nexedi / babeld

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.

Pointless, but clearer to me.

This protects against clock stepping if CLOCK_MONOTONIC is implemented.

Recent kernels don't include RTA_DST in the default route.  This fixes
incorrect parsing of such entries.  Reported by Robert Lukan.

This saves 512 bytes of BSS.

This would cause an infinite loop when the clock was stepped.