Add support for DNS lookups using native APIs

The QDnsLookup class provides asynchronous APIs for performing
DNS lookups. For now, the following lookups are supported:
- A and AAAA
- CNAME as defined per RFC 1035
- MX as defined per RFC 1035
- NS as defined per RFC 1035
- PTR as defined per RFC 1035
- SRV as defined per RFC 2782
- TXT as defined per RFC 1035

Task-number: QTBUG-10481
Change-Id: I46c1741ec23615863eeca3a1231d5e3f8942495e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/doc/src/snippets/code/src_network_kernel_qdnslookup.cpp b/doc/src/snippets/code/src_network_kernel_qdnslookup.cpp
new file mode 100644
index 0000000000..f2e530ff96
--- /dev/null
+++ b/doc/src/snippets/code/src_network_kernel_qdnslookup.cpp
@@ -0,0 +1,73 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Jeremy Lainé <jeremy.laine@m4x.org>
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
+**     the names of its contributors may be used to endorse or promote
+**     products derived from this software without specific prior written
+**     permission.
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+//! [0]
+void MyObject::lookupServers()
+{
+    // Create a DNS lookup.
+    dns = new QDnsLookup(this);
+    connect(dns, SIGNAL(finished()),
+            this, SLOT(handleServers()));
+
+    // Find the XMPP servers for gmail.com
+    dns->setType(QDnsLookup::SRV);
+    dns->setName("_xmpp-client._tcp.gmail.com");
+    dns->lookup();
+}
+//! [0]
+
+
+//! [1]
+void MyObject::handleServers()
+{
+    // Check the lookup succeeded.
+    if (dns->error() != QDnsLookup::NoError) {
+        qWarning("DNS lookup failed");
+        dns->deleteLater();
+        return;
+    }
+
+    // Handle the results.
+    foreach (const QDnsServiceRecord &record, dns->serviceRecords()) {
+        ...
+    }
+    dns->deleteLater();
+}
+//! [1]