netdev - Re: [PATCH] net: Add ndo_gso

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Message-ID: <CAJ3xEMgPb9BhvtifmTzy6bS9WDf3jUx6dnx4418KNTjGNPreHQ@mail.gmail.com>
Date:	Sun, 5 Oct 2014 22:13:37 +0300
From:	Or Gerlitz <gerlitz.or@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Alexander Duyck <alexander.h.duyck@...el.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Thomas Graf <tgraf@...g.ch>,
	Pravin Shelar <pshelar@...ira.com>,
	Andy Zhou <azhou@...ira.com>
Subject: Re: [PATCH] net: Add ndo_gso_check

On Sun, Oct 5, 2014 at 9:49 PM, Tom Herbert <therbert@...gle.com> wrote:
> On Sun, Oct 5, 2014 at 7:04 AM, Or Gerlitz <gerlitz.or@...il.com> wrote:
>> On Thu, Oct 2, 2014 at 2:06 AM, Tom Herbert <therbert@...gle.com> wrote:
>>> On Wed, Oct 1, 2014 at 1:58 PM, Or Gerlitz <gerlitz.or@...il.com> wrote:
>>>> On Tue, Sep 30, 2014 at 6:34 PM, Tom Herbert <therbert@...gle.com> wrote:
>>>>> On Tue, Sep 30, 2014 at 7:30 AM, Or Gerlitz <gerlitz.or@...il.com> wrote:
>> [...]
>>> Solution #4: apply this patch and implement the check functions as
>>> needed in those 4 or 5 drivers. If a device can only do VXLAN/NVGRE
>>> then I believe the check function is something like:
>>>
>>> bool mydev_gso_check(struct sk_buff *skb, struct net_device *dev)
>>> {
>>>         if ((skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) &&
>>>             ((skb->inner_protocol_type != ENCAP_TYPE_ETHER ||
>>>               skb->protocol != htons(ETH_P_TEB) ||
>>>               skb_inner_mac_header(skb) - skb_transport_header(skb) != 12)
>>>                 return false;
>>>
>>>         return true;
>>> }
>>
>> Yep, such helper can can be basically made to work and let the 4-5
>> drivers that can
>> do GSO offloading for vxlan but not for any FOU/GUE packets signal
>> that to the stack.
>>
>> Re the 12 constant, you were referring to the udp+vxlan headers? it's 8+8
>>
>> Also, we need a way for drivers that can support VXLAN or NVGRE but
>> not concurrently
>> on the same port @ the same time to only let vxlan packet to pass
>> successfully through the helper.

> Or, there should be no difference in GSO processing between VXLAN and
> NVGRE. Can you explain why you feel you need to differentiate them for GSO?


RX wise, Linux tells the driver that UDP port X would be used for
VXLAN, right? and indeed, it's possible for some HW implementations
not to support RX offloading (checksum) for both VXLAN and NVGRE @ the
same time over the same port. But TX/GRO wise, you're probably
correct. The thing is that from the user POV they need solution that
works for both RX and TX offloading.
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