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Send UDP identity packets without capabilities only if needed

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Instead of always doing so on MacOS, do it only when we get a
DatagramTooLargeError. On MacOS, the size is limited only for
broadcast but not for unicast.
This commit is contained in:
Albert Vaca Cintora 2023-06-25 22:50:47 +02:00
parent a04d9480a4
commit 17dcf80f2d
2 changed files with 27 additions and 39 deletions
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64
core/backends/lan/lanlinkprovider.cpp
View file

@ -149,41 +149,9 @@ void LanLinkProvider::broadcastUdpIdentityPacket()
qWarning() << "Not broadcasting UDP because KDECONNECT_DISABLE_UDP_BROADCAST is set";
return;
}
sendUdpIdentityPacket(getBroadcastAddresses());
}
void LanLinkProvider::sendUdpIdentityPacket(const QList<QHostAddress> &destinations)
{
qCDebug(KDECONNECT_CORE()) << "Broadcasting identity packet";
NetworkPacket np = KdeConnectConfig::instance().deviceInfo().toIdentityPacket();
np.set(QStringLiteral("tcpPort"), m_tcpPort);
#if defined(Q_OS_MAC) || defined(Q_OS_FREEBSD)
// On macOS and FreeBSD, the too large UDP packet (larger than MTU) causes
// incomplete transmission.
// We remove the capacitilities to reduce the discovery packet to the min
// MTU of the interfaces with broadcast feature.
int mtu = 1500;
for (const QNetworkInterface &iface : QNetworkInterface::allInterfaces()) {
if ((iface.flags() & QNetworkInterface::IsUp) && (iface.flags() & QNetworkInterface::IsRunning) && (iface.flags() & QNetworkInterface::CanBroadcast)) {
int ifaceMtu = iface.maximumTransmissionUnit();
if (ifaceMtu < mtu && ifaceMtu > 0) {
mtu = ifaceMtu;
}
}
}
QByteArray payload = np.serialize();
if (payload.length() > mtu) {
// First try to drop the less important outgoing capabilities
np.set(QStringLiteral("outgoingCapabilities"), QStringList());
payload = np.serialize();
}
if (payload.length() > mtu) {
// If still too large, drop the incoming capabilities
np.set(QStringLiteral("incomingCapabilities"), QStringList());
payload = np.serialize();
}
#endif
QList<QHostAddress> addresses = getBroadcastAddresses();
#if defined(Q_OS_WIN) || defined(Q_OS_FREEBSD)
// On Windows and FreeBSD we need to broadcast from every local IP address to reach all networks
@ -196,17 +164,18 @@ void LanLinkProvider::sendUdpIdentityPacket(const QList<QHostAddress> &destinati
if (sourceAddress.protocol() == QAbstractSocket::IPv4Protocol && sourceAddress != QHostAddress::LocalHost) {
qCDebug(KDECONNECT_CORE()) << "Broadcasting as" << sourceAddress;
sendSocket.bind(sourceAddress);
sendUdpPacket(sendSocket, np, destinations);
sendUdpIdentityPacket(sendSocket, addresses);
sendSocket.close();
}
}
}
}
#else
sendUdpPacket(m_udpSocket, np, destinations);
sendUdpIdentityPacket(addresses);
#endif
}
QList<QHostAddress> LanLinkProvider::getBroadcastAddresses()
{
const QStringList customDevices = KdeConnectConfig::instance().customDevices();
@ -230,12 +199,31 @@ QList<QHostAddress> LanLinkProvider::getBroadcastAddresses()
return destinations;
}
void LanLinkProvider::sendUdpPacket(QUdpSocket &socket, const NetworkPacket &np, const QList<QHostAddress> &addresses)
void LanLinkProvider::sendUdpIdentityPacket(const QList<QHostAddress> &addresses)
{
const QByteArray payload = np.serialize();
sendUdpIdentityPacket(m_udpSocket, addresses);
}
void LanLinkProvider::sendUdpIdentityPacket(QUdpSocket &socket, const QList<QHostAddress> &addresses)
{
DeviceInfo myDeviceInfo = KdeConnectConfig::instance().deviceInfo();
NetworkPacket identityPacket = myDeviceInfo.toIdentityPacket();
identityPacket.set(QStringLiteral("tcpPort"), m_tcpPort);
const QByteArray payload = identityPacket.serialize();
for (auto &address : addresses) {
socket.writeDatagram(payload, address, m_udpBroadcastPort);
qint64 bytes = socket.writeDatagram(payload, address, m_udpBroadcastPort);
if (bytes == -1 && socket.error() == QAbstractSocket::DatagramTooLargeError) {
// On macOS and FreeBSD, UDP broadcasts larger than MTU get dropped. See:
// https://opensource.apple.com/source/xnu/xnu-3789.1.32/bsd/netinet/ip_output.c.auto.html#:~:text=/*%20don%27t%20allow%20broadcast%20messages%20to%20be%20fragmented%20*/
// We remove the capabilities to reduce the size of the packet.
// This should only happen for broadcasts, so UDP packets sent from MDNS discoveries should still work.
qWarning() << "Identity packet to" << address << "got rejected because it was too large. Retrying without including the capabilities";
identityPacket.set(QStringLiteral("outgoingCapabilities"), QStringList());
identityPacket.set(QStringLiteral("incomingCapabilities"), QStringList());
const QByteArray smallPayload = identityPacket.serialize();
socket.writeDatagram(smallPayload, address, m_udpBroadcastPort);
}
}
}

2
core/backends/lan/lanlinkprovider.h
View file

@ -70,7 +70,7 @@ private:
void onNetworkConfigurationChanged(const QNetworkConfiguration &config);
void addLink(QSslSocket *socket, const DeviceInfo &deviceInfo);
QList<QHostAddress> getBroadcastAddresses();
void sendUdpPacket(QUdpSocket &socket, const NetworkPacket &np, const QList<QHostAddress> &addresses);
void sendUdpIdentityPacket(QUdpSocket &socket, const QList<QHostAddress> &addresses);
void broadcastUdpIdentityPacket();
Server *m_server;