From e2783e75b540b5c42c15ba01da93c0825e565e6a Mon Sep 17 00:00:00 2001
From: kx1t <15090643+kx1t@users.noreply.github.com>
Date: Wed, 7 Aug 2024 15:35:52 -0400
Subject: [PATCH] Add zonetable external load mechanism; make remote pyalive
 check configurable; add license headers; bug fixes (#76)

* auto dns/port selection based on zone

* add zone map

* Update README.md

* make use of zonetable persistent across all functions

* make logging more consistent

* cleanup

* cleanup

* made ImAlive more robust

* add EU zones

* improve zonetable to auto-extract zone names; add EU zones

* Update README.md

* add FALLBACK_IMALIVE_SERVICE

* Update zonetable

* implement zonetable auto updates

* Update imalive

* Update zonetable-update

* Update zonetable-update

* Update zonetable

* change to test zonetable downloads

* Create imalive-original

* Update Dockerfile

* Update imalive

* Update zonetable-update

* Update zonetable

* Update zonetable-update

* Update zonetable

* Update imalive

* Update imalive

* Update imalive

* Update imalive

* Update zonetable

* Update zonetable-update

* Update zonetable-update

* Update zonetable

* Update imalive

* Update zonetable

* Update zonetable-update

* Update zonetable

* Update 50-radarvirtuel

* Update 55-mlat-client

* Update imalive

* Update mlat-client

* Update radarvirtuel

* Update zonetable-update

* Update healthcheck.sh

* remove file
---
 Dockerfile                                    |   2 +
 .../s6-rc.d/user/contents.d/zonetable-update  |   0
 .../dependencies.d/50-radarvirtuel            |   0
 .../dependencies.d/55-mlat-client             |   0
 .../s6-overlay/s6-rc.d/zonetable-update/run   |   2 +
 .../s6-overlay/s6-rc.d/zonetable-update/type  |   1 +
 rootfs/etc/s6-overlay/scripts/50-radarvirtuel |  16 ++
 rootfs/etc/s6-overlay/scripts/55-mlat-client  |  16 ++
 rootfs/etc/s6-overlay/scripts/imalive         | 146 ++++++++++--------
 rootfs/etc/s6-overlay/scripts/mlat-client     |  16 ++
 rootfs/etc/s6-overlay/scripts/radarvirtuel    |  16 ++
 .../etc/s6-overlay/scripts/zonetable-update   |  43 ++++++
 rootfs/home/healthcheck/healthcheck.sh        |  16 ++
 rootfs/home/zonetable                         |  26 +++-
 14 files changed, 234 insertions(+), 66 deletions(-)
 create mode 100644 rootfs/etc/s6-overlay/s6-rc.d/user/contents.d/zonetable-update
 create mode 100644 rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/dependencies.d/50-radarvirtuel
 create mode 100644 rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/dependencies.d/55-mlat-client
 create mode 100755 rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/run
 create mode 100644 rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/type
 create mode 100755 rootfs/etc/s6-overlay/scripts/zonetable-update

