[Bug 1602755] Re: Tunnel offload indications not stripped from encapsulated packets, causing performance overhead

[Leann Ogasawara]

Looks like we have picked this up in Yakkety for 16.10 already.  Will
mark that task Fix Committed.

git describe --contains a09a4c8dd1ec7f830e1fb9e59eb72bddc965d168
v4.6-rc1~38^2~35^2

It's been requested we consider this for SRU for Xenial.

** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu)
       Status: New => Fix Committed

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https://bugs.launchpad.net/bugs/1602755

Title:
  Tunnel offload indications not stripped from encapsulated packets,
  causing performance overhead

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  New

Bug description:
  Commit:
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=a09a4c8dd1ec7f830e1fb9e59eb72bddc965d168

  Description:

  tunnels: Remove encapsulation offloads on decap.

  If a packet is either locally encapsulated or processed through GRO
  it is marked with the offloads that it requires. However, when it is
  decapsulated these tunnel offload indications are not removed. This
  means that if we receive an encapsulated TCP packet, aggregate it with
  GRO, decapsulate, and retransmit the resulting frame on a NIC that does
  not support encapsulation, we won't be able to take advantage of hardware
  offloads even though it is just a simple TCP packet at this point.

  This fixes the problem by stripping off encapsulation offload indications
  when packets are decapsulated.

  The performance impacts of this bug are significant. In a test where a
  Geneve encapsulated TCP stream is sent to a hypervisor, GRO'ed, decapsulated,
  and bridged to a VM performance is improved by 60% (5Gbps->8Gbps) as a
  result of avoiding unnecessary segmentation at the VM tap interface.

  Reported-by: Ramu Ramamurthy <sramamur at linux.vnet.ibm.com>
  Fixes: 68c33163 ("v4 GRE: Add TCP segmentation offload for GRE")
  Signed-off-by: Jesse Gross <jesse at kernel.org>
  Signed-off-by: David S. Miller <davem at davemloft.net>

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