netdev - Re: [PATCH net-next v6 04/11] tcp: directly drop skb in cookie check for ipv6

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Date: Mon, 19 Feb 2024 12:57:08 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	kernelxing@...cent.com, kuba@...nel.org, netdev@...r.kernel.org, 
	pabeni@...hat.com
Subject: Re: [PATCH net-next v6 04/11] tcp: directly drop skb in cookie check
 for ipv6

On Mon, Feb 19, 2024 at 12:38 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> From: Jason Xing <kerneljasonxing@...il.com>
> Date: Mon, 19 Feb 2024 11:28:31 +0800
> > 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>
> > --
> > v6
> > Link: https://lore.kernel.org/all/c987d2c79e4a4655166eb8eafef473384edb37fb.camel@redhat.com/
> > Link: https://lore.kernel.org/all/CAL+tcoAgSjwsmFnDh_Gs9ZgMi-y5awtVx+4VhJPNRADjo7LLSA@mail.gmail.com/
> > 1. take one case into consideration, behave like old days, or else it will trigger errors.
> >
> > 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   | 7 +++----
> >  2 files changed, 7 insertions(+), 4 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..4cfeedfb871f 100644
> > --- a/net/ipv6/tcp_ipv6.c
> > +++ b/net/ipv6/tcp_ipv6.c
> > @@ -1653,12 +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 != sk) {
> > +             if (nsk && nsk != sk) {
> >                       if (tcp_child_process(sk, nsk, skb))
> >                               goto reset;
> > +             }
> > +             if (!nsk || nsk != sk) {
>
> !nsk is redundant, when nsk is NULL, nsk != sk is true.
>
> We can keep the original nsk != sk check and call tcp_child_process()
> only when nsk is not NULL:
>
> ---8<---
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 57b25b1fc9d9..0c180bb8187f 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1653,11 +1653,8 @@ 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 (tcp_child_process(sk, nsk, skb))
> +                       if (nsk && tcp_child_process(sk, nsk, skb))
>                                 goto reset;
>                         if (opt_skb)
>                                 __kfree_skb(opt_skb);
> ---8<---

Agreed. It looks much better. I'll take it. Thanks!