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

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Message-ID: <20250326043213.5fce3b81@kernel.org>
Date: Wed, 26 Mar 2025 04:32:13 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: netdev@...r.kernel.org, Jay Vosburgh <jv@...sburgh.net>, Andrew Lunn
 <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, 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, Liang Li
 <liali@...hat.com>
Subject: Re: [PATCH net] bonding: use permanent address for MAC swapping if
 device address is same

On Wed, 26 Mar 2025 10:22:58 +0000 Hangbin Liu wrote:
> > I don't know much about bonding, but this seems like a problem already
> > to me. Assuming both eth0 and eth1 are on the same segment we now have
> > two interfaces with the same MAC on the network. Shouldn't we override
> > the address of eth0 to a random one when it leaves?  
> 
> Can we change an interface mac to random value after leaving bond's control?
> It looks may break user's other configures.

Hard to speculate but leaving two interfaces with the same MAC is even
worse? I guess nobody hit this problem in practice.

> > looks like this is on ctrl path, just always use memcmp directly ?
> > not sure if this helper actually.. helps.  
> 
> This is just to align with bond_hw_addr_copy(). If you think it's not help.
> I can use memcmp() directly.

Yes, I don't think it helps.