Long live QNetworkDatagram!

This commit adds a new class called QNetworkDatagram that encapsulates
the IP packet header and UDP/IP stack metadata along with the actual
payload data. It can be used for both receiving as well as sending data.

It's called QNetworkDatagram so it can be used by QSctpSocket too, when
that lands.

[ChangeLog][QtNetwork] Added QNetworkDatagram class, along with new
function receiveDatagram in QUdpSocket that returns it and an overload
to writeDatagram that can accept it.

Change-Id: Iee8cbc07c4434ce9b560ffff13ca467f425ddc3d
Reviewed-by: Alex Trotsenko <alex1973tr@gmail.com>
Reviewed-by: Richard J. Moore <rich@kde.org>

9 files changed, 783 insertions, 19 deletions

diff --git a/src/network/doc/snippets/code/src_network_socket_qudpsocket.cpp b/src/network/doc/snippets/code/src_network_socket_qudpsocket.cpp
index 9e491f802e..a98e31b10b 100644
--- a/src/network/doc/snippets/code/src_network_socket_qudpsocket.cpp
+++ b/src/network/doc/snippets/code/src_network_socket_qudpsocket.cpp
@@ -61,14 +61,7 @@ void Server::initSocket()
 void Server::readPendingDatagrams()
 {
     while (udpSocket->hasPendingDatagrams()) {
-        QByteArray datagram;
-        datagram.resize(udpSocket->pendingDatagramSize());
-        QHostAddress sender;
-        quint16 senderPort;
-
-        udpSocket->readDatagram(datagram.data(), datagram.size(),
-                                &sender, &senderPort);
-
+        QNetworkDatagram datagram = udpSocket->receiveDatagram();
         processTheDatagram(datagram);
     }
 }
diff --git a/src/network/kernel/kernel.pri b/src/network/kernel/kernel.pri
index b50ca0d1c4..1c97c53cc7 100644
--- a/src/network/kernel/kernel.pri
+++ b/src/network/kernel/kernel.pri
@@ -11,6 +11,7 @@ HEADERS += kernel/qauthenticator.h \
            kernel/qhostaddress_p.h \
            kernel/qhostinfo.h \
            kernel/qhostinfo_p.h \
+           kernel/qnetworkdatagram.h \
            kernel/qnetworkdatagram_p.h \
            kernel/qnetworkinterface.h \
            kernel/qnetworkinterface_p.h \
@@ -22,9 +23,10 @@ SOURCES += kernel/qauthenticator.cpp \
            kernel/qdnslookup.cpp \
            kernel/qhostaddress.cpp \
            kernel/qhostinfo.cpp \
-           kernel/qurlinfo.cpp \
+           kernel/qnetworkdatagram.cpp \
+           kernel/qnetworkinterface.cpp \
            kernel/qnetworkproxy.cpp \
-	   kernel/qnetworkinterface.cpp
+           kernel/qurlinfo.cpp
 
