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List:       busybox
Subject:    Re: [PATCH 1/1] ifupdown: add write lock around ifstate access
From:       Danomi Manchego <danomimanchego123 () gmail ! com>
Date:       2016-09-29 21:34:21
Message-ID: CANxTyt7qGETcn8B+DyOLADuqs41=r6H4NxuKUnCHRACe270CNw () mail ! gmail ! com
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Denys,

On Thu, Sep 29, 2016 at 12:25 PM, Denys Vlasenko
<vda.linux@googlemail.com> wrote:
> On Thu, Sep 29, 2016 at 5:04 AM, Danomi Manchego
> <danomimanchego123@gmail.com> wrote:
>> So that concurrent access on systems with multiple
>> network interfaces correctly update the ifstate file.
>
> Two or more concurrent ifups or ifdowns
> are likely to trample over many more things than /var/run/ifstate
>
> For example, what about routing table entries they are removing
> and adding?

In our systems, we serialize ip route updates, dhcp updates, and
resolv.conf mods through a proprietary application, so we didn't run
into those issues.  We just needed a reliable if-up.d/if-down.d basis
to dispatch messages to our app.

I suppose that if you were updating those files directly in the
if-xxx.d scripts, then it would be the script writer's responsibility
to use something like flock to protect the shared assets.

Danomi -
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