This basically means that:
* there are some more levels of indirection and asynchronicity, mostly
in cleanup procedures, requiring correct lock ordering
* all the internal table operations (prune, next hop update) are done
without blocking the other parts of BIRD
* the protocols may get their own loops very soon
This commit prevents use-after-free of routes belonging to protocols
which have been already destroyed, delaying also all the protocols'
shutdown until all of their routes have been finally propagated through
all the pipes down to the appropriate exports.
The use-after-free was somehow hypothetic yet theoretically possible in
rare conditions, when one BGP protocol authors a lot of routes and the
user deletes that protocol by reconfiguring in the same time as next hop
update is requested, causing rte_better() to be called on a
not-yet-pruned network prefix while the owner protocol has been already
freed.
In parallel execution environments, this would happen an inter-thread
use-after-free, causing possible heisenbugs or other nasty problems.
Routes are now allocated only when they are just to be inserted to the
table. Updating a route needs a locally allocated route structure.
Ownership of the attributes is also now not transfered from protocols to
tables and vice versa but just borrowed which should be easier to handle
in a multithreaded environment.
Add support to set or read outgoing MPLS labels using filters. Currently
this supports the addition of one label per route for the first next hop.
Minor changes by committer.
Broken detection of top-level case caused crash when return was called
from top-of-stack position. It should behave as reject/accept.
Thanks to Damian Zaremba for the bugreport.
Add 'weight' route attribute that allows to get and set ECMP weight of
nexthops. Similar to 'gw' attribute, it is limited to the first nexthop,
but it is useful for handling BGP multipath, where an ECMP route is
merged from multiple regular routes.
Implement regex-like '+' operator in BGP path masks to match previous
path mask item multiple times. This is useful as ASNs may appear
multiple times in paths due to path prepending for traffic engineering
purposes.
Do not apply dynamic type check for second argument of AND/OR, as it is
not evaluated immediately like regular argument would be.
Thanks to Mikael for the bugreport.
Most expressions can be type-validated in parse time. It is not
strong enough to eliminate runtime checks, but at least one gets
errors immediately during reconfigure.
Function bodies were compared in post-parse time, yet the result was not
used and the functions were incorrectly considered the same as before.
Now the result is used to reload affected protocols.
