From 71d17c50d6a316311d59bbfe48b91f3e5258ebd4 Mon Sep 17 00:00:00 2001
From: Dylan T <odigiman@gmail.com>
Date: Tue, 29 Jan 2019 12:51:53 +0000
Subject: [PATCH] Fixed internal IP detection (#2711), closes #2702

---
 src/pocketmine/network/upnp/UPnP.php  |  4 +---
 src/pocketmine/utils/Internet.php     | 31 +++++++++++++++++++++++++++
 src/pocketmine/wizard/SetupWizard.php |  8 +++++--
 3 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/src/pocketmine/network/upnp/UPnP.php b/src/pocketmine/network/upnp/UPnP.php
index aa9c3a733..305cd1746 100644
--- a/src/pocketmine/network/upnp/UPnP.php
+++ b/src/pocketmine/network/upnp/UPnP.php
@@ -29,9 +29,7 @@ namespace pocketmine\network\upnp;
 use pocketmine\utils\Internet;
 use pocketmine\utils\Utils;
 use function class_exists;
-use function gethostbyname;
 use function is_object;
-use function trim;
 
 abstract class UPnP{
 
@@ -46,7 +44,7 @@ abstract class UPnP{
 			throw new \RuntimeException("UPnP requires the com_dotnet extension");
 		}
 
-		$myLocalIP = gethostbyname(trim(`hostname`));
+		$myLocalIP = Internet::getInternalIP();
 
 		/** @noinspection PhpUndefinedClassInspection */
 		$com = new \COM("HNetCfg.NATUPnP");
diff --git a/src/pocketmine/utils/Internet.php b/src/pocketmine/utils/Internet.php
index 268e2784d..ebd704bda 100644
--- a/src/pocketmine/utils/Internet.php
+++ b/src/pocketmine/utils/Internet.php
@@ -32,10 +32,17 @@ use function curl_init;
 use function curl_setopt_array;
 use function explode;
 use function preg_match;
+use function socket_close;
+use function socket_connect;
+use function socket_create;
+use function socket_getsockname;
+use function socket_last_error;
+use function socket_strerror;
 use function strip_tags;
 use function strtolower;
 use function substr;
 use function trim;
+use const AF_INET;
 use const CURLINFO_HEADER_SIZE;
 use const CURLINFO_HTTP_CODE;
 use const CURLOPT_AUTOREFERER;
@@ -51,6 +58,8 @@ use const CURLOPT_RETURNTRANSFER;
 use const CURLOPT_SSL_VERIFYHOST;
 use const CURLOPT_SSL_VERIFYPEER;
 use const CURLOPT_TIMEOUT_MS;
+use const SOCK_DGRAM;
+use const SOL_UDP;
 
 class Internet{
 	public static $ip = false;
@@ -98,6 +107,28 @@ class Internet{
 		return false;
 	}
 
+	/**
+	 * Returns the machine's internal network IP address. If the machine is not behind a router, this may be the same
+	 * as the external IP.
+	 *
+	 * @return string
+	 * @throws InternetException
+	 */
+	public static function getInternalIP() : string{
+		$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
+		try{
+			if(!@socket_connect($sock, "8.8.8.8", 65534)){
+				throw new InternetException("Failed to get internal IP: " . trim(socket_strerror(socket_last_error($sock))));
+			}
+			if(!@socket_getsockname($sock, $name)){
+				throw new InternetException("Failed to get internal IP: " . trim(socket_strerror(socket_last_error($sock))));
+			}
+			return $name;
+		}finally{
+			socket_close($sock);
+		}
+	}
+
 	/**
 	 * GETs an URL using cURL
 	 * NOTE: This is a blocking operation and can take a significant amount of time. It is inadvisable to use this method on the main thread.
diff --git a/src/pocketmine/wizard/SetupWizard.php b/src/pocketmine/wizard/SetupWizard.php
index 398d25358..0cd3f1d1e 100644
--- a/src/pocketmine/wizard/SetupWizard.php
+++ b/src/pocketmine/wizard/SetupWizard.php
@@ -30,9 +30,9 @@ namespace pocketmine\wizard;
 use pocketmine\lang\BaseLang;
 use pocketmine\utils\Config;
 use pocketmine\utils\Internet;
+use pocketmine\utils\InternetException;
 use function base64_encode;
 use function fgets;
-use function gethostbyname;
 use function random_bytes;
 use function sleep;
 use function strtolower;
@@ -223,7 +223,11 @@ LICENSE;
 		if($externalIP === false){
 			$externalIP = "unknown (server offline)";
 		}
-		$internalIP = gethostbyname(trim(`hostname`));
+		try{
+			$internalIP = Internet::getInternalIP();
+		}catch(InternetException $e){
+			$internalIP = "unknown (" . $e->getMessage() . ")";
+		}
 
 		$this->error($this->lang->translateString("ip_warning", ["EXTERNAL_IP" => $externalIP, "INTERNAL_IP" => $internalIP]));
 		$this->error($this->lang->get("ip_confirm"));