QDnsLookup: Add support for custom DNS server

Implemented the use of the new QDnsLookup property "nameserver".

On the Linux platform, we can specify both IPv4 and IPv6 addresses
for the nameserver.

On Windows since we are using DnsQuery_W(), which does not have a
way of accepting IPv6 addresses, passing IPv6 nameserver address
is not supported.

On OSX/BSD platforms, specifying IPv6 addresses for nameserver
require access to the __res_state_ext structure which is in a
private header of libresolv (this header is different for BSDs and
OSX). If this feature has to be enabled in the future, we have to
figure out a way to access this struct by either accessing the
private header or by specifying one of our own. Currently, I'm
disabling it till such a solution is arrived at.

Nameserver support on different platforms:

  Platform   |      IPv4     |     IPv6
-------------+---------------+---------------
  Linux/X11  |   supported   |  supported
-------------+---------------+---------------
  Windows    |   supported   |  not supported
-------------+---------------+---------------
  OSX        |   supported   |  not supported
-------------+---------------+---------------
  WinRT      | not supported |  not supported
-------------+---------------+---------------
  Others     |   supported   |  not supported
             |  (not tested) |
-------------+---------------+---------------

Task-number: QTBUG-30166
Change-Id: Iedbddf15b9a62738ce4c2cfa0fce051514d64766
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

6 files changed, 72 insertions, 9 deletions

diff --git a/src/network/kernel/qdnslookup.cpp b/src/network/kernel/qdnslookup.cpp
index e776a8eb76..97a402901e 100644
--- a/src/network/kernel/qdnslookup.cpp
+++ b/src/network/kernel/qdnslookup.cpp
@@ -482,7 +482,7 @@ void QDnsLookup::lookup()
     Q_D(QDnsLookup);
     d->isFinished = false;
     d->reply = QDnsLookupReply();
-    d->runnable = new QDnsLookupRunnable(d->type, QUrl::toAce(d->name));
+    d->runnable = new QDnsLookupRunnable(d->type, QUrl::toAce(d->name), d->nameserver);
     connect(d->runnable, SIGNAL(finished(QDnsLookupReply)),
             this, SLOT(_q_lookupFinished(QDnsLookupReply)),
             Qt::BlockingQueuedConnection);
@@ -990,7 +990,7 @@ void QDnsLookupRunnable::run()
     }
 
     // Perform request.
-    query(requestType, requestName, &reply);
+    query(requestType, requestName, nameserver, &reply);
 
     // Sort results.
     if (!theDnsLookupSeedStorage()->hasLocalData()) {
diff --git a/src/network/kernel/qdnslookup_android.cpp b/src/network/kernel/qdnslookup_android.cpp
index dff81dba0c..1ace5727c2 100644
--- a/src/network/kernel/qdnslookup_android.cpp
+++ b/src/network/kernel/qdnslookup_android.cpp
@@ -43,10 +43,11 @@
 
 QT_BEGIN_NAMESPACE
 
-void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, QDnsLookupReply *reply)
+void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, const QHostAddress &nameserver, QDnsLookupReply *reply)
 {
     Q_UNUSED(requestType);
     Q_UNUSED(requestName);
+    Q_UNUSED(nameserver);
     Q_UNUSED(reply);
     qWarning() << Q_FUNC_INFO << "Not yet supported on Android";
     reply->error = QDnsLookup::ResolverError;
diff --git a/src/network/kernel/qdnslookup_p.h b/src/network/kernel/qdnslookup_p.h
index 4bd3bd7603..7c0b0e862a 100644
--- a/src/network/kernel/qdnslookup_p.h
+++ b/src/network/kernel/qdnslookup_p.h
@@ -112,9 +112,10 @@ class QDnsLookupRunnable : public QObject, public QRunnable
     Q_OBJECT
 
 public:
-    QDnsLookupRunnable(QDnsLookup::Type type, const QByteArray &name)
+    QDnsLookupRunnable(QDnsLookup::Type type, const QByteArray &name, const QHostAddress &nameserver)
         : requestType(type)
         , requestName(name)
+        , nameserver(nameserver)
     { }
     void run();
 
@@ -122,9 +123,10 @@ signals:
     void finished(const QDnsLookupReply &reply);
 
 private:
-    static void query(const int requestType, const QByteArray &requestName, QDnsLookupReply *reply);
+    static void query(const int requestType, const QByteArray &requestName, const QHostAddress &nameserver, QDnsLookupReply *reply);
     QDnsLookup::Type requestType;
     QByteArray requestName;
+    QHostAddress nameserver;
 };
 
 class QDnsLookupThreadPool : public QThreadPool
diff --git a/src/network/kernel/qdnslookup_unix.cpp b/src/network/kernel/qdnslookup_unix.cpp
index 9fb488cee6..26834dff57 100644
--- a/src/network/kernel/qdnslookup_unix.cpp
+++ b/src/network/kernel/qdnslookup_unix.cpp
@@ -115,7 +115,7 @@ static void resolveLibrary()
         local_res_nquery = res_nquery_proto(lib.resolve("res_nquery"));
 }
 
