adding dbus and avahi to enable shairport-sync to work correctly

Dockerfile

@@ -30,6 +30,7 @@ RUN set -ex \
 ENV \
 START_SNAPCLIENT=false \
 START_AIRPLAY=false \
+START_AVAHI=false \
 SNAPCLIENT_OPTS="" \
 SNAPSERVER_OPTS=""
 

README.md

@@ -54,6 +54,7 @@ services:
       #   => Don't use quotes for SNAPCLIENT_OPTS="" !
       # - HOST_AUDIO_GROUP=<AUDIO-GID> # set to GID of host audio group
       - START_AIRPLAY=false # set to 'true' to enable Airplay support via Shairport-sync
+      - START_AVAHI=false # set to 'true' to enable Avahi for Airplay 
     restart: "unless-stopped"
     ports:
       - 1704:1704

docker-compose.example.yml

@@ -14,6 +14,7 @@ services:
       #   => Don't use quotes for SNAPCLIENT_OPTS="" !
       # - HOST_AUDIO_GROUP=<AUDIO-GID> # set to GID of host audio group
       - START_AIRPLAY=false # set to 'true' to enable Airplay support via Shairport-sync
+      - START_AVAHI=false # set to 'true' to enable Avahi for Airplay 
     restart: "unless-stopped"
     ports:
       - 1704:1704   # port for the actual audio streaming

root/etc/s6-overlay/s6-rc.d/init-snapcast-config/run

@@ -30,3 +30,9 @@ if [ "$START_AIRPLAY" = 'true' ]; then
 else
   echo "Not starting DBUS. Set 'START_AIRPLAY=true' to start it and enable Airplay support."
 fi
+
+if [ "$START_AVAHI" = 'true' ]; then
+  echo "Starting Avahi for Airplay"
+else
+  echo "Not starting Avahi. Set 'START_AVAHI=true' to start it and enable Avahi support."
+fi

root/etc/s6-overlay/s6-rc.d/svc-avahi/finish

@@ -0,0 +1,2 @@
+#!/command/execlineb -S0
+/run/s6/basedir/bin/halt

root/etc/s6-overlay/s6-rc.d/svc-avahi/notification-fd

@@ -0,0 +1 @@
+3

root/etc/s6-overlay/s6-rc.d/svc-avahi/run

@@ -0,0 +1,6 @@
+#!/usr/bin/with-contenv bash
+
+if [ "$START_AVAHI" = 'true' ]; then
+  exec s6-notifyoncheck -d -n 300 -w 1000 -c "dbus-send --system / org.freedesktop.Avahi.Server.GetState" \
+    avahi-daemon --no-chroot
+fi

root/etc/s6-overlay/s6-rc.d/svc-avahi/type

@@ -0,0 +1 @@
+longrun