Init ipoib_neigh.dgid

Ipoib can miss a change in dgid under some conditions. The problem is caused when ipoib_neigh->dgid contains a stale address. The fix is to set ipoib_neigh->dgid to zero in ipoib_neigh_alloc().

Detail description: A systems using bonding on its ipoib interface has switched it active slave interface from interface A to B and back to A setting up the situation for this bug. The system that fails will not correctly processes the 2nd address change.

When an address has changed neighbor->ha is updated with the new address. Each neighbor has an associated ipoib_neigh. ipoib_neigh->dgid also holds a copy of the remote node's hardware address. When an address changes neighbor->ha is updated by the network layer (arp code) with the new address. Ipoib detects this change in ipoib_start_xmit() by comparing neighbor->ha with ipoib_neigh->dgid. The bug is that ipoib_neigh->dgid already contains the new address(A) thus the change from B to A is missed by ipoib. Here is the sequence of events:

ipoib_neigh->dgid = A neighbor->ha=A

The address is switched to B (the first switch)

neighbor->ha=B

The change is seen in ipoib_start_xmit(). neighbor->ha != ipoib_neigh->dgid

The ipoib_neigh is released, and a new one is allocated.

The memory allocation system returned the same chunk of memory that was just released, therefore ipoib_neigh->dgid still contains A at this point.

ipoib_neigh->dgid should be updated in neigh_add_path(), but if the following conditions are true dgid is not updated.

1) __path_find() returns a path

2) path->ah is NULL

The remote system now switches from address B to A, neighbor->ha is updated to A.

Now we have: ipoib_neigh->dgid = A neighbor->ha=A

Since the address are the same ipoib won't process the change in address.

------------------------------------------------------

 drivers/infiniband/ulp/ipoib/ipoib_main.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

index 2bf5116..25ef50b 100644
@@ -884,6 +884,7 @@ struct ipoib_neigh *ipoib_neigh_alloc(struct neighbour *neighbour,
 
 	neigh->neighbour = neighbour;
 	neigh->dev = dev;
+	memset(&neigh->dgid.raw, 0, sizeof(union ib_gid));
 	*to_ipoib_neigh(neighbour) = neigh;
 	skb_queue_head_init(&neigh->queue);
 	ipoib_cm_set(neigh, NULL);

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html

thanks, applied at last
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html