diff --git a/Dockerfile b/Dockerfile
index 38ec7b6..1a42e8e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -18,6 +18,8 @@ RUN --mount=type=bind,from=downloader,source=/,target=/downloader/ \
     # Needed to run the mlat_client:
     KEPT_PACKAGES+=(python3-minimal) && \
     KEPT_PACKAGES+=(python3-pkg-resources) && \
+    # Needed for the new ImAlive:
+    KEPT_PACKAGES+=(tcpdump) && \
     #
     # Install all these packages:
     apt-get update -q -y && \
diff --git a/rootfs/etc/s6-overlay/s6-rc.d/user/contents.d/zonetable-update b/rootfs/etc/s6-overlay/s6-rc.d/user/contents.d/zonetable-update
new file mode 100644
index 0000000..e69de29
diff --git a/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/dependencies.d/50-radarvirtuel b/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/dependencies.d/50-radarvirtuel
new file mode 100644
index 0000000..e69de29
diff --git a/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/dependencies.d/55-mlat-client b/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/dependencies.d/55-mlat-client
new file mode 100644
index 0000000..e69de29
diff --git a/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/run b/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/run
new file mode 100755
index 0000000..9e17aa9
--- /dev/null
+++ b/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/run
@@ -0,0 +1,2 @@
+#!/bin/sh
+exec /etc/s6-overlay/scripts/zonetable-update
diff --git a/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/type b/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/type
new file mode 100644
index 0000000..5883cff
--- /dev/null
+++ b/rootfs/etc/s6-overlay/s6-rc.d/zonetable-update/type
@@ -0,0 +1 @@
+longrun
diff --git a/rootfs/etc/s6-overlay/scripts/50-radarvirtuel b/rootfs/etc/s6-overlay/scripts/50-radarvirtuel
index 7f3b3a5..9c8ee88 100755
--- a/rootfs/etc/s6-overlay/scripts/50-radarvirtuel
+++ b/rootfs/etc/s6-overlay/scripts/50-radarvirtuel
@@ -1,6 +1,22 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash disable=SC1091,SC2015,SC2145,SC2154
 
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
 source /scripts/common
 "${s6wrap[@]}" echo "Initializing RadarVirtuel..."
 
diff --git a/rootfs/etc/s6-overlay/scripts/55-mlat-client b/rootfs/etc/s6-overlay/scripts/55-mlat-client
index 3f915f6..b67f608 100755
--- a/rootfs/etc/s6-overlay/scripts/55-mlat-client
+++ b/rootfs/etc/s6-overlay/scripts/55-mlat-client
@@ -1,6 +1,22 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash disable=SC1091,SC2015,SC2145,SC2154
 
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
 source /scripts/common
 
 "${s6wrap[@]}" echo "Initializing mlat-client..."
diff --git a/rootfs/etc/s6-overlay/scripts/imalive b/rootfs/etc/s6-overlay/scripts/imalive
index 03e8464..e1489f7 100755
--- a/rootfs/etc/s6-overlay/scripts/imalive
+++ b/rootfs/etc/s6-overlay/scripts/imalive
@@ -1,20 +1,42 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash disable=SC1091,SC2015,SC2145,SC2154
 
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
 source /scripts/common
 
-KEEPALIVE_ALIVE=600   # keepalive timer in seconds if previous run was fine
-KEEPALIVE_DEAD=60     # keepalive timer in seconds if previous run failed
-                      # dont make this shorter than 60 secs to allow services to be properly restarted after a failure
-CONNECTION_TIMEOUT=10 # timeout when checking ability to connect using netcat
+while [[ -f /run/zonetable.lock ]]; do sleep 1; done
+touch /run/zonetable.lock
+source /home/zonetable
+rm -f /run/zonetable.lock
+
+KEEPALIVE_ALIVE="${KEEPALIVE_ALIVE:-600}"     # keepalive timer in seconds if previous run was fine
+KEEPALIVE_DEAD="${KEEPALIVE_DEAD:-60}"        # keepalive timer in seconds if previous run failed
+                                              # dont make this shorter than 60 secs to allow services to be properly restarted after a failure
+CONNECTION_TIMEOUT="{CONNECTION_TIMEOUT:-10}" # timeout when checking ability to connect using netcat
 ALIVE=true
 mkdir -p /run/imalive
 touch /run/imalive/errors
 "${s6wrap[@]}" echo "Started as an s6 service"
 
 RV_SERVER="${RV_SERVER:-mg22.adsbnetwork.com:50050}"
+FALLBACK_IMALIVE_SERVICE="${FALLBACK_IMALIVE_SERVICE:-http://mg22.adsbnetwork.com/rtools/pyalive.php}"
 [[ "${RV_SERVER%%:*}" == "mg2.adsbnetwork.com" ]] && RV_SERVER="mg22.adsbnetwork.com:${RV_SERVER##*:}" || true
-source /home/zonetable
+
 if [[ -n "$zone_id" ]]; then
   RV_SERVER="${zone_dns}:${zone_port}"
 fi
@@ -40,91 +62,85 @@ do
         "${s6wrap[@]}" echo "Running ImAlive..."
     fi
 
