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

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Message-ID: <Z_yl7tQne6YTcU6S@fedora>
Date: Mon, 14 Apr 2025 06:06:38 +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

Hi Jay,
On Mon, Apr 07, 2025 at 09:35:03AM +0000, Hangbin Liu wrote:
> > 	So this patch's change wouldn't actually resolve the MAC
> > conflict until a failover takes place?  I.e., if we only do step 4 but
> > not step 5 or 6, eth0 and eth1 will both have the same MAC address.  Am
> > I understanding correctly?
> 
> Yes, you are right. At step 4, there is no failover, so eth0 is still using
> it's own mac address. How about set the mac at enslave time, with this we
> can get correct mac directly. e.g.

Any comments for the new approach?

Thanks
Hangbin
> 
> 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;
> +			}
> +		}
>  	}
> 
> Thanks
> Hangbin