User can specify list of route attributes in the configuration file
and run route aggregation on the export side of the pipe protocol.
Routes are sorted and for every group of equivalent routes
new route is created and exported to the routing table.
It is also possible to specify filter which will run for every
route before aggregation.
Furthermore, it will be possible to set attributes of new routes
according to attributes of the aggregated routes.
This is a work in progress.
The patch adds support for channels, structures connecting protocols and
tables and handling most interactions between them. The documentation is
missing yet.
The nest-protocol interaction is changed to better handle multitable
protocols. Multitable protocols now declare that by 'multitable' field,
which tells nest that a protocol handles things related to proto-rtable
interaction (table locking, announce hook adding, reconfiguration of
filters) itself.
Filters and stats are moved to announce hooks, a protocol could have
different filters and stats to different tables.
The patch is based on one from Alexander V. Chernikov, thanks.
It seems that by adding one pipe-specific exception to route
announcement code and by adding one argument to rt_notify() callback i
could completely eliminate the need for the phantom protocol instance
and therefore make the code more straightforward. It will also fix some
minor bugs (like ignoring debug flag changes from the command line).
