QDnsLookup: allow looking up the root domain

[ChangeLog][QtNetwork][QDnsLookup] It is now possible to look up the
root DNS domain, by setting the name property to an empty string. This
query is usually done while setting the query type to NS.

Change-Id: I5f7f427ded124479baa6fffd175f688395941610
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/network/kernel/qdnslookup.cpp b/src/network/kernel/qdnslookup.cpp
index 0356633735..c310c7e28e 100644
--- a/src/network/kernel/qdnslookup.cpp
+++ b/src/network/kernel/qdnslookup.cpp
@@ -343,6 +343,10 @@ bool QDnsLookup::isFinished() const
     \property QDnsLookup::name
     \brief the name to lookup.
 
+    If the name to look up is empty, QDnsLookup will attempt to resolve the
+    root domain of DNS. That query is usually performed with QDnsLookup::type
+    set to \l{QDnsLookup::Type}{NS}.
+
     \note The name will be encoded using IDNA, which means it's unsuitable for
     querying SRV records compatible with the DNS-SD specification.
 */
@@ -1050,6 +1054,10 @@ QDnsTextRecord &QDnsTextRecord::operator=(const QDnsTextRecord &other)
 
 static QDnsLookupRunnable::EncodedLabel encodeLabel(const QString &label)
 {
+    QDnsLookupRunnable::EncodedLabel::value_type rootDomain = u'.';
+    if (label.isEmpty())
+        return QDnsLookupRunnable::EncodedLabel(1, rootDomain);
+
     QString encodedLabel = qt_ACE_do(label, ToAceOnly, ForbidLeadingDot);
 #ifdef Q_OS_WIN
     return encodedLabel;