feat: ✨ add tzdata to Dockerfile for timezone config

You can now set your timezone with the environment variable
`TZ="Europe/Berlin"`

.gitchangelog.rc

@@ -82,24 +82,34 @@ ignore_regexps = [
 ## whenever you are tweaking this variable.
 ##
 section_regexps = [
-    ('New', [
-        r'^:sparkles\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+    ('Features', [
+        r'^[fF]eat\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
      ]),
-    ('Changes', [
-        r'^:wrench\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+    ('Added', [
+        r'^[aA]dd\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+     ]),
+    ('Changed', [
+        r'^[cC]hange\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+     ]),
+    ('Deprecated', [
+        r'^[dD]epricated\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+     ]),
+    ('Removed', [
+        r'^[rR]emove\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
      ]),
     ('Fix', [
-        r'^:bug\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+        r'^[fF]ix\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+     ]),
+    ('Security', [
+        r'^[sS]ec\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
      ]),
     ('Documentation', [
-        r'^:memo\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
-     ]),     
-    ('Remove', [
-        r'^:fire\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
+        r'^[dD]oc\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n]*)$',
      ]),
 
-    ('Other', None ## Match all lines
-     ),
+
+    #('Other', None ## Match all lines
+    # ),
 
 ]
 
@@ -148,7 +158,7 @@ body_process = ReSub(r'((^|\n)[A-Z]\w+(-\w+)*: .*(\n\s+.*)*)+$', r'') | strip
 ##
 ## Available constructs are those listed in ``body_process`` doc.
 subject_process = (strip |
-    ReSub(r'^([cC]hg|[fF]ix|[nN]ew)\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n@]*)(@[a-z]+\s+)*$', r'\4') |
+    ReSub(r'^([cC]hg|[fF]ix|[nN]ew|[dD]oc|[fF]eat|[aA]dd|[cC]hange)\s*:\s*((dev|use?r|pkg|test|doc)\s*:\s*)?([^\n@]*)(@[a-z]+\s+)*$', r'\4') |
     SetIfEmpty("No commit message.") | ucfirst | final_dot)
 
 

.github/workflows/shellcheck.yml

@@ -0,0 +1,16 @@
+name: Run shellcheck with reviewdog
+on: [pull_request]
+jobs:
+  shellcheck:
+    name: runner / shellcheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: shellcheck
+        uses: reviewdog/action-shellcheck@v1.9.0
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          reporter: github-pr-review
+          path: "."
+          pattern: "*.sh"
+          exclude: "./.git/*"

.pre-commit-config.yaml

@@ -15,11 +15,3 @@ repos:
     - id: mdformat
       additional_dependencies:
       - mdformat-gfm # GitHub Flavored Markdown support
-  - repo: https://codeberg.org/frnmst/md-toc
-    rev: 8.0.1  # or a specific git tag from md-toc
-    hooks:
-    - id: md-toc
-      args:
-        - "--in-place"
-        - "github"
-        - "--header-levels 6"

CHANGELOG.md

@@ -1,97 +1,114 @@
 # Changelog
 
 
-## (unreleased)
+## 0.3.0 (2022-05-26)
+
+### Features
+
+* ✨ validate ip address respons from ip check web service. [Eduard Veit]
+
+* ✨ check internet connection for selected ip versions. [Eduard Veit]
+
+* 🎨 colorful info, debug and error messages. [Eduard Veit]
+
+### Fix
+
+* Abort on all dig errors. [Eduard Veit]
 
 ### Documentation
 
-* :memo: update README.md. [Eduard Veit]
+* 📝 add labels to Dockerfile. [Eduard Veit]
 
-### Other
 
-* :recycle: normalizing pre-commit configuration to a top-level map. [Eduard Veit]
+## 0.2.0 (2021-09-24)
 
-* :recycle: refactorings. [Eduard Veit]
+### Features
 
-* Feature: :sparkles: add pre-commit git hook for shellcheck. [Eduard Veit]
+* ✨ enable parameter extensions for `docker run --interactive` [Eduard Veit]
 
-* Refactor: :recycle: remove unused help message. [Eduard Veit]
+### Changed
+
+* Handle dns server selection. [Eduard Veit]
+
+### Documentation
+
+* 📝 update CHANGELOG.md. [Eduard Veit]
+
+* 📝 document docker parameters. [Eduard Veit]
+
+* 📝 change default dns server setting. [Eduard Veit]
+
+* 📝 update CHANGELOG. [Eduard Veit]
+
+* 📝 update README.md. [Eduard Veit]
 
