Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 10 Aug 2021 10:04:26 -0700
From:   John Fastabend <john.fastabend@gmail.com>
To:     Cong Wang <xiyou.wangcong@gmail.com>,
        John Fastabend <john.fastabend@gmail.com>
Cc:     Jiang Wang <jiang.wang@bytedance.com>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        "Cong Wang ." <cong.wang@bytedance.com>,
        Xiongchun Duan <duanxiongchun@bytedance.com>,
        xieyongji@bytedance.com, chaiwen.cc@bytedance.com,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jakub Sitnicki <jakub@cloudflare.com>,
        Lorenz Bauer <lmb@cloudflare.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
        Johan Almbladh <johan.almbladh@anyfinetworks.com>,
        LKML <linux-kernel@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
Message-ID: <6112b19a30160_1c2c820888@john-XPS-13-9370.notmuch>
In-Reply-To: <CAM_iQpXiqhfL9M04x1hvJ_6zCCUoDAv1_ywysu=O7wnCUuJaTw@mail.gmail.com>
References: <20210727001252.1287673-1-jiang.wang@bytedance.com>
 <20210727001252.1287673-3-jiang.wang@bytedance.com>
 <6100363add8a9_199a412089@john-XPS-13-9370.notmuch>
 <CAM_iQpVedTzRbf-bC7WuGMFYF=qnUxbnUdqJ9+FaxrTAn5DkTw@mail.gmail.com>
 <6101a56bf2a11_1e1ff620813@john-XPS-13-9370.notmuch>
 <CAM_iQpXiqhfL9M04x1hvJ_6zCCUoDAv1_ywysu=O7wnCUuJaTw@mail.gmail.com>
Subject: Re: [PATCH bpf-next v1 2/5] af_unix: add unix_stream_proto for
 sockmap
Mime-Version: 1.0
Content-Type: text/plain;
 charset=utf-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Cong Wang wrote:
> On Wed, Jul 28, 2021 at 11:44 AM John Fastabend
> <john.fastabend@gmail.com> wrote:
> >
> > Cong Wang wrote:
> > > On Tue, Jul 27, 2021 at 9:37 AM John Fastabend <john.fastabend@gmail.com> wrote:
> > > > Do we really need an unhash hook for unix_stream? I'm doing some testing
> > > > now to pull it out of TCP side as well. It seems to be an artifact of old
> > > > code that is no longer necessary. On TCP side at least just using close()
> > > > looks to be enough now.
> > >
> > > How do you handle the disconnection from remote without ->unhash()?
> >
> > Would close() not work for stream/dgram sockets?
> 
> close() is called when the local closes the sockets, but when the remote
> closes or disconnects it, unhash() is called. This is why TCP calls unhash()
> to remove the socket from established socket hash table. unhash() itself
> might not make much sense for AF_UNIX as it probably does not need a
> hash table to track established ones, however, the idea is the same, that
> is, we have to handle remote disconnections here.

Following up on this series. Leaving a socket in the sockmap until close()
happens is not paticularly problematic, but does consume space in the map
so unhash() is slightly better I guess. Thanks.

> 
> Thanks.