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Date: Wed, 30 Apr 2014 22:46:30 -0400
From: Rich Felker <>
Subject: Re: Requirement for proper DNS resolving / source port = 0

On Thu, May 01, 2014 at 03:31:57AM +0200, Stefan de Konink wrote:
> On Thursday, May 1, 2014 3:19:57 AM CEST, Rich Felker wrote:
> >One further idea -- could you send the output of strace (using the -o
> >option to write a log file, and -f if the program you're using is
> >multithreaded or forking) showing a failed lookup? This might help
> >understand what's happening.
> it with some sleepdeprivation.
> The problem was that I disabled CONFIG_PROC_SYSCTL, this resulted in
> the fact that /proc/sys was not mounted and probably
> net.ipv4.ip_local_port_range could not be used.

It's probably a kernel bug that these properties don't even have
working defaults without CONFIG_PROC_SYSCTL, but disabling that option
gives you a badly crippled kernel anyway...

> I don't know if any of the musl and/or busybox code explicitly
> depends on this. But it is one out of two problems [1] that I am
> breaking my head over today.

There's no explicit dependence. musl is simply using bind and connect
and expecting them to work. It does not access /proc/sys (although it
does use /proc for some other purposes, mainly for /proc/self/fd/%d).
This is covered (albeit not in complete detail) in the manual, which
can be found at:


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