QDnsLookup: add support for setting the port number of the server

I couldn't make my Windows 10 or 11 query a non-standard port. It kept
complaining about "The parameter is incorrect.", so as a result the unit
test doesn't actually test the new feature there. I can't find a single
example of this on the Internet; my speculation is that the backend API
that DnsQueryEx uses does not support setting port numbers
(DnsQuery_{A,W} didn't offer that option).

[ChangeLog][QtNetwork][QDnsLookup] Added setNameserverPort().

Change-Id: I3e3bfef633af4130a03afffd175d60a581cc0a9c
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

2 files changed, 95 insertions, 6 deletions

diff --git a/tests/auto/network/kernel/qdnslookup/tst_qdnslookup.cpp b/tests/auto/network/kernel/qdnslookup/tst_qdnslookup.cpp
index 1d0da9dbe3..568f0d84b8 100644
--- a/tests/auto/network/kernel/qdnslookup/tst_qdnslookup.cpp
+++ b/tests/auto/network/kernel/qdnslookup/tst_qdnslookup.cpp
@@ -7,7 +7,11 @@
 #include <QSignalSpy>
 
 #include <QtNetwork/QDnsLookup>
+
+#include <QtCore/QRandomGenerator>
 #include <QtNetwork/QHostAddress>
+#include <QtNetwork/QNetworkDatagram>
+#include <QtNetwork/QUdpSocket>
 
 using namespace Qt::StringLiterals;
 static const int Timeout = 15000; // 15s
@@ -35,6 +39,7 @@ private slots:
 
     void lookupReuse();
     void lookupAbortRetry();
+    void setNameserverLoopback();
     void bindingsAndProperties();
 };
 
@@ -351,6 +356,62 @@ void tst_QDnsLookup::lookupAbortRetry()
     QCOMPARE(lookup.hostAddressRecords().first().value(), QHostAddress("2001:db8::1"));
 }
 
+void tst_QDnsLookup::setNameserverLoopback()
+{
+#ifdef Q_OS_WIN
+    // Windows doesn't like sending DNS requests to ports other than 53, so
+    // let's try it first.
+    constexpr quint16 DesiredPort = 53;
+#else
+    // Trying to bind to port 53 will fail on Unix systems unless this test is
+    // run as root, so we try mDNS's port (to help decoding in a packet capture).
+    constexpr quint16 DesiredPort = 5353;   // mDNS
+#endif
+    // random loopback address so multiple copies of this test can run
+    QHostAddress desiredAddress(0x7f000000 | QRandomGenerator::system()->bounded(0xffffff));
+
+    QUdpSocket server;
+    if (!server.bind(desiredAddress, DesiredPort)) {
+        // port in use, try a random one
+        server.bind(QHostAddress::LocalHost, 0);
+    }
+    QCOMPARE(server.state(), QUdpSocket::BoundState);
+
+    QDnsLookup lookup(QDnsLookup::Type::A, u"somelabel.somedomain"_s);
+    QSignalSpy spy(&lookup, SIGNAL(finished()));
+    lookup.setNameserver(server.localAddress(), server.localPort());
+
+    // QDnsLookup is threaded, so we can answer on the main thread
+    QObject::connect(&server, &QUdpSocket::readyRead,
+                     &QTestEventLoop::instance(), &QTestEventLoop::exitLoop);
+    QObject::connect(&lookup, &QDnsLookup::finished,
+                     &QTestEventLoop::instance(), &QTestEventLoop::exitLoop);
+    lookup.lookup();
+    QTestEventLoop::instance().enterLoop(5);
+    QVERIFY(!QTestEventLoop::instance().timeout());
+    QVERIFY2(spy.isEmpty(), qPrintable(lookup.errorString()));
+
+    QNetworkDatagram dgram = server.receiveDatagram();
+    QByteArray data = dgram.data();
+    QCOMPARE_GT(data.size(), HeaderSize);
+
+    quint8 opcode = (quint8(data.at(3)) >> 4) & 0xF;
+    QCOMPARE(opcode, 0);        // standard query
+
+    // send an NXDOMAIN reply to release the lookup thread
+    QByteArray reply = data;
+    reply[2] = 0x80;    // header->qr = true;
+    reply[3] = 3;       // header->rcode = NXDOMAIN;
+    server.writeDatagram(dgram.makeReply(reply));
+    server.close();
+
+    // now check that the QDnsLookup finished
+    QTestEventLoop::instance().enterLoop(5);
+    QVERIFY(!QTestEventLoop::instance().timeout());
+    QCOMPARE(spy.size(), 1);
+    QCOMPARE(lookup.error(), QDnsLookup::NotFoundError);
+}
+
 void tst_QDnsLookup::bindingsAndProperties()
 {
     QDnsLookup lookup;
@@ -383,14 +444,23 @@ void tst_QDnsLookup::bindingsAndProperties()
     QProperty<QHostAddress> nameserverProp;
     lookup.bindableNameserver().setBinding(Qt::makePropertyBinding(nameserverProp));
     const QSignalSpy nameserverChangeSpy(&lookup, &QDnsLookup::nameserverChanged);
+    const QSignalSpy nameserverPortChangeSpy(&lookup, &QDnsLookup::nameserverPortChanged);
 
