[PATCH] net/mlx5: fix lro update tcp header cksum error

[PATCH] net/mlx5: fix lro update tcp header cksum error

[jiangheng (G)]

csum is the sum of three 16 bits value
it must be folded twice to ensure that the upper 16 bits are 0
---
 drivers/net/mlx5/mlx5_rx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/mlx5/mlx5_rx.c b/drivers/net/mlx5/mlx5_rx.c
index a2be523e9e..ae537dfffa 100644
--- a/drivers/net/mlx5/mlx5_rx.c
+++ b/drivers/net/mlx5/mlx5_rx.c
@@ -1090,6 +1090,7 @@ mlx5_lro_update_tcp_hdr(struct rte_tcp_hdr *__rte_restrict tcp,
    tcp->cksum = 0;
    csum += rte_raw_cksum(tcp, (tcp->data_off >> 4) * 4);
    csum = ((csum & 0xffff0000) >> 16) + (csum & 0xffff);
+   csum = ((csum & 0xffff0000) >> 16) + (csum & 0xffff);
    csum = (~csum) & 0xffff;
    if (csum == 0)
        csum = 0xffff;
--
2.27.0

RE: [PATCH] net/mlx5: fix lro update tcp header cksum error

[Slava Ovsiienko]

Hi,  Jiangheng

You are right, the corner case of sum of 3 is 0x1FFFF gives the wrong result.
Could you,  please, format the patch according to the rules and send v2 ?
- add Fixes: tag with reference to appropriate commit
- add Cc: stable@dpdk.org
- fix typos in commit message - capitalize sentences, add trailing points, etc.

With best regards,
Slava

> -----Original Message-----
> From: jiangheng (G) <jiangheng14@huawei.com>
> Sent: среда, 12 апреля 2023 г. 14:39
> To: dev@dpdk.org; Matan Azrad <matan@nvidia.com>; Slava Ovsiienko
> <viacheslavo@nvidia.com>
> Subject: [PATCH] net/mlx5: fix lro update tcp header cksum error
> 
> csum is the sum of three 16 bits value
> it must be folded twice to ensure that the upper 16 bits are 0
> ---
>  drivers/net/mlx5/mlx5_rx.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/mlx5/mlx5_rx.c b/drivers/net/mlx5/mlx5_rx.c index
> a2be523e9e..ae537dfffa 100644
> --- a/drivers/net/mlx5/mlx5_rx.c
> +++ b/drivers/net/mlx5/mlx5_rx.c
> @@ -1090,6 +1090,7 @@ mlx5_lro_update_tcp_hdr(struct rte_tcp_hdr
> *__rte_restrict tcp,
>     tcp->cksum = 0;
>     csum += rte_raw_cksum(tcp, (tcp->data_off >> 4) * 4);
>     csum = ((csum & 0xffff0000) >> 16) + (csum & 0xffff);
> +   csum = ((csum & 0xffff0000) >> 16) + (csum & 0xffff);
>     csum = (~csum) & 0xffff;
>     if (csum == 0)
>         csum = 0xffff;
> --
> 2.27.0