Add Harbor Gateway auto-detection for client routing

scripts/harbor-network-monitor.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+export LC_ALL=C
+
+RUNTIME_DIR="${HARBOR_RUNTIME_DIR:-$HOME/.vpn-proxy-client/.runtime}"
+STATE_FILE="$RUNTIME_DIR/network.json"
+ROUTE_BIN="${HARBOR_ROUTE_BIN:-/sbin/route}"
+ARP_BIN="${HARBOR_ARP_BIN:-/usr/sbin/arp}"
+NETSTAT_BIN="${HARBOR_NETSTAT_BIN:-/usr/sbin/netstat}"
+
+route_info="$($ROUTE_BIN -n get default 2>/dev/null || true)"
+gateway="$(awk '/^[[:space:]]*gateway:/{print $2; exit}' <<<"$route_info")"
+network_interface="$(awk '/^[[:space:]]*interface:/{print $2; exit}' <<<"$route_info")"
+
+if [[ -z "$gateway" || -z "$network_interface" ]]; then
+  read -r gateway network_interface < <(
+    "$NETSTAT_BIN" -rn -f inet 2>/dev/null \
+      | awk '$1 == "default" && $2 ~ /^[0-9]+\./ { print $2, $4; exit }'
+  ) || true
+fi
+
+if [[ ! "$gateway" =~ ^([0-9]{1,3}\.){3}[0-9]{1,3}$ ]]; then
+  gateway=""
+  network_interface=""
+fi
+if [[ ! "$network_interface" =~ ^[a-zA-Z0-9._-]{1,32}$ ]]; then
+  network_interface=""
+fi
+
+mac=""
+if [[ -n "$gateway" ]]; then
+  mac="$($ARP_BIN -n "$gateway" 2>/dev/null | awk '/ at /{print $4; exit}' || true)"
+  if [[ ! "$mac" =~ ^[a-fA-F0-9]{2}(:[a-fA-F0-9]{2}){5}$ ]]; then
+    mac=""
+  else
+    mac="$(printf '%s' "$mac" | tr '[:upper:]' '[:lower:]')"
+  fi
+fi
+
+mkdir -p "$RUNTIME_DIR"
+tmp="$(mktemp "${STATE_FILE}.XXXXXX")"
+trap 'rm -f "$tmp"' EXIT
+printf '{"gateway":"%s","interface":"%s","mac":"%s","observedAt":"%s"}\n' \
+  "$gateway" "$network_interface" "$mac" "$(date -u '+%Y-%m-%dT%H:%M:%SZ')" > "$tmp"
+mv "$tmp" "$STATE_FILE"