[xdp-hints] Re: [PATCH bpf V9 1/6] selftests/bpf: xdp_hw_metadata remove bpf_printk and add counters

[Stanislav Fomichev <sdf@google.com>]

On Wed, Apr 12, 2023 at 11:35 AM Jesper Dangaard Brouer
<brouer@redhat.com> wrote:
>
> The tool xdp_hw_metadata can be used by driver developers
> implementing XDP-hints metadata kfuncs.
>
> Remove all bpf_printk calls, as the tool already transfers all the
> XDP-hints related information via metadata area to AF_XDP
> userspace process.
>
> Add counters for providing remaining information about failure and
> skipped packet events.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Acked-by: Stanislav Fomichev <sdf@google.com>

nit: maybe those ++ should be __sync_add_and_fetch instead? Then you
should be able to drop volatile..

> ---
>  .../testing/selftests/bpf/progs/xdp_hw_metadata.c  |   36 ++++++++++++--------
>  tools/testing/selftests/bpf/xdp_hw_metadata.c      |    4 ++
>  2 files changed, 24 insertions(+), 16 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> index 4c55b4d79d3d..8a042343cb0c 100644
> --- a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> +++ b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> @@ -12,6 +12,10 @@ struct {
>         __type(value, __u32);
>  } xsk SEC(".maps");
>
> +volatile __u64 pkts_skip = 0;
> +volatile __u64 pkts_fail = 0;
> +volatile __u64 pkts_redir = 0;
> +
>  extern int bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx,
>                                          __u64 *timestamp) __ksym;
>  extern int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx,
> @@ -26,7 +30,7 @@ int rx(struct xdp_md *ctx)
>         struct udphdr *udp = NULL;
>         struct iphdr *iph = NULL;
>         struct xdp_meta *meta;
> -       int ret;
> +       int err;
>
>         data = (void *)(long)ctx->data;
>         data_end = (void *)(long)ctx->data_end;
> @@ -46,17 +50,20 @@ int rx(struct xdp_md *ctx)
>                         udp = NULL;
>         }
>
> -       if (!udp)
> +       if (!udp) {
> +               pkts_skip++;
>                 return XDP_PASS;
> +       }
>
> -       if (udp->dest != bpf_htons(9091))
> +       /* Forwarding UDP:9091 to AF_XDP */
> +       if (udp->dest != bpf_htons(9091)) {
> +               pkts_skip++;
>                 return XDP_PASS;
> +       }
>
> -       bpf_printk("forwarding UDP:9091 to AF_XDP");
> -
> -       ret = bpf_xdp_adjust_meta(ctx, -(int)sizeof(struct xdp_meta));
> -       if (ret != 0) {
> -               bpf_printk("bpf_xdp_adjust_meta returned %d", ret);
> +       err = bpf_xdp_adjust_meta(ctx, -(int)sizeof(struct xdp_meta));
> +       if (err) {
> +               pkts_fail++;
>                 return XDP_PASS;
>         }
>
> @@ -65,20 +72,19 @@ int rx(struct xdp_md *ctx)
>         meta = data_meta;
>
>         if (meta + 1 > data) {
> -               bpf_printk("bpf_xdp_adjust_meta doesn't appear to work");
> +               pkts_fail++;
>                 return XDP_PASS;
>         }
>
> -       if (!bpf_xdp_metadata_rx_timestamp(ctx, &meta->rx_timestamp))
> -               bpf_printk("populated rx_timestamp with %llu", meta->rx_timestamp);
> -       else
> +       err = bpf_xdp_metadata_rx_timestamp(ctx, &meta->rx_timestamp);
> +       if (err)
>                 meta->rx_timestamp = 0; /* Used by AF_XDP as not avail signal */
>
> -       if (!bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash))
> -               bpf_printk("populated rx_hash with %u", meta->rx_hash);
> -       else
> +       err = bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash);
> +       if (err)
>                 meta->rx_hash = 0; /* Used by AF_XDP as not avail signal */
>
> +       pkts_redir++;
>         return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
>  }
>
> diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> index 1c8acb68b977..3b942ef7297b 100644
> --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
> +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> @@ -212,7 +212,9 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd)
>         while (true) {
>                 errno = 0;
>                 ret = poll(fds, rxq + 1, 1000);
> -               printf("poll: %d (%d)\n", ret, errno);
> +               printf("poll: %d (%d) skip=%llu fail=%llu redir=%llu\n",
> +                      ret, errno, bpf_obj->bss->pkts_skip,
> +                      bpf_obj->bss->pkts_fail, bpf_obj->bss->pkts_redir);
>                 if (ret < 0)
>                         break;
>                 if (ret == 0)
>
>