While having the filter code still reentrant if we really need,
the compiler can now do constant propagation and address the
thread local storage directly to save some computation time.
This is a major change of how the filters are interpreted. If everything
works how it should, it should not affect you unless you are hacking the
filters themselves.
Anyway, this change should make a huge improvement in the filter performance
as previous benchmarks showed that our major problem lies in the
recursion itself.
There are also some changes in nest and protocols, related mostly to
spreading const declarations throughout the whole BIRD and also to
refactored dynamic attribute definitions. The need of these came up
during the whole work and it is too difficult to split out these
not-so-related changes.
The static filter state was messy and blocked the planned parallel
execution of filters. Anyway, this will be also slower as the state
structure must be passed almost everywhere with us.
For local route marking purposes, local custom route attributes may be
defined. These attributes are seamlessly stripped after export filter to
every real protocol like Kernel, BGP or OSPF, they however pass through
pipes. We currently allow at most 256 custom attributes.
This should be much faster than currently used bgp communities
for marking routes.
Use ACCESS_RTE to guard **f_rte, use ACCESS_EATTRS to guard **f_eattrs.
Use f_rta_cow() before writing to rta or eattrs, use f_rte_cow() before
writing preference (stored in rte).
Do not access eattrs indirectly through (*f_rte)->attrs->eattrs, it is
way too slow. The cached pointer is faster.
This is a fundamental change of an original (1999) concept of route
processing inside BIRD. During import/export, there was a temporary
ea_list created which was to be used instead of the another one inside
the route itself.
This led to some confusion, quirks, and strange filter code that handled
extended route attributes. Dropping it now.
The protocol interface has changed in an uniform way -- the
`struct ea_list *attrs` argument has been removed from store_tmp_attrs(),
import_control(), rt_notify() and get_route_info().
