[xdp-hints] Re: [PATCH bpf-next v4 08/15] veth: Support RX XDP metadata

[Stanislav Fomichev <sdf@google.com>]

On Tue, Dec 13, 2022 at 7:55 AM Jesper Dangaard Brouer
<jbrouer@redhat.com> wrote:
>
>
> On 13/12/2022 03.35, Stanislav Fomichev wrote:
> > The goal is to enable end-to-end testing of the metadata for AF_XDP.
> >
> > Cc: John Fastabend <john.fastabend@gmail.com>
> > Cc: David Ahern <dsahern@gmail.com>
> > Cc: Martin KaFai Lau <martin.lau@linux.dev>
> > Cc: Jakub Kicinski <kuba@kernel.org>
> > Cc: Willem de Bruijn <willemb@google.com>
> > Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> > Cc: Anatoly Burakov <anatoly.burakov@intel.com>
> > Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
> > Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
> > Cc: Maryam Tahhan <mtahhan@redhat.com>
> > Cc: xdp-hints@xdp-project.net
> > Cc: netdev@vger.kernel.org
> > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > ---
> >   drivers/net/veth.c | 24 ++++++++++++++++++++++++
> >   1 file changed, 24 insertions(+)
> >
> > diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> > index 04ffd8cb2945..d5491e7a2798 100644
> > --- a/drivers/net/veth.c
> > +++ b/drivers/net/veth.c
> > @@ -118,6 +118,7 @@ static struct {
> >
> >   struct veth_xdp_buff {
> >       struct xdp_buff xdp;
> > +     struct sk_buff *skb;
> >   };
> >
> >   static int veth_get_link_ksettings(struct net_device *dev,
> > @@ -602,6 +603,7 @@ static struct xdp_frame *veth_xdp_rcv_one(struct veth_rq *rq,
> >
> >               xdp_convert_frame_to_buff(frame, xdp);
> >               xdp->rxq = &rq->xdp_rxq;
> > +             vxbuf.skb = NULL;
> >
> >               act = bpf_prog_run_xdp(xdp_prog, xdp);
> >
> > @@ -823,6 +825,7 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
> >       __skb_push(skb, skb->data - skb_mac_header(skb));
> >       if (veth_convert_skb_to_xdp_buff(rq, xdp, &skb))
> >               goto drop;
> > +     vxbuf.skb = skb;
> >
> >       orig_data = xdp->data;
> >       orig_data_end = xdp->data_end;
> > @@ -1601,6 +1604,21 @@ static int veth_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> >       }
> >   }
> >
> > +static int veth_xdp_rx_timestamp(const struct xdp_md *ctx, u64 *timestamp)
> > +{
> > +     *timestamp = ktime_get_mono_fast_ns();
>
> This should be reading the hardware timestamp in the SKB.
>
> Details: This hardware timestamp in the SKB is located in
> skb_shared_info area, which is also available for xdp_frame (currently
> used for multi-buffer purposes).  Thus, when adding xdp-hints "store"
> functionality, it would be natural to store the HW TS in the same place.
> Making the veth skb/xdp_frame code paths able to share code.

Does something like the following look acceptable as well?

*timestamp = skb_hwtstamps(_ctx->skb)->hwtstamp;
if (!*timestamp)
        *timestamp = ktime_get_mono_fast_ns(); /* sw fallback */

Because I'd like to be able to test this path in the selftests. As
long as I get some number from veth_xdp_rx_timestamp, I can test it.
No amount of SOF_TIMESTAMPING_{SOFTWARE,RX_SOFTWARE,RAW_HARDWARE}
triggers non-zero hwtstamp for xsk receive path. Any suggestions?


> > +     return 0;
> > +}
> > +
> > +static int veth_xdp_rx_hash(const struct xdp_md *ctx, u32 *hash)
> > +{
> > +     struct veth_xdp_buff *_ctx = (void *)ctx;
> > +
> > +     if (_ctx->skb)
> > +             *hash = skb_get_hash(_ctx->skb);
> > +     return 0;
> > +}
> > +
> >   static const struct net_device_ops veth_netdev_ops = {
> >       .ndo_init            = veth_dev_init,
> >       .ndo_open            = veth_open,
> > @@ -1622,6 +1640,11 @@ static const struct net_device_ops veth_netdev_ops = {
> >       .ndo_get_peer_dev       = veth_peer_dev,
> >   };
> >
> > +static const struct xdp_metadata_ops veth_xdp_metadata_ops = {
> > +     .xmo_rx_timestamp               = veth_xdp_rx_timestamp,
> > +     .xmo_rx_hash                    = veth_xdp_rx_hash,
> > +};
> > +
> >   #define VETH_FEATURES (NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HW_CSUM | \
> >                      NETIF_F_RXCSUM | NETIF_F_SCTP_CRC | NETIF_F_HIGHDMA | \
> >                      NETIF_F_GSO_SOFTWARE | NETIF_F_GSO_ENCAP_ALL | \
> > @@ -1638,6 +1661,7 @@ static void veth_setup(struct net_device *dev)
> >       dev->priv_flags |= IFF_PHONY_HEADROOM;
> >
> >       dev->netdev_ops = &veth_netdev_ops;
> > +     dev->xdp_metadata_ops = &veth_xdp_metadata_ops;
> >       dev->ethtool_ops = &veth_ethtool_ops;
> >       dev->features |= NETIF_F_LLTX;
> >       dev->features |= VETH_FEATURES;
>