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

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Date:   Wed, 26 Jun 2019 18:48:53 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     mirq-linux@...e.qmqm.pl
Cc:     YueHaibing <yuehaibing@...wei.com>, davem@...emloft.net,
        sdf@...gle.com, jianbol@...lanox.com, jiri@...lanox.com,
        willemb@...gle.com, sdf@...ichev.me, 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

Wed, Jun 26, 2019 at 06:13:38PM CEST, mirq-linux@...e.qmqm.pl wrote:
>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?

validate_xmit_skb->validate_xmit_vlan


>
>Best Regards,
>Michał Mirosław