This is a reimplementation of commit 0f2be469f8
by Alexander Zubkov. In the master branch, changes in commit eb937358
broke setting of channel preference for alien routes learned during
scan. The preference was set only for async routes.
The original solution is extended here to accomodate for v3 specifics.
Remove compile-time sysdep option CONFIG_ALL_TABLES_AT_ONCE, replace it
with runtime ability to run either separate table scans or shared scan.
On Linux, use separate table scans by default when the netlink socket
option NETLINK_GET_STRICT_CHK is available, but retreat to shared scan
when it fails.
Running separate table scans has advantages where some routing tables are
managed independently, e.g. when multiple routing daemons are running on
the same machine, as kernel routing table modification performance is
significantly reduced when the table is modified while it is being
scanned.
Thanks Daniel Gröber for the original patch and Toke Høiland-Jørgensen
for suggestions.
The learnt routes are now pushed all into the connected table, not only
the best one. This shouldn't do any damage in well managed setups, yet
it should be noted that it is a change of behavior.
If anybody misses a feature which they implemented by misusing this
internal learn table, let us know, we'll consider implementing it in a
better way.
Passing protocol to preexport was in fact a historical relic from the
old times when channels weren't a thing. Refactoring that to match
current extensibility needs.
There were quite a lot of conflicts in flowspec validation code which
ultimately led to some code being a bit rewritten, not only adapted from
this or that branch, yet it is still in a limit of a merge.
For now, all route attributes are stored as eattrs in ea_list. This
should make route manipulation easier and it also allows for a layered
approach of route attributes where updates from filters will be stored
as an overlay over the previous version.