+    # Get the latest zonetable values:
+    while [[ -f /run/zonetable.lock ]]; do sleep 1; done
+    touch /run/zonetable.lock
+    source /home/zonetable
+    rm -f /run/zonetable.lock
+    if [[ -n "$zone_id" ]]; then
+      RV_SERVER="${zone_dns}:${zone_port}"
+    fi
+
     ALIVE=true
     # kx1t: retrieve station name from $FEEDER_KEY docker env variable
     st=${FEEDER_KEY%%:*}
     timestamp=$(date "+%s")
-    #echo " $st Current Time : $ts"
-    #
-    # 07-AUG-2024 -- added the following code because at the moment, MG21 is providing a "ko" unduely due to server side MongoDB issues
-    #                once fixed, we can revert to the original line
-    # ORIGINAL:
-    # if ! STATUS="$(curl -sSL "${RV_SERVER%%:*}"/rtools/pyalive.php?stid="${st,,}" 2>&1)"; then 
-    # NEW: (revert this 1 line once MG21 is fixed)
-    if ! STATUS="$(curl -sSL "${RV_SERVER%%:*}"/rtools/pyalive.php?stid="${st,,}" 2>&1)" || [[ "${STATUS%%-*}" == "ko" ]]; then 
-        if STATUS="$(curl -sSL http://mg22.adsbnetwork.com/rtools/pyalive.php?stid="${st,,}" 2>&1)"; then
-            "${s6wrap[@]}" echo "ImAlive status on ${RV_SERVER%%:*} wasn't available, fell back to mg22.adsbnetwork.com"
-        else
-            STATUS=""
-        fi
-    fi
-    # STATUS now contains either "ok-12345678" or "ko-12345678"
-    # If STATUS is empty then there was a connection error
-    # where ok/ko means OK or not OK and 12345678 is the secs since epoch
-    # STATUS can also contain the error page if the server returns an error
-
-    status="${STATUS%%-*}"
-    remote_timestamp="${STATUS##*-}"
-
-    # check the ImAlive server:
-    if grep -o "404 Not Found" <<< "$STATUS" >/dev/null 2>&1; then
-         "${s6wrap[@]}" echo "ImAlive Server returned 404-Not Found. Restarting ANFeeder \"just in case\"..."
-        killall /home/py/ANfeeder >/dev/null 2>&1
+
+    if ! chk_disabled "${FALLBACK_IMALIVE_SERVICE}"; then
+      if ! STATUS="$(curl -sSL "${RV_SERVER%%:*}"/rtools/pyalive.php?stid="${st,,}" 2>&1)"; then 
+          if STATUS="$(curl -sSL "${FALLBACK_IMALIVE_SERVICE}"?stid="${st,,}" 2>&1)"; then
+              "${s6wrap[@]}" echo "ImAlive status on ${RV_SERVER%%:*} wasn't available, fell back to mg22.adsbnetwork.com"
+          else
+              STATUS=""
+          fi
+      fi
+      # STATUS now contains either "ok-12345678" or "ko-12345678"
+      # If STATUS is empty then there was a connection error
+      # where ok/ko means OK or not OK and 12345678 is the secs since epoch
+      # STATUS can also contain the error page if the server returns an error
+
+      status="${STATUS%%-*}"
+      remote_timestamp="${STATUS##*-}"
+
+      # check the ImAlive server:
+      if grep -o "404 Not Found" <<< "$STATUS" >/dev/null 2>&1; then
+        "${s6wrap[@]}" echo "ImAlive Server returned 404-Not Found. Restarting ANFeeder \"just in case\"..."
         ALIVE="404 failure for ${RV_SERVER%%:*}/rtools/pyalive.php?stid=$st"
-    elif [[ -z  "$STATUS" ]]; then
+      elif [[ -z  "$STATUS" ]]; then
          "${s6wrap[@]}" echo "ImAlive Server cannot be reached: network failure. Restarting ANFeeder \"just in case\"..."
-        killall /home/py/ANfeeder >/dev/null 2>&1
         ALIVE="no network failure"
-    elif [[ $timestamp -lt $(( remote_timestamp - 10 )) ]]; then
+      elif [[ $timestamp -lt $(( remote_timestamp - 10 )) ]]; then
         # kx1t: using killall to restart the service instead of the RestartANfeeder.sh script
          "${s6wrap[@]}" echo "ImAlive Server: time stamp discrepancy: local $(date -d @"$timestamp") / remote $(date -d @"$remote_timestamp"); restarting ANfeeder"
         # kx1t: added warning that Docker image cannot resync NTP
          "${s6wrap[@]}" echo "Warning - Please make sure your host machine uses an accurate external time source!"
-        killall /home/py/ANfeeder >/dev/null 2>&1
         ALIVE="time discrepancy failure"
-    elif [[ "$status" == "ko" ]]; then
+      elif [[ "$status" == "ko" ]]; then
         # kx1t: using s6 to restart the service
         "${s6wrap[@]}" echo "ImAlive Server says that no data is received: Restarting ANfeeder"
-        killall /home/py/ANfeeder >/dev/null 2>&1
         ALIVE="no data received by server failure"
-    elif [[ "$status" == "ok" ]]; then
+      elif [[ "$status" == "ok" ]]; then
         chk_enabled "${VERBOSE}" && "${s6wrap[@]}" echo "ImAlive Server: connection is fine!"
-    else
-        "${s6wrap[@]}" echo "ImAlife error: $STATUS. Restarting ANfeeder"
-        killall /home/py/ANfeeder >/dev/null 2>&1
+      else
+        "${s6wrap[@]}" echo "ImAlive error: $STATUS. Restarting ANfeeder"
         ALIVE="$STATUS"
+      fi
+    else
+      "${s6wrap[@]}" echo "Server Check-in is disabled - skipped querying ${RV_SERVER%%:*}"
     fi
 