 unix {
     !integrity: SOURCES += kernel/qdnslookup_unix.cpp
diff --git a/src/network/kernel/qnetworkdatagram.cpp b/src/network/kernel/qnetworkdatagram.cpp
new file mode 100644
index 0000000000..7a1b168b74
--- /dev/null
+++ b/src/network/kernel/qnetworkdatagram.cpp
@@ -0,0 +1,535 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 Intel Corporation.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtNetwork module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qnetworkdatagram.h"
+#include "qnetworkdatagram_p.h"
+
+#ifndef QT_NO_UDPSOCKET
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QNetworkDatagram
+    \brief The QNetworkDatagram class provides the data and matadata of a UDP datagram.
+    \since 5.7
+    \ingroup network
+    \inmodule QtNetwork
+    \reentrant
+
+    QNetworkDatagram can be used with the \l QUdpSocket class to represent the full
+    information contained in a UDP (User Datagram Protocol) datagram.
+    QNetworkDatagram encapsulates the following information of a datagram:
+    \list
+      \li the payload data;
+      \li the sender address and port number;
+      \li the destination address and port number;
+      \li the remaining hop count limit (on IPv4, this field is usually called "time to live" - TTL);
+      \li the network interface index the datagram was received on or to be sent on.
+    \endlist
+
+    QUdpSocket will try to match a common behavior as much as possible on all
+    operating systems, but not all of the metadata above can be obtained in
+    some operating systems. Metadata that cannot be set on the datagram when
+    sending with QUdpSocket::writeDatagram() will be silently discarded.
+
+    Upon reception, the senderAddress() and senderPort() properties contain the
+    address and port of the peer that sent the datagram, while
+    destinationAddress() and destinationPort() contain the target that was
+    contained in the datagram. That is usually an address local to the current
+    machine, but it can also be an IPv4 broadcast address (such as
+    "255.255.255.255") or an IPv4 or IPv6 multicast address. Applications may
+    find it useful to determine if the datagram was sent specifically to this
+    machine via unicast addressing or whether it was sent to multiple destinations.
+
+    When sending, the senderAddress() and senderPort() should contain the local
+    address to be used when sending. The sender address must be an address that
+    is assigned to this machine, which can be obtained using
+    \l{QNetworkInterface}, and the port number must be the port number that the
+    socket is bound to. Either field can be left unset and will be filled in by
+    the operating system with default values. The destinationAddress() and
+    destinationPort() fields may be set to a target address different from the
+    one the UDP socket is currently associated with.
+
+    Usually, when sending a datagram in reply to a datagram previously
+    received, one will set the destinationAddress() to be the senderAddress()
+    of the incoming datagram and similarly for the port numbers. To facilitate
+    this common process, QNetworkDatagram provides the function makeReply().
+
+    The hopCount() function contains, for a received datagram, the remaining
+    hop count limit for the packet. When sending, it contains the hop count
+    limit to be set. Most protocols will leave this value set to the default
+    and let the operating system decide on the best value to be used.
+    Multicasting over IPv4 often uses this field to indicate the scope of the
+    multicast group (link-local, local to an organization or global).
+
+    The interfaceIndex() function contains the index of the operating system's
+    interface that received the packet. This value is the same one that can be
+    set on a QHostAddress::scopeId() property and matches the
+    QNetworkInterface::index() property. When sending packets to global
+    addresses, it is not necessary to set the interface index as the operating
+    system will choose the correct one using the system routing table. This
+    property is important when sending datagrams to link-local destinations,
+    whether unicast or multicast.
+
+    \section1 Feature support
+
+    Some features of QNetworkDatagram are not supported in all operating systems.
+    Only the address and ports of the remote host (sender in received packets
+    and destination for outgoing packets) are supported in all systems. On most
+    operating systems, the other features are supported only for IPv6. Software
+    should check at runtime whether the rest could be determined for IPv4
+    addresses.
+
+    The current feature support is as follows:
+
+    \table
+      \header   \li Operating system    \li Local address   \li Hop count       \li Interface index
+      \row      \li FreeBSD             \li Supported       \li Supported       \li Only for IPv6
+      \row      \li Linux               \li Supported       \li Supported       \li Supported
+      \row      \li OS X                \li Supported       \li Supported       \li Only for IPv6
+      \row      \li Other Unix supporting RFC 3542 \li Only for IPv6 \li Only for IPv6 \li Only for IPv6
+      \row      \li Windows XP and older \li Not supported  \li Not supported   \li Not supported
+      \row      \li Windows Vista & up  \li Supported       \li Supported       \li Supported
+      \row      \li Windows CE          \li Not supported   \li Not supported   \li Not supported
+      \row      \li Windows RT          \li Not supported   \li Not supported   \li Not supported
+    \endtable
+
+    \sa QUdpSocket, QNetworkInterface
+ */
+
+/*!
+    Creates a QNetworkDatagram object with no payload data and undefined destination address.
+
+    The payload can be modified by using setData() and the destination address
+    can be set with setDestination().
+