 
 ## 0.1.2 (2021-04-23)
 
 ### Documentation
 
-* :memo: document environment variables. [Eduard Veit]
-
-### Other
-
-* :recycle: refactor: method extractions and other beautifications. [Eduard Veit]
+* 📝 document environment variables. [Eduard Veit]
 
 
 ## 0.1.1 (2021-04-23)
 
 ### Fix
 
-* :bug: fix loop and error handling in case of connection issues. [Eduard Veit]
+* 🐛 fix loop and error handling in case of connection issues. [Eduard Veit]
 
 
 ## 0.1.0 (2021-04-22)
 
-### New
+### Features
 
-* :sparkles: add Dockerfile. [Eduard Veit]
+* ✨ add Dockerfile. [Eduard Veit]
 
-* :sparkles: add loop mode. [Eduard Veit]
+* ✨ add loop mode. [Eduard Veit]
 
-* :sparkles: add support for Duck DNS as DynDNS2 provider. [Eduard Veit]
+* ✨ add support for Duck DNS as DynDNS2 provider. [Eduard Veit]
 
-* :sparkles: add support for deSEC as DynDNS2 provider. [Eduard Veit]
+* ✨ add support for deSEC as DynDNS2 provider. [Eduard Veit]
 
-* :sparkles: add completion. [Eduard Veit]
+* ✨ add completion. [Eduard Veit]
 
-  :sparkles: add man page
+  ✨ add man page
 
-* :sparkles: replace getopt with argbash. [Eduard Veit]
+* 🔃 replace getopt with argbash. [Eduard Veit]
 
-* :sparkles: add interpretaton of status codes and act accordingly. [Eduard Veit]
+* ✨ add interpretaton of status codes and act accordingly. [Eduard Veit]
 
-* :sparkles: make network interface configurable. [Eduard Veit]
+* ✨ make network interface configurable. [Eduard Veit]
 
-* :sparkles: add DynDNS2 support for dynv6.com. [Eduard Veit]
+* ✨ add DynDNS2 support for dynv6.com. [Eduard Veit]
 
-* :sparkles: add .gitchangelog.rc. [Eduard Veit]
+### Added
 
-* :sparkles: add dynb.sh. [Eduard Veit]
+* 📝 README.md. [Eduard Veit]
+
+* ✨ dynb.sh. [Eduard Veit]
+
+### Changed
+
+* 🔃 rename environment variables. [Eduard Veit]
 
 ### Fix
 
-* :bug: fix sourcing of config file. [Eduard Veit]
+* 🐛 fix error handling. [Eduard Veit]
 
-  :recycle: do some shellcheck fixes
+* 🐛 fix sourcing of config file. [Eduard Veit]
+
+  ♻️ do some shellcheck fixes
 
 ### Documentation
 
-* :memo: document example of an docker-compose.yml file. [Eduard Veit]
+* 📝 document example of an docker-compose.yml file. [Eduard Veit]
 
-* :memo: document loop mode and dig as requirement. [Eduard Veit]
+* 📝 document `loop mode` and mention `dig` as requirement. [Eduard Veit]
 
-* :memo: update example of .env in README.md. [Eduard Veit]
+* 📝 update example of .env in README.md. [Eduard Veit]
 
-* :memo: add CHANGELOG.md. [Eduard Veit]
+* 📝 CHANGELOG.md. [Eduard Veit]
 
-* :memo: add example.env. [Eduard Veit]
-
-* :memo: write README.md. [Eduard Veit]
-
-### Other
-
-* :recycle: refactor: rename environment variables. [Eduard Veit]
-
-* :recycle: refactor, fix and debug error handling. [Eduard Veit]
-
-* :recycle: refactor main code. [Eduard Veit]
-
-* Initial commit. [EV21]
+* 📝 add example.env. [Eduard Veit]
 
 

Dockerfile

@@ -1,5 +1,21 @@
 FROM alpine:latest
-RUN apk update && apk add bash curl jq bind-tools
+
+RUN \
+apk update \
+&& \
+apk add \
+bash \
+curl \
+jq \
+bind-tools \
+tzdata
+
 WORKDIR /usr/src/app
+
 COPY . .
-CMD /bin/bash /usr/src/app/dynb.sh
+
+ENTRYPOINT ["/bin/bash", "/usr/src/app/dynb.sh"]
+
+LABEL org.opencontainers.image.source="https://github.com/EV21/dynb"
+LABEL org.opencontainers.image.description="DynB - dynamic DNS update client."
+LABEL org.opencontainers.image.licenses="MIT"

README.md

@@ -14,7 +14,10 @@ IPv4 (A) and IPv6 (AAAA) record updates are supported.
 - [⚙ Configuration](#-configuration)
 - [🏃 Run](#-run)
 - [⏰ Cron](#-cron)
+  - [loop mode](#loop-mode)
+  - [crontab](#crontab)
 - [🐟 docker](#-docker)
+- [environment variables](#environment-variables)
 
