resolved: mDNS stack conflicts with avahi

[yuwata]

Submission type

• Bug report
• Request for enhancement (RFE)

NOTE: Do not submit anything other than bug reports or RFEs via the issue tracker!

systemd version the issue has been seen with

I've found this bug on 4317cf9. Maybe it has been seen since 01c901e.

NOTE: Do not submit bug reports about anything but the two most recently released systemd versions upstream!

Used distribution

Fedora 25 x86_64 with almost latest systemd git snapshot.

In case of bug report: Expected behaviour you didn't see

systemd-resolved works fine with avahi-daemon.

In case of bug report: Unexpected behaviour you saw

If both systemd-resolved and avahi-daemon is enabled, I get the following error messages that states avahi and resolved's mDNS stack conflicts with each other.

$ journalctl -b
(snip)
Mar 03 21:36:39 systemd[1]: Starting Avahi mDNS/DNS-SD Stack...
Mar 03 21:36:39 avahi-daemon[7343]: Found user 'avahi' (UID 70) and group 'avahi' (GID 70).
Mar 03 21:36:39 avahi-daemon[7343]: Successfully dropped root privileges.
Mar 03 21:36:39 avahi-daemon[7343]: avahi-daemon 0.6.32 starting up.
Mar 03 21:36:39 avahi-daemon[7343]: WARNING: No NSS support for mDNS detected, consider installing nss-mdns!
Mar 03 21:36:39 dbus-daemon[396]: [system] Successfully activated service 'org.freedesktop.Avahi'
Mar 03 21:36:39 systemd[1]: Started Avahi mDNS/DNS-SD Stack.
Mar 03 21:36:39 avahi-daemon[7343]: Successfully called chroot().
Mar 03 21:36:39 avahi-daemon[7343]: Successfully dropped remaining capabilities.
Mar 03 21:36:39 avahi-daemon[7343]: No service file found in /etc/avahi/services.
Mar 03 21:36:39 avahi-daemon[7343]: *** WARNING: Detected another IPv4 mDNS stack running on this host. This makes mDNS unreliable and is thus not recommended. ***
Mar 03 21:36:39 avahi-daemon[7343]: *** WARNING: Detected another IPv6 mDNS stack running on this host. This makes mDNS unreliable and is thus not recommended. ***
(snip)
Mar 03 21:37:45 systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring.
Mar 03 21:37:45 systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring.
Mar 03 21:37:46 systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring.
Mar 03 21:37:46 systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring.
Mar 03 21:37:49 systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring.
Mar 03 21:37:49 systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring.
(snip)

In case of bug report: Steps to reproduce the problem

start systemd-resolved.service and avahi-daemon.service

[krob7591]

Not on you guy's level, but I can hack a little. If you wanna stop the "systemd-resolved[2379]: Got mDNS UDP packet on unknown scope. Ignoring" annoying messages, edit avahi-daemon.conf...set "disallow-other-stacks= yes". Check the man page of avahi-daemon.conf to see what it does.