Re: [musl] Resolver routines, Postfix DNSSEC troubles - how to check for incompatibilities?

[Rich Felker <dalias@libc.org>]

On Mon, Apr 13, 2020 at 07:51:23PM +0200, Christian wrote:
> Am Montag, den 13.04.2020, 12:38 -0400 schrieb Rich Felker:
> > On Mon, Apr 13, 2020 at 05:52:34PM +0200, Florian Weimer wrote:
> >
> > * Christian:
> >
> >
> > So Viktor did some digging:
> >
> > "The comment on line 25:
> >
> >
> https://github.com/runtimejs/musl-libc/blob/master/include/resolv.h#L25
> >
> > is not encouraging.  It suggests that _res is unused. If so, Postfix
> > DNS does not work correctly with this C library.  And not just for
> > DANE, since Postfix is also unable to to control RES_DEFNAMES and
> > RES_DNSRCH.
> >
> > Are these changes to the RES_DEFNAMES and RES_DNSRCH flags really
> > necessary? Why doesn't Postfix use res_query (or perhaps res_send) as
> > appropriate?
> >
> > But to actually answer these questions, modifying the flags is
> > presumably because traditional req_query builds an rfc1035 query or
> > edns query based on these flags derived from from resolv.conf, and
> > Postfix either assumes or wants to support the case where resolv.conf
> > is not already configured for edns, perhaps because it was generated
> > by a dhcp client.
> >
> > Rich
> >
> >
> 
> I can't tell you much on the coding or why it is this way. I am merely
> a user that found the incompatibility. If this is of interest, you
> might want to get in contact with Viktor, e.g. via the postfix users
> mailing list.
> 
> FYI: I just moved my config to a glibc setup in debian and it is
> working without issues, hence confirming Viktors finding, that Postfix
> won't work with musl

Thanks. I'll see if I can reply into the postfix-users thread.

Rich