[zebra] Bug #268, Fix race between add/delete of routes, sanitise rib queueing

[zebra] Bug #268, Fix race between add/delete of routes, sanitise rib queueing

2006-07-27 Paul Jakma <paul.jakma@sun.com>

	* rib.h: (struct rib) Add a route_node rn_status flag field,
	  this has to be copied every time head RIB of a route_node
	  changes.
	  Remove the rib lock field, not needed - see below.
	  Add a status field for RIB-private flags.
	* zebra_rib.c: Add a global for the workqueue hold time, useful
	  for testing.
	  (general) Fix for bug #268. Problem originally
	  detailed by Simon Bryden in [quagga-dev 4001].
	  Essentially, add/delete of a RIB must happen /before/ the
	  queue. Best-path selection (ie rib_process) and reaping of
	  freed RIBs can then be done after queueing. Only the route_node
	  is queued - no important RIB state (i.e. whether a RIB is to be
	  deleted) is queued.
	  (struct zebra_queue_node_t) Disappears, no longer need to
	  track multiple things on the queue, only the route_node.
	  (rib_{lock,unlock}) removed, RIBs no longer need to be
	  refcounted, no longer queued.
	  (rib_queue_qnode_del) Removed, deleted RIBs no longer deleted
	  via the queue.
	  (rib_queue_add_qnode) deleted
	  (rib_queue_add) Only the route_node is queued for best-path
	  selection, we can check whether it is already queued or
	  not and avoid queueing same node twice - struct rib * argument
	  is not needed.
	  (rib_link/unlink) (un)link RIB from route_node.
	  (rib_{add,del}node) Front-end to updates of a RIB.
	  (rib_process) Reap any deleted RIBs via rib_unlink.
	  Unset the route_node 'QUEUED' flag.
	  (General) Remove calls to rib_queue_add where add/del node was
	  called - not needed, update calls where not.
	  Ignore RIB_ENTRY_REMOVEd ribs in loops through route_nodes