     # check the SOURCE_HOST connection
-    # if ! check_tcp4_connection_established ANY ANY $(get_ipv4 ${SOURCE_HOST%%:*}) ${SOURCE_HOST##*:} >/dev/null 2>&1
-    # if [[ $(timeout --preserve-status $CONNECTION_TIMEOUT netcat -z -v "${SOURCE_HOST%%:*}" "${SOURCE_HOST##*:}" 2>/dev/null ; echo $?) != "0" ]]
-    if [[ "$(grep captured <<< "$(timeout --preserve-status 3 tcpdump -p src "${SOURCE_HOST%%:*}" and port "${SOURCE_HOST##*:}" 2>/dev/stdout 1>/dev/null)" | awk '{print $1}')" == "0" ]]
-    then
-        "${s6wrap[@]}" echo "Your data source at $SOURCE_HOST appears to be down. Restarting ANfeeder."
-        killall /home/py/ANfeeder >/dev/null 2>&1
+    if [[ "$(grep captured <<< "$(timeout --preserve-status 3 tcpdump -p src "${SOURCE_HOST%%:*}" and port "${SOURCE_HOST##*:}" 2>/dev/stdout 1>/dev/null)" | awk '{print $1}')" == "0" ]]; then
+        "${s6wrap[@]}" echo "Your data source at $SOURCE_HOST appears to be down. Restarting ANfeeder"
         ALIVE="cannot establish connection to SOURCE HOST $SOURCE_HOST"
     else
-        chk_enabled "${VERBOSE}"  && "${s6wrap[@]}" echo "$SOURCE_HOST can be reached! "
+        if chk_enabled "${VERBOSE}"; then "${s6wrap[@]}" echo "$SOURCE_HOST is sending data to the container"; fi
     fi
 
