NOISSUE Resolve minecraft server using DNS SRV

api/logic/launch/steps/LookupServerAddress.cpp

@@ -0,0 +1,95 @@
+#include "LookupServerAddress.h"
+
+#include <launch/LaunchTask.h>
+
+LookupServerAddress::LookupServerAddress(LaunchTask *parent) :
+    LaunchStep(parent), m_dnsLookup(new QDnsLookup(this))
+{
+    connect(m_dnsLookup, &QDnsLookup::finished, this, &LookupServerAddress::on_dnsLookupFinished);
+
+    m_dnsLookup->setType(QDnsLookup::SRV);
+}
+
+void LookupServerAddress::setLookupAddress(const QString &lookupAddress)
+{
+    m_lookupAddress = lookupAddress;
+    m_dnsLookup->setName(QString("_minecraft._tcp.%1").arg(lookupAddress));
+}
+
+void LookupServerAddress::setPort(quint16 port)
+{
+    m_port = port;
+}
+
+void LookupServerAddress::setOutputAddressPtr(MinecraftServerTargetPtr output)
+{
+    m_output = std::move(output);
+}
+
+bool LookupServerAddress::abort()
+{
+    m_dnsLookup->abort();
+    emitFailed("Aborted");
+    return true;
+}
+
+void LookupServerAddress::executeTask()
+{
+    m_dnsLookup->lookup();
+}
+
+void LookupServerAddress::on_dnsLookupFinished()
+{
+    if (isFinished())
+    {
+        // Aborted
+        return;
+    }
+
+    if (m_dnsLookup->error() != QDnsLookup::NoError)
+    {
+        emit logLine(QString("Failed to resolve server address (this is NOT an error!) %1: %2\n")
+            .arg(m_dnsLookup->name(), m_dnsLookup->errorString()), MessageLevel::MultiMC);
+        resolve(m_lookupAddress, m_port); // Technically the task failed, however, we don't abort the launch
+                                                      // and leave it up to minecraft to fail (or maybe not) when connecting
+        return;
+    }
+
+    const auto records = m_dnsLookup->serviceRecords();
+    if (records.empty())
+    {
+        emit logLine(
+                QString("Failed to resolve server address %1: the DNS lookup succeeded, but no records were returned.\n")
+                .arg(m_dnsLookup->name()), MessageLevel::Warning);
+        resolve(m_lookupAddress, m_port); // Technically the task failed, however, we don't abort the launch
+                                                      // and leave it up to minecraft to fail (or maybe not) when connecting
+        return;
+    }
+
+    const auto &firstRecord = records.at(0);
+
+    if (firstRecord.port() != m_port && m_port != 0)
+    {
+        emit logLine(
+                QString("DNS record for %1 suggested %2 as server port, but user supplied %3. Using user override,"
+                        " but the port may be wrong!\n").arg(m_dnsLookup->name(), QString::number(firstRecord.port()), QString::number(m_port)),
+                        MessageLevel::Warning);
+    }
+    else if (m_port == 0)
+    {
+        m_port = firstRecord.port();
+    }
+
+    emit logLine(QString("Resolved server address %1 to %2 with port %3\n").arg(
+            m_dnsLookup->name(), firstRecord.target(), QString::number(m_port)),MessageLevel::MultiMC);
+    resolve(firstRecord.target(), m_port);
+}
+
+void LookupServerAddress::resolve(const QString &address, quint16 port)
+{
+    m_output->address = address;
+    m_output->port = port;
+
+    emitSucceeded();
+    m_dnsLookup->deleteLater();
+}

api/logic/launch/steps/LookupServerAddress.h

@@ -0,0 +1,51 @@
+/* Copyright 2013-2021 MultiMC Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <launch/LaunchStep.h>
+#include <QObjectPtr.h>
+#include <QDnsLookup>
+
+#include "minecraft/launch/MinecraftServerTarget.h"
+
+class LookupServerAddress: public LaunchStep {
+Q_OBJECT
+public:
+    explicit LookupServerAddress(LaunchTask *parent);
+    virtual ~LookupServerAddress() {};
+
+    virtual void executeTask();
+    virtual bool abort();
+    virtual bool canAbort() const
+    {
+        return true;
+    }
+
+    void setLookupAddress(const QString &lookupAddress);
+    void setPort(quint16 port);
+    void setOutputAddressPtr(MinecraftServerTargetPtr output);
+
+private slots:
+    void on_dnsLookupFinished();
+
+private:
+    void resolve(const QString &address, quint16 port);
+
+    QDnsLookup *m_dnsLookup;
+    QString m_lookupAddress;
+    quint16 m_port;
+    MinecraftServerTargetPtr m_output;
+};