Subject: Re: [PATCH net] bonding: only set speed/duplex to unknown, if getting speed failed

From: Hangbin Liu <[email-masked]>
Date: Fri, 30 Jan 2026 12:36:19 +0000

On Fri, Jan 30, 2026 at 12:19:04PM +0100, Thomas Bogendoerfer wrote:
> bond_update_speed_duplex() first set speed/duplex to unknown and
> then asks slave driver for current speed/duplex. Since getting
> speed/duplex might take longer there is a race, where this false state
> is visible by /proc/net/bonding. With commit 691b2bf14946 ("bonding:

The patch looks good to me. But based on your description, I don't think
the fixes tag is correct.

Thanks
Hangbin
>  update port speed when getting bond speed") this race gets more visible,
> if user space is calling ethtool on a regular base.
> 
> Fix this by only setting speed/duplex to unknown, if link speed is
> really unknown/unusable.
> 
> Fixes: 691b2bf14946 ("bonding: update port speed when getting bond speed")
> Signed-off-by: Thomas Bogendoerfer <[email-masked]>
> ---
>  drivers/net/bonding/bond_main.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index e7caf400a59c..4cdf89b21ca0 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -791,26 +791,29 @@ static int bond_update_speed_duplex(struct slave *slave)
>  	struct ethtool_link_ksettings ecmd;
>  	int res;
>  
> -	slave->speed = SPEED_UNKNOWN;
> -	slave->duplex = DUPLEX_UNKNOWN;
> -
>  	res = __ethtool_get_link_ksettings(slave_dev, &ecmd);
>  	if (res < 0)
> -		return 1;
> +		goto speed_duplex_unknown;
>  	if (ecmd.base.speed == 0 || ecmd.base.speed == ((__u32)-1))
> -		return 1;
> +		goto speed_duplex_unknown;
>  	switch (ecmd.base.duplex) {
>  	case DUPLEX_FULL:
>  	case DUPLEX_HALF:
>  		break;
>  	default:
> -		return 1;
> +		goto speed_duplex_unknown;
>  	}
>  
>  	slave->speed = ecmd.base.speed;
>  	slave->duplex = ecmd.base.duplex;
>  
>  	return 0;
> +
> +speed_duplex_unknown:
> +	slave->speed = SPEED_UNKNOWN;
> +	slave->duplex = DUPLEX_UNKNOWN;
> +
> +	return 1;
>  }
>  
>  const char *bond_slave_link_status(s8 link)
> -- 
> 2.43.0
>