Implement detection of local IPv6 addresses

app/backend/computermanager.cpp

@@ -878,7 +878,7 @@ private:
 
                 // If this wasn't added via mDNS but it is a RFC 1918 IPv4 address and not a VPN,
                 // go ahead and do the STUN request now to populate an external address.
-                if (!m_Mdns && addressIsSiteLocalV4 && !newComputer->isReachableOverVpn()) {
+                if (!m_Mdns && addressIsSiteLocalV4 && newComputer->getActiveAddressReachability() != NvComputer::RI_VPN) {
                     quint32 addr;
                     int err = LiFindExternalAddressIP4("stun.moonlight-stream.org", 3478, &addr);
                     if (err == 0) {

app/backend/nvcomputer.cpp

@@ -293,7 +293,7 @@ bool NvComputer::wake() const
     return success;
 }
 
-bool NvComputer::isReachableOverVpn() const
+NvComputer::ReachabilityType NvComputer::getActiveAddressReachability() const
 {
     NvAddress copyOfActiveAddress;
 
@@ -301,7 +301,7 @@ bool NvComputer::isReachableOverVpn() const
         QReadLocker readLocker(&lock);
 
         if (activeAddress.isNull()) {
-            return false;
+            return ReachabilityType::RI_UNKNOWN;
         }
 
         // Grab a copy of the active address to avoid having to hold
@@ -332,48 +332,55 @@ bool NvComputer::isReachableOverVpn() const
                     if (nic.type() == QNetworkInterface::Virtual ||
                             nic.type() == QNetworkInterface::Ppp) {
                         // Treat PPP and virtual interfaces as likely VPNs
-                        return true;
+                        return ReachabilityType::RI_VPN;
                     }
 
                     if (nic.maximumTransmissionUnit() != 0 && nic.maximumTransmissionUnit() < 1500) {
                         // Treat MTUs under 1500 as likely VPNs
-                        return true;
+                        return ReachabilityType::RI_VPN;
                     }
 #endif
 
                     if (nic.flags() & QNetworkInterface::IsPointToPoint) {
                         // Treat point-to-point links as likely VPNs.
                         // This check detects OpenVPN on Unix-like OSes.
-                        return true;
+                        return ReachabilityType::RI_VPN;
                     }
 
                     if (nic.hardwareAddress().startsWith("00:FF", Qt::CaseInsensitive)) {
                         // OpenVPN TAP interfaces have a MAC address starting with 00:FF on Windows
-                        return true;
+                        return ReachabilityType::RI_VPN;
                     }
 
                     if (nic.humanReadableName().startsWith("ZeroTier")) {
                         // ZeroTier interfaces always start with "ZeroTier"
-                        return true;
+                        return ReachabilityType::RI_VPN;
                     }
 
                     if (nic.humanReadableName().contains("VPN")) {
-                        // This one is just a final heuristic if all else fails
+                        // This one is just a final VPN heuristic if all else fails
-                        return true;
+                        return ReachabilityType::RI_VPN;
                     }
 
-                    // Didn't meet any of our VPN heuristics
+                    // Didn't meet any of our VPN heuristics. Let's see if it's on-link.
-                    return false;
+                    Q_ASSERT(addr.prefixLength() >= 0);
+                    if (addr.prefixLength() >= 0 && s.localAddress().isInSubnet(addr.ip(), addr.prefixLength())) {
+                        return ReachabilityType::RI_LAN;
+                    }
+
+                    // Default to unknown if nothing else matched
+                    return ReachabilityType::RI_UNKNOWN;
                 }
             }
         }
 
         qWarning() << "No match found for address:" << s.localAddress();
-        return false;
+        return ReachabilityType::RI_UNKNOWN;
     }
     else {
         // If we fail to connect, just pretend that it's not a VPN
-        return false;
+        qWarning() << "Unable to check for reachability within 3 seconds";
+        return ReachabilityType::RI_UNKNOWN;
     }
 }
 

app/backend/nvcomputer.h

@@ -35,8 +35,15 @@ public:
     bool
     wake() const;
 
-    bool
+    enum ReachabilityType
-    isReachableOverVpn() const;
+    {
+        RI_UNKNOWN,
+        RI_LAN,
+        RI_VPN,
+    };
+
+    ReachabilityType
+    getActiveAddressReachability() const;
 
     QVector<NvAddress>
     uniqueAddresses() const;

app/streaming/session.cpp

@@ -1227,17 +1227,27 @@ bool Session::startConnectionAsync()
                     m_Preferences->packetSize);
     }
     else {
-        // isReachableOverVpn() does network I/O, so we only attempt to check
+        // Use 1392 byte video packets by default
-        // VPN reachability if we've already contacted the PC successfully
+        m_StreamConfig.packetSize = 1392;
-        if (m_Computer->isReachableOverVpn()) {
+
-            // It looks like our route to this PC is over a VPN.
+        // getActiveAddressReachability() does network I/O, so we only attempt to check
+        // reachability if we've already contacted the PC successfully.
+        switch (m_Computer->getActiveAddressReachability()) {
+        case NvComputer::RI_LAN:
+            // This address is on-link, so treat it as a local address
+            // even if it's not in RFC 1918 space or it's an IPv6 address.
+            m_StreamConfig.streamingRemotely = STREAM_CFG_LOCAL;
+            break;
+        case NvComputer::RI_VPN:
+            // It looks like our route to this PC is over a VPN, so cap at 1024 bytes.
             // Treat it as remote even if the target address is in RFC 1918 address space.
             m_StreamConfig.streamingRemotely = STREAM_CFG_REMOTE;
             m_StreamConfig.packetSize = 1024;
-        }
+            break;
-        else {
+        default:
+            // If we don't have reachability info, let moonlight-common-c decide.
             m_StreamConfig.streamingRemotely = STREAM_CFG_AUTO;
-            m_StreamConfig.packetSize = 1392;
+            break;
         }
     }