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

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Message-ID: <aAmucicgHHTeNTSA@fedora>
Date: Thu, 24 Apr 2025 03:22:26 +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 Wed, Apr 23, 2025 at 09:27:40AM -0700, Jay Vosburgh wrote:
> Hangbin Liu <liuhangbin@...il.com> wrote:
> 
> >On Sun, Apr 20, 2025 at 10:10:24PM -0700, Jay Vosburgh wrote:
> >> >I'm not familiar with infiniband devices. Can we use eth_random_addr()
> >> >to set random addr for infiniband devices? And what about other device
> >> >type? Just return error directly?
> >> 
> >> 	Infiniband devices have fixed MAC addresses that cannot be
> >> changed.  Bonding permits IB devices only in active-backup mode, and
> >> will set fail_over_mac to active (fail_over_mac=follow is not permitted
> >> for IB).
> >> 
> >> 	I don't understand your questions about other device types or
> >> errors, could you elaborate?
> >> 
> >
> >I mean what if other device type enslaves, other than ethernet or infiniband.
> >I'm not sure if we can set random mac address for these devices. Should we
> >ignore all none ethernet device or devices that don't support
> >ndo_set_mac_address?
> 
> 	Devices without ndo_set_mac_address are already handled; they
> are limited to active-backup mode and fail_over_mac is set to active
> (just like Infiniband).

Thanks, I saw this.
> 
> 	I'm not aware of any network device types other than Ethernet
> (which to bonding is anything with dev->type == ARPHRD_ETHER) or
> Infiniband in use with bonding.  If there are any, and the driver
> supports ndo_set_mac_address, and it fails for a random MAC if they try
> to use fail_over_mac=follow, then I'll look forward to the bug report.

OK, this makes me feel much better :)

> 
> 	If you're thinking of devices that are type ARPHRD_ETHER but
> aren't actual ethernet (virtual devices, veth, et al, perhaps?), then
> I'm not sure why those would require fail_over_mac=follow, as its reason
> for existence is for multiport devices that can't handle multiple ports
> programmed to the same MAC, which shouldn't matter for virtual devices
> or single port physical devices.

Thank for all your explanations.

Best Regards
Hangbin