+    If the destination address is left undefined, QUdpSocket::writeDatagram()
+    will attempt to send the datagram to the address last associated with, by
+    using QUdpSocket::connectToHost().
+ */
+QNetworkDatagram::QNetworkDatagram()
+    : d(new QNetworkDatagramPrivate)
+{
+}
+
+/*!
+    Creates a QNetworkDatagram object and sets \a data as the payload data, along with
+    \a destinationAddress and \a port as the destination address of the datagram.
+ */
+QNetworkDatagram::QNetworkDatagram(const QByteArray &data, const QHostAddress &destinationAddress, quint16 port)
+    : d(new QNetworkDatagramPrivate(data, destinationAddress, port))
+{
+}
+
+/*!
+    Creates a copy of the \a other datagram, including the payload and metadata.
+
+    To create a datagram suitable for sending in a reply, use QNetworkDatagram::makeReply();
+ */
+QNetworkDatagram::QNetworkDatagram(const QNetworkDatagram &other)
+    : d(new QNetworkDatagramPrivate(*other.d))
+{
+}
+
+/*! \internal */
+QNetworkDatagram::QNetworkDatagram(QNetworkDatagramPrivate &dd)
+    : d(&dd)
+{
+}
+
+/*!
+    Copies the \a other datagram, including the payload and metadata.
+
+    To create a datagram suitable for sending in a reply, use QNetworkDatagram::makeReply();
+ */
+QNetworkDatagram &QNetworkDatagram::operator=(const QNetworkDatagram &other)
+{
+    *d = *other.d;
+    return *this;
+}
+
+/*!
+    Clears the payload data and metadata in this QNetworkDatagram object, resetting
+    them to their default values.
+ */
+void QNetworkDatagram::clear()
+{
+    d->data.clear();
+    d->header.senderAddress.clear();
+    d->header.destinationAddress.clear();
+    d->header.hopLimit = -1;
+    d->header.ifindex = 0;
+}
+
+/*!
+    \fn QNetworkDatagram::isNull() const
+    Returns true if this QNetworkDatagram object is null. This function is the
+    opposite of isValid().
+ */
+
+/*!
+    Returns true if this QNetworkDatagram object is valid. A valid QNetworkDatagram
+    object contains at least one sender or receiver address. Valid datagrams
+    can contain empty payloads.
+ */
+bool QNetworkDatagram::isValid() const
+{
+    return d->header.senderAddress.protocol() != QAbstractSocket::UnknownNetworkLayerProtocol ||
+           d->header.destinationAddress.protocol() != QAbstractSocket::UnknownNetworkLayerProtocol;
+}
+
+/*!
+    Returns the sender address associated with this datagram. For a datagram
+    received from the network, it is the address of the peer node that sent the
+    datagram. For an outgoing datagrams, it is the local address to be used
+    when sending.
+
+    If no sender address was set on this datagram, the returned object will
+    report true to QHostAddress::isNull().
+
+    \sa destinationAddress(), senderPort(), setSender()
+*/
+QHostAddress QNetworkDatagram::senderAddress() const
+{
+    return d->header.senderAddress;
+}
+
+/*!
+    Returns the destination address associated with this datagram. For a
+    datagram received from the network, it is the address the peer node sent
+    the datagram to, which can either be a local address of this machine or a
+    multicast or broadcast address. For an outgoing datagrams, it is the
+    address the datagram should be sent to.
+
+    If no destination address was set on this datagram, the returned object
+    will report true to QHostAddress::isNull().
+
+    \sa senderAddress(), destinationPort(), setDestination()
+*/
+QHostAddress QNetworkDatagram::destinationAddress() const
+{
+    return d->header.destinationAddress;
+}
+
+/*!
+    Returns the port number of the sender associated with this datagram. For a
+    datagram received from the network, it is the port number that the peer
+    node sent the datagram from. For an outgoing datagram, it is the local port
+    the datagram should be sent from.
+
+    If no sender address was associated with this datagram, this function
+    returns -1.
+
+    \sa senderAddress(), destinationPort(), setSender()
+*/
+int QNetworkDatagram::senderPort() const
+{
+    return d->header.senderAddress.protocol() == QAbstractSocket::UnknownNetworkLayerProtocol
+            ? -1 : d->header.senderPort;
+}
+
+/*!
+    Returns the port number of the destination associated with this datagram.
+    For a datagram received from the network, it is the local port number that
+    the peer node sent the datagram to. For an outgoing datagram, it is the
+    peer port the datagram should be sent to.
+
+    If no destination address was associated with this datagram, this function
+    returns -1.
+
+    \sa destinationAddress(), senderPort(), setDestination()
+*/
+int QNetworkDatagram::destinationPort() const
+{
+    return d->header.destinationAddress.protocol() == QAbstractSocket::UnknownNetworkLayerProtocol
+            ? -1 : d->header.destinationPort;
+}
+
+/*!
+    Sets the sender address associated with this datagram to be the address \a
+    address and port number \a port. The sender address and port numbers are
+    usually set by \l QUdpSocket upon reception, so there's no need to call
+    this function on a received datagram.
+
+    For outgoing datagrams, this function can be used to set the address the
+    datagram should carry. The address \a address must usually be one of the
+    local addresses assigned to this machine, which can be obtained using \l
+    QNetworkInterface. If left unset, the operating system will choose the most
+    appropriate address to use given the destination in question.
+
+    The port number \a port must be the port number associated with the socket,
+    if there is one. The value of 0 can be used to indicate that the operating
+    system should choose the port number.
+
+    \sa QUdpSocket::writeDatagram(), senderAddress(), senderPort(), setDestination()
+ */
+void QNetworkDatagram::setSender(const QHostAddress &address, quint16 port)
+{
+    d->header.senderAddress = address;
+    d->header.senderPort = port;
+}
+
+/*!
