[Bug 1616196] Re: unable to stop avahi-daemon (dbus always restarts it)

[Simon Déziel]

Hi Trent,

On 2016-08-23 05:17 PM, Trent Lloyd wrote:
> The d-bus activation thing is a quirk of systemd, it actually tells you
> when you run stop.  You need to use disable (as well as stop) to both
> stop it and prevent re-activation.

Disabling and stopping the socket and the service works for the manual
case, thanks.

> root at ubuntu:~# systemctl stop avahi-daemon
> Warning: Stopping avahi-daemon.service, but it can still be activated by:
>   avahi-daemon.socket
> 
> You're right about the ifupdown script, though.

Unfortunately for me because I'm trying to remotely disable avahi-daemon
for clients connecting to a corporate VPN where "domain.local" is used
as the DNS zone.

I haven't found any valid workaround for the ifupdown script so I now
have to instruct every clients to do the disable/stop steps themselves.
This in turn has some undesired ramifications as avahi remains inactive
even when they are off of the VPN.

> The good news on the one hand is that upstream hopefully soon nss-mdns
will be improved to no longer need this trick.

I just noticed that you are an avahi developer so maybe it's my lucky
day :)

I don't know why but avahi doesn't seem to limit itself to resolving
single DNS label under ".local"? Currently, it will blackhole queries
for "server.domain.local". This makes it close to impossible to use a
DNS zone under ".local". While I know that using ".local" isn't ideal,
it was the recommended way in the past [1] and it's how many networks
are setup.

The RFC [2] mentions that ".local" is for single labels and OS X also
implementation this rule [3]. Do you think it would be possible for
avahi to also implement this behavior?

Best regards,
Simon


1: https://en.wikipedia.org/wiki/.local#Microsoft_recommendations
2: https://tools.ietf.org/html/rfc6762#section-3
3: https://support.apple.com/en-us/HT201275

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https://bugs.launchpad.net/bugs/1616196

Title:
  unable to stop avahi-daemon (dbus always restarts it)

Status in avahi package in Ubuntu:
  New

Bug description:
  When avahi-daemon is stopped, dbus always revives it.

  Steps to reproduce:

  1. sudo systemctl stop avahi-daemon.socket
  2. sudo systemctl stop avahi-daemon.service
  3. ps aux| grep avahi # should return nothing

  Currently, dbus revives it right away as shown in syslog:

  Aug 23 15:17:22 simon-vm avahi-daemon[4036]: Got SIGTERM, quitting.
  Aug 23 15:17:22 simon-vm avahi-daemon[4036]: Leaving mDNS multicast group on interface ens3.IPv6 with address 2001:470:b1c3:7946::a4.
  Aug 23 15:17:22 simon-vm avahi-daemon[4036]: Leaving mDNS multicast group on interface ens3.IPv4 with address 172.24.26.52.
  Aug 23 15:17:22 simon-vm avahi-daemon[4036]: avahi-daemon 0.6.32-rc exiting.
  Aug 23 15:17:22 simon-vm dbus[1647]: [system] Activating via systemd: service name='org.freedesktop.Avahi' unit='dbus-org.freedesktop.Avahi.service'
  Aug 23 15:17:22 simon-vm systemd[1]: Stopping Avahi mDNS/DNS-SD Stack...
  Aug 23 15:17:22 simon-vm systemd[1]: Stopped Avahi mDNS/DNS-SD Stack.
  Aug 23 15:17:22 simon-vm systemd[1]: Listening on Avahi mDNS/DNS-SD Stack Activation Socket.
  Aug 23 15:17:22 simon-vm systemd[1]: Starting Avahi mDNS/DNS-SD Stack...

  
  This automatic revival defeats the purpose of the up script [*] to deactivate avahi when .local is a regular DNS zone (not mDNS). This also goes against the principle of least surprise.

  *: /etc/network/if-{down,up}.d/avahi-daemon

  Additional information:

  # lsb_release -rd
  Description:	Ubuntu 16.04.1 LTS
  Release:	16.04

  # apt-cache policy avahi-daemon dbus systemd
  avahi-daemon:
    Installed: 0.6.32~rc+dfsg-1ubuntu2
    Candidate: 0.6.32~rc+dfsg-1ubuntu2
    Version table:
   *** 0.6.32~rc+dfsg-1ubuntu2 500
          500 http://ca.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
          100 /var/lib/dpkg/status
  dbus:
    Installed: 1.10.6-1ubuntu3
    Candidate: 1.10.6-1ubuntu3
    Version table:
   *** 1.10.6-1ubuntu3 500
          500 http://ca.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
          100 /var/lib/dpkg/status
  systemd:
    Installed: 229-4ubuntu7
    Candidate: 229-4ubuntu7
    Version table:
   *** 229-4ubuntu7 500
          500 http://ca.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       229-4ubuntu4 500
          500 http://ca.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: avahi-daemon 0.6.32~rc+dfsg-1ubuntu2 [modified: usr/lib/avahi/avahi-daemon-check-dns.sh]
  ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
  Uname: Linux 4.4.0-36-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.1
  Architecture: amd64
  Date: Tue Aug 23 15:09:40 2016
  InstallationDate: Installed on 2016-08-22 (0 days ago)
  InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Beta amd64 (20160819)
  ProcEnviron:
   LANGUAGE=en_CA:en
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_CA.UTF-8
   SHELL=/bin/bash
  SourcePackage: avahi
  UpgradeStatus: No upgrade log present (probably fresh install)

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