 <!-- /TOC -->
 
@@ -132,11 +135,17 @@ then enter :point_down: to run dynb every five minutes.
 */5 * * * * $HOME/.local/bin/dynb >> $HOME/.local/share/dynb/dynb-cron.log
 ```
 
+alternative with docker and parameters::
+
+```bash
+*/5 * * * * docker run --interactive --tty --rm --network host ev21/dynb:latest --ip-mode 64 --update-method domrobot --domain dyndns.example.com --username user42 --password SuperSecretPassword
+```
+
 Note, cron typically does not use the users PATH variable.
 
 ## 🐟 docker
 
-This is an example of a `docker-compose.yml` file. If you are using IPv6 make sure the routing works properly with your docker container.
+This is an example of a `docker-compose.yml` file. If you are using IPv6 make sure the routing works properly with your docker container. Note: [IPv6 networking](https://docs.docker.com/config/daemon/ipv6/) is only supported on Docker daemons running on Linux hosts.
 
 ```yaml
 version: '3.4'
@@ -146,17 +155,15 @@ services:
     image: ev21/dynb
     container_name: dynb
     network_mode: host
-    build:
-      context: .
-      dockerfile: ./Dockerfile
     environment:
       - DYNB_DYN_DOMAIN=dyndns.example.com
-      - DYNB_SERVICE_PROVIDER=inwx
+      - DYNB_SERVICE_PROVIDER=desec
       - DYNB_UPDATE_METHOD=dyndns
       - DYNB_IP_MODE=64
       - DYNB_USERNAME=User42
       - DYNB_PASSWORD=SuperSecretPassword
       - DYNB_INTERVAL=60
+      - TZ=Europe/Berlin
 ```
 
 ## environment variables

dynb.sh

@@ -51,6 +51,7 @@ _network_interface=
 ######################################################
 ## You don't need to change the following variables ##
 _INWX_JSON_API_URL=https://api.domrobot.com/jsonrpc/
+_internet_connectivity_test_server=https://www.google.de
 _new_IPv4=
 _new_IPv6=
 _dns_records=
@@ -65,7 +66,7 @@ _response=
 _statusHostname=
 _statusUsername=
 _statusPassword=
-_version=0.1.2
+_version=0.3.2
 _userAgent="DynB/$_version github.com/EV21/dynb"
 _configFile=$HOME/.local/share/dynb/.env
 _statusFile=/tmp/dynb.status
@@ -73,41 +74,77 @@ _debug=0
 _minimum_looptime=60
 _loopMode=0
 
-function loopMode() {
-  if [[ $_loopMode -eq 1 ]]; then
-    return 0
-  else
-    return 1
+# Ansi color code variables
+yellow_color="\e[0;33m"
+green_color="\e[0;92m"
+expand_bg="\e[K"
+red_color_bg="\e[0;101m${expand_bg}"
+bold="\e[1m"
+reset_color_modification="\e[0m"
+
+REGEX_IPv4="^(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$"
+REGEX_IPv6="^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$"
+
+function is_IPv4_address
+{
+  local ip=$1
+  if [[ $ip =~ $REGEX_IPv4 ]]
+  then return 0
+  else return 1
   fi
 }
 
-function debugMode() {
-  if [[ $_debug -eq 1 ]]; then
-    return 0
-  else
-    return 1
+function is_IPv6_address
+{
+  local ip=$1
+  if [[ $ip =~ $REGEX_IPv6 ]]
+  then return 0
+  else return 1
   fi
 }
 
-function infoMessage() {
-  echo "$(logtime) INFO: $*"
-}
-
-function debugMessage() {
-  if debugMode; then
-    echo "$(logtime) DEBUG: $*"
+function loopMode
+{
+  if [[ $_loopMode -eq 1 ]]
+  then return 0
+  else return 1
   fi
 }
 
-function errorMessage() { printf "$(logtime) ERROR: %s\n" "$*" >&2; }
+function debugMode
+{
+  if [[ $_debug -eq 1 ]]
+  then return 0
+  else return 1
+  fi
+}
 
-function logtime() {
+function infoMessage
+{
+  echo -e "${green_color}$(logtime) INFO: $*${reset_color_modification}"
+}
+
+function debugMessage
+{
+  if debugMode
+  then echo -e "${yellow_color}$(logtime) DEBUG: ${*}${reset_color_modification}"
+  fi
+}
+
+function errorMessage
+{
+  echo -e "${red_color_bg}${bold}$(logtime) ERROR: $*${reset_color_modification}" >&2
+}
+
+function logtime
+{
   LOGTIME=$(date "+%Y-%m-%d %H:%M:%S")
   echo "[$LOGTIME]"
 }
 
