[95/98] IPoIB: Clear ipoib_neigh.dgid in ipoib_neigh_alloc()

From: Greg KH
Date: Tue Jan 26 2010 - 18:44:48 EST

2.6.32-stable review patch. If anyone has any objections, please let us know.


From: David J. Wilder <dwilder@xxxxxxxxxx>

commit 0cd4d0fd9b0a4e10c091fc6316d1bf92885dcd9c upstream.

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

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@xxxxxxxxxx>
Signed-off-by: Roland Dreier <rolandd@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

drivers/infiniband/ulp/ipoib/ipoib_main.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -884,6 +884,7 @@ struct ipoib_neigh *ipoib_neigh_alloc(st

neigh->neighbour = neighbour;
neigh->dev = dev;
+ memset(&neigh->dgid.raw, 0, sizeof (union ib_gid));
*to_ipoib_neigh(neighbour) = neigh;
ipoib_cm_set(neigh, NULL);

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