Known issues:

  - we create a neighbour entry before the first successful challenge;
  - we compute HMAC for each HMAC TLV rather than just once;
  - we only support sending one HMAC TLV;
  - we don't support key rotation.
Co-authored-by: Clara Do <clarado_perso@yahoo.fr>
Co-authored-by: Weronika Kolodziejak <weronika.kolodziejak@gmail.com>

Thanks to Dave Taht.

That patch was fixing a little bug, but makes another bigger one.
The previous patch fixes both.

This reverts commit e687a58f.

Share the data better.

When the v6 prefix is ::/0, then it is considered as less specific than
any v4-mapped prefix.

Remark that "no source prefix" is encoded by "src_plen == 0".  This
might be an issue, since "src_plen == 0" means ::/0, a v6 prefix.  So
the route (1.1.1.1/32 from 0.0.0.0/0) is internally represented by
(1.1.1.1/32 from ::/0).  When compared with  (::/0 from 2001:db8::/32),
the two source prefixes are comparable.  This is not a problem in
practice, since 2 pairs of prefixes are disjoint whether the dst
prefixes or the src prefixes are disjoint.

parse_msec() is not specific to milliseconds, it can parse any
fixed-point string.  It can be used, for instance, to parse a
fixed-point string written in milliseconds and interpret it as an
integer in microseconds.

This is needed for the stability aware code.

Stress the asymmetry with timeval_add_msec, which is purely functional.

Stress the asymmetry with timeval_add_msec, which is purely functional.

Pointless, but clearer to me.