Messages in this thread | | | Subject | Re: [PATCH net v2] veth: xdp: use head instead of hard_start | From | Toshiaki Makita <> | Date | Thu, 2 Apr 2020 09:47:03 +0900 |
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On 2020/04/02 1:15, Jesper Dangaard Brouer wrote: ... > [PATCH RFC net-next] veth: adjust hard_start offset on redirect XDP frames > > When native XDP redirect into a veth device, the frame arrives in the > xdp_frame structure. It is then processed in veth_xdp_rcv_one(), > which can run a new XDP bpf_prog on the packet. Doing so requires > converting xdp_frame to xdp_buff, but the tricky part is that > xdp_frame memory area is located in the top (data_hard_start) memory > area that xdp_buff will point into. > > The current code tried to protect the xdp_frame area, by assigning > xdp_buff.data_hard_start past this memory. This results in 32 bytes > less headroom to expand into via BPF-helper bpf_xdp_adjust_head(). > > This protect step is actually not needed, because BPF-helper > bpf_xdp_adjust_head() already reserve this area, and don't allow > BPF-prog to expand into it. Thus, it is safe to point data_hard_start > directly at xdp_frame memory area. > > Cc: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
FYI: This mail address is deprecated.
> Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring") > Reported-by: Mao Wenan <maowenan@huawei.com> > Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
FWIW,
Acked-by: Toshiaki Makita <toshiaki.makita1@gmail.com>
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