+    Sets the destination address associated with this datagram to be the
+    address \a address and port number \a port. The destination address and
+    port numbers are usually set by \l QUdpSocket upon reception, so there's no
+    need to call this function on a received datagram.
+
+    For outgoing datagrams, this function can be used to set the address the
+    datagram should be sent to. It can be the unicast address used to
+    communicate with the peer or a broadcast or multicast address to send to a
+    group of devices.
+
+    \sa QUdpSocket::writeDatagram(), destinationAddress(), destinationPort(), setSender()
+ */
+void QNetworkDatagram::setDestination(const QHostAddress &address, quint16 port)
+{
+    d->header.destinationAddress = address;
+    d->header.destinationPort = port;
+}
+
+/*!
+    Returns the hop count limit associated with this datagram. The hop count
+    limit is the number of nodes that are allowed to forward the IP packet
+    before it expires and an error is sent back to the sender of the datagram.
+    In IPv4, this value is usually known as "time to live" (TTL).
+
+    If this datagram was received from the network, this is the remaining hop
+    count of the datagram after reception and was decremented by 1 by each node
+    that forwarded the packet. A value of -1 indicates that the hop limit count
+    not be obtained.
+
+    If this is an outgoing datagram, this is the value to be set in the IP header
+    upon sending. A value of -1 indicates the operating system should choose
+    the value.
+
+    \sa setHopLimit()
+ */
+int QNetworkDatagram::hopLimit() const
+{
+    return d->header.hopLimit;
+}
+
+/*!
+    Sets the hop count limit associated with this datagram to \a count. The hop
+    count limit is the number of nodes that are allowed to forward the IP
+    packet before it expires and an error is sent back to the sender of the
+    datagram. In IPv4, this value is usually known as "time to live" (TTL).
+
+    It is usually not necessary to call this function on datagrams received
+    from the network.
+
+    If this is an outgoing packet, this is the value to be set in the IP header
+    upon sending. The valid range for the value is 1 to 255. This function also
+    accepts a value of -1 to indicate that the operating system should choose
+    the value.
+
+    \sa hopLimit()
+ */
+void QNetworkDatagram::setHopLimit(int count)
+{
+    d->header.hopLimit = count;
+}
+
+/*!
+    Returns the interface index this datagram is associated with. The interface
+    index is a positive number that uniquely identifies the network interface
+    in the operating system. This number matches the value returned by
+    QNetworkInterface::index() for the interface.
+
+    If this datagram was received from the network, this is the index of the
+    interface that the packet was received from. If this is an outgoing
+    datagram, this is the index of the interface that the datagram should be
+    sent on.
+
+    A value of 0 indicates that the interface index is unknown.
+
+    \sa setInterfaceIndex()
+ */
+uint QNetworkDatagram::interfaceIndex() const
+{
+    return d->header.ifindex;
+}
+
+/*!
+    Sets the interface index this datagram is associated with to \a index. The
+    interface index is a positive number that uniquely identifies the network
+    interface in the operating system. This number matches the value returned
+    by QNetworkInterface::index() for the interface.
+
+    It is usually not necessary to call this function on datagrams received
+    from the network.
+
+    If this is an outgoing packet, this is the index of the interface the
+    datagram should be sent on. A value of 0 indicates that the operating
+    system should choose the interface based on other factors.
+
+    Note that the interface index can also be set with
+    QHostAddress::setScopeId() for IPv6 destination addresses and then with
+    setDestination(). If the scope ID set in the destination address and \a
+    index are different and neither is zero, it is undefined which interface
+    the operating system will send the datagram on.
+
+    \sa setInterfaceIndex()
+ */
+void QNetworkDatagram::setInterfaceIndex(uint index)
+{
+    d->header.ifindex = index;
+}
+
+/*!
+    Returns the data payload of this datagram. For a datagram received from the
+    network, it contains the payload of the datagram. For an outgoing datagram,
+    it is the datagram to be sent.
+
+    Note that datagrams can be transmitted with no data, so the returned
+    QByteArray may be empty.
+
+    \sa setData()
+ */
+QByteArray QNetworkDatagram::data() const
+{
+    return d->data;
+}
+
+/*!
+    Sets the data payload of this datagram to \a data. It is usually not
+    necessary to call this function on received datagrams. For outgoing
+    datagrams, this function sets the data to be sent on the network.
+
+    Since datagrams can empty, an empty QByteArray is a valid value for \a
+    data.
+
+    \sa data()
+ */
+void QNetworkDatagram::setData(const QByteArray &data)
+{
+    d->data = data;
+}
+
+/*!
+    \fn QNetworkDatagram QNetworkDatagram::makeReply(const QByteArray &data) const
+
+    Creates a new QNetworkDatagram representing a reply to this incoming datagram
+    and sets the payload data to \a data. This function is a very convenient
+    way of responding to a datagram back to the original sender.
+
+    Example:
+    \code
+        void Server::readPendingDatagrams()
+        {
+            while (udpSocket->hasPendingDatagrams()) {
+                QNetworkDatagram datagram = udpSocket->receiveDatagram();
+                QByteArray replyData = processThePayload(datagram.data());
+                udpSocket->writeDatagram(datagram.makeReply(replyData));
+            }
+        }
+    \endcode
+
+    This function is especially convenient since it will automatically copy
+    parameters from this datagram to the new datagram as appropriate:
