netdev - [Question] Bonding: change bond dev_addr when fail_over

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Message-ID: <Z49yXz1dx2ZzqhC1@fedora>
Date: Tue, 21 Jan 2025 10:09:35 +0000
From: Hangbin Liu <liuhangbin@...il.com>
To: Jay Vosburgh <jv@...sburgh.net>
Cc: netdev@...r.kernel.org, Liang Li <liali@...hat.com>
Subject: [Question] Bonding: change bond dev_addr when fail_over_mac=2

Hi Jay,

Our QE reported that, when setup bonding with fail_over_mac=2. Then release
the first enslaved device. The bond and other slave's mac address with
conflicts with the release device. e.g.

# modprobe bonding mode=1 miimon=100 max_bonds=1 fail_over_mac=2
# ip link set bond0 up
# ifenslave bond0 eth0 eth1
# ifenslave -d bond0 eth0

Then we can see the bond0 and eth1 both still using eth0's address.

I saw in __bond_release_one() we have 

        if (!all && (!bond->params.fail_over_mac ||
                     BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP)) {
                if (ether_addr_equal_64bits(bond_dev->dev_addr, slave->perm_hwaddr) &&
                    bond_has_slaves(bond))
                        slave_warn(bond_dev, slave_dev, "the permanent HWaddr of slave - %pM - is still in use by bond - set the HWaddr of slave to a different address to avoid conflicts\n",
                                   slave->perm_hwaddr);
        }

So why not just change the bond_dev->dev_addr to another slave's perm_hwaddr
instead of keep using the released one?

Thanks
Hangbin