linux-kernel - Re: [PATCH net-next 1/3] net: core: add helper tcp_v6_gso_csum

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Date:   Tue, 18 Feb 2020 10:25:19 -0800
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Realtek linux nic maintainers <nic_swsd@...ltek.com>,
        Jay Cliburn <jcliburn@...il.com>,
        Chris Snook <chris.snook@...il.com>,
        Rasesh Mody <rmody@...vell.com>,
        Sudarsana Kalluru <skalluru@...vell.com>,
        GR-Linux-NIC-Dev@...vell.com,
        Christian Benvenuti <benve@...co.com>,
        Govindarajulu Varadarajan <_govind@....com>,
        Parvi Kaustubhi <pkaustub@...co.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Guo-Fu Tseng <cooldavid@...ldavid.org>,
        Shannon Nelson <snelson@...sando.io>,
        Pensando Drivers <drivers@...sando.io>,
        Timur Tabi <timur@...nel.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        Ronak Doshi <doshir@...are.com>,
        "VMware, Inc." <pv-drivers@...are.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        linux-hyperv@...r.kernel.org,
        Linux USB Mailing List <linux-usb@...r.kernel.org>
Subject: Re: [PATCH net-next 1/3] net: core: add helper tcp_v6_gso_csum_prep

On Mon, Feb 17, 2020 at 1:41 PM Heiner Kallweit <hkallweit1@...il.com> 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@...il.com>
> ---
>  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@...ux.intel.com>