 # The main domain as an identifier for the dns zone is required for the updateRecord call
-function getMainDomain() {
+function getMainDomain
+{
   request=$(
     echo "{}" |
       jq '(.method="nameserver.list")' |
@@ -126,7 +163,8 @@ function getMainDomain() {
   _main_domain=$(echo "$_response" | jq --raw-output '.domain')
 }
 
-function fetchDNSRecords() {
+function fetchDNSRecords
+{
   request=$(
     echo "{}" |
       jq '(.method="'nameserver.info'")' |
@@ -150,47 +188,54 @@ function fetchDNSRecords() {
 
 # requires parameter A or AAAA
 # result to stdout
-function getRecordID() {
-  echo "$_dns_records" | jq "select(.type == \"${1}\") | .id"
+function getRecordID
+{
+  echo "$_dns_records" |
+    jq "select(.type == \"${1}\") | .id"
 }
 
 # requires parameter A or AAAA
 # result to stdout
 function getDNSIP() {
-  echo "$_dns_records" | jq --raw-output "select(.type == \"${1}\") | .content"
+  echo "$_dns_records" |
+    jq --raw-output "select(.type == \"${1}\") | .content"
 }
 
 # requires parameter
 # 1. param: 4 or 6 for ip version
 # 2. param: IP check server address
 # result to stdout
-function getRemoteIP() {
-  if [[ -n $_DNS_checkServer ]]; then
+function getRemoteIP
+{
+  local ip_version=$1
+  local ip_check_server=$2
   curl --silent "$_interface_str" --user-agent "$_userAgent" \
-      --ipv"${1}" --dns-servers "$_DNS_checkServer" --location "${2}"
-  else
-    curl --silent "$_interface_str" --user-agent "$_userAgent" \
-      --ipv"${1}" --location "${2}"
-  fi
+    --ipv"${ip_version}" --location "${ip_check_server}"
+  local curls_status_code=$?
   # shellcheck disable=2181
-  if [[ $? -gt 0 ]]; then
-    errorMessage "IPCheck (getRemoteIP ${1}) request failed"
+  if [[ $curls_status_code -gt 0 ]]; then
+    errorMessage "IPCheck (getRemoteIP $ip_version) request failed"
     exit 1
   fi
 }
 
 # requires parameter
 # 1. param: 4 or 6 as ip version
-function updateRecord() {
-  if [[ ${1} == 4 ]]; then
+function updateRecord
+{
+  local ip_version=$1
+  if [[ ${ip_version} == 4 ]]
+  then
     ID=$(getRecordID A)
     IP=$_new_IPv4
   fi
-  if [[ ${1} == 6 ]]; then
+  if [[ ${ip_version} == 6 ]]
+  then
     ID=$(getRecordID AAAA)
     IP=$_new_IPv6
   fi
-  if [[ $IP != "" ]]; then
+  if [[ $IP != "" ]]
+  then
     request=$(
       echo "{}" |
         jq '(.method="nameserver.updateRecord")' |
@@ -209,12 +254,13 @@ function updateRecord() {
         --request POST $_INWX_JSON_API_URL \
         --data "$request"
     )
-    echo -e "$(echo "$_response" | jq --raw-output '.msg')\n Domain: $DYNB_DYN_DOMAIN\n new IPv${1}: $IP"
+    infoMessage "$(echo "$_response" | jq --raw-output '.msg')\n Domain: $DYNB_DYN_DOMAIN\n New IPv${1}: $IP"
   fi
 }
 
 # using DynDNS2 protocol
-function dynupdate() {
+function dynupdate
+{
   # default parameter values
   myip_str=myip
   myipv6_str=myipv6
@@ -350,12 +396,14 @@ function dynupdate() {
   esac
 }
 
-function setStatus() {
+function setStatus
+{
   echo "_status=$1; _eventTime=$2; _errorCounter=$3; _statusHostname=$4; _statusUsername=$5; _statusPassword=$6" >/tmp/dynb.status
 }
 
 # handle errors from past update requests
-function checkStatus() {
+function checkStatus
+{
   case $_status in
     nochg*)
       if [[ _errorCounter -gt 1 ]]; then
@@ -368,8 +416,7 @@ function checkStatus() {
       if [[ "$_statusHostname" == "$DYNB_DYN_DOMAIN" && ("$_statusUsername" == "$DYNB_USERNAME" || $_statusUsername == "$DYNB_TOKEN") ]]; then
         errorMessage "Hostname supplied does not exist under specified account, enter new login credentials before performing an additional request."
         return 1
-      else
-        rm "$_statusFile"
+      else rm "$_statusFile"
       fi
