netdev - Re: No GSOs to i40e with VXLAN

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Message-ID: <CA+mtBx9UGO7h9S3Q90LwvPeO66UBAn1OFThGLdviKFmHsP+wug@mail.gmail.com>
Date:	Sat, 14 Jun 2014 11:38:26 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Joseph Gasparakis <joseph.gasparakis@...el.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
Subject: Re: No GSOs to i40e with VXLAN

I was able to debug the issue (thanks for lending me the machines with
i40 Eric!). Problem is that SKB_GSO_* bits are out of sync with the
corresponding NETIF flags. I post a fix today along with adding the
BUILD_BUG_ONs in net_gso_ok that are intended to detect this.

Thanks,
Tom

On Fri, Jun 13, 2014 at 9:38 PM, Joseph Gasparakis
<joseph.gasparakis@...el.com> wrote:
>
>
> On Fri, 13 Jun 2014, Tom Herbert wrote:
>
>> On Fri, Jun 13, 2014 at 5:15 PM, Joseph Gasparakis
>> <joseph.gasparakis@...el.com> wrote:
>> > Hi all,
>> >
>> > I quickly tested VXLAN on i40e with net-next with commit id
>> > f9da455b93f6ba076935b4ef4589f61e529ae046 and the i40e driver has stopped
>> > receiving GSOs even when advertising tx-udp_tnl-segmentation which means
>> > our VXLAN segmentation offload. I am guessing this has something to do
>> > with Tom's recent UDP work but this is just a guess as unfortunatly I
>> > do not have the time to debug this, but I am signing up to review and test
>> > patches fixing this issue.
>> >
>> I verified tunnel offload works properly with bnx2x (I'm using simple
>> vxlan interfaces not OVS).
>>
>
> Ok, I will try to have a quick look at bnx2x and i40e and see the
> differences in what the two drivers advertise in terms of netdev features and
> hw_enc_features.
>
>> One possibility I can think of is that UDP checksums are somehow
>> enabled. If you're using IPv6 this probably the case (but I assume
>> you're seeing this with IPv4). If checksums are inadvertently enabled
>> somehow in IPv4 this should should up in tcpdump on the Ethernet
>> interface.
>
> Let me explain a bit my setup:
>
> I am using two linux boxes back to back, on my DUT I have an i40e and I
> am bringing a vxlan interface in both machines. No bridge, no VMs, no OVS.
>
> I am using some simple perl scripts using TCP sockets to send a number of
> bytes from DUT to my link partner and even if I send 50k in one message I
> don't see any GSOs. Instead I get many non-GSO skbs leading me to the
> conclusion that the stack must have segmented the skb before passing it on
> to the driver. I am also using netperf with TCP_STREAM and I don't see any
> GSOs either. All the above done using IPv4 only. And if I do the same on
> the i40e interface instead of vxlan I do see GSOs again.
>
> Both these tests would result to the stack sending GSOs last time I did a
> smoke test on vxlan and i40e (about 3 weeks ago or so...).
>
> The checksum offloads seem to be working as before however.
>
> Thanks
>
> Joseph
>
>>
>> Thanks,
>> Tom
>>
>> > The driver still gets GSOs with non VXLAN traffic (tested with TCP).
>> >
>> > Thanks
>> >
>> > Joseph
>>
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