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

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Date:	Mon, 15 Aug 2016 11:38:26 +0900
From:	Toshiaki Makita <toshiaki.makita1@...il.com>
To:	Hadar Hen Zion <hadarh@....mellanox.co.il>,
	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
Cc:	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 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