       return 0
       ;;
@@ -377,8 +424,7 @@ function checkStatus() {
       if [[ "$_statusUsername" == "$DYNB_USERNAME" && "$_statusPassword" == "$DYNB_PASSWORD" ]]; then
         errorMessage "Invalid username password combination."
         return 1
-      else
-        rm "$_statusFile"
+      else rm "$_statusFile"
       fi
       return 0
       ;;
@@ -402,20 +448,20 @@ function checkStatus() {
       ;;
     911 | 5*)
       delta=$(($(date +%s) - _eventTime))
-      if [[ $delta -lt 1800 ]]; then
+      if [[ $delta -lt 1800 ]]
+      then
         errorMessage "$_status: The provider currently has an fatal error. DynB will wait for next update until 30 minutes have passed since last request, $(date --date=@$delta -u +%M) minutes already passed."
         return 1
-      else
-        rm "$_statusFile"
+      else rm "$_statusFile"
       fi
       return 0
       ;;
     *)
-      if [[ _errorCounter -gt 1 ]]; then
+      if [[ _errorCounter -gt 1 ]]
+      then
         errorMessage "An unknown response code has repeatedly been received. $_response"
         return 1
-      else
-        return 0
+      else return 0
       fi
       ;;
   esac
@@ -423,178 +469,192 @@ function checkStatus() {
 
 # requires parameter
 # 1. param: 4 or 6 for IP version
-function ipHasChanged() {
-  case ${1} in
+function ipHasChanged
+{
+  local ip_version=$1
+  case ${ip_version} in
     4)
       remote_ip=$(getRemoteIP 4 $_ipv4_checker)
-      if [[ $DYNB_UPDATE_METHOD == domrobot ]]; then
-        dns_ip=$(getDNSIP A)
-      else
-        if [[ -n $_DNS_checkServer ]]; then
-          dig_response=$(dig @"${_DNS_checkServer}" in a +short "$DYNB_DYN_DOMAIN")
-        else
-          dig_response=$(dig in a +short "$DYNB_DYN_DOMAIN")
+      if ! is_IPv4_address "$remote_ip"
+      then
+        errorMessage "The response from the IP check server is not an IPv4 address: $remote_ip"
+        return 1
       fi
-        if [[ $dig_response == ";; connection timed out; no servers could be reached" ]]; then
+      if [[ $DYNB_UPDATE_METHOD == domrobot ]]
+      then dns_ip=$(getDNSIP A)
+      else
+        if [[ -n $_DNS_checkServer ]]
+        then dig_response=$(dig @"${_DNS_checkServer}" in a +short "$DYNB_DYN_DOMAIN")
+        else dig_response=$(dig in a +short "$DYNB_DYN_DOMAIN")
+        fi
+        if [[ $dig_response == ";; connection timed out; no servers could be reached" ]]
+        then
           errorMessage "DNS request failed $dig_response"
-          return 0
+          return 1
         fi
-        dns_ip=$dig_response
+        # If the dns resolver lists multiple records in the answer section we filter the first line
+        # using short option "-n" and not "--lines" because of alpines limited BusyBox head command
+        dns_ip=$(echo "$dig_response" | head -n 1)
       fi
       _new_IPv4=$remote_ip
-      debugMessage "New IPv4: $_new_IPv4 old was: $dns_ip"
+      debugMessage "IPv4 from remote IP check server: $_new_IPv4, IPv4 from DNS: $dns_ip"
       ;;
     6)
       remote_ip=$(getRemoteIP 6 $_ipv6_checker)
-      if [[ $DYNB_UPDATE_METHOD == domrobot ]]; then
-        dns_ip=$(getDNSIP AAAA)
-      else
-        if [[ -n $_DNS_checkServer ]]; then
-          dig_response=$(dig @"${_DNS_checkServer}" in aaaa +short "$DYNB_DYN_DOMAIN")
-        else
-          dig_response=$(dig in aaaa +short "$DYNB_DYN_DOMAIN")
-        fi
-        if [[ $dig_response == ";; connection timed out; no servers could be reached" ]]; then
-          errorMessage "DNS request failed $dig_response"
-          return 0
-        fi
-        dns_ip=$dig_response
-      fi
-      _new_IPv6=$remote_ip
-      debugMessage "New IPv6: $_new_IPv6 old was: $dns_ip"
