From 60c81030b35c5503cef34521a2c86360d4d2d366 Mon Sep 17 00:00:00 2001
From: biodigitalfish <11165243+biodigitalfish@users.noreply.github.com>
Date: Thu, 2 Nov 2023 17:17:35 +1300
Subject: [PATCH] Add validSubnetMask function

This function is used to validate a subnetmask

Signed-off-by: biodigitalfish <11165243+biodigitalfish@users.noreply.github.com>
---
 scripts/pi-hole/php/func.php | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/scripts/pi-hole/php/func.php b/scripts/pi-hole/php/func.php
index b345ca87d7..cac5dd7bec 100644
--- a/scripts/pi-hole/php/func.php
+++ b/scripts/pi-hole/php/func.php
@@ -67,6 +67,28 @@ function validIP($address)
     return !filter_var($address, FILTER_VALIDATE_IP) === false;
 }
 
+function validSubnetMask($subnetMask)
+{
+    $octets = explode('.', $subnetMask);
+    if (count($octets) != 4) {
+        return false;
+    }
+
+    $subnetBinary = '';
+    foreach ($octets as $octet) {
+        if (!is_numeric($octet) || $octet < 0 || $octet > 255) {
+            return false;
+        }
+        $subnetBinary .= str_pad(decbin($octet), 8, '0', STR_PAD_LEFT);
+    }
+
+    if (strpos($subnetBinary, '01') !== false) {
+        return false;
+    }
+
+    return true;
+}
+
 function validCIDRIP($address)
 {
     // This validation strategy has been taken from ../js/groups-common.js