IPoIB: Clear ipoib_neigh.dgid in ipoib_neigh_alloc()
IPoIB can miss a change in destination GID 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(). This can happen when a system using bonding on its IPoIB interfaces has switched its active interface from interface A to B and back to A. The system that fails over will not correctly processes the 2nd address change, as described below. 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 may already contain 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 and 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 so ipoib_neigh is released, and a new one is allocated. The allocator may return 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 again : ipoib_neigh->dgid = A and neighbor->ha = A Since the addresses are the same ipoib won't process the change in address. Fix this by zeroing out the dgid field when allocating a new struct ipoib_neigh. Signed-off-by: David Wilder <dwilder@us.ibm.com> Signed-off-by: Roland Dreier <rolandd@cisco.com>
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@ -884,6 +884,7 @@ struct ipoib_neigh *ipoib_neigh_alloc(struct neighbour *neighbour,
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neigh->neighbour = neighbour;
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neigh->dev = dev;
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memset(&neigh->dgid.raw, 0, sizeof (union ib_gid));
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*to_ipoib_neigh(neighbour) = neigh;
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skb_queue_head_init(&neigh->queue);
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ipoib_cm_set(neigh, NULL);
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