+
+    \list
+      \li this datagram's sender address and port are copied to the new
+          datagram's destination address and port;
+      \li this datagram's interface index, if any, is copied to the new
+          datagram's interface index;
+      \li this datagram's destination address and port are copied to the new
+          datagram's sender address and port only if the address is IPv6
+          global (non-multicast) address;
+      \li the hop count limit on the new datagram is reset to the default (-1);
+    \endlist
+
+    If QNetworkDatagram is modified in a future version of Qt to carry further
+    metadata, this function will copy that metadata as appropriate.
+
+    This datagram's destination address is not copied if it is an IPv4 address
+    because it is not possible to tell an IPv4 broadcast address apart from a
+    regular IPv4 address without an exhaustive search of all addresses assigned
+    to this machine. Attempting to send a datagram with the sender address
+    equal to the broadcast address is likely to fail. However, this should not
+    affect the communication as network interfaces with multiple IPv4 addresses
+    are uncommon, so the address the operating system will select will likely
+    be one the peer will understand.
+
+    \note This function comes with both rvalue- and lvalue-reference qualifier
+    overloads, so it is a good idea to make sure this object is rvalue, if
+    possible, before calling makeReply, so as to make better use of move
+    semantics. To achieve that, the example above would use:
+    \code
+            udpSocket->writeDatagram(std::move(datagram).makeReply(replyData));
+    \endcode
+ */
+
+static bool isNonMulticast(const QHostAddress &addr)
+{
+    // is it a multicast address?
+    return !addr.isMulticast();
+}
+
+QNetworkDatagram QNetworkDatagram::makeReply_helper(const QByteArray &data) const
+{
+    QNetworkDatagramPrivate *x = new QNetworkDatagramPrivate(data, d->header.senderAddress, d->header.senderPort);
+    x->header.ifindex = d->header.ifindex;
+    if (isNonMulticast(d->header.destinationAddress)) {
+        x->header.senderAddress = d->header.destinationAddress;
+        x->header.senderPort = d->header.destinationPort;
+    }
+    return QNetworkDatagram(*x);
+}
+
+void QNetworkDatagram::makeReply_helper_inplace(const QByteArray &data)
+{
+    d->data = data;
+    d->header.hopLimit = -1;
+    qSwap(d->header.destinationPort, d->header.senderPort);
+    qSwap(d->header.destinationAddress, d->header.senderAddress);
+    if (!isNonMulticast(d->header.senderAddress))
+        d->header.senderAddress.clear();
+}
+
+void QNetworkDatagram::destroy(QNetworkDatagramPrivate *d)
+{
+    Q_ASSUME(d);
+    delete d;
+}
+
+QT_END_NAMESPACE
+
+#endif // QT_NO_UDPSOCKET
diff --git a/src/network/kernel/qnetworkdatagram.h b/src/network/kernel/qnetworkdatagram.h
new file mode 100644
index 0000000000..6cbea13afc
--- /dev/null
+++ b/src/network/kernel/qnetworkdatagram.h
@@ -0,0 +1,122 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 Intel Corporation.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtNetwork module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QNETWORKDATAGRAM_H
+#define QNETWORKDATAGRAM_H
+
+#include <QtCore/qbytearray.h>
+#include <QtNetwork/qhostaddress.h>
+
+#ifndef QT_NO_UDPSOCKET
+
+QT_BEGIN_NAMESPACE
+
+class QNetworkDatagramPrivate;
+class QUdpSocketPrivate;
+
+class Q_NETWORK_EXPORT QNetworkDatagram
+{
+public:
+    QNetworkDatagram();
+    QNetworkDatagram(const QByteArray &data, const QHostAddress &destinationAddress = QHostAddress(),
+                     quint16 port = 0); // implicit
+    QNetworkDatagram(const QNetworkDatagram &other);
+    QNetworkDatagram &operator=(const QNetworkDatagram &other);
+    ~QNetworkDatagram()
+    { if (d) destroy(d); }
+
+    QNetworkDatagram(QNetworkDatagram &&other) Q_DECL_NOTHROW
+        : d(other.d)
+    { other.d = Q_NULLPTR; }
+    QNetworkDatagram &operator=(QNetworkDatagram &&other) Q_DECL_NOTHROW
+    { swap(other); return *this; }
+
+    void swap(QNetworkDatagram &other) Q_DECL_NOTHROW
+    { qSwap(d, other.d); }
+
+    void clear();
+    bool isValid() const;
+    bool isNull() const
+    { return !isValid(); }
+
+    uint interfaceIndex() const;
+    void setInterfaceIndex(uint index);
+
+    QHostAddress senderAddress() const;
+    QHostAddress destinationAddress() const;
+    int senderPort() const;
+    int destinationPort() const;
+    void setSender(const QHostAddress &address, quint16 port = 0);
+    void setDestination(const QHostAddress &address, quint16 port);
+
+    int hopLimit() const;
+    void setHopLimit(int count);
+
+    QByteArray data() const;
+    void setData(const QByteArray &data);
+
+#ifdef Q_COMPILER_REF_QUALIFIERS
+    QNetworkDatagram makeReply(const QByteArray &payload) const &
+    { return makeReply_helper(payload); }
+    QNetworkDatagram makeReply(const QByteArray &payload) &&
+    { makeReply_helper_inplace(payload); return *this; }
+#else
+    QNetworkDatagram makeReply(const QByteArray &paylaod) const
+    { return makeReply_helper(paylaod); }
+#endif
+
+private:
+    QNetworkDatagramPrivate *d;
+    friend class QUdpSocket;
+
+    explicit QNetworkDatagram(QNetworkDatagramPrivate &dd);
+    QNetworkDatagram makeReply_helper(const QByteArray &data) const;
+    void makeReply_helper_inplace(const QByteArray &data);
+    static void destroy(QNetworkDatagramPrivate *d);
+};
+
+Q_DECLARE_SHARED(QNetworkDatagram)
+
+QT_END_NAMESPACE
+
+Q_DECLARE_METATYPE(QNetworkDatagram)
+
+#endif // QT_NO_UDPSOCKET
+
+#endif // QNETWORKDATAGRAM_H
diff --git a/src/network/kernel/qnetworkdatagram_p.h b/src/network/kernel/qnetworkdatagram_p.h
index 4941d8c94b..7e9a14decb 100644
--- a/src/network/kernel/qnetworkdatagram_p.h
+++ b/src/network/kernel/qnetworkdatagram_p.h
@@ -73,6 +73,18 @@ public:
     quint16 destinationPort;
 };
 
