From ea352a640a97b61b0749b6251a21def06fbc7e0b Mon Sep 17 00:00:00 2001
From: mykola2312 <49044616+mykola2312@users.noreply.github.com>
Date: Wed, 16 Mar 2022 16:32:15 +0200
Subject: [PATCH] Add loopback <-> external IP translation

---
 announce.php | 10 +++++++++-
 network.php  | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 network.php

diff --git a/announce.php b/announce.php
index 4ef9586..bb55ea3 100644
--- a/announce.php
+++ b/announce.php
@@ -1,5 +1,6 @@
 <?php
 require("../php/config.php");
+require("network.php");
 $DB_NAME = "torrent";
 $ANN_MIN_INTERVAL = 15;
 $ANN_INTERVAL = 60;
@@ -106,6 +107,8 @@ if (isset($_GET["port"])) {
     bad_request("No port");
 }
 
+$externalIp = get_external_ip();
+
 $date = new DateTime("now");
 $now = $date->format('Y-m-d H:i:s');
 
@@ -114,7 +117,7 @@ $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
 
 $stmt = $conn->prepare("REPLACE INTO `tracker` (info_hash, ip, port, update_time) VALUES (:info_hash, :ip, :port, :update_time)");
 $stmt->bindValue(":info_hash", $hash, PDO::PARAM_STR);
-$stmt->bindValue(":ip", $ip, PDO::PARAM_STR);
+$stmt->bindValue(":ip", is_loopback($ip) ? $externalIp : $ip, PDO::PARAM_STR);
 $stmt->bindValue(":port", $port, PDO::PARAM_INT);
 $stmt->bindValue(":update_time", $now, PDO::PARAM_STR);
 $stmt->execute();
@@ -127,6 +130,11 @@ $stmt->execute();
 $stmt->bindColumn(1, $peerIp);
 $stmt->bindColumn(2, $peerPort);
 while ($stmt->fetch(PDO::FETCH_BOUND)) {
+	if (is_loopback($peerIp) && !is_loopback($ip)) {
+		$peerIp = $externalIp;
+	} else if ($peerIp == $externalIp && is_loopback($ip)) {
+		$peerIp = ip4_loopback();
+	}
     $peers .= pack("Nn", inet_pton($peerIp), $peerPort);
 }
 
diff --git a/network.php b/network.php
new file mode 100644
index 0000000..91e2f57
--- /dev/null
+++ b/network.php
@@ -0,0 +1,47 @@
+<?php
+
+function ip4_loopback()
+{
+    return inet_pton("127.0.0.1");
+}
+
+function ip6_loopback()
+{
+    return inet_pton("::1");
+}
+
+function ip_address($ip)
+{
+    $ipAddr = inet_pton($ip);
+    if ($ipAddr == false) {
+        throw new Exception("invalid ip address");
+    }
+
+    return $ipAddr;
+}
+
+function is_loopback($ip)
+{
+    $ipAddr = ip_address($ip);
+    return $ipAddr == ip4_loopback() || $ipAddr == ip6_loopback();
+}
+
+function get_external_ip()
+{
+    $ch = curl_init();
+    curl_setopt($ch, CURLOPT_URL, "http://ident.me");
+    curl_setopt($ch, CURLOPT_PORT, 80);
+    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
+    $result = curl_exec($ch);
+    curl_close($ch);
+
+    if (result == false) {
+        throw new Exception("request to ident.me failed");
+    } else if (inet_pton($result) == false) {
+        throw new Exception("ident.me respond invalid ip");
+    }
+
+    return $result;
+}
+
+?>
\ No newline at end of file