Re: Re: Would love to see reconsideration for domain and search

[Rich Felker <dalias@libc.org>]

On Sun, Oct 25, 2015 at 06:26:43PM -0700, Isaac Dunham wrote:
> On Sat, Oct 24, 2015 at 06:02:15PM -0400, Rich Felker wrote:
> > The only place adding search support might negatively impact existing
> > musl users is by causing hostnames with no dots to be queried with the
> > (often useless and unwanted) default domain set by dhcp before
> > failing. My preference would probably be having musl default to
> > ndots=0 rather than ndots=1 so that search has to be enabled
> > explicitly. Are there any reasons this would be undesirable?
> 
> Could you explain what this all would mean to someone who has only a
> general understanding of how DNS works, a home network, and a desire
> to set up a local DNS server?
> 
> I have a couple use-cases in mind, which I think involve either the
> "search" or "domain" keywords in resolv.conf; I'll describe them in case
> they pertain.
> 
> 1: the university I attended had a bunch of resources which were available
> as sub-domains. The way DHCP/DNS/resolv.conf was set up, local sites
> (for example, http://myweb.csuchico.edu/) were available using only the
> bare subdomain (in the same example, http://myweb/); I forget whether
> they used "domain" or "search" for this. This was something I
> appreciated.

Yes, this is what adding search domain support would allow. Note that
with ndots=1, "myweb" would work, but "myweb.math" would not.

> 2: On my home network (configured via DHCP, no DNS server yet), I have a
> network printer that advertises itself using a name in the general format
> of MFC0000DEADBEEF (where 0000DEADBEEF is the MAC address, stripped of
> separators). It uses this hostname for DHCP and avahi.
> However, this name is only available for avahi clients like cups; I
> want to be able to access it by the same name from non-avahi programs
> like 'ping', 'links', etcetera, since it's rather annoying to have a
> 'magic' name that usually works in your printing daemon, but no way
> to map it to an IP for any troupleshooting/configuration tools.
> 
> Currently, I've got it set up so the printer has a static lease and I
> thus know the IP, but I want to use DNS because that's the only way all
> tools on all computers on the network will automatically know that
> MFC0000DEADBEEF is (for example) IP 192.168.255.255.
> It would be rather annoying to have some tools where I can use that name,
> and some where I need to specify "mfc0000deadbeef.local" instead.

Doing this requires dunning a local nameserver that joins the avahi
(mdns, I think) results under some domain you control with the global
dns namespace. I suspect dnsmasq or one of the other dns servers made
for home network use can do this but I haven't checked. In principle
it's even possible with BIND and some scripting to query mdns and use
the results to update dynamic dns entries but that's rather ugly.

Rich