+class QNetworkDatagramPrivate
+{
+public:
+    QNetworkDatagramPrivate(const QByteArray &data = QByteArray(),
+                            const QHostAddress &dstAddr = QHostAddress(), quint16 port = 0)
+        : data(data), header(dstAddr, port)
+    {}
+
+    QByteArray data;
+    QIpPacketHeader header;
+};
+
 QT_END_NAMESPACE
 
 #endif // QNETWORKDATAGRAM_P_H
diff --git a/src/network/kernel/qnetworkinterface.cpp b/src/network/kernel/qnetworkinterface.cpp
index c64d8e13cd..22d2e6bb70 100644
--- a/src/network/kernel/qnetworkinterface.cpp
+++ b/src/network/kernel/qnetworkinterface.cpp
@@ -536,7 +536,7 @@ QList<QNetworkAddressEntry> QNetworkInterface::addressEntries() const
         QNetworkInterface::interfaceFromName(name).index()
     \endcode
 
-    \sa interfaceFromName(), interfaceNameFromIndex()
+    \sa interfaceFromName(), interfaceNameFromIndex(), QNetworkDatagram::interfaceIndex()
 */
 int QNetworkInterface::interfaceIndexFromName(const QString &name)
 {
@@ -596,7 +596,7 @@ QNetworkInterface QNetworkInterface::interfaceFromIndex(int index)
         QNetworkInterface::interfaceFromIndex(index).name()
     \endcode
 
