Re: [PATCH v9 bpf-next 01/14] net: skbuff: add data_len field to skb_shared_info

On Tue, Jun 29, 2021 at 12:18 PM Lorenzo Bianconi
[off-list ref] wrote:

quoted

On 29/06/2021 20.37, Jakub Kicinski wrote:

quoted

On Tue, 29 Jun 2021 11:18:38 -0700 Alexander Duyck wrote:

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On Tue, Jun 29, 2021 at 10:08 AM Jakub Kicinski [off-list ref] wrote:

quoted

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ack, I agree. I will fix it in v10.

Why is XDP mb incompatible with LRO? I thought that was one of the use
cases (mentioned by Willem IIRC).

XDP is meant to be a per packet operation with support for TX and
REDIRECT, and LRO isn't routable. So we could put together a large LRO
frame but we wouldn't be able to break it apart again. If we allow
that then we are going to need a ton more exception handling added to
the XDP paths.

As far as GSO it would require setting many more fields in order to
actually make it offloadable by any hardware.

It would require more work, but TSO seems to be explicitly stated
as what the series builds towards (in the cover letter). It's fine
to make choices we'd need to redo later, I guess, I'm just trying
to understand the why.

This is also my understanding that LRO and TSO is what this patchset is
working towards.

Sorry, I don't agree or understand this requested change.

My understanding here is to use gso_size to store paged length of the
xdp multi-buffer. When converting the xdp_frame to a skb we will need
to overwrite it to support gro/lro. Is my understanding correct?

Yes, I was thinking just of the xdp_buff, not the xdp_frame. My focus
for right now is mostly around the Rx side of things, xdp_buff to skb,
and around the XDP_TX path. If we want to drop/move where we keep the
data length when doing the conversion I would be fine with that.