better open port detection

Author: stangri

Makefile

@@ -3,7 +3,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=https-dns-proxy
 PKG_VERSION:=2025.09.11
-PKG_RELEASE:=4
+PKG_RELEASE:=5
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://github.com/baranyaib90/https_dns_proxy/

files/etc/init.d/https-dns-proxy

@@ -71,9 +71,23 @@ dnsmasq_restart() { /etc/init.d/dnsmasq restart >/dev/null 2>&1; }
 is_alnum() { case "$1" in (*[![:alnum:]_\ @]*|"") return 1;; esac; }
 is_fw4_restart_needed() { [ "$(uci_get "$packageName" 'config' 'force_dns' '1')" = '1' ]; }
 is_mac_address() { expr "$1" : '[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]$' >/dev/null; }
-is_integer() { case "$1" in ''|*[!0-9]*) return 1;; esac; }
+is_integer() { case "$1" in ''|*[!0-9]*) return 1;; esac; [ "$1" -ge 1 ] && [ "$1" -le 65535 ] || return 1; return 0; }
 is_ipv4() { expr "$1" : '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' >/dev/null; }
 is_ipv6() { ! is_mac_address "$1" && str_contains "$1" ":"; }
+is_port_listening() {
+	local hex
+	is_integer "$1" || return 1
+	hex="$(printf '%04X' "$1")"
+	# TCP: state 0A == LISTEN
+	if awk -v h="$hex" 'NR>1{split($2,a,":"); if (toupper(a[2])==h && $4=="0A") {found=1}} END{exit found?0:1}' /proc/net/tcp /proc/net/tcp6 2>/dev/null; then
+		return 0
+	fi
+	# UDP: presence indicates a bound socket
+	if awk -v h="$hex" 'NR>1{split($2,a,":"); if (toupper(a[2])==h) {found=1}} END{exit found?0:1}' /proc/net/udp /proc/net/udp6 2>/dev/null; then
+		return 0
+	fi
+	return 1
+}
 is_resolver_working() { 
 	local heartbeat_domain heartbeat_sleep_timeout heartbeat_wait_timeout
 	config_load "$packageName"
@@ -274,7 +288,7 @@ start_instance() {
 		json_add_array firewall
 		for iface in ${force_dns_src_interface/,/ }; do
 			for p in ${force_dns_port/,/ }; do
-				if netstat -tuln | grep 'LISTEN' | grep ":${p}" >/dev/null 2>&1 || [ "$p" = '53' ]; then
+				if is_port_listening "$p"; then
 					json_add_object ''
 					json_add_string type 'redirect'
 					json_add_string target 'DNAT'