netdev - Re: [PATCH bpf-next v2 20/20] selftests/bpf: check checksum level in xdp

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Date: Thu, 6 Jul 2023 12:25:10 +0200
From: Jesper Dangaard Brouer <jbrouer@...hat.com>
To: Larysa Zaremba <larysa.zaremba@...el.com>, bpf@...r.kernel.org
Cc: brouer@...hat.com, 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>,
 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: [PATCH bpf-next v2 20/20] selftests/bpf: check checksum level in
 xdp_metadata



On 03/07/2023 20.12, Larysa Zaremba wrote:
> Verify, whether kfunc in xdp_metadata test correctly returns checksum level
> of zero.
> 
> Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
> ---
>   tools/testing/selftests/bpf/prog_tests/xdp_metadata.c | 3 +++
>   tools/testing/selftests/bpf/progs/xdp_metadata.c      | 7 +++++++
>   2 files changed, 10 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> index 50ac9f570bc5..6c71d712932e 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_metadata.c
> @@ -228,6 +228,9 @@ static int verify_xsk_metadata(struct xsk *xsk)
>   	if (!ASSERT_EQ(meta->rx_vlan_proto, VLAN_PID, "rx_vlan_proto"))
>   		return -1;
>   
> +	if (!ASSERT_NEQ(meta->rx_csum_lvl, 0, "rx_csum_lvl"))
> +		return -1;

Not-equal ("NEQ") to 0 feels weird here.
Below you set meta->rx_csum_lvl=1 in case meta->rx_csum_lvl==0.

Thus, test can pass if meta->rx_csum_lvl happens to be a random value.
We could set meta->rx_csum_lvl to 42 in case meta->rx_csum_lvl==0, and
then use a ASSERT_EQ==42 to be more certain of the case we are testing 
are fulfilled.


> +
>   	xsk_ring_cons__release(&xsk->rx, 1);
>   	refill_rx(xsk, comp_addr);
>   
> diff --git a/tools/testing/selftests/bpf/progs/xdp_metadata.c b/tools/testing/selftests/bpf/progs/xdp_metadata.c
> index 382984a5d1c9..6f7223d581b7 100644
> --- a/tools/testing/selftests/bpf/progs/xdp_metadata.c
> +++ b/tools/testing/selftests/bpf/progs/xdp_metadata.c
> @@ -26,6 +26,8 @@ extern int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx, __u32 *hash,
>   extern int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx,
>   					__u16 *vlan_tag,
>   					__be16 *vlan_proto) __ksym;
> +extern int bpf_xdp_metadata_rx_csum_lvl(const struct xdp_md *ctx,
> +					__u8 *csum_level) __ksym;
>   
>   SEC("xdp")
>   int rx(struct xdp_md *ctx)
> @@ -62,6 +64,11 @@ int rx(struct xdp_md *ctx)
>   	bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash, &meta->rx_hash_type);
>   	bpf_xdp_metadata_rx_vlan_tag(ctx, &meta->rx_vlan_tag, &meta->rx_vlan_proto);
>   
> +	/* Same as with timestamp, zero is expected */
> +	ret = bpf_xdp_metadata_rx_csum_lvl(ctx, &meta->rx_csum_lvl);
> +	if (!ret && meta->rx_csum_lvl == 0)
> +		meta->rx_csum_lvl = 1;
> +

IMHO it is more human-readable-code to rename "ret" variable "err".

I know you are just reusing variable "ret", so it's not really your fault.



>   	return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
>   }
>