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From:   Menglong Dong <menglong8.dong@gmail.com>
Date:   Thu, 17 Mar 2022 13:25:13 +0800
Message-ID: <CADxym3Z_o6P+jSu5sUZDQf4bGUj4f4tGEYi7a9z+wRjYu0o1xw@mail.gmail.com>
Subject: Re: [PATCH net-next v3 2/3] net: icmp: introduce __ping_queue_rcv_skb()
 to report drop reasons
To:     David Ahern <dsahern@kernel.org>
Cc:     Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, xeb@mail.ru,
        David Miller <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Menglong Dong <imagedong@tencent.com>,
        Eric Dumazet <edumazet@google.com>, Martin Lau <kafai@fb.com>,
        Talal Ahmad <talalahmad@google.com>,
        Kees Cook <keescook@chromium.org>,
        Alexander Lobakin <alobakin@pm.me>,
        Hao Peng <flyingpeng@tencent.com>,
        Mengen Sun <mengensun@tencent.com>, dongli.zhang@oracle.com,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Biao Jiang <benbjiang@tencent.com>
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On Thu, Mar 17, 2022 at 11:56 AM David Ahern <dsahern@kernel.org> wrote:
>
> On 3/16/22 12:31 AM, menglong8.dong@gmail.com wrote:
> > diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
> > index 3ee947557b88..9a1ea6c263f8 100644
> > --- a/net/ipv4/ping.c
> > +++ b/net/ipv4/ping.c
> > @@ -934,16 +934,24 @@ int ping_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
> >  }
> >  EXPORT_SYMBOL_GPL(ping_recvmsg);
> >
> > -int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
> > +static enum skb_drop_reason __ping_queue_rcv_skb(struct sock *sk,
> > +                                              struct sk_buff *skb)
> >  {
> > +     enum skb_drop_reason reason;
> > +
> >       pr_debug("ping_queue_rcv_skb(sk=%p,sk->num=%d,skb=%p)\n",
> >                inet_sk(sk), inet_sk(sk)->inet_num, skb);
> > -     if (sock_queue_rcv_skb(sk, skb) < 0) {
> > -             kfree_skb(skb);
> > +     if (sock_queue_rcv_skb_reason(sk, skb, &reason) < 0) {
> > +             kfree_skb_reason(skb, reason);
> >               pr_debug("ping_queue_rcv_skb -> failed\n");
> > -             return -1;
> > +             return reason;
> >       }
> > -     return 0;
> > +     return SKB_NOT_DROPPED_YET;
> > +}
> > +
> > +int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
> > +{
> > +     return __ping_queue_rcv_skb(sk, skb) ?: -1;
> >  }
> >  EXPORT_SYMBOL_GPL(ping_queue_rcv_skb);
> >
>
> This is a generic proto callback and you are now changing its return
> code in a way that seems to conflict with existing semantics

The return value of ping_queue_rcv_skb() seems not changed.
In the previous code, -1 is returned on failure and 0 for success.
This logic isn't changed, giving __ping_queue_rcv_skb() != 0 means
failure and -1 is returned. Isn't it?