linux-kernel - Re: [PATCH net-next] inet: do not set backlog if listen fails

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Date:   Fri, 5 Oct 2018 09:54:20 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] inet: do not set backlog if listen fails

On Wed, Oct 3, 2018 at 11:41 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
>
> On 10/03/2018 08:07 AM, Yafang Shao wrote:
> > These two backlog members are not necessary set in inet_csk_listen_start().
> > Regarding sk_max_ack_backlog, it will be set in the caller inet_listen
> > and dccp_listen_start.
> > Regraing sk_ack_backlog, it is better to put it together with
> > sk_max_ack_backlog in the same function and only set on success.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> > ---
> >  net/dccp/proto.c                | 1 +
> >  net/ipv4/af_inet.c              | 1 +
> >  net/ipv4/inet_connection_sock.c | 3 ---
> >  3 files changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/dccp/proto.c b/net/dccp/proto.c
> > index 875858c..34d48cd 100644
> > --- a/net/dccp/proto.c
> > +++ b/net/dccp/proto.c
> > @@ -959,6 +959,7 @@ int inet_dccp_listen(struct socket *sock, int backlog)
> >               err = dccp_listen_start(sk, backlog);
> >               if (err)
> >                       goto out;
> > +             sk->sk_ack_backlog = 0;
>
>
> This is racy, remember that dccp and tcp have lockless listeners.
>
> Do not change sk_ack_backlog after a TCP/DCCP socket is ready to accept new flows.

Understood. Thanks for your explanation.