diff mbox series

bpf: fix the xdp_adjust_tail sample prog issue

Message ID 20240929124134.24288-1-chenyuan_fl@163.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series bpf: fix the xdp_adjust_tail sample prog issue | expand

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Commit Message

Yuan Chen Sept. 29, 2024, 12:41 p.m. UTC 
From: Yuan Chen <chenyuan@kylinos.cn>

During the xdp_adjust_tail test, probabilistic failure occurs and SKB package
is discarded by the kernel. After checking the issues by tracking SKB package,
it is identified that they were caused by checksum errors. Refer to checksum
of the arch/arm64/include/asm/checksum.h for fixing.

Fixes: c6ffd1ff7856 (bpf: add bpf_xdp_adjust_tail sample prog)
Signed-off-by: Yuan Chen <chenyuan@kylinos.cn>
---
 samples/bpf/xdp_adjust_tail_kern.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Alexei Starovoitov Sept. 29, 2024, 5:56 p.m. UTC | #1 
On Sun, Sep 29, 2024 at 5:41 AM Yuan Chen <chenyuan_fl@163.com> wrote:
>
> From: Yuan Chen <chenyuan@kylinos.cn>
>
> During the xdp_adjust_tail test, probabilistic failure occurs and SKB package
> is discarded by the kernel. After checking the issues by tracking SKB package,
> it is identified that they were caused by checksum errors. Refer to checksum
> of the arch/arm64/include/asm/checksum.h for fixing.
>
> Fixes: c6ffd1ff7856 (bpf: add bpf_xdp_adjust_tail sample prog)
> Signed-off-by: Yuan Chen <chenyuan@kylinos.cn>
> ---
>  samples/bpf/xdp_adjust_tail_kern.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/samples/bpf/xdp_adjust_tail_kern.c b/samples/bpf/xdp_adjust_tail_kern.c
> index ffdd548627f0..3543ddd62ef4 100644
> --- a/samples/bpf/xdp_adjust_tail_kern.c
> +++ b/samples/bpf/xdp_adjust_tail_kern.c
> @@ -57,7 +57,8 @@ static __always_inline void swap_mac(void *data, struct ethhdr *orig_eth)
>
>  static __always_inline __u16 csum_fold_helper(__u32 csum)
>  {
> -       return ~((csum & 0xffff) + (csum >> 16));
> +       csum += (csum >> 16) | (csum << 16);
> +       return ~(__sum16)(csum >> 16);
>  }

progs/xdping_kern.c is doing it differently:
static __always_inline __u16 csum_fold_helper(__wsum sum)
{
        sum = (sum & 0xffff) + (sum >> 16);
        return ~((sum & 0xffff) + (sum >> 16));
}

Let's make it common.

pw-bot: cr
diff mbox series

Patch

diff --git a/samples/bpf/xdp_adjust_tail_kern.c b/samples/bpf/xdp_adjust_tail_kern.c
index ffdd548627f0..3543ddd62ef4 100644
--- a/samples/bpf/xdp_adjust_tail_kern.c
+++ b/samples/bpf/xdp_adjust_tail_kern.c
@@ -57,7 +57,8 @@  static __always_inline void swap_mac(void *data, struct ethhdr *orig_eth)
 
 static __always_inline __u16 csum_fold_helper(__u32 csum)
 {
-	return ~((csum & 0xffff) + (csum >> 16));
+	csum += (csum >> 16) | (csum << 16);
+	return ~(__sum16)(csum >> 16);
 }
 
 static __always_inline void ipv4_csum(void *data_start, int data_size,