On Fri, May 28, 2021 at 10:44 AM Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote:
>
> Introduce flag field in xdp_buff and xdp_frame data structure in order
> to report xdp_buffer metadata. For the moment just hw checksum hints
> are defined but flags field will be reused for xdp multi-buffer
> For the moment just CHECKSUM_UNNECESSARY is supported.
> CHECKSUM_COMPLETE will need to set csum value in metada space.
>
Lorenzo,
This isn't sufficient for the checksum-unnecessary interface, we'd
also need ability to set csum_level for cases the device validated
more than one checksum.
IMO, we shouldn't support CHECKSUM_UNNECESSARY for new uses like this.
For years now, the Linux community has been pleading with vendors to
provide CHECKSUM_COMPLETE which is far more useful and robust than
CHECSUM_UNNECESSARY, and yet some still haven't got with the program
even though we see more and more instances where CHECKSUM_UNNECESSARY
doesn't even work at all (e.g. cases with SRv6, new encaps device
doesn't understand). I believe it's time to take a stand! :-)
Tom
> Signed-off-by: David Ahern <dsahern@xxxxxxxxxx>
> Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
> ---
> include/net/xdp.h | 36 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index 5533f0ab2afc..e81ac505752b 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -66,6 +66,13 @@ struct xdp_txq_info {
> struct net_device *dev;
> };
>
> +/* xdp metadata bitmask */
> +#define XDP_CSUM_MASK GENMASK(1, 0)
> +enum xdp_flags {
> + XDP_CSUM_UNNECESSARY = BIT(0),
> + XDP_CSUM_COMPLETE = BIT(1),
> +};
> +
> struct xdp_buff {
> void *data;
> void *data_end;
> @@ -74,6 +81,7 @@ struct xdp_buff {
> struct xdp_rxq_info *rxq;
> struct xdp_txq_info *txq;
> u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/
> + u16 flags; /* xdp_flags */
> };
>
> static __always_inline void
> @@ -81,6 +89,7 @@ xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq)
> {
> xdp->frame_sz = frame_sz;
> xdp->rxq = rxq;
> + xdp->flags = 0;
> }
>
> static __always_inline void
> @@ -95,6 +104,18 @@ xdp_prepare_buff(struct xdp_buff *xdp, unsigned char *hard_start,
> xdp->data_meta = meta_valid ? data : data + 1;
> }
>
> +static __always_inline void
> +xdp_buff_get_csum(struct xdp_buff *xdp, struct sk_buff *skb)
> +{
> + switch (xdp->flags & XDP_CSUM_MASK) {
> + case XDP_CSUM_UNNECESSARY:
> + skb->ip_summed = CHECKSUM_UNNECESSARY;
> + break;
> + default:
> + break;
> + }
> +}
> +
> /* Reserve memory area at end-of data area.
> *
> * This macro reserves tailroom in the XDP buffer by limiting the
> @@ -122,8 +143,21 @@ struct xdp_frame {
> */
> struct xdp_mem_info mem;
> struct net_device *dev_rx; /* used by cpumap */
> + u16 flags; /* xdp_flags */
> };
>
> +static __always_inline void
> +xdp_frame_get_csum(struct xdp_frame *xdpf, struct sk_buff *skb)
> +{
> + switch (xdpf->flags & XDP_CSUM_MASK) {
> + case XDP_CSUM_UNNECESSARY:
> + skb->ip_summed = CHECKSUM_UNNECESSARY;
> + break;
> + default:
> + break;
> + }
> +}
> +
> #define XDP_BULK_QUEUE_SIZE 16
> struct xdp_frame_bulk {
> int count;
> @@ -180,6 +214,7 @@ void xdp_convert_frame_to_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
> xdp->data_end = frame->data + frame->len;
> xdp->data_meta = frame->data - frame->metasize;
> xdp->frame_sz = frame->frame_sz;
> + xdp->flags = frame->flags;
> }
>
> static inline
> @@ -206,6 +241,7 @@ int xdp_update_frame_from_buff(struct xdp_buff *xdp,
> xdp_frame->headroom = headroom - sizeof(*xdp_frame);
> xdp_frame->metasize = metasize;
> xdp_frame->frame_sz = xdp->frame_sz;
> + xdp_frame->flags = xdp->flags;
>
> return 0;
> }
> --
> 2.31.1
>
