netdev - Re: [PATCH net-next v5 04/11] tcp: directly drop skb in cookie check for ipv6

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Message-ID: <CAL+tcoAgSjwsmFnDh_Gs9ZgMi-y5awtVx+4VhJPNRADjo7LLSA@mail.gmail.com>
Date: Thu, 15 Feb 2024 19:08:20 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, kuniyu@...zon.com
Cc: netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v5 04/11] tcp: directly drop skb in cookie check
 for ipv6

On Thu, Feb 15, 2024 at 9:20 AM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> From: Jason Xing <kernelxing@...cent.com>
>
> Like previous patch does, only moving skb drop logical code to
> cookie_v6_check() for later refinement.
>
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> --
> v5
> Link: https://lore.kernel.org/netdev/CANn89iKz7=1q7e8KY57Dn3ED7O=RCOfLxoHQKO4eNXnZa1OPWg@mail.gmail.com/
> 1. avoid duplication of these opt_skb tests/actions (Eric)
> ---
>  net/ipv6/syncookies.c |  4 ++++
>  net/ipv6/tcp_ipv6.c   | 11 ++++-------
>  2 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
> index 6b9c69278819..ea0d9954a29f 100644
> --- a/net/ipv6/syncookies.c
> +++ b/net/ipv6/syncookies.c
> @@ -177,6 +177,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
>         struct sock *ret = sk;
>         __u8 rcv_wscale;
>         int full_space;
> +       SKB_DR(reason);
>
>         if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
>             !th->ack || th->rst)
> @@ -256,10 +257,13 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
>         ireq->ecn_ok &= cookie_ecn_ok(net, dst);
>
>         ret = tcp_get_cookie_sock(sk, skb, req, dst);
> +       if (!ret)
> +               goto out_drop;
>  out:
>         return ret;
>  out_free:
>         reqsk_free(req);
>  out_drop:
> +       kfree_skb_reason(skb, reason);
>         return NULL;
>  }
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 57b25b1fc9d9..1ca4f11c3d6f 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1653,16 +1653,13 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
>         if (sk->sk_state == TCP_LISTEN) {
>                 struct sock *nsk = tcp_v6_cookie_check(sk, skb);
>
> -               if (!nsk)
> -                       goto discard;
> -
> -               if (nsk != sk) {
> +               if (nsk && nsk != sk) {
>                         if (tcp_child_process(sk, nsk, skb))
>                                 goto reset;
> -                       if (opt_skb)
> -                               __kfree_skb(opt_skb);
> -                       return 0;
>                 }
> +               if (opt_skb)
> +                       __kfree_skb(opt_skb);
> +               return 0;

Oops, the above lines went wrong, which could cause the error that
Paolo reported in my patch[0/11] email.

The error could happen when if:
    nsk != NULL && nsk == sk
it will return 0, which is against old behaviour :(

I will fix this...

>         } else
>                 sock_rps_save_rxhash(sk, skb);
>
> --
> 2.37.3
>