linux-kernel - Re: [PATCH net v2] bonding: fix feature flag setting at init time

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Date:   Wed, 2 Dec 2020 18:41:18 +0100
From:   Ivan Vecera <ivecera@...hat.com>
To:     Jarod Wilson <jarod@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Davis <tadavis@....gov>, netdev@...r.kernel.org
Subject: Re: [PATCH net v2] bonding: fix feature flag setting at init time

On Wed,  2 Dec 2020 12:30:53 -0500
Jarod Wilson <jarod@...hat.com> wrote:

> Don't try to adjust XFRM support flags if the bond device isn't yet
> registered. Bad things can currently happen when netdev_change_features()
> is called without having wanted_features fully filled in yet. Basically,
> this code was racing against register_netdevice() filling in
> wanted_features, and when it got there first, the empty wanted_features
> led to features also getting emptied out, which was definitely not the
> intended behavior, so prevent that from happening.
> 
> Originally, I'd hoped to stop adjusting wanted_features at all in the
> bonding driver, as it's documented as being something only the network
> core should touch, but we actually do need to do this to properly update
> both the features and wanted_features fields when changing the bond type,
> or we get to a situation where ethtool sees:
> 
>     esp-hw-offload: off [requested on]
> 
> I do think we should be using netdev_update_features instead of
> netdev_change_features here though, so we only send notifiers when the
> features actually changed.
> 
> v2: rework based on further testing and suggestions from ivecera
> 
> Fixes: a3b658cfb664 ("bonding: allow xfrm offload setup post-module-load")
> Reported-by: Ivan Vecera <ivecera@...hat.com>
> Suggested-by: Ivan Vecera <ivecera@...hat.com>
> Cc: Jay Vosburgh <j.vosburgh@...il.com>
> Cc: Veaceslav Falico <vfalico@...il.com>
> Cc: Andy Gospodarek <andy@...yhouse.net>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Thomas Davis <tadavis@....gov>
> Cc: netdev@...r.kernel.org
> Signed-off-by: Jarod Wilson <jarod@...hat.com>
> ---
>  drivers/net/bonding/bond_main.c    | 10 ++++------
>  drivers/net/bonding/bond_options.c |  6 +++++-
>  2 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index e0880a3840d7..5fe5232cc3f3 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -4746,15 +4746,13 @@ void bond_setup(struct net_device *bond_dev)
>  				NETIF_F_HW_VLAN_CTAG_FILTER;
>  
>  	bond_dev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
> -#ifdef CONFIG_XFRM_OFFLOAD
> -	bond_dev->hw_features |= BOND_XFRM_FEATURES;
> -#endif /* CONFIG_XFRM_OFFLOAD */
>  	bond_dev->features |= bond_dev->hw_features;
>  	bond_dev->features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_STAG_TX;
>  #ifdef CONFIG_XFRM_OFFLOAD
> -	/* Disable XFRM features if this isn't an active-backup config */
> -	if (BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP)
> -		bond_dev->features &= ~BOND_XFRM_FEATURES;
> +	bond_dev->hw_features |= BOND_XFRM_FEATURES;
> +	/* Only enable XFRM features if this is an active-backup config */
> +	if (BOND_MODE(bond) == BOND_MODE_ACTIVEBACKUP)
> +		bond_dev->features |= BOND_XFRM_FEATURES;
>  #endif /* CONFIG_XFRM_OFFLOAD */
>  }
>  
> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
> index 9abfaae1c6f7..19205cfac751 100644
> --- a/drivers/net/bonding/bond_options.c
> +++ b/drivers/net/bonding/bond_options.c
> @@ -768,11 +768,15 @@ static int bond_option_mode_set(struct bonding *bond,
>  		bond->params.tlb_dynamic_lb = 1;
>  
>  #ifdef CONFIG_XFRM_OFFLOAD
> +	if (bond->dev->reg_state != NETREG_REGISTERED)
> +		goto noreg;
> +
>  	if (newval->value == BOND_MODE_ACTIVEBACKUP)
>  		bond->dev->wanted_features |= BOND_XFRM_FEATURES;
>  	else
>  		bond->dev->wanted_features &= ~BOND_XFRM_FEATURES;
> -	netdev_change_features(bond->dev);
> +	netdev_update_features(bond->dev);
> +noreg:
>  #endif /* CONFIG_XFRM_OFFLOAD */
>  
>  	/* don't cache arp_validate between modes */

Tested-by: Ivan Vecera <ivecera@...hat.com>