On Tue, May 3, 2016 at 5:41 AM, Or Gerlitz [off-list ref] wrote:

On 5/2/2016 6:41 PM, Alexander Duyck wrote:

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Just one more piece to clarify... in the general case (e.g inner
packet size 1.5k...64k), the last segment would not have the same
length as the other segments, what happens on that case?

Actually in the case of GSO partial we have go through the software
segmentation code and trim off any last bit that doesn't match the MSS
of the rest of the frame.  That way you end up with one frame that has
some number of MSS sized chunks, and then one remainder if there is a
frame that would be a different size.

OK, thanks for further clarifying this, will look on the docs you pointed
etc. From what you wrote here I understand it's indeed possible for one
frame to be of different size from the rest, but the LCO thing still works
somehow..

We split the one that would be a different size off via GSO.  So we
end up sending up 2 frames to the device if there is going to be one
piece that doesn't quite match.  We split that one piece off via GSO.
That is one of the reasons why I referred to it as partial GSO as all
we are using the software segmentation code for is to make sure we
have the GSO block consists of segments that are all the same size.

- Alex