Refactor healthcheck script to use dig for TCP checks

Co-authored-by: j.boehm <[email protected]>

Author: cursoragent

target/unbound/rootfs/usr/local/bin/healthcheck.sh

@@ -1,14 +1,15 @@
 #!/bin/sh
 set -e
 
-# 1. test connection to 0.0.0.0:53 (UDP via dig) and TCP via nc
+# UDP check
 if ! dig @127.0.0.1 -p 53 github.com +time=2 +tries=1 +short >/dev/null 2>&1; then
-    echo "Healthcheck failed: dig to 127.0.0.1:53"
+    echo "Healthcheck failed: dig UDP to 127.0.0.1:53"
     exit 1
 fi
 
-if ! nc -z 0.0.0.0 53; then
-    echo "Healthcheck failed: cannot connect to 0.0.0.0:53 (TCP)"
+# TCP check (no nc dependency)
+if ! dig +tcp @127.0.0.1 -p 53 github.com +time=2 +tries=1 +short >/dev/null 2>&1; then
+    echo "Healthcheck failed: dig TCP to 127.0.0.1:53"
     exit 1
 fi