netdev - Re: [PATCH net-next v4 4/5] tcp: directly drop skb in cookie check for ipv6

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Message-ID: <CAL+tcoBgjNjLCXD716G-yc2gTiPF+-tyKF3Tz6CQBXBSDe3Tfg@mail.gmail.com>
Date: Wed, 14 Feb 2024 01:09:06 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	dsahern@...nel.org, kuniyu@...zon.com, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v4 4/5] tcp: directly drop skb in cookie check
 for ipv6

On Tue, Feb 13, 2024 at 11:30 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Feb 13, 2024 at 2:42 PM 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>
> > ---
> >  net/ipv6/syncookies.c | 4 ++++
> >  net/ipv6/tcp_ipv6.c   | 7 +++++--
> >  2 files changed, 9 insertions(+), 2 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..27639ffcae2f 100644
> > --- a/net/ipv6/tcp_ipv6.c
> > +++ b/net/ipv6/tcp_ipv6.c
> > @@ -1653,8 +1653,11 @@ 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) {
> > +                       if (opt_skb)
> > +                               __kfree_skb(opt_skb);
> > +                       return 0;
> > +               }
> >
> >                 if (nsk != sk) {
> >                         if (tcp_child_process(sk, nsk, skb))
> > --
>
> or perhaps try to avoid duplication of these opt_skb tests/actions.
>
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 57b25b1fc9d9d529e3c53778ef09b65b1ac4c9d5..1ca4f11c3d6f3af2a0148f0e50dfea96b8ba3a53
> 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;
>         } else
>                 sock_rps_save_rxhash(sk, skb);

Thanks for your advice. Will update it:)

Thanks,
Jason