Implementing link priorities

Now that devices can potentially be connected via both network and bluetooth simultaneously we should prioritise connections over the highest performing link (probably wifi/network). To this end the
m_deviceLinks are now sorted based on priority with the fastest links first; this means that when Device::sendPacket is scheduling to send a packet, it should always use the fastest link first.

core/backends/bluetooth/bluetoothlinkprovider.h

@@ -37,6 +37,11 @@ public:
         return QStringLiteral("BluetoothLinkProvider");
     }
 
+    int priority() override
+    {
+        return 10;
+    }
+
 public Q_SLOTS:
     virtual void onNetworkChange() override;
     virtual void onStart() override;

core/backends/devicelink.cpp

@@ -14,6 +14,7 @@ DeviceLink::DeviceLink(const QString &deviceId, LinkProvider *parent)
     connect(this, &QObject::destroyed, [this, deviceId, parent]() {
         parent->onLinkDestroyed(deviceId, this);
     });
+    this->priorityFromProvider = parent->priority();
 }
 
 #include "moc_devicelink.cpp"

core/backends/devicelink.h

@@ -25,10 +25,18 @@ public:
         return deviceInfo().id;
     }
 
+    int priority() const
+    {
+        return priorityFromProvider;
+    }
+
     virtual bool sendPacket(NetworkPacket &np) = 0;
 
     virtual DeviceInfo deviceInfo() const = 0;
 
+private:
+    int priorityFromProvider;
+
 Q_SIGNALS:
     void receivedPacket(const NetworkPacket &np);
 };

core/backends/lan/lanlinkprovider.h

@@ -43,6 +43,11 @@ public:
         return QStringLiteral("LanLinkProvider");
     }
 
+    int priority() override
+    {
+        return 20;
+    }
+
     void sendUdpIdentityPacket(const QList<QHostAddress> &addresses);
 
     static void configureSslSocket(QSslSocket *socket, const QString &deviceId, bool isDeviceTrusted);

core/backends/linkprovider.h

@@ -22,6 +22,7 @@ public:
     LinkProvider();
 
     virtual QString name() = 0;
+    virtual int priority() = 0;
 
 public Q_SLOTS:
     virtual void onStart() = 0;

core/backends/loopback/loopbacklinkprovider.h

@@ -22,6 +22,10 @@ public:
     {
         return QStringLiteral("LoopbackLinkProvider");
     }
+    int priority() override
+    {
+        return 0;
+    }
 
     void onStart() override;
     void onStop() override;

core/daemon.cpp

@@ -158,7 +158,7 @@ void Daemon::onNewDeviceLink(DeviceLink *link)
 {
     QString id = link->deviceId();
 
-    // qCDebug(KDECONNECT_CORE) << "Device discovered" << id << "via" << dl->name();
+    qCDebug(KDECONNECT_CORE) << "Device discovered" << id << "via link with priority" << link->priority();
 
     if (d->m_devices.contains(id)) {
         qCDebug(KDECONNECT_CORE) << "It is a known device" << link->deviceInfo().name;

core/device.cpp

@@ -276,6 +276,10 @@ void Device::addLink(DeviceLink *link)
 
     d->m_deviceLinks.append(link);
 
+    std::sort(d->m_deviceLinks.begin(), d->m_deviceLinks.end(), [](DeviceLink *a, DeviceLink *b) {
+        return a->priority() > b->priority();
+    });
+
     connect(link, &QObject::destroyed, this, &Device::linkDestroyed);
     connect(link, &DeviceLink::receivedPacket, this, &Device::privateReceivedPacket);