./system/codeigniter/system/core/Input.php function ip_address()

gistfile1.php

	/**
	* Fetch the IP Address
	*
	* @access	public
	* @return	string
	*/
	public function ip_address()
	{
		if ($this->ip_address !== FALSE)
		{
			return $this->ip_address;
		}

		if (config_item('proxy_ips') != '' && $this->server('HTTP_X_FORWARDED_FOR') && $this->server('REMOTE_ADDR'))
		{
			$has_ranges = strpos($proxies, '/') !== false;
			$proxies = preg_split('/[\s,]/', config_item('proxy_ips'), -1, PREG_SPLIT_NO_EMPTY);
			$proxies = is_array($proxies) ? $proxies : array($proxies);

			if ($has_ranges)
			{
				$long_ip = ip2long($_SERVER['REMOTE_ADDR']);
				$bit_32 = 1 << 32;

				// Go through each of the IP Addresses to check for and
				// test against range notation
				foreach($proxies as $ip)
				{
					list($address, $mask_length) = explode('/', $ip);

					// Generate the bitmask for a 32 bit IP Address
					$bitmask = $bit_32 - (1 << (32 - (int)$mask_length));
					
					if (($long_ip & $bitmask) == $address)
					{
						$this->ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
						break;
					}
				}

			} 
			else 
			{
				$this->ip_address = in_array($_SERVER['REMOTE_ADDR'], $proxies) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : $_SERVER['REMOTE_ADDR'];
			}
		}
		elseif ($this->server('HTTP_CLIENT_IP'))
		{
			$this->ip_address = $_SERVER['HTTP_CLIENT_IP'];
		}
		elseif ($this->server('HTTP_X_FORWARDED_FOR'))
		{
			$this->ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
		}
		elseif ($this->server('REMOTE_ADDR'))
		{
			$this->ip_address = $_SERVER['REMOTE_ADDR'];
		}

		if ($this->ip_address === FALSE)
		{
			return $this->ip_address = '0.0.0.0';
		}

		if (strpos($this->ip_address, ',') !== FALSE)
		{
			$x = explode(',', $this->ip_address);
			$this->ip_address = trim(end($x));
		}

		if ( ! $this->valid_ip($this->ip_address))
		{
			return $this->ip_address = '0.0.0.0';
		}

		return $this->ip_address;
	}