netdev - Re: [PATCH] selftests/net: enable lo.accept_local in psock

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Date:   Mon, 23 May 2022 17:19:41 +0800
From:   Yun Lu <luyun_611@....com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, netdev@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] selftests/net: enable lo.accept_local in psock_snd test

On 2022/5/20 下午9:52, Willem de Bruijn wrote:

> On Fri, May 20, 2022 at 2:40 AM Yun Lu <luyun_611@....com> wrote:
>> From: luyun <luyun@...inos.cn>
>>
>> The psock_snd test sends and recievs packets over loopback, but the
>> parameter lo.accept_local is disabled by default, this test will
>> fail with Resource temporarily unavailable:
>> sudo ./psock_snd.sh
>> dgram
>> tx: 128
>> rx: 142
>> ./psock_snd: recv: Resource temporarily unavailable
> I cannot reproduce this failure.
>
> Passes on a machine with accept_local 0.
>
> accept_local is defined as
>
> "
> accept_local - BOOLEAN
>      Accept packets with local source addresses. In combination
>      with suitable routing, this can be used to direct packets
>      between two local interfaces over the wire and have them
>      accepted properly.
> "
I did this test on my system(Centos 8.3 X86_64):

[root@...alhost net]# sysctl net.ipv4.conf.lo.accept_local
net.ipv4.conf.lo.accept_local = 0
[root@...alhost net]# ./psock_snd -d
tx: 128
rx: 142
./psock_snd: recv: Resource temporarily unavailable
[root@...alhost net]# sysctl -w net.ipv4.conf.lo.accept_local=1
net.ipv4.conf.lo.accept_local = 1
[root@...alhost net]# ./psock_snd -d
tx: 128
rx: 142
rx: 100
OK

This failure does seem to be related to accept_local.

Also, it's reported on Ubuntu:
https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/1812618