Remove the trailing token from empty acknowledgment packets

When sending Acknowledgment packets with code 0.00, the message should
be empty (RFC-7252 section 12.1). An empty message should have no token
(token length is 0), and no bytes should appear after the message ID
(RFC-7252 section 4.1, section 3). Since Reset packets have the same
structure (only the packet type differs), unified the packet creation
for both cases in one method.

Fixes: QTBUG-94763
Pick-to: 6.2 6.1 5.15
Change-Id: If2619ad6f4f5dba500e04ab10dbbbf08e4887aef
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

3 files changed, 10 insertions, 27 deletions

diff --git a/src/coap/qcoapinternalrequest.cpp b/src/coap/qcoapinternalrequest.cpp
index 48a2b9f..a6b8c04 100644
--- a/src/coap/qcoapinternalrequest.cpp
+++ b/src/coap/qcoapinternalrequest.cpp
@@ -103,34 +103,18 @@ bool QCoapInternalRequest::isValid() const
 /*!
     \internal
     Initialize parameters to transform the QCoapInternalRequest into an
-    acknowledgment message with the message id \a messageId and the given
-    \a token.
-*/
-void QCoapInternalRequest::initForAcknowledgment(quint16 messageId, const QByteArray &token)
-{
-    Q_D(QCoapInternalRequest);
-
-    setMethod(QtCoap::Method::Invalid);
-    d->message.setType(QCoapMessage::Type::Acknowledgment);
-    d->message.setMessageId(messageId);
-    d->message.setToken(token);
-    d->message.setPayload(QByteArray());
-    d->message.clearOptions();
-}
+    empty message (RST or ACK) with the message id \a messageId.
 
-/*!
-    \internal
-    Initialize parameters to transform the QCoapInternalRequest into a
-    Reset message (RST) with the message id \a messageId.
-
-    A Reset message should contain only the \a messageId.
+    An empty message should contain only the \a messageId.
 */
-void QCoapInternalRequest::initForReset(quint16 messageId)
+void QCoapInternalRequest::initEmptyMessage(quint16 messageId, QCoapMessage::Type type)
 {
     Q_D(QCoapInternalRequest);
 
+    Q_ASSERT(type == QCoapMessage::Type::Acknowledgment || type == QCoapMessage::Type::Reset);
+
     setMethod(QtCoap::Method::Invalid);
-    d->message.setType(QCoapMessage::Type::Reset);
+    d->message.setType(type);
     d->message.setMessageId(messageId);
     d->message.setToken(QByteArray());
     d->message.setPayload(QByteArray());
diff --git a/src/coap/qcoapinternalrequest_p.h b/src/coap/qcoapinternalrequest_p.h
index f6875b3..6073df4 100644
--- a/src/coap/qcoapinternalrequest_p.h
+++ b/src/coap/qcoapinternalrequest_p.h
@@ -65,8 +65,7 @@ public:
 
     bool isValid() const override;
 
-    void initForAcknowledgment(quint16 messageId, const QByteArray &token);
-    void initForReset(quint16 messageId);
+    void initEmptyMessage(quint16 messageId, QCoapMessage::Type type);
 
     QByteArray toQByteArray() const;
     void setMessageId(quint16);
diff --git a/src/coap/qcoapprotocol.cpp b/src/coap/qcoapprotocol.cpp
index c9e720d..3121ea4 100644
--- a/src/coap/qcoapprotocol.cpp
+++ b/src/coap/qcoapprotocol.cpp
@@ -596,8 +596,8 @@ void QCoapProtocolPrivate::sendAcknowledgment(QCoapInternalRequest *request) con
     ackRequest.setTargetUri(request->targetUri());
 
     auto internalReply = lastReplyForToken(request->token());
-    ackRequest.initForAcknowledgment(internalReply->message()->messageId(),
-                                     internalReply->message()->token());
+    ackRequest.initEmptyMessage(internalReply->message()->messageId(),
+                                QCoapMessage::Type::Acknowledgment);
     ackRequest.setConnection(request->connection());
     sendRequest(&ackRequest);
 }
@@ -618,7 +618,7 @@ void QCoapProtocolPrivate::sendReset(QCoapInternalRequest *request) const
     resetRequest.setTargetUri(request->targetUri());
 
     auto lastReply = lastReplyForToken(request->token());
-    resetRequest.initForReset(lastReply->message()->messageId());
+    resetRequest.initEmptyMessage(lastReply->message()->messageId(), QCoapMessage::Type::Reset);
     resetRequest.setConnection(request->connection());
     sendRequest(&resetRequest);
 }