[PATCH] babel: Rework seqno request handling to track sender, not destination

[Toke Høiland-Jørgensen]

Juliusz Chroboczek <jch at irif.fr> writes:

>> Right, so after going after this a couple of times, I think I see the
>> discrepancy here: in Bird we're currently doing retransmission at every
>> hop;
>
> Yep, that's the intent of RFC 8966 Section 3.8.1 (I agree it's not
> perfectly clear):
>
>    A single request MUST NOT be duplicated: it MUST NOT be forwarded to
>    a multicast address, and it MUST NOT be forwarded to multiple neighbours.
>
> The goal is to have a bound on the number of requests in flight for
> a given prefix: it's at most equal to the number of routers that are at
> the border of the subnetwork for which the prefix became unfeasible.  If
> you start resending requests within the network, you're multiplying a term
> that's exponential in the diameter of the feasible part of the network.
> And exponentials make me nervous.

Right, makes sense. I'll send a v2 of the patch reworking the handling
to only resend requests we originated (and get rid of the neighbour in
the request state).

-Toke