Date: Wed, 30 Apr 2014 21:18:14 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Requirement for proper DNS resolving / source port = 0 On Thu, May 01, 2014 at 03:08:26AM +0200, Stefan de Konink wrote: > Hi, > > I am setting up an embedded system, and consider that I have not set > up anything other then I have explicitly described. > > I am using a Linux kernel 3.14.2, and have set up kernel > autoconfiguration (ip=dhcp). That having said, I am able to ping > external hosts using busybox. > > My current problem is that I am unable to resolve hostnames in my > system. The file /etc/resolv.conf is in place, and I am observing > outgoing DNS requests. The strange thing about them is that the > source port is actually 0, not illegal, but it isn't getting any > replies. > > I have tried to add /etc/hosts and /etc/services. I am able to ping > localhost, which does resolve to an IP address using the entry from > /etc/hosts. > > Is this a bad kernel configuration? Does anyone have a hint where to > look for? > > My guess it is related to here... and I guess it is expecting udp > port randomization, which does not seem to happen. Any clues? Binding port 0 and calling connect should yield a kernel-assigned source port. If this isn't happening, I think something is wrong with your kernel, but I don't know exactly what. If there's an easy way we could detect and work around this situation I wouldn't mind trying to handle it, but I don't know how and didn't even expect for it to be possible. Rich
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