Re: [PATCH RFC v1 01/15] xdp: add frame size to xdp_buff

Jakub Kicinski
2020-03-17T20:42:47Z

On Tue, 17 Mar 2020 18:29:12 +0100 Jesper Dangaard Brouer wrote:
> XDP have evolved to support several frame sizes, but xdp_buff was not
> updated with this information. The frame size (frame_sz) member of
> xdp_buff is introduced to know the real size of the memory the frame is
> delivered in.
>
> When introducing this also make it clear that some tailroom is
> reserved/required when creating SKBs using build_skb().
>
> It would also have been an option to introduce a pointer to
> data_hard_end (with reserved offset). The advantage with frame_sz is
> that (like rxq) drivers only need to setup/assign this value once per
> NAPI cycle. Due to XDP-generic (and some drivers) it's not possible to
> store frame_sz inside xdp_rxq_info, because it's varies per packet as it
> can be based/depend on packet length.

Do you reckon it would be too ugly to make xdp-generic suffer and have
it set the length in rxq per packet? We shouldn't handle multiple
packets from the same rxq in parallel, no?