-      ;;
-    *) ;;
-
-  esac
-
-  if [[ "$remote_ip" == "$dns_ip" ]]; then
-    return 0
-  else
+      if ! is_IPv6_address "$remote_ip"
+      then
+        errorMessage "The response from the IP check server is not an IPv6 address: $remote_ip"
         return 1
       fi
+      if [[ $DYNB_UPDATE_METHOD == domrobot ]]
+      then dns_ip=$(getDNSIP AAAA)
+      else
+        if [[ -n $_DNS_checkServer ]]
+        then dig_response=$(dig @"${_DNS_checkServer}" in aaaa +short "$DYNB_DYN_DOMAIN")
+        else dig_response=$(dig in aaaa +short "$DYNB_DYN_DOMAIN")
+        fi
+        exitcode=$?
+        if [[ $exitcode -gt 0 ]]
+        then
+          errorMessage "DNS request failed with exit code: $exitcode $dig_response"
+          return 1
+        fi
+        # If the dns server lists multiple records in the answer section we filter the first line
+        dns_ip=$(echo "$dig_response" | head -n 1)
+      fi
+      _new_IPv6=$remote_ip
+      debugMessage "IPv6 from remote IP check server: $_new_IPv6, IPv4 from DNS: $dns_ip"
+      ;;
+    *) ;;
+  esac
+
+  if [[ "$remote_ip" == "$dns_ip" ]]
+  then return 1
+  else
+    case ${ip_version} in
+    4) infoMessage "New IPv4: $_new_IPv4 old was: $dns_ip";;
+    6) infoMessage "New IPv6: $_new_IPv6 old was: $dns_ip";;
+    esac
+    return 0
+  fi
 }
 
-################
-## parameters ##
-################
-
-function handleParameters() {
+function handleParameters
+{
   # shellcheck disable=SC2154
-  if [[ $_arg_version == "on" ]]; then
-    echo $_version
-    exit 0
+  if [[ $_arg_version == "on" ]]
+  then echo $_version; exit 0
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_link == "on" ]]; then
-    ln --verbose --symbolic "$(realpath "$0")" "$HOME/.local/bin/dynb"
-    exit 0
+  if [[ $_arg_link == "on" ]]
+  then ln --verbose --symbolic "$(realpath "$0")" "$HOME/.local/bin/dynb"; exit 0
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_reset == "on" ]]; then
-    rm --verbose "$_statusFile"
-    exit 0
+  if [[ $_arg_reset == "on" ]] && test -f "$_statusFile"
+  then rm --verbose "$_statusFile"; exit 0
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_debug == "on" ]]; then
-    _debug=1
+  if [[ $_arg_debug == "on" ]]
+  then _debug=1
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_update_method != "" ]]; then
-    DYNB_UPDATE_METHOD=$_arg_update_method
+  if [[ $_arg_update_method != "" ]]
+  then DYNB_UPDATE_METHOD=$_arg_update_method
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_ip_mode != "" ]]; then
-    DYNB_IP_MODE=$_arg_ip_mode
+  if [[ $_arg_ip_mode != "" ]]
+  then DYNB_IP_MODE=$_arg_ip_mode
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_domain != "" ]]; then
-    DYNB_DYN_DOMAIN=$_arg_domain
+  if [[ $_arg_domain != "" ]]
+  then DYNB_DYN_DOMAIN=$_arg_domain
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_service_provider != "" ]]; then
-    DYNB_SERVICE_PROVIDER=$_arg_service_provider
+  if [[ $_arg_service_provider != "" ]]
+  then DYNB_SERVICE_PROVIDER=$_arg_service_provider
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_username != "" ]]; then
-    DYNB_USERNAME=$_arg_username
+  if [[ $_arg_username != "" ]]
+  then DYNB_USERNAME=$_arg_username
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_password != "" ]]; then
-    DYNB_PASSWORD=$_arg_password
+  if [[ $_arg_password != "" ]]
+  then DYNB_PASSWORD=$_arg_password
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_token != "" ]]; then
-    DYNB_TOKEN=$_arg_token
+  if [[ $_arg_token != "" ]]
+  then DYNB_TOKEN=$_arg_token
   fi
   # shellcheck disable=SC2154
-  if [[ $_arg_interval != "" ]]; then
-    DYNB_INTERVAL=$_arg_interval
+  if [[ $_arg_interval != "" ]]