-    \sa interfaceFromIndex(), interfaceIndexFromName()
+    \sa interfaceFromIndex(), interfaceIndexFromName(), QNetworkDatagram::interfaceIndex()
 */
 QString QNetworkInterface::interfaceNameFromIndex(int index)
 {
diff --git a/src/network/socket/qnativesocketengine.cpp b/src/network/socket/qnativesocketengine.cpp
index 9ba9d5317e..9af3aa0d31 100644
--- a/src/network/socket/qnativesocketengine.cpp
+++ b/src/network/socket/qnativesocketengine.cpp
@@ -111,7 +111,7 @@
     \value WantAll              this is a catch-all value to indicate the caller is
                                 interested in all the available information
 
-    \sa readDatagram()
+    \sa readDatagram(), QNetworkDatagram
 */
 
 #include "qnativesocketengine_p.h"
diff --git a/src/network/socket/qudpsocket.cpp b/src/network/socket/qudpsocket.cpp
index 083648bc23..d78379fb39 100644
--- a/src/network/socket/qudpsocket.cpp
+++ b/src/network/socket/qudpsocket.cpp
@@ -55,10 +55,10 @@
     datagrams.
 
     The most common way to use this class is to bind to an address and port
-    using bind(), then call writeDatagram() and readDatagram() to transfer
-    data. If you want to use the standard QIODevice functions read(),
-    readLine(), write(), etc., you must first connect the socket directly to a
-    peer by calling connectToHost().
+    using bind(), then call writeDatagram() and readDatagram() /
+    receiveDatagram() to transfer data. If you want to use the standard
+    QIODevice functions read(), readLine(), write(), etc., you must first
+    connect the socket directly to a peer by calling connectToHost().
 
     The socket emits the bytesWritten() signal every time a datagram
     is written to the network. If you just want to send datagrams,
@@ -67,7 +67,7 @@
     The readyRead() signal is emitted whenever datagrams arrive. In
     that case, hasPendingDatagrams() returns \c true. Call
     pendingDatagramSize() to obtain the size of the first pending
-    datagram, and readDatagram() to read it.
+    datagram, and readDatagram() or receiveDatagram() to read it.
 
     \note An incoming datagram should be read when you receive the readyRead()
     signal, otherwise this signal will not be emitted for the next datagram.
@@ -94,11 +94,12 @@
     \l{multicastreceiver}{Multicast Receiver} examples illustrate how
     to use QUdpSocket in applications.
 
-    \sa QTcpSocket
+    \sa QTcpSocket, QNetworkDatagram
 */
 
 #include "qudpsocket.h"
 #include "qhostaddress.h"
+#include "qnetworkdatagram.h"
 #include "qnetworkinterface.h"
 #include "qabstractsocket_p.h"
 
@@ -358,7 +359,101 @@ qint64 QUdpSocket::writeDatagram(const char *data, qint64 size, const QHostAddre
 
