Re: [PATCH net-next 1/3] net: core: add helper tcp_v6_gso_csum_prep

[Alexander Duyck]

On Mon, Feb 17, 2020 at 1:41 PM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
>
> Several network drivers for chips that support TSO6 share the same code
> for preparing the TCP header. A difference is that some reset the
> payload_len whilst others don't do this. Let's factor out this common
> code to a new helper.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> ---
>  include/net/ip6_checksum.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/include/net/ip6_checksum.h b/include/net/ip6_checksum.h
> index 7bec95df4..ef0130023 100644
> --- a/include/net/ip6_checksum.h
> +++ b/include/net/ip6_checksum.h
> @@ -76,6 +76,18 @@ static inline void __tcp_v6_send_check(struct sk_buff *skb,
>         }
>  }
>
> +static inline void tcp_v6_gso_csum_prep(struct sk_buff *skb,
> +                                       bool clear_payload_len)
> +{
> +       struct ipv6hdr *ipv6h = ipv6_hdr(skb);
> +       struct tcphdr *th = tcp_hdr(skb);
> +
> +       if (clear_payload_len)
> +               ipv6h->payload_len = 0;
> +
> +       th->check = ~tcp_v6_check(0, &ipv6h->saddr, &ipv6h->daddr, 0);
> +}
> +
>  #if IS_ENABLED(CONFIG_IPV6)
>  static inline void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb)
>  {

So functionally I believe this is correct. The only piece I have a
question about is if we should just force the clear_payload_len as
always being the case since the value should either be
ignored/overwritten in any GSO case anyway.

Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>