tipc: fix compatibility bug in link monitoring

commit 8172981 ("tipc: fix link priority propagation") introduced a compatibility problem between TIPC versions newer than Linux 4.6 and those older than Linux 4.4. In versions later than 4.4, link STATE messages only contain a non-zero link priority value when the sender wants the receiver to change its priority. This has the effect that the receiver resets itself in order to apply the new priority. This works well, and is consistent with the said commit. However, in versions older than 4.4 a valid link priority is present in all sent link STATE messages, leading to cyclic link establishment and reset on the 4.6+ node. We fix this by adding a test that the received value should not only be valid, but also differ from the current value in order to cause the receiving link endpoint to reset. Reported-by: Amar Nv <[email protected]> Signed-off-by: Jon Maloy <[email protected]> Signed-off-by: David S. Miller <[email protected]>
kyagi · Nov 26, 2016 · f796755 · f796755
1 parent 97db8af
commit f796755
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/net/tipc/link.c b/net/tipc/link.c
@@ -1492,8 +1492,9 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 		if (in_range(peers_tol, TIPC_MIN_LINK_TOL, TIPC_MAX_LINK_TOL))
 			l->tolerance = peers_tol;
 
-		if (peers_prio && in_range(peers_prio, TIPC_MIN_LINK_PRI,
-					   TIPC_MAX_LINK_PRI)) {
+		/* Update own prio if peer indicates a different value */
+		if ((peers_prio != l->priority) &&
+		    in_range(peers_prio, 1, TIPC_MAX_LINK_PRI)) {
 			l->priority = peers_prio;
 			rc = tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
 		}