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

[Jesper Dangaard Brouer <jbrouer@redhat.com>]

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.

> +	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;