+  then DYNB_INTERVAL=$_arg_interval
   fi
 
-  if [[ -z $DYNB_INTERVAL ]]; then
-    _loopMode=0
-  elif [[ $DYNB_INTERVAL -lt _minimum_looptime ]]; then
+  if [[ -z $DYNB_INTERVAL ]]
+  then _loopMode=0
+  elif [[ $DYNB_INTERVAL -lt _minimum_looptime ]]
+  then
     DYNB_INTERVAL=$_minimum_looptime
     _loopMode=1
-  else
-    _loopMode=1
+  else _loopMode=1
   fi
-  if [[ $_network_interface != "" ]]; then
-    _interface_str="--interface $_network_interface"
+  if [[ $_network_interface != "" ]]
+  then _interface_str="--interface $_network_interface"
   fi
 
-  if [[ $DYNB_IP_MODE == d* ]]; then
+  if [[ $DYNB_IP_MODE == d* ]]
+  then
     _is_IPv4_enabled=true
     _is_IPv6_enabled=true
   fi
-  if [[ $DYNB_IP_MODE == *4* ]]; then
-    _is_IPv4_enabled=true
+  if [[ $DYNB_IP_MODE == *4* ]]
+  then _is_IPv4_enabled=true
   fi
-  if [[ $DYNB_IP_MODE == *6* ]]; then
-    _is_IPv6_enabled=true
+  if [[ $DYNB_IP_MODE == *6* ]]
+  then _is_IPv6_enabled=true
   fi
 
-  if [[ $DYNB_DEBUG == true ]]; then
-    _debug=1
+  if [[ $DYNB_DEBUG == true ]]
+  then _debug=1
   fi
   # shellcheck disable=SC2154
-  if [[ -n $DYNB_IPv4_CHECK_SITE ]]; then
-    _ipv4_checker=$DYNB_IPv4_CHECK_SITE
+  if [[ -n $DYNB_IPv4_CHECK_SITE ]]
+  then _ipv4_checker=$DYNB_IPv4_CHECK_SITE
   fi
   # shellcheck disable=SC2154
-  if [[ -n $DYNB_IPv6_CHECK_SITE ]]; then
-    _ipv6_checker=$DYNB_IPv6_CHECK_SITE
+  if [[ -n $DYNB_IPv6_CHECK_SITE ]]
+  then _ipv6_checker=$DYNB_IPv6_CHECK_SITE
   fi
-  if [[ -n $DYNB_DNS_CHECK_SERVER ]]; then
-    _DNS_checkServer=$DYNB_DNS_CHECK_SERVER
+  if [[ -n $DYNB_DNS_CHECK_SERVER ]]
+  then _DNS_checkServer=$DYNB_DNS_CHECK_SERVER
   fi
   return 0
 }
 
-##################
-## dependencies ##
-##################
-
-function checkDependencies() {
+function checkDependencies
+{
   failCounter=0
   for i in curl dig; do
-    if ! command -v $i >/dev/null 2>&1; then
+    if ! command -v $i >/dev/null 2>&1
+    then
       errorMessage "could not find \"$i\", DynB depends on it. "
       ((failCounter++))
     fi
   done
   [[ -x $(command -v jq 2>/dev/null) ]] || {
-    if [[ $DYNB_UPDATE_METHOD != dyndns* ]]; then
+    if [[ $DYNB_UPDATE_METHOD != dyndns* ]]
+    then
       echo "This script depends on jq and it is not available." >&2
       ((failCounter++))
     fi
   }
-  if [[ failCounter -gt 0 ]]; then
-    exit 1
+  if [[ failCounter -gt 0 ]]
+  then exit 1
   fi
 }
 
-function doUnsets() {
+function doUnsets
+{
   unset _network_interface
   unset _DNS_checkServer
   unset _dns_records
@@ -622,83 +682,121 @@ function doUnsets() {
   unset DYNB_DEBUG
 }
 
-function doDomrobotUpdates() {
+function doDomrobotUpdates
+{
   getMainDomain
   fetchDNSRecords
-  if [[ $_is_IPv4_enabled == true ]]; then
-    ipHasChanged 4
-    if [[ $? == 1 ]]; then
-      updateRecord 4
-    else
-      debugMessage "Skip IPv4 record update, it is already up to date"
+  if [[ $_is_IPv4_enabled == true ]]
+  then
+    if ipHasChanged 4
+    then updateRecord 4
+    else debugMessage "Skip IPv4 record update, it is already up to date"
     fi
   fi
-  if [[ $_is_IPv6_enabled == true ]]; then
-    ipHasChanged 6
-    if [[ $? == 1 ]]; then
-      updateRecord 6
-    else
-      debugMessage "Skip IPv6 record update, it is already up to date"
+  if [[ $_is_IPv6_enabled == true ]]
+  then
+    if ipHasChanged 6
+    then updateRecord 6
+    else debugMessage "Skip IPv6 record update, it is already up to date"
     fi
   fi
 }
 
-function doDynDNS2Updates() {
+function doDynDNS2Updates
+{
   changed=0
-  if [[ $_is_IPv4_enabled == true ]]; then
-    ipHasChanged 4
-    ((changed += $?))
+  if [[ $_is_IPv4_enabled == true ]] && ipHasChanged 4
