Adjust the socket address family before bind()/connect()/sendto()

If our socket is already of a given type (probably due to a previous
call to bind()), then constrain the incoming target address to be of the
same family. On some OSs, trying to send or connect to an IPv4 address
from an IPv6 socket will fail with EINVAL, even if the socket is not in
"v6only" mode.

bind() can't be called after already being bound, but the function can
still be called on a socket created by the user and passed on with
setSocketDescriptor().

Change-Id: I209a1f8d0c782c6b6de2b39ea4cfad74d63f3293
Reviewed-by: Richard J. Moore <rich@kde.org>

src/network/socket/qnativesocketengine.cpp

@@ -281,6 +281,38 @@ void QNativeSocketEnginePrivate::setError(QAbstractSocket::SocketError error, Er
     }
 }
 
+/*!
+    \internal
+
+    Adjusts the incoming \a address family to match the currently bound address
+    (if any). This function will convert v4-mapped IPv6 addresses to IPv4 and
+    vice-versa. All other address types and values will be left unchanged.
+ */
+QHostAddress QNativeSocketEnginePrivate::adjustAddressProtocol(const QHostAddress &address) const
+{
+    QAbstractSocket::NetworkLayerProtocol targetProtocol = socketProtocol;
+    if (Q_LIKELY(targetProtocol == QAbstractSocket::UnknownNetworkLayerProtocol))
+        return address;
+
+    QAbstractSocket::NetworkLayerProtocol sourceProtocol = address.protocol();
+
+    if (targetProtocol == QAbstractSocket::AnyIPProtocol)
+        targetProtocol = QAbstractSocket::IPv6Protocol;
+    if (targetProtocol == QAbstractSocket::IPv6Protocol && sourceProtocol == QAbstractSocket::IPv4Protocol) {
+        // convert to IPv6 v4-mapped address. This always works
+        return QHostAddress(address.toIPv6Address());
+    }
+
+    if (targetProtocol == QAbstractSocket::IPv4Protocol && sourceProtocol == QAbstractSocket::IPv6Protocol) {
+        // convert to IPv4 if the source is a v4-mapped address
+        quint32 ip4 = address.toIPv4Address();
+        if (ip4)
+            return QHostAddress(ip4);
+    }
+
+    return address;
+}
+
 bool QNativeSocketEnginePrivate::checkProxy(const QHostAddress &address)
 {
     if (address.isLoopback())
@@ -506,7 +538,7 @@ bool QNativeSocketEngine::connectToHost(const QHostAddress &address, quint16 por
 
     d->peerAddress = address;
     d->peerPort = port;
-    bool connected = d->nativeConnect(address, port);
+    bool connected = d->nativeConnect(d->adjustAddressProtocol(address), port);
     if (connected)
         d->fetchConnectionParameters();
 
@@ -566,7 +598,7 @@ bool QNativeSocketEngine::bind(const QHostAddress &address, quint16 port)
 
     Q_CHECK_STATE(QNativeSocketEngine::bind(), QAbstractSocket::UnconnectedState, false);
 
-    if (!d->nativeBind(address, port))
+    if (!d->nativeBind(d->adjustAddressProtocol(address), port))
         return false;
 
     d->fetchConnectionParameters();
@@ -776,7 +808,7 @@ qint64 QNativeSocketEngine::writeDatagram(const char *data, qint64 size,
     Q_D(QNativeSocketEngine);
     Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::writeDatagram(), -1);
     Q_CHECK_TYPE(QNativeSocketEngine::writeDatagram(), QAbstractSocket::UdpSocket, -1);
-    return d->nativeSendDatagram(data, size, host, port);
+    return d->nativeSendDatagram(data, size, d->adjustAddressProtocol(host), port);
 }
 
 /*!

src/network/socket/qnativesocketengine_p.h

@@ -232,6 +232,7 @@ public:
     };
 
     void setError(QAbstractSocket::SocketError error, ErrorString errorString) const;
+    QHostAddress adjustAddressProtocol(const QHostAddress &address) const;
 
     // native functions
     int option(QNativeSocketEngine::SocketOption option) const;