Merge pull request #1092 from hoffie/fix-633-stop-cloudflare-traffic

Server: Stop opening a TCP connection for external IP detection

ChangeLog

@@ -44,6 +44,9 @@
 
 - Avoid screen from sleeping or starting screen saver for Mac (#834)
 
+- stop sending traffic to CloudFlare as part of the external IP detection
+  logic (#633, #1092), suggested by atsampson, coded by hoffie
+
 
 
 ### 3.6.2 (2020-12-12) ###

src/global.h

@@ -109,10 +109,12 @@ LED bar:      lbr
 #define SOFTWARE_MANUAL_URL              "https://jamulus.io/wiki/Software-Manual"
 
 // determining server internal address uses well-known host and port
-// (You can change the service used here to something like Cloudflare (1.1.1.1), Google DNS (8.8.8.8), or something else reliable)
-#define WELL_KNOWN_HOST                  "1.1.1.1" // CloudFlare
-#define WELL_KNOWN_PORT                  53        // DNS
-#define IP_LOOKUP_TIMEOUT                500       // ms
+// We just need a valid, public Internet IP here. We will not send any
+// traffic there as we will only set up an UDP socket without sending any
+// data.
+#define WELL_KNOWN_HOST                  "1.1.1.1"           // CloudFlare
+#define WELL_KNOWN_PORT                  DEFAULT_PORT_NUMBER
+#define IP_LOOKUP_TIMEOUT                500                 // ms
 
 // system sample rate (the sound card and audio coder works on this sample rate)
 #define SYSTEM_SAMPLE_RATE_HZ            48000 // Hz

src/serverlist.cpp

@@ -53,6 +53,7 @@ CServerListManager::CServerListManager ( const quint16  iNPortNum,
         // User-supplied --serverpublicip
         qhaServerPublicIP = QHostAddress ( strServerPublicIP );
     }
+    qDebug() << "Using" << qhaServerPublicIP.toString() << "as external IP.";
     SlaveCurLocalHostAddress = CHostAddress ( qhaServerPublicIP, iNPortNum );
 
     // prepare the server info information

src/util.cpp

@@ -1025,7 +1025,10 @@ bool NetworkUtil::ParseNetworkAddress ( QString       strAddress,
 
 CHostAddress NetworkUtil::GetLocalAddress()
 {
-    QTcpSocket socket;
+    QUdpSocket socket;
+    // As we are using UDP, the connectToHost() does not generate any traffic at all.
+    // We just require a socket which is pointed towards the Internet in
+    // order to find out the IP of our own external interface:
     socket.connectToHost ( WELL_KNOWN_HOST, WELL_KNOWN_PORT );
 
     if ( socket.waitForConnected ( IP_LOOKUP_TIMEOUT ) )

src/util.h

@@ -25,7 +25,7 @@
 #pragma once
 
 #include <QCoreApplication>
-#include <QTcpSocket>
+#include <QUdpSocket>
 #include <QHostAddress>
 #include <QHostInfo>
 #ifndef HEADLESS