Build KarlDNS self-hosted DynDNS service

scripts/karldns-update.sh

@@ -0,0 +1,93 @@
+#!/bin/sh
+set -eu
+
+CONFIG_FILE="${KARLDNS_CONFIG:-${XDG_CONFIG_HOME:-$HOME/.config}/karldns/updater.env}"
+
+if [ -r "$CONFIG_FILE" ]; then
+  # shellcheck disable=SC1090
+  . "$CONFIG_FILE"
+fi
+
+: "${KARLDNS_UPDATE_URL:?KARLDNS_UPDATE_URL is required in $CONFIG_FILE or the environment}"
+KARLDNS_BASE_URL="${KARLDNS_BASE_URL:-https://karldns.de}"
+KARLDNS_LOCK_FILE="${KARLDNS_LOCK_FILE:-/tmp/karldns-updater.lock}"
+KARLDNS_CACHE_FILE="${KARLDNS_CACHE_FILE:-${XDG_CACHE_HOME:-$HOME/.cache}/karldns/last-ip}"
+KARLDNS_CURL="${KARLDNS_CURL:-curl}"
+KARLDNS_IP_URL="${KARLDNS_IP_URL:-$KARLDNS_BASE_URL/ip}"
+KARLDNS_IPV4="${KARLDNS_IPV4:-auto}"
+KARLDNS_IPV6="${KARLDNS_IPV6:-auto}"
+case "$KARLDNS_UPDATE_URL" in
+  *"<ipaddr>"*|*"<ip6addr>"*) KARLDNS_UPDATE_URL="${KARLDNS_UPDATE_URL%%\?*}" ;;
+esac
+
+mkdir -p "$(dirname "$KARLDNS_CACHE_FILE")"
+mkdir -p "$(dirname "$KARLDNS_LOCK_FILE")" 2>/dev/null || true
+
+if command -v flock >/dev/null 2>&1; then
+  exec 9>"$KARLDNS_LOCK_FILE"
+  if ! flock -n 9; then
+    exit 0
+  fi
+else
+  lock_dir="${KARLDNS_LOCK_FILE}.d"
+  if ! mkdir "$lock_dir" 2>/dev/null; then
+    exit 0
+  fi
+  trap 'rmdir "$lock_dir"' EXIT INT TERM
+fi
+
+ipv4=""
+ipv6=""
+if [ "$KARLDNS_IPV4" = "auto" ]; then
+  ipv4="$("$KARLDNS_CURL" -4 -fsS --max-time 15 "$KARLDNS_IP_URL" 2>/dev/null | tr -d '[:space:]' || true)"
+elif [ "$KARLDNS_IPV4" != "off" ]; then
+  ipv4="$KARLDNS_IPV4"
+fi
+if [ "$KARLDNS_IPV6" = "auto" ]; then
+  ipv6="$("$KARLDNS_CURL" -6 -fsS --max-time 15 "$KARLDNS_IP_URL" 2>/dev/null | tr -d '[:space:]' || true)"
+elif [ "$KARLDNS_IPV6" != "off" ]; then
+  ipv6="$KARLDNS_IPV6"
+fi
+
+case "$ipv4" in *" "*) echo "KarlDNS: invalid IPv4 discovery result" >&2; exit 1 ;; esac
+case "$ipv6" in *" "*) echo "KarlDNS: invalid IPv6 discovery result" >&2; exit 1 ;; esac
+public_ip="${ipv4}|${ipv6}"
+has_discovered_ip=0
+if [ -n "$ipv4" ] || [ -n "$ipv6" ]; then
+  has_discovered_ip=1
+fi
+
+last_ip=""
+if [ -r "$KARLDNS_CACHE_FILE" ]; then
+  last_ip="$(cat "$KARLDNS_CACHE_FILE")"
+fi
+
+if [ "$has_discovered_ip" = "1" ] && [ "$public_ip" = "$last_ip" ] && [ "${KARLDNS_FORCE:-0}" != "1" ]; then
+  echo "KarlDNS: unchanged ${ipv4:-no-ipv4} ${ipv6:-no-ipv6}"
+  exit 0
+fi
+
+if [ "$has_discovered_ip" = "1" ]; then
+  set -- --get "$KARLDNS_UPDATE_URL"
+  if [ -n "$ipv4" ]; then
+    set -- "$@" --data-urlencode "myip=$ipv4"
+  fi
+  if [ -n "$ipv6" ]; then
+    set -- "$@" --data-urlencode "myipv6=$ipv6"
+  fi
+  response="$("$KARLDNS_CURL" -fsS --max-time 20 "$@")"
+else
+  response="$("$KARLDNS_CURL" -fsS --max-time 20 "$KARLDNS_UPDATE_URL")"
+fi
+case "$response" in
+  good*|nochg*)
+    if [ "$has_discovered_ip" = "1" ]; then
+      printf '%s\n' "$public_ip" > "$KARLDNS_CACHE_FILE"
+    fi
+    echo "KarlDNS: $response"
+    ;;
+  *)
+    echo "KarlDNS: update failed: $response" >&2
+    exit 1
+    ;;
+esac