Bug 2368463

When I invoke the `QPrintDialog` with `avahi-daemon.service` enabled, the time elapsed until the modal print window appears is ⪆ 8s. When disabled, invocation is instantaneous.

Reproducibility:

:	Always.

Steps to Reproduce:

:	1.	`sudo systemctl start avahi-daemon.service`:

		> ~~~YAML
		> ● avahi-daemon.service - Avahi mDNS/DNS-SD Stack
		>     Loaded: loaded (/usr/lib/systemd/system/avahi-daemon.service; disabled; preset: enabled)
		>    Drop-In: /usr/lib/systemd/system/service.d
		>             └─10-timeout-abort.conf
		>     Active: active (running) since Fri 2025-05-23 20:31:06 BST; 18min ago
		> Invocation: 9c282b6215cc4106bf249678c1b8488b
		> TriggeredBy: ● avahi-daemon.socket
		>   Main PID: 147627 (avahi-daemon)
		>     Status: "avahi-daemon 0.8 starting up."
		>      Tasks: 2 (limit: 37207)
		>     Memory: 888K (peak: 1.1M)
		>        CPU: 68ms
		>     CGroup: /system.slice/avahi-daemon.service
		>             ├─147627 "avahi-daemon: running [Beedell.local]"
		>             └─147629 "avahi-daemon: chroot helper"
		> 
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Joining mDNS multicast group on interface lo.IPv6 with address ::1.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: New relevant interface lo.IPv6 for mDNS.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Joining mDNS multicast group on interface lo.IPv4 with address 127.0.0.1.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: New relevant interface lo.IPv4 for mDNS.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Network interface enumeration completed.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Registering new address record for fdce:b268:c9db:0:3ff3:b235:c981:2418 on enp74s0.*.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Registering new address record for 192.168.1.178 on enp74s0.IPv4.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Registering new address record for ::1 on lo.*.
		> May 23 20:31:06 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Registering new address record for 127.0.0.1 on lo.IPv4.
		> May 23 20:31:07 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Server startup complete. Host name is Beedell.local. Local service cookie is 1282367389.
		> ~~~

	2.	Invoke the undermentioned script:

		~~~py
		import sys
		from PySide6.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton
		from PySide6.QtPrintSupport import QPrinter, QPrintDialog

		class PrintDialogApp(QWidget):
		   def __init__(self):
		       super().__init__()
		       self.setWindowTitle("Print Dialog (PySide6)")

		       layout = QVBoxLayout()
		       self.print_button = QPushButton("Open Print Dialog")
		       self.print_button.clicked.connect(self.open_print_dialog)
		       layout.addWidget(self.print_button)

		       self.setLayout(layout)

		   def open_print_dialog(self):
		       printer = QPrinter()
		       dialog = QPrintDialog(printer, self)
		       if dialog.exec():
		           print("Print dialog accepted")
		       else:
		           print("Print dialog canceled")

		if __name__ == "__main__":
		   app = QApplication(sys.argv)
		   window = PrintDialogApp()
		   window.show()
		   sys.exit(app.exec())
		~~~

	3.	Click the button.

	4.	`sudo systemctl stop avahi-daemon.service`:

		> ~~~YAML
		> ○ avahi-daemon.service - Avahi mDNS/DNS-SD Stack
		>     Loaded: loaded (/usr/lib/systemd/system/avahi-daemon.service; disabled; preset: enabled)
		>    Drop-In: /usr/lib/systemd/system/service.d
		>             └─10-timeout-abort.conf
		>     Active: inactive (dead) since Fri 2025-05-23 21:03:38 BST; 3s ago
		>   Duration: 32min 31.926s
		> Invocation: 9c282b6215cc4106bf249678c1b8488b
		> TriggeredBy: ● avahi-daemon.socket
		>    Process: 147627 ExecStart=/usr/bin/avahi-daemon -s (code=exited, status=0/SUCCESS)
		>   Main PID: 147627 (code=exited, status=0/SUCCESS)
		>     Status: "avahi-daemon 0.8 starting up."
		>   Mem peak: 1.3M
		>        CPU: 136ms
		> 
		> May 23 20:31:07 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Server startup complete. Host name is Beedell.local. Local service cookie is 1282367389.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Got SIGTERM, quitting.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Leaving mDNS multicast group on interface enp74s0.IPv6 with address fdce:b268:c9db:0:3ff3:b235:c981:2418.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY systemd[1]: Stopping avahi-daemon.service - Avahi mDNS/DNS-SD Stack...
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Leaving mDNS multicast group on interface enp74s0.IPv4 with address 192.168.1.178.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Leaving mDNS multicast group on interface lo.IPv6 with address ::1.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: Leaving mDNS multicast group on interface lo.IPv4 with address 127.0.0.1.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY avahi-daemon[147627]: avahi-daemon 0.8 exiting.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY systemd[1]: avahi-daemon.service: Deactivated successfully.
		> May 23 21:03:38 Beedell.RokeJulianLockhart.desktop.SSV2AY systemd[1]: Stopped avahi-daemon.service - Avahi mDNS/DNS-SD Stack.
		> ~~~

	5.	Invoke the script.

	6.	Click the button. This is instantaneous.

Actual Results:

:	With the service enabled, loading Qt print modals takes ⪆ 9s. Without it enabled, doing so is instantaneous.

Expected Results:

:	It should be instantaneous.

Additional Information:

:	Already reported upstream at https://github.com/avahi/avahi/issues/701#issue-3087466051, but I've yet to hear a response. This replaces https://bugzilla.redhat.com/show_bug.cgi?id=2367102.