netdev - Re: [xdp-hints] [PATCH bpf-next 05/11] veth: Support rx timestamp metadata for xdp

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Message-ID: <87h6z0i449.fsf@toke.dk>
Date:   Tue, 15 Nov 2022 17:17:42 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Stanislav Fomichev <sdf@...gle.com>, bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org
Subject: Re: [xdp-hints] [PATCH bpf-next 05/11] veth: Support rx timestamp
 metadata for xdp

Stanislav Fomichev <sdf@...gle.com> writes:

> The goal is to enable end-to-end testing of the metadata
> for AF_XDP. Current rx_timestamp kfunc returns current
> time which should be enough to exercise this new functionality.
>
> Cc: John Fastabend <john.fastabend@...il.com>
> Cc: David Ahern <dsahern@...il.com>
> Cc: Martin KaFai Lau <martin.lau@...ux.dev>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Cc: Jesper Dangaard Brouer <brouer@...hat.com>
> Cc: Anatoly Burakov <anatoly.burakov@...el.com>
> Cc: Alexander Lobakin <alexandr.lobakin@...el.com>
> Cc: Magnus Karlsson <magnus.karlsson@...il.com>
> Cc: Maryam Tahhan <mtahhan@...hat.com>
> Cc: xdp-hints@...-project.net
> Cc: netdev@...r.kernel.org
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> ---
>  drivers/net/veth.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 2a4592780141..c626580a2294 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -25,6 +25,7 @@
>  #include <linux/filter.h>
>  #include <linux/ptr_ring.h>
>  #include <linux/bpf_trace.h>
> +#include <linux/bpf_patch.h>
>  #include <linux/net_tstamp.h>
>  
>  #define DRV_NAME	"veth"
> @@ -1659,6 +1660,18 @@ static int veth_xdp(struct net_device *dev, struct netdev_bpf *xdp)
>  	}
>  }
>  
> +static void veth_unroll_kfunc(const struct bpf_prog *prog, u32 func_id,
> +			      struct bpf_patch *patch)
> +{
> +	if (func_id == xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_TIMESTAMP_SUPPORTED)) {
> +		/* return true; */
> +		bpf_patch_append(patch, BPF_MOV64_IMM(BPF_REG_0, 1));
> +	} else if (func_id == xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_TIMESTAMP)) {
> +		/* return ktime_get_mono_fast_ns(); */
> +		bpf_patch_append(patch, BPF_EMIT_CALL(ktime_get_mono_fast_ns));
> +	}
> +}

So these look reasonable enough, but would be good to see some examples
of kfunc implementations that don't just BPF_CALL to a kernel function
(with those helper wrappers we were discussing before).

-Toke