Static IPv6 route with a link-local next-hop

[Ondrej Zajicek]

On Wed, Jul 08, 2015 at 07:29:26PM +0200, Baptiste Jonglez wrote:
> Hi,
> 
> Since this was non-obvious to get working, I'm sharing this here.
> 
> To add a static route via a link-local next-hop, this configuration works:
> 
>     protocol direct {
>       interface "eth0";
>     }
> 
>     protocol static {
>       route 2001:db8::/32 via fe80::1%eth0;
>     }
> 
> 
> If the "protocol direct" is omitted, then Bird never uses the route,
> and doesn't give any reason why in the logs (even with debug activated).

Hi

Not sure what problem you hit here, but it works for me without
the protocol direct:

bird> show route
2001:db8::/32      via fe80::1 on eth1 [static1 22:15:25] * (200)

> Another difficulty is that all of the following are syntactically correct:
> 
>   route 2001:db8:1::/48 via "eth0";
>   route 2001:db8:2::/48 via fe80::1%eth0;
>   route 2001:db8:3::/48 via "fe80::1%eth0";
>   route 2001:db8:4::/48 via fe80::1;
> 
> However, only the first two forms are legal:
> 
> - « via "eth0" » adds a directly connected route (which is probably not
>   what you want depending on your use-case, but fully legal)
> 
> - « via fe80::1%eth0 » gives the expected result, a static route via
>   fe80::1 on interface eth0.
> 
> - « via "fe80::1%eth0" » fails silently.  I guess the parser takes all
>   this as an interface name, which (obviously) does not exist.

Yes


> - « via fe80::1 » fails at runtime with « Static route destination fe80::1
>   is invalid. Ignoring. » in the logs, which is a very sensible behaviour.

Perhaps it should fail at configure-time


> I think this is intricate enough to be noted somewhere in a documentation
> or wiki.  Is this wiki [https://gitlab.labs.nic.cz/labs/bird/wikis/home]
> open to contributions?

It is true that it should be documented in the static route documentation.

Generally, link-local address handling in BIRD is in most cases
afterthought and often it is not very elegant. For static protocol, i
would perhaps prefer the syntax similar to 'ip' tool:

route 2001:db8:1::/48 via 2001:db8:2::1;
route 2001:db8:2::/48 dev eth0;
route 2001:db8:3::/48 via fe80::1 dev eth0;


-- 
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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