[PATCH v1 net-next 00/15] nvme-tcp receive offloads

[Boris Pismenny]

On 14/01/2021 6:47, David Ahern wrote:
> On 1/13/21 6:27 PM, Sagi Grimberg wrote:
>>> Changes since RFC v1:
>>> =========================================
>>> * Split mlx5 driver patches to several commits
>>> * Fix nvme-tcp handling of recovery flows. In particular, move queue
>>> offlaod
>>>    init/teardown to the start/stop functions.
>>
>> I'm assuming that you tested controller resets and network hiccups
>> during traffic right?
> 
> I had questions on this part as well -- e.g., what happens on a TCP
> retry? packets arrive, sgl filled for the command id, but packet is
> dropped in the stack (e.g., enqueue backlog is filled, so packet gets
> dropped)
> 

On re-transmission the HW context's expected tcp sequence number doesn't
match. As a result, the received packet is un-offloaded and software
will do the copy/crc for its data.

As a general rule, if HW context expected sequence numbers don't match,
then there's no offload.