1 files changed, 78 insertions, 0 deletions
diff --git a/inc/iputil.inc.php b/inc/iputil.inc.php
new file mode 100644
index 00000000..a50f22eb
--- /dev/null
+++ b/inc/iputil.inc.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+class IpUtil
+{
+
+	public static function rangeToCidr(int $start, int $end): string
+	{
+		$value = $start ^ $end;
+		if (!self::isAllOnes($value))
+			return 'NOT SUBNET: ' . long2ip($start) . '-' . long2ip($end);
+		$ones = self::bitLength($value);
+		return long2ip($start) . '/' . (32 - $ones);
+	}
+
+	public static function isValidSubnetRange(int $start, int $end): bool
+	{
+		return self::isAllOnes($start ^ $end);
+	}
+
+	/**
+	 * Return number of bits required to represent
+	 * this number.
+	 * !! Assumes given number is 2^n - 1 !!
+	 */
+	private static function bitLength(int $value): int
+	{
+		// This is log(value) / log(2)
+		// It should actually be $value + 1, but floating point errors
+		// start to happen either way at higher values, so with
+		// the round() thrown in, it doesn't matter...
+		return (int)round(log($value) / 0.69314718055995);
+	}
+
+	/**
+	 * Is the given number just ones if converted to
+	 * binary (ignoring leading zeros)?
+	 */
+	private static function isAllOnes(int $value): bool
+	{
+		return ($value & ($value + 1)) === 0;
+	}
+
+	/**
+	 * Parse network range in CIDR notion, return
+	 * ['start' => (int), 'end' => (int)] representing
+	 * the according start and end addresses as integer
+	 * values. Returns false on malformed input.
+	 *
+	 * @param string $cidr 192.168.101/24, 1.2.3.4/16, ...
+	 * @return array{start: int, end: int}|null start and end address, false on error
+	 */
+	public static function parseCidr(string $cidr): ?array
+	{
+		$parts = explode('/', $cidr);
+		if (count($parts) !== 2) {
+			$ip = ip2long($cidr);
+			if ($ip === false)
+				return null;
+			return ['start' => $ip, 'end' => $ip];
+		}
+		$ip = $parts[0];
+		$bits = $parts[1];
+		if (!is_numeric($bits) || $bits < 0 || $bits > 32)
+			return null;
+		$dots = substr_count($ip, '.');
+		if ($dots < 3) {
+			$ip .= str_repeat('.0', 3 - $dots);
+		}
+		$ip = ip2long($ip);
+		if ($ip === false)
+			return null;
+		$bits = (int)((2 ** (32 - $bits)) - 1);
+		return ['start' => $ip & ~$bits, 'end' => $ip | $bits];
+	}
+
+}