netdev - Re: route/max_size sysctl in ipv4

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Message-ID: <CAOxq_8Pp7fwsV3Y+-LNheziQzP8FXqT3ohgMt7SeEs6+nuGxMg@mail.gmail.com>
Date:	Wed, 7 Jan 2015 19:40:48 -0800
From:	Ani Sinha <ani@...sta.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: route/max_size sysctl in ipv4

On Wed, Jan 7, 2015 at 6:19 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Wed, 2015-01-07 at 17:25 -0800, Ani Sinha wrote:
>> hey guys,
>>
>> On Tue, Jan 6, 2015 at 5:56 PM, Ani Sinha <ani@...sta.com> wrote:
>> > On Mon, Jan 5, 2015 at 4:51 PM, David Miller <davem@...emloft.net> wrote:
>> >
>> >> The sysctl is kept so that scripts reading it don't suddenly stop
>> >> working.  We can't just remove sysctl values.
>> >
>> > Interestingly, one of our scripts did break. It broke because now this
>> > sysctl is only available in the global net namespace and not in the
>> > child namespaces. If not breaking scripts is the fundamental logic in
>> > keeping in sysctl intact, would you guys be open to accepting a patch
>> > where we make this sysctl available for all net namespaces?
>>
>> Any thoughts on this?
>
> AFAIK, this sysctl (and others) always have been global.
>
> Only /proc/sys/net/ipv4/route/flush is per ns

my apologies for not conveying my thoughts clearer. Eric, you are
correct. However, notice that except /proc/sys/net/ipv4/route/flush,
rest of the sysctls are not available from a child net namespace.

>
> namespaces usage can indeed remove some sysctl :
> Only initial namespace show them.

yes, this is what I am talking about.

>
> Presumably the global sysctl could be shadowed as read only, but still
> some scripts expecting them being rw would break anyway.

true but at least those scripts which does only read the values will
continue to function in a child namespace. In our case, our script
only reads the max_size sysctl but since it operates from within a
child namespace, it doesn't find it.

thoughts?
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