     Sends the datagram \a datagram to the host address \a host and at
     port \a port.
+
+    The function returns the number of bytes sent if it succeeded or -1 if it
+    encountered an error.
+*/
+
+/*!
+    \overload
+
+    Sends the datagram \a datagram to the host address and port numbers
+    contained in \a datagram, using the network interface and hop count limits
+    also set there. If the destination address and port numbers are unset, this
+    function will send to the address that was passed to connectToHost().
+
+    If the destination address is IPv6 with a non-empty
+    \l{QHostAddress::scopeId()}{scope id} but differs from the interface index
+    in \a datagram, it is undefined which interface the operating system will
+    choose to send on.
+
+    The function returns the number of bytes sent if it succeeded or -1 if it
+    encountered an error.
+
+    \warning Calling this function on a connected UDP socket may
+    result in an error and no packet being sent. If you are using a
+    connected socket, use write() to send datagrams.
+
+    \sa QNetworkDatagram::setDestination(), QNetworkDatagram::setHopLimit(), QNetworkDatagram::setInterfaceIndex()
+*/
+qint64 QUdpSocket::writeDatagram(const QNetworkDatagram &datagram)
+{
+    Q_D(QUdpSocket);
+#if defined QUDPSOCKET_DEBUG
+    qDebug("QUdpSocket::writeDatagram(%p, %i, \"%s\", %i)",
+           datagram.d->data.constData(),
+           datagram.d->data.size(),
+           datagram.destinationAddress().toString().toLatin1().constData(),
+           datagram.destinationPort());
+#endif
+    if (!d->doEnsureInitialized(QHostAddress::Any, 0, datagram.destinationAddress()))
+        return -1;
+    if (state() == UnconnectedState)
+        bind();
+
+    qint64 sent = d->socketEngine->writeDatagram(datagram.d->data,
+                                                 datagram.d->data.size(),
+                                                 datagram.d->header);
+    d->cachedSocketDescriptor = d->socketEngine->socketDescriptor();
+
+    if (sent >= 0) {
+        emit bytesWritten(sent);
+    } else {
+        d->setErrorAndEmit(d->socketEngine->error(), d->socketEngine->errorString());
+    }
+    return sent;
+}
+
+/*!
+    Receives a datagram no larger than \a maxSize bytes and returns it in the
+    QNetworkDatagram object, along with the sender's host address and port. If
+    possible, this function will also try to determine the datagram's
+    destination address, port, and the number of hop counts at reception time.
+
+    On failure, returns a QNetworkDatagram that reports \l
+    {QNetworkDatagram::isValid()}{not valid}.
+
+    If \a maxSize is too small, the rest of the datagram will be lost. If \a
+    maxSize is 0, the datagram will be discarded. If \a maxSize is -1 (the
+    default), this function will attempt to read the entire datagram.
+
+    \sa writeDatagram(), hasPendingDatagrams(), pendingDatagramSize()
 */
+QNetworkDatagram QUdpSocket::receiveDatagram(qint64 maxSize)
+{
+    Q_D(QUdpSocket);
+
+#if defined QUDPSOCKET_DEBUG
+    qDebug("QUdpSocket::receiveDatagram(%lld)", maxSize);
+#endif
+    QT_CHECK_BOUND("QUdpSocket::receiveDatagram()", QNetworkDatagram());
+
+    if (maxSize < 0)
+        maxSize = d->socketEngine->pendingDatagramSize();
+    if (maxSize < 0)
+        return QNetworkDatagram();
+
+    QNetworkDatagram result(QByteArray(maxSize, Qt::Uninitialized));
+    qint64 readBytes = d->socketEngine->readDatagram(result.d->data.data(), maxSize, &result.d->header,
+                                                     QAbstractSocketEngine::WantAll);
+    d->hasPendingData = false;
+    d->socketEngine->setReadNotificationEnabled(true);
+    if (readBytes < 0)
+        d->setErrorAndEmit(d->socketEngine->error(), d->socketEngine->errorString());
+    else if (readBytes != result.d->data.size())
+        result.d->data.truncate(readBytes);
+    return result;
+}
 
 /*!
     Receives a datagram no larger than \a maxSize bytes and stores
@@ -404,6 +499,7 @@ qint64 QUdpSocket::readDatagram(char *data, qint64 maxSize, QHostAddress *addres
         d->setErrorAndEmit(d->socketEngine->error(), d->socketEngine->errorString());
     return readBytes;
 }
+
 #endif // QT_NO_UDPSOCKET
 
 QT_END_NAMESPACE
diff --git a/src/network/socket/qudpsocket.h b/src/network/socket/qudpsocket.h
index cf2f05c86d..f32235b5f3 100644
--- a/src/network/socket/qudpsocket.h
+++ b/src/network/socket/qudpsocket.h
@@ -48,6 +48,7 @@ QT_BEGIN_NAMESPACE
 
 #ifndef QT_NO_UDPSOCKET
 
+class QNetworkDatagram;
 class QNetworkInterface;
 class QUdpSocketPrivate;
 
@@ -72,7 +73,10 @@ public:
 
     bool hasPendingDatagrams() const;
     qint64 pendingDatagramSize() const;
+    QNetworkDatagram receiveDatagram(qint64 maxSize = -1);
     qint64 readDatagram(char *data, qint64 maxlen, QHostAddress *host = Q_NULLPTR, quint16 *port = Q_NULLPTR);
+
+    qint64 writeDatagram(const QNetworkDatagram &datagram);
     qint64 writeDatagram(const char *data, qint64 len, const QHostAddress &host, quint16 port);
     inline qint64 writeDatagram(const QByteArray &datagram, const QHostAddress &host, quint16 port)
         { return writeDatagram(datagram.constData(), datagram.size(), host, port); }