disable coredns in client mode or if 53 is in use

Dockerfile

@@ -26,6 +26,7 @@ RUN \
 	jq \
 	libc6 \
 	libelf-dev \
+	net-tools \
 	openresolv \
 	perl \
 	pkg-config \

Dockerfile.aarch64

@@ -26,6 +26,7 @@ RUN \
 	jq \
 	libc6 \
 	libelf-dev \
+	net-tools \
 	openresolv \
 	perl \
 	pkg-config \

Dockerfile.armhf

@@ -26,6 +26,7 @@ RUN \
 	jq \
 	libc6 \
 	libelf-dev \
+	net-tools \
 	openresolv \
 	perl \
 	pkg-config \

README.md

@@ -291,7 +291,7 @@ Once registered you can define the dockerfile to use with `-f Dockerfile.aarch64
 
 ## Versions
 
-* **06.10.20:** - Disable CoreDNS when Host networking is detected.
+* **06.10.20:** - Disable CoreDNS in client mode, or if port 53 is already in use in server mode.
 * **04.10.20:** - Allow to specify a list of names as PEERS and add ALLOWEDIPS environment variable. Also, add peer name/id to each one of the peer sections in wg0.conf. Important: Existing users need to delete `/config/templates/peer.conf` and restart
 * **27.09.20:** - Cleaning service binding example to have accurate PreDown script.
 * **06.08.20:** - Replace resolvconf with openresolv due to dns issues when a client based on this image is connected to a server also based on this image. Add IPv6 info to readme. Display kernel version in logs.

readme-vars.yml

@@ -103,7 +103,7 @@ app_setup_block: |
   
 # changelog
 changelogs:
-  - { date: "06.10.20:", desc: "Disable CoreDNS when Host networking is detected." }
+  - { date: "06.10.20:", desc: "Disable CoreDNS in client mode, or if port 53 is already in use in server mode." }
   - { date: "04.10.20:", desc: "Allow to specify a list of names as PEERS and add ALLOWEDIPS environment variable. Also, add peer name/id to each one of the peer sections in wg0.conf. Important: Existing users need to delete `/config/templates/peer.conf` and restart" }
   - { date: "27.09.20:", desc: "Cleaning service binding example to have accurate PreDown script." }
   - { date: "06.08.20:", desc: "Replace resolvconf with openresolv due to dns issues when a client based on this image is connected to a server also based on this image. Add IPv6 info to readme. Display kernel version in logs." }

root/etc/cont-init.d/30-config

@@ -266,22 +266,19 @@ if [ -n "$PEERS" ]; then
     fi
   fi
 else
-  echo "**** Client mode selected."
+  echo "**** Client mode selected. ****"
   if [ ! -f /config/wg0.conf ]; then
     echo "**** No client conf found. Provide your own client conf as \"/config/wg0.conf\" and restart the container. ****"
     sleep infinity
   fi
-fi
-
-# set up or disable CoreDNS
-if ip addr show dev docker0 > /dev/null 2>&1; then
-  echo "Host networking detected, disabling CoreDNS"
+  echo "**** Disabling CoreDNS ****"
   rm -rf /etc/services.d/coredns
-else
-  [[ ! -f /config/coredns/Corefile ]] && \
-    cp /defaults/Corefile /config/coredns/Corefile
 fi
 
+# set up CoreDNS
+[[ ! -f /config/coredns/Corefile ]] && \
+  cp /defaults/Corefile /config/coredns/Corefile
+
 # permissions
 chown -R abc:abc \
 	/config

root/etc/services.d/coredns/run

@@ -2,5 +2,10 @@
 
 cd /config/coredns
 
-exec \
-    /app/coredns -dns.port=53
+if netstat -apn | grep -q ":53 "; then
+  echo "Another service is using port 53, disabling CoreDNS"
+  sleep infinity
+else
+  exec \
+    /app/coredns -dns.port=53
+fi