-void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, QDnsLookupReply *reply)
+void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, const QHostAddress &nameserver, QDnsLookupReply *reply)
 {
     // Load dn_expand, res_ninit and res_nquery on demand.
     static QBasicAtomicInt triedResolve = Q_BASIC_ATOMIC_INITIALIZER(false);
@@ -142,6 +142,43 @@ void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestN
         reply->errorString = tr("Resolver initialization failed");
         return;
     }
+
+    //Check if a nameserver was set. If so, use it
+    if (!nameserver.isNull()) {
+        if (nameserver.protocol() == QAbstractSocket::IPv4Protocol) {
+            state.nsaddr_list[0].sin_addr.s_addr = htonl(nameserver.toIPv4Address());
+            state.nscount = 1;
+        } else if (nameserver.protocol() == QAbstractSocket::IPv6Protocol) {
+#if defined(Q_OS_LINUX)
+            struct sockaddr_in6 *ns;
+            ns = state._u._ext.nsaddrs[0];
+            // nsaddrs will be NULL if no nameserver is set in /etc/resolv.conf
+            if (!ns) {
+                // Memory allocated here will be free'd in res_close() as we
+                // have done res_init() above.
+                ns = (struct sockaddr_in6*) calloc(1, sizeof(struct sockaddr_in6));
+                Q_CHECK_PTR(ns);
+                state._u._ext.nsaddrs[0] = ns;
+            }
+            // Set nsmap[] to indicate that nsaddrs[0] is an IPv6 address
+            // See: https://sourceware.org/ml/libc-hacker/2002-05/msg00035.html
+            state._u._ext.nsmap[0] = MAXNS + 1;
+            state._u._ext.nscount6 = 1;
+            ns->sin6_family = AF_INET6;
+            ns->sin6_port = htons(53);
+
+            Q_IPV6ADDR ipv6Address = nameserver.toIPv6Address();
+            for (int i=0; i<16; i++) {
+                ns->sin6_addr.s6_addr[i] = ipv6Address[i];
+            }
+#else
+            qWarning() << Q_FUNC_INFO << "IPv6 addresses for nameservers is currently not supported";
+            reply->error = QDnsLookup::ResolverError;
+            reply->errorString = tr("IPv6 addresses for nameservers is currently not supported");
+            return;
+#endif
+        }
+    }
 #ifdef QDNSLOOKUP_DEBUG
     state.options |= RES_DEBUG;
 #endif
diff --git a/src/network/kernel/qdnslookup_win.cpp b/src/network/kernel/qdnslookup_win.cpp
index bf80a23297..6f58e64440 100644
--- a/src/network/kernel/qdnslookup_win.cpp
+++ b/src/network/kernel/qdnslookup_win.cpp
@@ -48,15 +48,33 @@
 
 #include <qt_windows.h>
 #include <windns.h>
+#include <memory.h>
 
 QT_BEGIN_NAMESPACE
 
-void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, QDnsLookupReply *reply)
+void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, const QHostAddress &nameserver, QDnsLookupReply *reply)
 {
     // Perform DNS query.
     PDNS_RECORD dns_records = 0;
     const QString requestNameUtf16 = QString::fromUtf8(requestName.data(), requestName.size());
-    const DNS_STATUS status = DnsQuery_W(reinterpret_cast<const wchar_t*>(requestNameUtf16.utf16()), requestType, DNS_QUERY_STANDARD, NULL, &dns_records, NULL);
+    IP4_ARRAY srvList;
+    memset(&srvList, 0, sizeof(IP4_ARRAY));
+    if (!nameserver.isNull()) {
+        if (nameserver.protocol() == QAbstractSocket::IPv4Protocol) {
+            // The below code is referenced from: http://support.microsoft.com/kb/831226
+            srvList.AddrCount = 1;
+            srvList.AddrArray[0] = htonl(nameserver.toIPv4Address());
+        } else if (nameserver.protocol() == QAbstractSocket::IPv6Protocol) {
+            // For supoprting IPv6 nameserver addresses, we'll need to switch
+            // from DnsQuey() to DnsQueryEx() as it supports passing an IPv6
+            // address in the nameserver list
+            qWarning() << Q_FUNC_INFO << "IPv6 addresses for nameservers is currently not supported";
+            reply->error = QDnsLookup::ResolverError;
+            reply->errorString = tr("IPv6 addresses for nameservers is currently not supported");
+            return;
+        }
+    }
+    const DNS_STATUS status = DnsQuery_W(reinterpret_cast<const wchar_t*>(requestNameUtf16.utf16()), requestType, DNS_QUERY_STANDARD, &srvList, &dns_records, NULL);
     switch (status) {
     case ERROR_SUCCESS:
         break;
diff --git a/src/network/kernel/qdnslookup_winrt.cpp b/src/network/kernel/qdnslookup_winrt.cpp
index a5d16e4b63..6ac944934a 100644
--- a/src/network/kernel/qdnslookup_winrt.cpp
+++ b/src/network/kernel/qdnslookup_winrt.cpp
@@ -42,6 +42,7 @@
 #include "qdnslookup_p.h"
 
 #include <qurl.h>
+#include <qdebug.h>
 
 #include <wrl.h>
 #include <windows.foundation.h>
@@ -59,8 +60,12 @@ using namespace ABI::Windows::Networking::Sockets;
 
 QT_BEGIN_NAMESPACE
 
-void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, QDnsLookupReply *reply)
+void QDnsLookupRunnable::query(const int requestType, const QByteArray &requestName, const QHostAddress &nameserver, QDnsLookupReply *reply)
 {
+    // TODO: Add nameserver support for winRT
+    if (!nameserver.isNull())
+        qWarning() << "Ignoring nameserver as its currently not supported on WinRT";
+
     // TODO: is there any way to do "proper" dns lookup?
     if (requestType != QDnsLookup::A && requestType != QDnsLookup::AAAA
             && requestType != QDnsLookup::ANY) {