netdev - Re: [PATCH net-next v7 03/11] tcp: use drop reasons in cookie check for ipv4

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Message-ID: <CAL+tcoCe1jjXD7357w+3Z8P+jv+rBxwzcZnf0S2-2YMLv=3AYA@mail.gmail.com>
Date: Thu, 22 Feb 2024 10:52:59 +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 v7 03/11] tcp: use drop reasons in cookie check
 for ipv4

On Wed, Feb 21, 2024 at 5:34 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Wed, Feb 21, 2024 at 3:57 AM Jason Xing <kerneljasonxing@...il.com> wrote:
> >
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Now it's time to use the prepared definitions to refine this part.
> > Four reasons used might enough for now, I think.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > --
> > v6:
> > Link: https://lore.kernel.org/netdev/20240215210922.19969-1-kuniyu@amazon.com/
> > 1. Not use NOMEM because of MPTCP (Kuniyuki). I chose to use NO_SOCKET as
> > an indicator which can be used as three kinds of cases to tell people that we're
> > unable to get a valid one. It's a relatively general reason like what we did
> > to TCP_FLAGS.
> > Any better ideas/suggestions are welcome :)
> >
> > v5:
> > Link: https://lore.kernel.org/netdev/CANn89i+iELpsoea6+C-08m6+=JkneEEM=nAj-28eNtcOCkwQjw@mail.gmail.com/
> > Link: https://lore.kernel.org/netdev/632c6fd4-e060-4b8e-a80e-5d545a6c6b6c@kernel.org/
> > 1. Use SKB_DROP_REASON_IP_OUTNOROUTES instead of introducing a new one (Eric, David)
> > 2. Reuse SKB_DROP_REASON_NOMEM to handle failure of request socket allocation (Eric)
> > 3. Reuse NO_SOCKET instead of introducing COOKIE_NOCHILD
> > ---
> >  net/ipv4/syncookies.c | 18 +++++++++++++-----
> >  1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
> > index 38f331da6677..1028429c78a5 100644
> > --- a/net/ipv4/syncookies.c
> > +++ b/net/ipv4/syncookies.c
> > @@ -421,8 +421,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
> >                 if (IS_ERR(req))
> >                         goto out;
> >         }
> > -       if (!req)
> > +       if (!req) {
> > +               SKB_DR_SET(reason, NO_SOCKET);
> >                 goto out_drop;
> > +       }
> >
> >         ireq = inet_rsk(req);
> >
> > @@ -434,8 +436,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
> >          */
> >         RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(net, skb));
> >
> > -       if (security_inet_conn_request(sk, skb, req))
> > +       if (security_inet_conn_request(sk, skb, req)) {
> > +               SKB_DR_SET(reason, SECURITY_HOOK);
> >                 goto out_free;
> > +       }
> >
> >         tcp_ao_syncookie(sk, skb, req, AF_INET);
> >
> > @@ -452,8 +456,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
> >                            ireq->ir_loc_addr, th->source, th->dest, sk->sk_uid);
> >         security_req_classify_flow(req, flowi4_to_flowi_common(&fl4));
> >         rt = ip_route_output_key(net, &fl4);
> > -       if (IS_ERR(rt))
> > +       if (IS_ERR(rt)) {
> > +               SKB_DR_SET(reason, IP_OUTNOROUTES);
> >                 goto out_free;
> > +       }
> >
> >         /* Try to redo what tcp_v4_send_synack did. */
> >         req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
> > @@ -476,10 +482,12 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
> >         /* ip_queue_xmit() depends on our flow being setup
> >          * Normal sockets get it right from inet_csk_route_child_sock()
> >          */
> > -       if (ret)
> > +       if (ret) {
> >                 inet_sk(ret)->cork.fl.u.ip4 = fl4;
> > -       else
> > +       } else {
> > +               SKB_DR_SET(reason, NO_SOCKET);
> >                 goto out_drop;
> > +       }
>
> You can avoid the else here
>
> diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
> index be88bf586ff9ffba2190a1fd60a1ed3ce5f73d06..d56b0e309cfc0a58dcd277881fe2b364ab3cc668
> 100644
> --- a/net/ipv4/syncookies.c
> +++ b/net/ipv4/syncookies.c
> @@ -475,8 +475,11 @@ struct sock *cookie_v4_check(struct sock *sk,
> struct sk_buff *skb)
>         /* ip_queue_xmit() depends on our flow being setup
>          * Normal sockets get it right from inet_csk_route_child_sock()
>          */
> -       if (ret)
> -               inet_sk(ret)->cork.fl.u.ip4 = fl4;
> +       if (!ret) {
> +               SKB_DR_SET(reason, NO_SOCKET);
> +               goto out_drop;
> +       }
> +       inet_sk(ret)->cork.fl.u.ip4 = fl4;
>  out:
>         return ret;
>  out_free:

Thanks for your suggestions. I will update it in the v8 patch.

Thanks,
Jason