When we lose a route and have no feasible alternate, we should send requests
straight away rather than waiting for a periodic update.  If we have an
unfeasible route, send according to that route and resend, otherwise do
a multicast.

Reported by janus.

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

This reverts commit e687a58f.

Quiet git more.

Share the data better.

route.c was the only routine in all of babeld that had tabs creep in.

ignore core gmon.out and cscope.out

I took the "const" inside disambiguation.c as definitive.

In order to address this, this patch removes the <linux/if_bridge.h>
inclusion, and instead defines BRCTL_GET_BRIDGES to the appropriate
value if it's not provided by the C library.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

The previous choice was not unique in the presence of multiple next hops.

The code assumes that route->channels is NULL when route->channels_len
is 0, such that free(route->channels) will work.

Think about this scenario:
  update(r, some channels)  # route->channels = malloc(…)
  update(r, no channel)  # free(route->channels)
  update(r, no channel)  # free(route->channels)

Thanks to Dave Taht for pointing the issue.

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.

This allows 0 to appear within a channel list, which is consistent with
draft-chroboczek-babel-diversity-routing-01.

Noted by Matthieu Boutier.