[Update] Prepare for native IPv6 NAT in Docker

update.sh

@@ -114,6 +114,65 @@ docker_garbage() {
   echo "If you want to cleanup further garbage collected by Docker, please make sure all containers are up and running before cleaning your system by executing \"docker system prune\""
 }
 
+in_array() {
+  local e match="$1"
+  shift
+  for e; do [[ "$e" == "$match" ]] && return 0; done
+  return 1
+}
+
+migrate_docker_nat() {
+  NAT_CONFIG='{"ipv6":true,"fixed-cidr-v6":"fd00:dead:beef:c0::/80","experimental":true,"ip6tables":true}'
+  # Min Docker version
+  DOCKERV_REQ=20.10.2
+  # Current Docker version
+  DOCKERV_CUR=$(docker version -f '{{.Server.Version}}')
+  if grep -qi "ipv6nat-mailcow" docker-compose.yml; then
+    echo -e "\e[32mNative IPv6 implementation available.\e[0m"
+    echo "This will enable experimental features in the Docker daemon and configure Docker to do the IPv6 NATing instead of ipv6nat-mailcow. This step is recommended."
+    echo "mailcow will try to roll back the changes if starting Docker fails after modifying the daemon.json configuration file."
+    read -r -p "Should we try to enable the native IPv6 implementation in Docker now (recommended)? [y/N] " dockernatresponse
+    if [[ ! "${dockernatresponse}" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
+      echo "OK, skipping this step."
+      return 0
+    fi
+  fi
+  # Sort versions and check if we are running a newer or equal version to req
+  if [ $(printf "${DOCKERV_REQ}\n${DOCKERV_CUR}" | sort -V | tail -n1) == "${DOCKERV_CUR}" ]; then
+    # If Dockerd daemon json exists
+    if [ -s /etc/docker/daemon.json ]; then
+      IFS=',' read -r -a dockerconfig <<< $(cat /etc/docker/daemon.json | tr -cd '[:alnum:],')
+      if ! in_array ipv6true "${dockerconfig[@]}" || \
+        ! in_array experimentaltrue "${dockerconfig[@]}" || \
+        ! in_array ip6tablestrue "${dockerconfig[@]}" || \
+        ! grep -qi "fixed-cidr-v6" /etc/docker/daemon.json; then
+          echo -e "\e[33mWarning:\e[0m You seem to have modified the /etc/docker/daemon.json configuration by yourself and not fully/correctly activated the native IPv6 NAT implementation."
+          echo "You will need to merge your existing configuration manually or fix/delete the existing daemon.json configuration before trying the update process again."
+          echo -e "Please merge the following content and restart the Docker daemon:\n"
+          echo ${NAT_CONFIG}
+          return 1
+      fi
+    else
+      echo "Working on IPv6 NAT, please wait..."
+      echo ${NAT_CONFIG} > /etc/docker/daemon.json
+      ip6tables -F -t nat
+      if ! systemctl restart docker.service; then
+        echo -e "\e[31mError:\e[0m Failed to activate IPv6 NAT! Reverting and exiting."
+        rm /etc/docker/daemon.json
+        systemctl reset-failed docker.service
+        systemctl restart docker.service
+        return 1
+      fi
+    fi
+    # Removing legacy container
+    sed -i '/ipv6nat-mailcow:$/,/^$/d' docker-compose.yml
+    echo -e "\e[32mGreat! \e[0mNative IPv6 NAT is active.\e[0m"
+  else
+    echo -e "\e[31mPlease upgrade Docker to version ${DOCKERV_REQ} or above.\e[0m"
+    return 0
+  fi
+}
+
 while (($#)); do
   case "${1}" in
     --check|-c)
@@ -182,6 +241,7 @@ if [ ${#DOTS} -lt 2 ]; then
 fi
 
 if grep --help 2>&1 | head -n 1 | grep -q -i "busybox"; then echo "BusyBox grep detected, please install gnu grep, \"apk add --no-cache --upgrade grep\""; exit 1; fi
+# This will also cover sort
 if cp --help 2>&1 | head -n 1 | grep -q -i "busybox"; then echo "BusyBox cp detected, please install coreutils, \"apk add --no-cache --upgrade coreutils\""; exit 1; fi
 if sed --help 2>&1 | head -n 1 | grep -q -i "busybox"; then echo "BusyBox sed detected, please install gnu sed, \"apk add --no-cache --upgrade sed\""; exit 1; fi
 
@@ -478,7 +538,7 @@ fi
 
 if [ ! $FORCE ]; then
   read -r -p "Are you sure you want to update mailcow: dockerized? All containers will be stopped. [y/N] " response
-  if [[ ! "$response" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
+  if [[ ! "${response}" =~ ^([yY][eE][sS]|[yY])+$ ]]; then
     echo "OK, exiting."
     exit 0
   fi