Re: [PATCH net] net/qlcnic: fix mac address restore in bond mode 5/6

From: Jarod Wilson
Date: Fri Nov 06 2015 - 11:25:32 EST

Jarod Wilson wrote:
The bonding driver saves a copy of slaves' original mac address and then
assigns whatever mac as needed to the slave, depending on mode. In at
least modes 5 and 6 (balance-tlb, balance-alb), it often ends up being the
mac address of another slave. On release from the bond, the original mac
address is supposed to get restored via a dev_set_mac_address() call in
the bonding driver's __bond_release_one() function, which calls the
slave's ndo_set_mac_address function, which for qlcnic, is

I didn't entirely flesh out this comment with some other relevant thoughts. The qlcnic interface getting assigned another interface's mac while in the bond is even more of a problem when you release the qlcnic interface and the interface that it was borrowing an address from, because now you have two interfaces in the system claiming to have the same mac address, which by itself can be problematic, and also causes problems if/when you try to add them back into a bond.

Now, this function tries to be somewhat intelligent and exit early if
you're trying to set the mac address to the same thing that is already
set. The problem here is that adapter->mac_addr isn't in sync with
netdev->dev_addr. The qlcnic driver still has the original mac stored in
adapter->mac_addr, while the bonding driver has updated netdev->dev_addr,
so qlcnic thinks we're trying to set the same address it already has.

I think the way to go here, since the function updates both netdev and
adapter's stored mac addresses, is to check if either of them doesn't
match the newly requested mac. Simply checking netdev's value only could
result in a similar mismatch and non-update, so look at both.

Jarod Wilson

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