Bug 505654 – net-dns/avahi should depend on sys-auth/nss-mdns

• Product: Gentoo Linux
• Status: RESOLVED INVALID

[Description Michael Gn. Gajda 2014-03-25 11:53:56 UTC]

Pleave forgive me, if my assumption and knowlege about avahi is incorrect.

As far as I understood, the AVAHI-Tools resolve other hosts in the mdns domain '.local'. Any programm not using the avahi-tools directly (but glib whatnot) cannot resolve .local hosts unless 'sys-auth/nss-mdns' is installed.

CUPS is an example of an application that finds and adds with AVAHI printers on the network and configures them as 'printername.local', which then is not able to resolve that hostname and print.

Do I have a false understanding of avahi/mdns or should 'sys-auth/nss-mdns' be a dependency of either 'net-dns/avahi' or maybe packages with the AVAHI useflag?

Reproducible: Always

[Comment 1 Anthony Basile 2014-05-31 13:55:58 UTC]

(In reply to gen.9.madblock from comment #0)
> Pleave forgive me, if my assumption and knowlege about avahi is incorrect.
> 
> As far as I understood, the AVAHI-Tools resolve other hosts in the mdns
> domain '.local'. Any programm not using the avahi-tools directly (but glib
> whatnot) cannot resolve .local hosts unless 'sys-auth/nss-mdns' is installed.
> 
> CUPS is an example of an application that finds and adds with AVAHI printers
> on the network and configures them as 'printername.local', which then is not
> able to resolve that hostname and print.
> 
> Do I have a false understanding of avahi/mdns or should 'sys-auth/nss-mdns'
> be a dependency of either 'net-dns/avahi' or maybe packages with the AVAHI
> useflag?
> 
> Reproducible: Always

Do you have a specific bug you are addressing here?  If so, what are the steps to reproduce it.

[Comment 2 Anthony Basile 2014-06-11 18:30:00 UTC]

(In reply to gen.9.madblock from comment #0)
> Pleave forgive me, if my assumption and knowlege about avahi is incorrect.
> 
> As far as I understood, the AVAHI-Tools resolve other hosts in the mdns
> domain '.local'. Any programm not using the avahi-tools directly (but glib
> whatnot) cannot resolve .local hosts unless 'sys-auth/nss-mdns' is installed.
> 
> CUPS is an example of an application that finds and adds with AVAHI printers
> on the network and configures them as 'printername.local', which then is not
> able to resolve that hostname and print.
> 
> Do I have a false understanding of avahi/mdns or should 'sys-auth/nss-mdns'
> be a dependency of either 'net-dns/avahi' or maybe packages with the AVAHI
> useflag?
> 
> Reproducible: Always

Okay no answer for a while, so I'll guess at what you are getting at: cups works just fine without nss-mdns as do many other programs.  You don't need to go thorugh glibc's resolver library to resolve multicast dsn.  You *can* if you want, but most apps don't.  So, if you install nss-mdns and add the correct lines to nssswitch.conf like

    hosts: files dns mdns4

then something like `dig @localhost myprinter.local` will return the IP of your printer.  But that doesn't stop some app from listening to mdns via its own library.  Eg on my home box: 

    avahi-resolve -n yellow.local

gives the ip addrss of that service.  And I don't have nss-mdns.

I hope that answers this concern.