Re: [homenet] draft-boutier-homenet-source-specific-routing-00

[Juliusz Chroboczek <[e-mail]>]

> In my example I assumed that every gateway announces a
> non-source-specific route too, so there should be no special code
> necessary for the "normal" routers.

Unless I'm missing something, that's not as simple as you make it.
Consider this:

  -- A -- B --

Suppose that A announces (::/0, alpha), and B announces (::/0, beta)
(two source-specific default routes).  Suppose further that, as you
suggest, both A and B announce default routes (::/0, ::/0).

What happens when A receives a packet that's not sourced in either
alpha or beta?  It will route it towards B (which, you will recall, is
announcing a non-specific default route).  Now B will send the packet
back to A, and you're in trouble.

So you cannot just announce a default route, you must redistribute
a blackhole route.  But then, you might end up overriding a bona fide
default route with your blackhole.  Grr.

I'm pretty sure various workarounds can be devised (such as using
a very high metric for the blackhole route, or adding a flag "this
route must be ignored by source-specific routers"), but I'd obviously
prefer avoiding such hacks.

-- Juliusz