Re: [PATCH bpf 2/2] selftests/bpf: Cover test_run csum validation after bpf_skb_change_tail()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] bpf: multi-line comments do not follow the preferred BPF style
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commit 5ce414e78d4de76ae6dba0dcb75c0182e95cd2d2
Author: Maxim Skokov <skokovmaksimevg@gmail.com>

selftests/bpf: Cover test_run csum validation after bpf_skb_change_tail()

This commit adds BPF_F_TEST_SKB_CHECKSUM_COMPLETE tests for tc programs
that modify the skb using bpf_skb_change_tail(), moving it out of
CHECKSUM_COMPLETE. It verifies that csum validation still correctly spots
invalid checksums.

> diff --git a/tools/testing/selftests/bpf/progs/skb_csum_complete.c b/tools/testing/selftests/bpf/progs/skb_csum_complete.c
> new file mode 100644
> index 0000000000000..8e8d53530899a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/skb_csum_complete.c
> @@ -0,0 +1,44 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <vmlinux.h>
> +#include <bpf/bpf_helpers.h>
> +
> +SEC("tc")
> +int change_tail_trim(struct __sk_buff *skb)
> +{
> +	/* Drops CHECKSUM_COMPLETE. skb->csum still covers the trimmed bytes,
> +	 * which hold the non-zero tcp.urg_ptr of pkt_v4, so it no longer
> +	 * matches the packet.
> +	 */

[Severity: Low]
This isn't a bug, but does this multi-line comment follow the preferred BPF
subsystem style? The global guidelines mandate that multi-line comments in BPF
files should have the opening '/*' on its own line, with the comment text
starting on the next line.

> +	if (bpf_skb_change_tail(skb, skb->len - 4, 0))
> +		return 1;
> +	return 0;
> +}
> +
> +SEC("tc")
> +int change_tail_grow_write(struct __sk_buff *skb)
> +{
> +	__u8 val = 0xab;
> +
> +	/* Drops CHECKSUM_COMPLETE. The new bytes are zero and do not change
> +	 * the sum, but the write below can no longer update skb->csum.
> +	 */

[Severity: Low]
This isn't a bug, but similar to the previous comment, shouldn't the opening
'/*' be on its own line to match the required kernel comment style for BPF
files?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261007181249.352831-1-skokovmaksimevg@gmail.com?part=2