Subject: Re: [PATCH bpf V8 2/7] selftests/bpf: Add counters to xdp_hw_metadata

From: Stanislav Fomichev <[email-masked]>
Date: Wed, 12 Apr 2023 09:56:01 -0700

On 04/12, Jesper Dangaard Brouer wrote:
> Add counters for skipped, failed and redirected packets.
> The xdp_hw_metadata program only redirects UDP port 9091.
> This helps users to quickly identify then packets are
> skipped and identify failures of bpf_xdp_adjust_meta.
> 
> Signed-off-by: Jesper Dangaard Brouer <[email-masked]>
> ---
>  .../testing/selftests/bpf/progs/xdp_hw_metadata.c  |   15 +++++++++++++--
>  tools/testing/selftests/bpf/xdp_hw_metadata.c      |    4 +++-
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> index b0104763405a..a07ef7534013 100644
> --- a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> +++ b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c
> @@ -25,6 +25,10 @@ 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,
> @@ -59,16 +63,21 @@ int rx(struct xdp_md *ctx)
>  			udp = NULL;
>  	}
>  
> -	if (!udp)
> +	if (!udp) {
> +		pkts_skip++;
>  		return XDP_PASS;
> +	}
>  
>  	/* Forwarding UDP:9091 to AF_XDP */
> -	if (udp->dest != bpf_htons(9091))
> +	if (udp->dest != bpf_htons(9091)) {
> +		pkts_skip++;
>  		return XDP_PASS;
> +	}
>  
>  	ret = bpf_xdp_adjust_meta(ctx, -(int)sizeof(struct xdp_meta));
>  	if (ret != 0) {

[..]

>  		bpf_printk("bpf_xdp_adjust_meta returned %d", ret);

Maybe let's remove these completely? Merge patch 1 and 2, remove printk,
add counters. We can add more counters in the future if the existing
ones are not enough.. WDYT?

> +		pkts_fail++;
>  		return XDP_PASS;
>  	}
>  
> @@ -78,6 +87,7 @@ int rx(struct xdp_md *ctx)
>  
>  	if (meta + 1 > data) {
>  		bpf_printk("bpf_xdp_adjust_meta doesn't appear to work");
> +		pkts_fail++;
>  		return XDP_PASS;
>  	}
>  
> @@ -91,6 +101,7 @@ int rx(struct xdp_md *ctx)
>  	else
>  		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)
> 
>