linux-kernel - Re: [PATCHv2 net] bonding: use permanent address for MAC swapping if device address is same

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Message-ID: <Z_8bfpQb_3fqYEcn@fedora>
Date: Wed, 16 Apr 2025 02:52:46 +0000
From: Hangbin Liu <liuhangbin@...il.com>
To: Jay Vosburgh <jv@...sburgh.net>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Simon Horman <horms@...nel.org>, Cosmin Ratiu <cratiu@...dia.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 net] bonding: use permanent address for MAC swapping if
 device address is same

On Tue, Apr 15, 2025 at 06:15:12PM -0700, Jay Vosburgh wrote:
> >> 
> >> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> >> index 950d8e4d86f8..0d4e1ddd900d 100644
> >> --- a/drivers/net/bonding/bond_main.c
> >> +++ b/drivers/net/bonding/bond_main.c
> >> @@ -2120,6 +2120,24 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev,
> >>  			slave_err(bond_dev, slave_dev, "Error %d calling set_mac_address\n", res);
> >>  			goto err_restore_mtu;
> >>  		}
> >> +	} else if (bond->params.fail_over_mac == BOND_FOM_FOLLOW &&
> >> +		   BOND_MODE(bond) == BOND_MODE_ACTIVEBACKUP &&
> >> +		   memcmp(slave_dev->dev_addr, bond_dev->dev_addr, bond_dev->addr_len) == 0) {
> >> +		/* Set slave to current active slave's permanent mac address to
> >> +		 * avoid duplicate mac address.
> >> +		 */
> >> +		curr_active_slave = rcu_dereference(bond->curr_active_slave);
> >> +		if (curr_active_slave) {
> >> +			memcpy(ss.__data, curr_active_slave->perm_hwaddr,
> >> +			       curr_active_slave->dev->addr_len);
> >> +			ss.ss_family = slave_dev->type;
> >> +			res = dev_set_mac_address(slave_dev, (struct sockaddr *)&ss,
> >> +					extack);
> >> +			if (res) {
> >> +				slave_err(bond_dev, slave_dev, "Error %d calling set_mac_address\n", res);
> >> +				goto err_restore_mtu;
> >> +			}
> >> +		}
> 
> 	Is this in replacement of the prior patch (that does stuff
> during failover), or in addition to?
> 
> 	I'm asking because in the above, if there is no
> curr_active_slave, e.g., all interfaces in the bond are down, the above
> would permit MAC conflict in the absence of logic in failover to resolve
> things.

Hmm, then how about use bond_for_each_slave() and find out the link
that has same MAC address with bond/new_slave?

Thanks
Hangbin