When restarting avahi-daemon while CUPS is running, CUPS looses connection

[michaelrsweet]

Version: 1.7.1
CUPS.org User: till.kamppeter

This is a follow-up to STR #4300

Original issue:

I use CUPS with shared printers and the shared printers are broadcasted by Avahi. This works well when avahi-daemon is started before cups and both keep running. But if I restart avahi-daemon while CUPS is running, CUPS looses connection to avahi-daemon and so stops broadcasting. What I expect is that CUPS reconnects after the restart of avahi-daemon. This can easily happen if for example the avahi-daemon package gets updated or the admin changes the configuration of avahi-daemon.

Suggestion for a solution:

While making cups-browsed runnable on-demand on mobile devices I have found a way to allow avahi-daemon to restart and reconnect. See the section

How to Write a Client That Can Deal with Daemon Restarts

on

http:https://avahi.sourcearchive.com/documentation/0.6.17/main.html

It is simply passing AVAHI_CLIENT_NO_FAIL to avahi_client_new(). With this I can run cups-browsed independent of avahi-daemon (not even important in which order avahi-daemon and cups-browsed are started), and whenever avahi-daemon is running, remote CUPS printers are detected and the appropriate local raw queues created and whenever avahi-daemon disappears, the local queues are taken down. The (re)connection with avahi-daemon (registering services in case of cupsd has to be done in the client callback function and so it happens automatically when avahi-daemon appears.

Perhaps one can use this also for cupsd.

[michaelrsweet]

CUPS.org User: mike

Fixed in Subversion repository.

[michaelrsweet]

"str4370.patch":

Index: scheduler/dirsvc.c

--- scheduler/dirsvc.c (revision 11597)
+++ scheduler/dirsvc.c (working copy)
@@ -193,8 +193,7 @@
{
int error; /* Error code, if any */

•  DNSSDClient = avahi_client_new(avahi_threaded_poll_get(DNSSDMaster), 0,
  

•                                 NULL, NULL, &error);
  

•  DNSSDClient = avahi_client_new(avahi_threaded_poll_get(DNSSDMaster), AVAHI_CLIENT_NO_FAIL, NULL, NULL, &error);
  

  if (DNSSDClient == NULL)
  {