relocate as function

The check for systemd-resolved DNSStubListener, and disabling as necessary is a new function, called just prior to start_service pihole-FTL.
The check for ubuntu bionic 18.04 specifically is removed.
The check if resolved is enabled is made with check_service_active()
An additional check that the dnsstublistener is enabled is made.

Signed-off-by: Rob Gill <rrobgill@protonmail.com>

automated install/basic-install.sh

@@ -1265,6 +1265,25 @@ check_service_active() {
   fi
 }
 
+# Systemd-resolved's DNSStubListener and dnsmasq can't share port 53. 
+# Resolved needs to remain in place for installer to download needed files
+# so this change needs to be made after installation is complete, but before resarting dnsmasq/ftl
+disable_resolved_stublistener() {
+  # Check if Systemd-resolved's DNSSTub listener is enabled and active on port 53
+  if check_service_active "systemd-resolved"; then
+    # Check if DNSStubListener is enabled
+    if ( grep '#DNSStubListener=yes' /etc/systemd/resolved.conf &> /dev/null ); then
+      # Disable the DNSStubListener to unbind it from port 53
+      # Note that this breaks dns functionality on host until dnsmasq/ftl are up and running
+      echo -e "Disabling systemd-resolved DNSStubListener"
+      # Make a backup of the original /etc/systemd/resolved.conf
+      # (This will need to be restored on uninstallation)
+      sed -i.orig 's/#DNSStubListener=yes/DNSStubListener=no/g' /etc/systemd/resolved.conf
+      systemctl restart systemd-resolved
+    fi
+  fi
+}
+
 update_package_cache() {
   # Running apt-get update/upgrade with minimal output can cause some issues with
   # requiring user input (e.g password for phpmyadmin see #218)
@@ -2304,24 +2323,8 @@ main() {
     fi
   fi
 
-  # resolved and dnsmasq can't share port 53. 
-  # resolved needs to remain in place for installer to download needed files
-  # so this change needs to be made after installation is complete, but before resarting dnsmasq/ftl
-
-  # Check if running ubuntu 18.04 bionic beaver, which ships with resolved active on port 53
-  # (This check may need to be broadened for other systems running resolved?)
-  if ( lsb_release -a | grep 'Ubuntu 18.04' &> /dev/null ); then
-    # Running ubuntu 18.04, so check if resolved is running,
-    if (systemctl is-enabled systemd-resolved | grep -c 'enabled' || true); then
-      # if resolveconf is running unbind it from port 53
-      # Note that this breaks dns functionality on host until dnsmasq/ftl are up and running
-      echo -e "Disabling systemd-resolved DNSStubListener"
-      # Make a backup of the original /etc/systemd/resolveconf.d
-      # (This will need to be restored on uninstallation)
-      sed -i.orig 's/#DNSStubListener=yes/DNSStubListener=no/g' /etc/systemd/resolved.conf
-      systemctl restart systemd-resolved
-    fi
-  fi
+  # Check for and if necessary disable systemd-resolved-DNSStubListener
+  disable_resolved_stublistener
 
   # Enable FTL
   start_service pihole-FTL