linux-kernel - Re: sysctl, argument parsing, possible bug

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Date:   Wed, 2 Aug 2017 23:53:54 +0200
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Massimo Sala <massimo.sala.71@...il.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: sysctl, argument parsing, possible bug

On Tue, Aug 01, 2017 at 02:54:51PM -0700, Cong Wang wrote:
> On Tue, Aug 1, 2017 at 2:34 PM, Massimo Sala <massimo.sala.71@...il.com> wrote:
> > Do you confirm it is a sysctl parsing bug ?
> >
> > Bosybox handles these cases, so I think also standalone sysctl have to.
> >
> > Or at least someone must update sysctl docs / MAN about this.
> >
> 
> Maybe, sysctl seems (I never look into it) just to interpret dot as
> a separator, unless it reads from the /proc/sys/ directory, it can
> not know eth0.100 is actually a netdev name.

Using echo or sysctl -w works for me, try upgrading your procps,
I have procps-3.3.12. Busybox sysctl fails though, so it would
seems this is an issue with busybox, go fix that.

With procps-3.3.12.:

Setting:

ergon:~ # cat /proc/sys/net/ipv4/conf/eth0.100/forwarding 
1

ergon:~ # sysctl -w net.ipv4.conf.eth0/100.forwarding=0
net.ipv4.conf.eth0/100.forwarding = 0

ergon:~ # cat /proc/sys/net/ipv4/conf/eth0.100/forwarding 
0

Querying:

ergon:~ # sysctl net.ipv4.conf.eth0/100.forwarding
net.ipv4.conf.eth0/100.forwarding = 0

With busybox:

ergon:~ # busybox-static sysctl net.ipv4.conf.eth0/100.forwarding
sysctl: error: 'net.ipv4.conf.eth0.100.forwarding' is an unknown key

  Luis