linux-kernel - Re: [PATCH v3 net-next 2/2] tcp: minor optimization around tcp

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Date:   Mon, 28 May 2018 09:36:23 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     laoar.shao@...il.com
Cc:     songliubraving@...com, David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 net-next 2/2] tcp: minor optimization around tcp_hdr()
 usage in tcp receive path

On Mon, May 28, 2018 at 8:36 AM Yafang Shao <laoar.shao@...il.com> wrote:

> This is additional to the commit ea1627c20c34 ("tcp: minor optimizations
around tcp_hdr() usage").
> At this point, skb->data is same with tcp_hdr() as tcp header has not
> been pulled yet.

> Cc: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> ---
>   net/ipv4/tcp_ipv4.c | 2 +-
>   net/ipv6/tcp_ipv6.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)

> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index adbdb50..d179386 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1486,7 +1486,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff
*skb)
>                                  sk->sk_rx_dst = NULL;
>                          }
>                  }
> -               tcp_rcv_established(sk, skb, tcp_hdr(skb));
> +               tcp_rcv_established(sk, skb, (const struct tcphdr
*)skb->data);
>                  return 0;
>          }

> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 7d47c2b..1c633ff 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1322,7 +1322,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct
sk_buff *skb)
>                          }
>                  }

> -               tcp_rcv_established(sk, skb, tcp_hdr(skb));
> +               tcp_rcv_established(sk, skb, (const struct tcphdr
*)skb->data);
>                  if (opt_skb)
>                          goto ipv6_pktoptions;
>                  return 0;
> --
> 1.8.3.1


I would rather remove the third parameter of tcp_rcv_established() instead
of duplicating the cast.