BGP: Fix 'deterministic med' to work with 'merge paths' (f6a6a776) · Commits · 戴 / Bird

proto/bgp/attrs.c

+19 −21

Original line number	Diff line number	Diff line
		@@ -1747,7 +1747,7 @@ bgp_rte_mergable(rte pri, rte sec)
		return 0;

		/* RFC 4271 9.1.2.1. Route resolvability test */
		if (!rte_resolvable(sec))
		if (rte_resolvable(pri) != rte_resolvable(sec))
		return 0;

		/* LLGR draft - depreference stale routes */
		@@ -1833,7 +1833,7 @@ bgp_rte_recalculate(rtable table, net net, rte new, rte old, rte *old_best)
		rte *key = new ? new : old;
		u32 lpref = key->pref;
		u32 lasn = bgp_get_neighbor(key);
		int old_is_group_best = 0;
		int old_suppressed = old ? old->u.bgp.suppressed : 0;

		/*
		* Proper RFC 4271 path selection is a bit complicated, it cannot be
		@@ -1880,7 +1880,7 @@ bgp_rte_recalculate(rtable table, net net, rte new, rte old, rte *old_best)
		* We could find the best-in-group and then make some shortcuts like
		* in rte_recalculate, but as we would have to walk through all
		* net->routes just to find it, it is probably not worth. So we
		* just have two simpler fast cases that use just the old route.
		* just have one simple fast case that use just the old route.
		* We also set suppressed flag to avoid using it in bgp_rte_better().
		*/

		@@ -1889,23 +1889,11 @@ bgp_rte_recalculate(rtable table, net net, rte new, rte old, rte *old_best)

		if (old)
		{
		old_is_group_best = !old->u.bgp.suppressed;
		old->u.bgp.suppressed = 1;
		int new_is_better = new && bgp_rte_better(new, old);

		/* The first case - replace not best with worse (or remove not best) */
		if (!old_is_group_best && !new_is_better)
		/* The fast case - replace not best with worse (or remove not best) */
		if (old_suppressed && !(new && bgp_rte_better(new, old)))
		return 0;

		/* The second case - replace the best with better */
		if (old_is_group_best && new_is_better)
		{
		/* new is best-in-group, the see discussion below - this is
		a special variant of NBG && OBG. From OBG we can deduce
		that same_group(old_best) iff (old == old_best) */
		new->u.bgp.suppressed = 0;
		return (old == old_best);
		}
		}

		/* The default case - find a new best-in-group route */
		@@ -1922,6 +1910,16 @@ bgp_rte_recalculate(rtable table, net net, rte new, rte old, rte *old_best)
		if (!r)
		return 0;

		/* Found if new is mergable with best-in-group */
		if (new && (new != r) && bgp_rte_mergable(r, new))
		new->u.bgp.suppressed = 0;

		/* Found all existing routes mergable with best-in-group */
		for (s=net->routes; rte_is_valid(s); s=s->next)
		if (use_deterministic_med(s) && same_group(s, lpref, lasn))
		if ((s != r) && bgp_rte_mergable(r, s))
		s->u.bgp.suppressed = 0;

		/* Found best-in-group */
		r->u.bgp.suppressed = 0;

		@@ -1935,9 +1933,9 @@ bgp_rte_recalculate(rtable table, net net, rte new, rte old, rte *old_best)
		* rte_recalculate() without ignore that possibility).
		*
		* There are three possible cases according to whether the old route
		* was the best in group (OBG, stored in old_is_group_best) and
		* whether the new route is the best in group (NBG, tested by r == new).
		* These cases work even if old or new is NULL.
		* was the best in group (OBG, i.e. !old_suppressed) and whether the
		* new route is the best in group (NBG, tested by r == new). These
		* cases work even if old or new is NULL.
		*
		* NBG -> new is a possible candidate for the best route, so we just
		* check for the first reason using same_group().
		@@ -1952,7 +1950,7 @@ bgp_rte_recalculate(rtable table, net net, rte new, rte old, rte *old_best)
		if (r == new)
		return old_best && same_group(old_best, lpref, lasn);
		else
		return old_is_group_best;
		return !old_suppressed;
		}

		struct rte *

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