+  then ((changed += 1))
   fi
-  if [[ $_is_IPv6_enabled == true ]]; then
-    ipHasChanged 6
-    ((changed += $?))
+  if [[ $_is_IPv6_enabled == true ]] && ipHasChanged 6
+  then ((changed += 1))
   fi
-  if [[ $changed -gt 0 ]]; then
-    if checkStatus; then
+  if [[ $changed -gt 0 ]]
+  then
+    if checkStatus
+    then
       debugMessage "checkStatus has no errors, try update"
-      if dynupdate; then
-        debugMessage "DynDNS2 update success"
+      if dynupdate
+      then debugMessage "DynDNS2 update success"
       else
         debugMessage "Save new status after dynupdate has failed"
         setStatus "$_response" "$(date +%s)" $((_errorCounter += 1)) "$DYNB_DYN_DOMAIN" "${DYNB_USERNAME}" "${DYNB_PASSWORD}${DYNB_TOKEN}"
       fi
-    else
-      debugMessage "Skip DynDNS2 update, checkStatus fetched previous error."
+    else debugMessage "Skip DynDNS2 update, checkStatus fetched previous error."
     fi
-  else
-    debugMessage "Skip DynDNS2 update, IPs are up to date or there is a connection problem"
+  else debugMessage "Skip DynDNS2 update, IPs are up to date or there is a connection problem"
   fi
 }
 
-function doUpdates() {
-  if [[ $DYNB_UPDATE_METHOD == "domrobot" ]]; then
-    doDomrobotUpdates
-  fi
-
-  if [[ $DYNB_UPDATE_METHOD == "dyndns" ]]; then
-    doDynDNS2Updates
+function doUpdates
+{
+  if [[ $DYNB_UPDATE_METHOD == "domrobot" ]]
+  then doDomrobotUpdates
+  elif [[ $DYNB_UPDATE_METHOD == "dyndns" ]]
+  then doDynDNS2Updates
   fi
 }
 
-#################
-## MAIN method ##
-#################
-function dynb() {
+function ipv6_is_not_working
+{
+  curl --ipv6 --head --silent --max-time 5 $_internet_connectivity_test_server > /dev/null
+  status_code=$?
+  if test $status_code -gt 0
+  then return 0
+  else return 1
+  fi
+}
+
+function ipv4_is_not_working
+{
+  curl --ipv4 --head --silent --max-time 5 $_internet_connectivity_test_server > /dev/null
+  status_code=$?
+  if test $status_code -gt 0
+  then return 0
+  else return 1
+  fi
+}
+
+function check_internet_connection
+{
+  if [[ $_is_IPv4_enabled == true ]]
+  then
+    if ipv4_is_not_working
+    then
+      _is_IPv4_enabled="false"
+      errorMessage "Your IPv4 internet connection does not work."
+    fi
+  fi
+  if [[ $_is_IPv6_enabled == true ]]
+  then
+    if ipv6_is_not_working
+    then
+      _is_IPv6_enabled="false"
+      errorMessage "Your IPv6 internet connection does not work."
+    fi
+  fi
+}
+
+function main
+{
   # shellcheck disable=SC1091,SC1090
   source "$(dirname "$(realpath "$0")")/dynb-parsing.sh"
 
   # shellcheck source=.env
-  if test -f "$_configFile"; then
+  if test -f "$_configFile"
+  then
     # shellcheck disable=SC1091
     source "$_configFile"
   else
     alternativeConfig="$(dirname "$(realpath "$0")")/.env"
-    if test -f "$alternativeConfig"; then
+    if test -f "$alternativeConfig"
+    then
       # shellcheck disable=SC1091
       source "$alternativeConfig"
     fi
   fi
-  if test -f "$_statusFile"; then
+  if test -f "$_statusFile"
+  then
     debugMessage "read previous status file"
     # shellcheck disable=SC1090
     source "$_statusFile"
@@ -707,24 +805,22 @@ function dynb() {
   ## parameters and checks
   handleParameters
   checkDependencies
+  check_internet_connection
 
-  if loopMode; then
-    while :; do
+  if loopMode
+  then
+    while : 
+    do
       doUpdates
+      debugMessage "wait $DYNB_INTERVAL seconds until next check"
       sleep $DYNB_INTERVAL
     done
-  else
-    doUpdates
+  else doUpdates
   fi
 
   doUnsets
   return 0
 }
-######################
-## END MAIN section ##
-######################
 
-dynb "${@}"
+main "${@}"
 exit $?
-
-# ] <-- needed because of Argbash