From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Mon, 28 Feb 2011 17:47:56 +0000 (-0800)
Subject: kernel - Major bridging functionality added (bug fixes)
X-Git-Tag: v2.11.0~266^2~10
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/0e66e711119cf137abe99cf30014c6b2d5c93199

kernel - Major bridging functionality added (bug fixes)

* The root bridge was not taking into account the peer's weightings when
  calculating path costs.

  In order to do this the root bridge must use available peer info.  The
  peer info should already include both the local and remote's path costs
  since 'we' are the root, so our path cost will already be directly
  incorporated in the path cost the peer reports to us.

* Fixes issue where not-weighted path costs on root bridge were not
  synchronized with the weighted path costs of one or more of its peers.
---

diff --git a/sys/net/bridge/bridgestp.c b/sys/net/bridge/bridgestp.c
index a7e7961d0f..1af681ae01 100644
--- a/sys/net/bridge/bridgestp.c
+++ b/sys/net/bridge/bridgestp.c
@@ -453,6 +453,7 @@ bstp_configuration_update(struct bridge_softc *sc)
 	uint64_t	designated_root = sc->sc_bridge_id;
 	uint64_t	designated_bridge = sc->sc_bridge_id;
 	uint32_t	designated_cost = 0xFFFFFFFFU;
+	uint32_t	designated_root_cost = 0xFFFFFFFFU;
 	uint16_t	designated_port = 65535;
 	struct bridge_iflist *root_port = NULL;
 	struct bridge_iflist *bif;
@@ -510,6 +511,7 @@ bstp_configuration_update(struct bridge_softc *sc)
 set_port:
 		designated_root = bif->bif_peer_root;
 		designated_cost = bif->bif_peer_cost + bif->bif_path_cost;
+		designated_root_cost = bif->bif_peer_cost;
 		designated_bridge = bif->bif_peer_bridge;
 		designated_port = bif->bif_peer_port;
 		root_port = bif;
@@ -546,11 +548,18 @@ set_port:
 		 * select the root port (IFBIF_DESIGNATED is set at the
 		 * end).
 		 *
-		 * We do NOT use peer info here.
+		 * Since we are the root the peer cost should already include
+		 * our path cost.  We still need the combined costs from both
+		 * our point of view and the peer's point of view to match
+		 * up with the peer.
+		 *
+		 * If we used ONLY our path cost here we would have no peer
+		 * path cost in the calculation and would reach a different
+		 * conclusion than our peer has reached.
 		 */
-		if (bif->bif_path_cost > designated_cost)
+		if (bif->bif_peer_cost > designated_cost)
 			continue;
-		if (bif->bif_path_cost < designated_cost)
+		if (bif->bif_peer_cost < designated_cost)
 			goto set_port2;
 
 		if (bif->bif_port_id > designated_port)
@@ -560,10 +569,13 @@ set_port:
 		/* degenerate case (possible peer collision w/our key */
 
 		/*
-		 * New port
+		 * New port.  Since we are the root, the root cost is always
+		 * 0.  Since we are the root the peer path should be our
+		 * path cost + peer path cost.
 		 */
 set_port2:
-		designated_cost = bif->bif_path_cost;
+		designated_cost = bif->bif_peer_cost;
+		designated_root_cost = 0;
 		designated_bridge = sc->sc_bridge_id;
 		designated_port = bif->bif_port_id;
 		root_port = bif;
@@ -584,8 +596,7 @@ set_port2:
 	 */
 	if (root_port) {
 		sc->sc_designated_root = designated_root;
-		sc->sc_designated_cost = designated_cost -
-					 root_port->bif_path_cost;
+		sc->sc_designated_cost = designated_root_cost;
 		sc->sc_designated_bridge = designated_bridge;
 		sc->sc_designated_port = designated_port;
 		root_port->bif_flags |= IFBIF_DESIGNATED | IFBIF_ROOT;