-    # check if the RV_SERVER can be reached
-    # Note - in the future we have to revisit this. `netcat -u` relies on ICMP Not Available messages from a UDP port to be
-    # returned in case of failure, and often these messages are not sent or are filtered on the way back.
-    # See https://serverfault.com/a/416269 for explanation
-    #
-    # In reality, false passes of this check aren't too important as we already pinged the ImAlive server to see that they think the connection is OK
-    #
-    # if ! check_udp4_connection_established ANY ANY $(get_ipv4 ${RV_SERVER%%:*}) ${RV_SERVER##*:} >/dev/null 2>&1
-    if [[ $(timeout --preserve-status $CONNECTION_TIMEOUT netcat -u -z -v "${RV_SERVER%%:*}" "${RV_SERVER##*:}" 2>/dev/null ; echo $?) != "0" ]]
-    then
-        "${s6wrap[@]}" echo "The RadarVirtuel server at $RV_SERVER appears to be down. Restarting ANfeeder."
-        killall /home/py/ANfeeder >/dev/null 2>&1
-        ALIVE="$RV_SERVER down failure"
+    # check if we see UDP data on the RV_SERVER port in 3 seconds, if that fails, try again for 30 secs
+    # this is so the check will pass in 3 secs during times of high traffic, but we'll check for a longer period of time during low traffic
+    if   (( $(grep captured <<< "$(timeout --preserve-status 3  tcpdump -p udp port "${RV_SERVER##*:}" 2>/dev/stdout 1>/dev/null)" | awk '{print $1}') > 0 )) \
+      || (( $(grep captured <<< "$(timeout --preserve-status 30 tcpdump -p udp port "${RV_SERVER##*:}" 2>/dev/stdout 1>/dev/null)" | awk '{print $1}') > 0 )); then
+          if chk_enabled "${VERBOSE}"; then "${s6wrap[@]}" echo "The container is sending data to $RV_SERVER"; fi
     else
-        if chk_enabled "${VERBOSE}"; then
-            "${s6wrap[@]}" echo "$RV_SERVER can be reached!"
-        fi
+          "${s6wrap[@]}" echo "The container is not sending any data to the RadarVirtuel server at $RV_SERVER. Restarting ANfeeder"
+          ALIVE="$RV_SERVER down failure"
     fi
 
-    [[ "$ALIVE" != "true" ]] && echo "$(date +%s) - $ALIVE" >> /run/imalive/errors || echo "" > /run/imalive/errors
+    if [[ "$ALIVE" != "true" ]]; then
+      killall /home/py/ANfeeder >/dev/null 2>&1 || true
+      echo "$(date +%s) - $ALIVE" >> /run/imalive/errors
+    else
+      echo "" > /run/imalive/errors
+    fi
 done
diff --git a/rootfs/etc/s6-overlay/scripts/mlat-client b/rootfs/etc/s6-overlay/scripts/mlat-client
index 9b91cf8..8edf20e 100755
--- a/rootfs/etc/s6-overlay/scripts/mlat-client
+++ b/rootfs/etc/s6-overlay/scripts/mlat-client
@@ -1,6 +1,22 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash disable=SC1091,SC2015,SC2145,SC2154
 
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
 source /scripts/common
 
 "${s6wrap[@]}" echo "Started as an s6 service"
diff --git a/rootfs/etc/s6-overlay/scripts/radarvirtuel b/rootfs/etc/s6-overlay/scripts/radarvirtuel
index ac72db0..2708eca 100755
--- a/rootfs/etc/s6-overlay/scripts/radarvirtuel
+++ b/rootfs/etc/s6-overlay/scripts/radarvirtuel
@@ -1,6 +1,22 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash disable=SC1091,SC2015,SC2145,SC2154
 