     nameserverProp = QHostAddress::LocalHost;
     QCOMPARE(nameserverChangeSpy.size(), 1);
+    QCOMPARE(nameserverPortChangeSpy.size(), 0);
     QCOMPARE(lookup.nameserver(), QHostAddress::LocalHost);
 
     nameserverProp.setBinding(lookup.bindableNameserver().makeBinding());
     lookup.setNameserver(QHostAddress::Any);
     QCOMPARE(nameserverProp.value(), QHostAddress::Any);
+    QCOMPARE(nameserverChangeSpy.size(), 2);
+    QCOMPARE(nameserverPortChangeSpy.size(), 0);
+
+    lookup.setNameserver(QHostAddress::LocalHostIPv6, 10053);
+    QCOMPARE(nameserverProp.value(), QHostAddress::LocalHostIPv6);
+    QCOMPARE(nameserverChangeSpy.size(), 3);
+    QCOMPARE(nameserverPortChangeSpy.size(), 1);
 }
 
 QTEST_MAIN(tst_QDnsLookup)
diff --git a/tests/manual/qdnslookup/main.cpp b/tests/manual/qdnslookup/main.cpp
index 3ddf84063e..19aeeeb4b8 100644
--- a/tests/manual/qdnslookup/main.cpp
+++ b/tests/manual/qdnslookup/main.cpp
@@ -6,6 +6,7 @@
 #include <QtCore/QElapsedTimer>
 #include <QtCore/QMetaEnum>
 #include <QtCore/QTimer>
+#include <QtCore/QUrl>
 #include <QtNetwork/QHostAddress>
 #include <QtNetwork/QHostInfo>
 #include <QtNetwork/QDnsLookup>
@@ -38,6 +39,24 @@ static int showHelp(const char *argv0, int exitcode)
     return exitcode;
 }
 
+static auto parseServerAddress(QString server)
+{
+    struct R {
+        QHostAddress address;
+        int port = -1;
+    } r;
+
+    // let's use QUrl to help us
+    QUrl url;
+    url.setAuthority(server);
+    if (!url.isValid() || !url.userInfo().isNull())
+        return r;           // failed
+
+    r.port = url.port();
+    r.address.setAddress(url.host());
+    return r;
+}
+
 static void printAnswers(const QDnsLookup &lookup)
 {
     printf("\n;; ANSWER:\n");
@@ -96,7 +115,7 @@ static void printResults(const QDnsLookup &lookup, QElapsedTimer::Duration durat
 
     printf("\n;; Query time: %lld ms\n", qint64(duration_cast<milliseconds>(duration).count()));
     if (QHostAddress server = lookup.nameserver(); !server.isNull())
-        printf(";; SERVER: %s#53\n", qPrintable(server.toString()));
+        printf(";; SERVER: %s#%d\n", qPrintable(server.toString()), lookup.nameserverPort());
 }
 
 int main(int argc, char *argv[])
@@ -138,15 +157,15 @@ int main(int argc, char *argv[])
 
     QDnsLookup lookup(type, domain);
     if (!server.isEmpty()) {
-        QHostAddress addr(server);
-        if (addr.isNull())
-            addr = QHostInfo::fromName(server).addresses().value(0);
-        if (addr.isNull()) {
+        auto addr = parseServerAddress(server);
+        if (addr.address.isNull()) {
             fprintf(stderr, "%s: could not parse name server address '%s'\n",
                     argv[0], qPrintable(server));
             return EXIT_FAILURE;
         }
-        lookup.setNameserver(addr);
+        lookup.setNameserver(addr.address);
+        if (addr.port > 0)
+            lookup.setNameserverPort(addr.port);
     }
 
     // execute the lookup