QSslSocket::waitForDisconnected(): flush write buffer before waiting

Otherwise, the plain socket might be blocked indefinitely on waiting for
socket activity.

This issue is tested by tst_QSslSocket::disconnectFromHostWhenConnected()
which was unstable in CI.

Task-number: QTBUG-64016
Change-Id: I6a1a111dea4d1d1adaf55e6a90c0c5f995a270af
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

1 files changed, 13 insertions, 1 deletions

diff --git a/src/network/ssl/qsslsocket.cpp b/src/network/ssl/qsslsocket.cpp
index 9d11506fcb..8eba5db9fe 100644
--- a/src/network/ssl/qsslsocket.cpp
+++ b/src/network/ssl/qsslsocket.cpp
@@ -1686,7 +1686,8 @@ bool QSslSocket::waitForDisconnected(int msecs)
 
     if (!d->plainSocket)
         return false;
-    if (d->mode == UnencryptedMode)
+    // Forward to the plain socket unless the connection is secure.
+    if (d->mode == UnencryptedMode && !d->autoStartHandshake)
         return d->plainSocket->waitForDisconnected(msecs);
 
     QElapsedTimer stopWatch;
@@ -1697,6 +1698,17 @@ bool QSslSocket::waitForDisconnected(int msecs)
         if (!waitForEncrypted(msecs))
             return false;
     }
+    // We are delaying the disconnect, if the write buffer is not empty.
+    // So, start the transmission.
+    if (!d->writeBuffer.isEmpty())
+        d->transmit();
+
+    // At this point, the socket might be disconnected, if disconnectFromHost()
+    // was called just after the connectToHostEncrypted() call. Also, we can
+    // lose the connection as a result of the transmit() call.
+    if (state() == UnconnectedState)
+        return true;
+
     bool retVal = d->plainSocket->waitForDisconnected(qt_subtract_from_timeout(msecs, stopWatch.elapsed()));
     if (!retVal) {
         setSocketState(d->plainSocket->state());