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

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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>

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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Tunnel offload indications not stripped from encapsulated packets, causing performance overhead
https://bugs.launchpad.net/bugs/1602755
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