No mDNS hostname lookup support

[hadess]

I tried a Flatpak'ed network application, and it couldn't connect to my NAS. Turns out there's no mdns support within the sandbox. Or support for "myhostname mymachines" hosts name services, that systemd added recently.

[alexlarsson]

Is this just a matter of libavahi not being in the runtime, or is this something more complex?

[hadess]

You need mdns4_minimal installed and setup in the runtime, which probably needs some sort of access to Avahi (D-Bus?) I'm worried that other types of NSS modules will need to be supported in the future (LDAP or NIS support?) and I wonder how we'd support that. Proxy through nscd?

[alexlarsson]

Yeah, simo wanted to talk to me about this. I don't think we can really set up NSS inside the sandbox, the solution is likely to be something like nscd instead.

[hadess]

On the one hand, it's nice to be able to resolve dot-local hostnames, on the other, what do we do when an app wants to funnel all the LDAP user names.

[ahayzen]

FWIW, this also affects auto discovery and broadcast of DAAP shares within Rhythmbox flathub/org.gnome.Rhythmbox3#4.

[ahayzen]

Follow up for Rhythmbox, we were able to use --system-talk-name=org.freedesktop.Avahi which allows this to work when the host has Avahi installed. flathub/org.gnome.Rhythmbox3#4

[hadess]

This bug is about mDNS lookups, not about access to Avahi for service discovery. Being able to talk to Avahi will not fix or work-around this bug.

You need mdns4_minimal installed and setup in the runtime, which probably needs some sort of access to Avahi (D-Bus?) I'm worried that other types of NSS modules will need to be supported in the future (LDAP or NIS support?) and I wonder how we'd support that. Proxy through nscd?

Adding mdns4_minimal to the runtime might be the way to fix this problem.

[evantandersen]

Hello, just piping in to share that this bug affects me! I'm using flatpak to run Barrier to control a VM, and I can't connect via hostname since that's discovered through mDNS.