Re: [PATCH v2] net/mlx5: fix lro update tcp header cksum error

[Thomas Monjalon <thomas@monjalon.net>]

Any comment on this patch?

13/04/2023 02:57, jiangheng (G):
> The variable csum is the sum of three 16 bits integers, the max value
> is 0x2FFFD. The corner case of sum of 3 is 0x1FFFF gives the wrong
> result: 0x1 + 0xFFFF = 0x10000, the upper 16 bits are not 0.
> It must be folded again to ensure that the upper 16 bits are 0.
> 
> Fixes: e4c2a16eb1de ("net/mlx5: handle LRO packets in Rx queue")
> Cc: stable@dpdk.org
> 
> Signed-off-by: jiangheng <jiangheng14@huawei.com>
> ---
>  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;
> > 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
> >
> > > 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