linux-kernel - Re: [PATCH] bonding: Always enable vlan tx offload

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Message-ID: <20190626161337.GA18953@qmqm.qmqm.pl>
Date:   Wed, 26 Jun 2019 18:13:38 +0200
From:   mirq-linux@...e.qmqm.pl
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     davem@...emloft.net, sdf@...gle.com, jianbol@...lanox.com,
        jiri@...lanox.com, willemb@...gle.com, sdf@...ichev.me,
        jiri@...nulli.us, j.vosburgh@...il.com, vfalico@...il.com,
        andy@...yhouse.net, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] bonding: Always enable vlan tx offload

On Wed, Jun 26, 2019 at 04:08:44PM +0800, YueHaibing wrote:
> We build vlan on top of bonding interface, which vlan offload
> is off, bond mode is 802.3ad (LACP) and xmit_hash_policy is
> BOND_XMIT_POLICY_ENCAP34.
> 
> Because vlan tx offload is off, vlan tci is cleared and skb push
> the vlan header in validate_xmit_vlan() while sending from vlan
> devices. Then in bond_xmit_hash, __skb_flow_dissect() fails to
> get information from protocol headers encapsulated within vlan,
> because 'nhoff' is points to IP header, so bond hashing is based
> on layer 2 info, which fails to distribute packets across slaves.
> 
> This patch always enable bonding's vlan tx offload, pass the vlan
> packets to the slave devices with vlan tci, let them to handle
> vlan implementation.
[...]
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 407f4095a37a..799fc38c5c34 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -4320,12 +4320,12 @@ void bond_setup(struct net_device *bond_dev)
>  	bond_dev->features |= NETIF_F_NETNS_LOCAL;
>  
>  	bond_dev->hw_features = BOND_VLAN_FEATURES |
> -				NETIF_F_HW_VLAN_CTAG_TX |
>  				NETIF_F_HW_VLAN_CTAG_RX |
>  				NETIF_F_HW_VLAN_CTAG_FILTER;
>  
>  	bond_dev->hw_features |= NETIF_F_GSO_ENCAP_ALL | NETIF_F_GSO_UDP_L4;
>  	bond_dev->features |= bond_dev->hw_features;
> +	bond_dev->features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_STAG_TX;
>  }
>  
>  /* Destroy a bonding device.
> 

I can see that bonding driver uses dev_queue_xmit() to pass packets to
slave links, but I can't see where in the path it does software fallback
for devices without HW VLAN tagging. Generally drivers that don't ever
do VLAN offload also ignore vlan_tci presence. Am I missing something
here?

Best Regards,
Michał Mirosław