Re: [homenet] HNCP: interaction with routing protocol?

Juliusz Chroboczek <jch@pps.univ-paris-diderot.fr> Fri, 18 December 2015 15:15 UTC

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From: Juliusz Chroboczek <jch@pps.univ-paris-diderot.fr>
Date: Fri, 18 Dec 2015 16:15:37 +0100
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Subject: Re: [homenet] HNCP: interaction with routing protocol?
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>> Shncpd has closer binding to the routing protocol, it marks its routes
>> as "proto 43" and expects the routing protocol to redistribute just
>> that; shncpd also occasionally inserts dummy "proto 43" routes into the
>> kernel, just so that they get redistributed into the routing protocol.

> Just redistributing protocol 43 will also make you miss the default
> route you get by DHCP from an uplink.

If you're announcing an external connection into the HNCP domain, shncpd
will install a proto 43 source-specific default route.  See route_externals
in prefix.c.

If you're not announcing an external connection, then indeed you need to
manually arrange redistribution of the default route.  Shncpd doesn't do
that for you, since it doesn't know whether forwarding is set up for the
route and whether there's the need to set up a source prefix for BCP38.

(This is where hnetd and shncd differ.  Hnetd is optimistic, it assumes
that forwarding is set up and that the default route has a suitable source
prefix attached.  Shncpd is pessimistic, and fears that redistributing
random default routes into the routing protocol will create blackholes.
Somebody once wrote that optimists and pessimists die the same way, they
just live differently.)

-- Juliusz