[ovs-dev] [PATCH] userspace-tso: Document the minimum kernel version.

Ilya Maximets i.maximets at ovn.org
Fri Mar 6 15:50:38 UTC 2020

On 3/2/20 8:51 PM, Flavio Leitner wrote:
> On Mon, Mar 02, 2020 at 01:11:35PM +0100, Ilya Maximets wrote:
>> On 2/28/20 11:58 PM, Flavio Leitner wrote:
>>> The kernel needs to be at least 4.19-rc7 to include the commit
>>> 9d2f67e43b73 ("net/packet: fix packet drop as of virtio gso")
>>> otherwise the TSO packets are dropped when using raw sockets.
>>> Fixes: 29cf9c1b3b9c ("userspace: Add TCP Segmentation Offload support")
>>> Reported-by: Yi Yang (杨燚)-云服务集团 <yangyi01 at inspur.com>
>>> Signed-off-by: Flavio Leitner <fbl at sysclose.org>
>>> ---
>>>  Documentation/topics/userspace-tso.rst | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>> This applies to branch-2.13 as well.
>>> diff --git a/Documentation/topics/userspace-tso.rst b/Documentation/topics/userspace-tso.rst
>>> index 0fbac93a5..da370e64f 100644
>>> --- a/Documentation/topics/userspace-tso.rst
>>> +++ b/Documentation/topics/userspace-tso.rst
>>> @@ -113,6 +113,10 @@ __ https://patches.dpdk.org/patch/64136/
>>>  This fix is expected to be included in the 19.11.1 release. When OVS migrates
>>>  to this DPDK release, this limitation can be removed.
>>> +All kernel devices that use the raw socket interface (veth, for example)
>>> +require a kernel with minimum version of 4.19-rc7 to include the commit:
>>> +9d2f67e43b73 ("net/packet: fix packet drop as of virtio gso").
>> I'm not very happy with this kind of documentation updates.  The main reason
>> is that every distribution uses their own custom kernel with some patches
>> backported or not.  In this particular case we seem to have issue with
>> particular ubuntu kernel that happened to not have this bug fix backported.
>> If someone uses non-lognterm upstream kernel that is out of its support
>> lifetime it's his/her responsibility to backport bugfixes.
>> Upstream LTS kernel 4.14 has this bugfix backported and there should be
>> no issues. Upstream LTS 4.9 might not have this issue at all and work
>> fine (I didn't check).
>> What we can document is that particular kernel version from the Ubuntu 16.04
>> distribution has an issue and should not be used along with userspace-tso.
>> Ideally, someone should file a bug for ubuntu kernel maintainers, so they
>> will backport relevant patch and update their kernel since it's still in a
>> supported state.  In this case we will have no need to document anything.
>> What do you think?
> I think worth for Ubuntu users to open a bug, so that this gets
> solved.
> But I think the documentation is still valid. Yi and I spent time
> to find the root cause and it is something out of OvS control, so
> the best we can do is document the requirement.
> Maybe we can word it differently so that the kernel version becomes
> less relevant. For example:
> "All kernel devices that use the raw socket interface (veth, for example)
> require the kernel commit 9d2f67e43b73 ("net/packet: fix packet drop
> as of virtio gso") in order to work properly. This commit was merged
> in upstream kernel 4.19-rc7, so make sure your kernel is either
> newer or contains the backport."
> How does that sound to you now?

That sounds better.  Thanks.

Best regards, Ilya Maximets.

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