On Tue, 26 May 2020 15:48:13 +0200
Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote:
> Introduce convert_to_xdp_buff utility routine to initialize xdp_buff
> fields from xdp_frames ones. Rely on convert_to_xdp_buff in veth xdp
> code
>
> Suggested-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> ---
> drivers/net/veth.c | 12 ++----------
> include/net/xdp.h | 10 ++++++++++
> 2 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index b586d2fa5551..dfbe553f967e 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -559,27 +559,19 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
> struct veth_xdp_tx_bq *bq,
> struct veth_stats *stats)
> {
> - void *hard_start = frame->data - frame->headroom;
> int len = frame->len, delta = 0;
> struct xdp_frame orig_frame;
> struct bpf_prog *xdp_prog;
> unsigned int headroom;
> struct sk_buff *skb;
>
> - /* bpf_xdp_adjust_head() assures BPF cannot access xdp_frame area */
> - hard_start -= sizeof(struct xdp_frame);
> -
> rcu_read_lock();
> xdp_prog = rcu_dereference(rq->xdp_prog);
> if (likely(xdp_prog)) {
> struct xdp_buff xdp;
> u32 act;
>
> - xdp.data_hard_start = hard_start;
> - xdp.data = frame->data;
> - xdp.data_end = frame->data + frame->len;
> - xdp.data_meta = frame->data - frame->metasize;
> - xdp.frame_sz = frame->frame_sz;
> + convert_to_xdp_buff(frame, &xdp);
> xdp.rxq = &rq->xdp_rxq;
>
> act = bpf_prog_run_xdp(xdp_prog, &xdp);
> @@ -626,7 +618,7 @@ static struct sk_buff *veth_xdp_rcv_one(struct veth_rq *rq,
> rcu_read_unlock();
>
> headroom = sizeof(struct xdp_frame) + frame->headroom - delta;
> - skb = veth_build_skb(hard_start, headroom, len, frame->frame_sz);
> + skb = veth_build_skb(frame, headroom, len, frame->frame_sz);
> if (!skb) {
> xdp_return_frame(frame);
> stats->rx_drops++;
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 90f11760bd12..5dbdd65866a9 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -106,6 +106,16 @@ void xdp_warn(const char *msg, const char *func, const int line);
>
> struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
>
> +static inline
> +void convert_to_xdp_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
> +{
> + xdp->data_hard_start = (void *)frame;
This assumption is problematic. You are suppose to deduct this from
frame->data pointer.
Currently the xdp_frame is designed and access such that is is possible
to use another memory area for xdp_frame. That would break after this
change.
This should instead be:
xdp->data_hard_start = frame->data - (frame->headroom + sizeof(struct xdp_frame));
> + xdp->data = frame->data;
> + xdp->data_end = frame->data + frame->len;
> + xdp->data_meta = frame->data - frame->metasize;
> + xdp->frame_sz = frame->frame_sz;
> +}
> +
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
