How to ask a DNS resolver listening on a different port than the tcp/udp 53

Michael Sierchio kudzu at
Fri Sep 27 23:20:08 UTC 2013

On Fri, Sep 27, 2013 at 4:11 PM, Frank Leonhardt <frank2 at> wrote:
> On 27/09/2013 23:08, Terje Elde wrote:
>> On 28. sep. 2013, at 00:03, Frank Leonhardt <frank2 at> wrote:
>>> If I understand the way it works correctly, the resolver pulls a list of
>>> the NS and hard-sets the port number for each to 53 (via a manifest
>>> constant) . See libc/resolv/res_init.c. All you need to do(!) is change this
>>> to a value of your choice and recompile libc
>> Sorry, but this is startin to look a lot like a complicated solution to a
>> problem that isn't really there...
> It was more of an explanation as to /why/ it's not easy to do what asked in
> the original reasonable-sounding question.

Beg to differ.  The question isn't reasonable.  There's no point in
having a dns recursive resolver listening on a port other than the one
that clients will contact it on.

Far better to have the authoritative server listen on and
use the routable address for the cache, which can forward requests for
the authoritative server when appropriate.

- M

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