netdev - Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from skb->vlan

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Date:	Mon, 15 Aug 2016 18:51:38 +0300
From:	Hadar Hen Zion <hadarh@....mellanox.co.il>
To:	Toshiaki Makita <toshiaki.makita1@...il.com>
Cc:	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
	Hadar Hen Zion <hadarh@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>, Jiri Pirko <jiri@...lanox.com>,
	Tom Herbert <tom@...bertland.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>
Subject: Re: [PATCH net-next 1/4] flow_dissector: Get vlan info from
 skb->vlan_tci instead of skb->data

On Mon, Aug 15, 2016 at 5:38 AM, Toshiaki Makita
<toshiaki.makita1@...il.com> wrote:
> On 16/08/14 (日) 23:58, Hadar Hen Zion wrote:
>>
>> On Fri, Aug 12, 2016 at 9:36 AM, Toshiaki Makita
>> <makita.toshiaki@....ntt.co.jp> wrote:
>>>
>>> On 2016/08/10 22:32, Hadar Hen Zion wrote:
>>>>
>>>> Early in the datapath skb_vlan_untag function is called, stripped
>>>> the vlan from the skb and set skb->vlan_tci and skb->vlan_proto fields.
>>>>
>>>> The current dissection doesn't handle vlan packets correctly.  Vlan
>>>> doesn't exist in skb->data anymore when applying flow dissection on the
>>>> skb, fix that.
>>>
>>>
>>> RPS (and flow-dissector called in RPS) is performed before vlan-strip in
>>> __netif_receive_skb_core().
>>
>>
>> right, I'll fix it to v2.
>>
>>> Also, in cases skb is tagged with multiple vlan headers (typical when
>>> using 802.1ad), the second level vlan tag is in skb->data.
>>
>>
>> Currently, flow_dissector doesn't support multiple vlan headers, only
>> one vlan_id field is present.
>> There aren't any flow_dissector "customers" yet for multiple vlan support.
>
>
> Sure, no need to store second level vlan tag information for now.
> The point is that current flow-dissector correctly skips any number of vlan
> tags and get hash value from IP/TCP/UDP headers, so RPS works for multiple
> vlan tagged packets.
>
> Thanks,
> Toshiaki Makita

ok, so we are on the same page.
The flow dissector will correctly skip any number of vlans regardless
if the first vlan is stripped or not.

I also found a dependency between my vlan addition to flower and mlx5
tc offload support so I'm working to fix it for V2.

Thanks,
Hadar