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

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?