netdev - Re: [PATCH] net: thunderbolt: Fix TCP/UDPv6 GSO checksum calculation

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Date: Mon, 11 Sep 2023 12:03:06 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: Michael Jamet <michael.jamet@...el.com>, Yehezkel Bernat <YehezkelShB@...il.com>, 
	"David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Alex Balcanquall <alex@...xbal.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: thunderbolt: Fix TCP/UDPv6 GSO checksum calculation

On Mon, Sep 11, 2023 at 11:50 AM Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
>
> Alex reported that running ssh over IPv6 does not work with
> Thunderbolt/USB4 networking driver. The reason for that is that driver
> should call skb_is_gso() before calling skb_is_gso_v6(), and it should
> not return false after calculates the checksum successfully. This probably
> was a copy paste error from the original driver where it was done
> properly.
>
> While there add checksum calculation for UDPv6 GSO packets as well.

This part does not belong to this patch, and should be submitted for net-next.

Note that this driver is not supposed to receive UDP GSO packets.

>
> Cc: stable@...r.kernel.org

What would be the Fixes: tag for this patch ?

> Reported-by: Alex Balcanquall <alex@...xbal.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/net/thunderbolt/main.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
> index 0c1e8970ee58..ba50a554478f 100644
> --- a/drivers/net/thunderbolt/main.c
> +++ b/drivers/net/thunderbolt/main.c
> @@ -1049,12 +1049,21 @@ static bool tbnet_xmit_csum_and_map(struct tbnet *net, struct sk_buff *skb,
>                 *tucso = ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
>                                             ip_hdr(skb)->daddr, 0,
>                                             ip_hdr(skb)->protocol, 0);
> -       } else if (skb_is_gso_v6(skb)) {
> -               tucso = dest + ((void *)&(tcp_hdr(skb)->check) - data);
> -               *tucso = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> -                                         &ipv6_hdr(skb)->daddr, 0,
> -                                         IPPROTO_TCP, 0);
> -               return false;
> +       } else if (skb_is_gso(skb)) {
> +               if (skb_is_gso_v6(skb)) {
> +                       tucso = dest + ((void *)&(tcp_hdr(skb)->check) - data);
> +                       *tucso = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +                                                 &ipv6_hdr(skb)->daddr, 0,
> +                                                 IPPROTO_TCP, 0);
> +               } else if (protocol == htons(ETH_P_IPV6) &&
> +                          (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)) {
> +                       tucso = dest + ((void *)&(udp_hdr(skb)->check) - data);
> +                       *tucso = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +                                                 &ipv6_hdr(skb)->daddr, 0,
> +                                                 IPPROTO_UDP, 0);

This is dead code in the current state of this driver.

> +               } else {
> +                       return false;
> +               }
>         } else if (protocol == htons(ETH_P_IPV6)) {
>                 tucso = dest + skb_checksum_start_offset(skb) + skb->csum_offset;
>                 *tucso = ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> --
> 2.40.1
>