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
 source /scripts/common
 
 START_DELAY=5s
diff --git a/rootfs/etc/s6-overlay/scripts/zonetable-update b/rootfs/etc/s6-overlay/scripts/zonetable-update
new file mode 100755
index 0000000..c8303f8
--- /dev/null
+++ b/rootfs/etc/s6-overlay/scripts/zonetable-update
@@ -0,0 +1,43 @@
+#!/command/with-contenv bash
+# shellcheck shell=bash disable=SC1091,SC2015,SC2145,SC2154
+
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
+source /scripts/common
+ZONETABLE_CHECK_INT="${ZONETABLE_CHECK_INT:-7200}"	# check every 2 hours
+ZONETABLE_URL="${ZONETABLE_URL:-https://raw.githubusercontent.com/sdr-enthusiasts/docker-radarvirtuel/main/rootfs/home/zonetable}"
+
+"${s6wrap[@]}" echo "[INFO] checking if zonetable needs to get updated"
+
+if curl -sSL "${ZONETABLE_URL}" -o /tmp/zonetable >/dev/null 2>&1; then 
+	if [[ -n "$(comm --nocheck-order -3 /home/zonetable /tmp/zonetable 2>/dev/null)" ]]; then
+		"${s6wrap[@]}" echo "[INFO] zonetable has changed, installing new version"
+		while [[ -f /run/zonetable.lock ]]; do sleep 1; done
+		touch /run/zonetable.lock
+	        mv -f /tmp/zonetable /home/zonetable
+	        chmod +x /home/zonetable
+		rm -f /run/zonetable.lock
+	else
+		"${s6wrap[@]}" echo "[INFO] zonetable has not changed since last check"
+		rm -f /tmp/zonetable
+	fi
+else
+	"${s6wrap[@]}" echo "[WARNING] couldn't reach the remote server with the latest zonetable - we will keep on using the current table"
+fi
+
+"${s6wrap[@]}" echo "[INFO] next zonetable update check will be at $(date -d "+$ZONETABLE_CHECK_INT seconds" | xargs)"
+sleep $ZONETABLE_CHECK_INT
diff --git a/rootfs/home/healthcheck/healthcheck.sh b/rootfs/home/healthcheck/healthcheck.sh
index 9aa54b7..00ae188 100755
--- a/rootfs/home/healthcheck/healthcheck.sh
+++ b/rootfs/home/healthcheck/healthcheck.sh
@@ -1,6 +1,22 @@
 #!/command/with-contenv bash
 #shellcheck shell=bash
 
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
+
 # Import healthchecks-framework
 # shellcheck disable=SC1091
 source /opt/healthchecks-framework/healthchecks.sh
diff --git a/rootfs/home/zonetable b/rootfs/home/zonetable
index e4f07c0..20927d9 100644
--- a/rootfs/home/zonetable
+++ b/rootfs/home/zonetable
@@ -1,7 +1,29 @@
 #shellcheck shell=bash disable=SC2154
 
-# associative array with the DNS, port, and boundary data for each zone.
+#---------------------------------------------------------------------------------------------
+# Copyright (C) 2023-2024, Ramon F. Kolb (kx1t) and contributors
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program.
+# If not, see <https://www.gnu.org/licenses/>.
+#---------------------------------------------------------------------------------------------
 
+# Define where to get the ImAlive service if the RV_SERVER fails for any reason
+# If FALLBACK_IMALIVE_SERVICE is set to "off"/"disabled"/"no"/0 etc, then ImAlive will always be skipped (also for the primary ImAlive Check)
+# This is implemented to create control to switch off ImAlive if the ImAlive server fails for any reason
+
+# FALLBACK_IMALIVE_SERVICE="http://mg22.adsbnetwork.com/rtools/pyalive.php"
+FALLBACK_IMALIVE_SERVICE="disabled"
+
+# associative array with the name, DNS, port, and boundary data for each zone.
 declare -A ZoneTable=(
     [EU001:name]="West-Portugal West-Spain"
     [EU001:dns]="mg22.adsbnetwork.com"
@@ -257,4 +279,6 @@ if [[ -n "$LON" ]] && [[ -n "$LAT" ]]; then
             break
         fi
     done
+else
+    unset zone_name zone_id zone_dns zone_port
 fi