openvswitch: same tcp session encapsulated with different udp src port for ovs vxlan tunnel

[Maxime Leroy]

[SRU Justification]

[Impact]

Packets encapsulated into a vxlan tunnel with openvswitch don't have the same udp source port for the first packet and the following ones of the same TCP flow in a DOCKER scenario usecase.

In fact, when using the kernel datapath, the upcall don't include skb hash info relatived. As VXLAN module uses
the skb hash to select UDP src port, the source port is different for the first packet.

More information can be found here:
https://mail.openvswitch.org/pipermail/ovs-dev/2019-October/364062.html

This has been fixed in the next release openvswitch 2.13 by the following upstream commits:
- 0442bfb11d6ccb ("ofproto-dpif-upcall: Echo HASH attribute back to datapath.")
- c4d8a4e0399910 ("ofproto-dpif: Fix using uninitialized execute hash.")
- 924d94a695a6ca ("ofproto-dpif-upcall: Fix using uninitialized upcall hash.")

https://github.com/openvswitch/ovs/commit/0442bfb11d6ccbf11754ef1d6de603b970465302
https://github.com/openvswitch/ovs/commit/c4d8a4e039991030c1298dbd1335d209cb437875
https://github.com/openvswitch/ovs/commit/924d94a695a6ca54b83d4bd42ec196ba53947c6d

The bug exists since the beginning of vxlan support in openvswitch.

== Fix ==

Backport the requested patches to Focal (5.4), Disco (5.0), Bionic (4.15) and
Xenial (4.4).

[James Page (james-page)]

Focal already has 2.13.3 which includes this fix.

[James Page (james-page)]

Does this also have a kernel side part to the fix to ensure that the skb hash is passed?

[James Page (james-page)]

It does and the focal 5.4 kernel does not include this fix:

https://kernel.ubuntu.com/git/ubuntu/ubuntu-focal.git/tree/include/uapi/linux/openvswitch.h

[James Page (james-page)]

Present in the Groovy 5.8 kernel and later:

https://kernel.ubuntu.com/git/ubuntu/ubuntu-groovy.git/tree/include/uapi/linux/openvswitch.h

[James Page (james-page)]

Commit that introduces the hash to the upcall to OVS:

https://kernel.ubuntu.com/git/ubuntu/ubuntu-groovy.git/commit/include/uapi/linux/openvswitch.h?id=bd1903b7c4596ba6f7677d0dfefd05ba5876707d

[James Page (james-page)]

Raising tasks for Linux as well - Groovy onwards is good so just focal and bionic targets now.

[James Page (james-page)]

For reference - this should be usable on Focal with the HWE kernel (rather than the 5.4 release kernel).

[Narendar R Pulimamidi (narendarpnr)]

above commit https://kernel.ubuntu.com/git/ubuntu/ubuntu-groovy.git/commit/include/uapi/linux/openvswitch.h?id=bd1903b7c4596ba6f7677d0dfefd05ba5876707d

is not available, any suggestion how to get that patch.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.