri, Oct 10, 2014 at 12:05:30PM +0200, Thomas Goldberg wrote:
> Hello,
> 
> we've OSPF running over a openvpn ptp tunnel and some problems with
> the routes injected by bird (v1.4.5).
...
> Shouldn't bird inject routes like this on the corresponding router
> (without having to learn them via the direct protocol)?
> 10.176.3.29/32 dev lo [o_internal 2014-10-09 00:00:00] * I (150/0) [10.176.3.29]

Hello

This is IMHO the same issue. It is an intentional behavior, BIRD does not
inject local address for links with peer addresses, mainly based on idea
that links with such addresses are just variants of 'unnumbered' ptp
links and these addresses are just general 'loopback' addresses and are
usually also used on other interfaces (like the explicit loopback
interface) [*].

Also note that it is usually simpler to add wanted addresses (using
explicit loopback interface or using 'stubnet' option) in use cases where
they should be propagated than remove unwanted addresses in use cases
where they should not be propagated.

But in retrospect i am not sure if this behavior was really a good idea.
Perhaps automatic adding of host routes should be configurable and
enabled by default for peer addresses to ensure that all addresses on
OSPF-enabled interfaces are reachable in OSPF area.

Any comments (esp. arguments for or against it) to this issue?



[*] i.e. configuration like:

ip addr add 10.0.0.1/32 dev lo / dummy0
ip addr add 10.0.0.1/32 peer 10.0.0.2/32 dev eth0
ip addr add 10.0.0.1/32 peer 10.0.0.3/32 dev eth1
ip addr add 10.0.0.1/32 peer 10.0.0.4/32 dev eth2

-- 
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."
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