Network: Fix up previous corruption patch

This is a fix-up for cff39fba10ffc10ee4dcfdc66ff6528eb26462d3.
That patch lead to some internal state issues that lead to the QTBUG-47048
or to QNetworkReply objects erroring with "Connection Closed" when
the server closed the Keep-Alive connection.

This patch changes the QNAM socket slot connections to be DirectConnection.
We don't close the socket anymore in slots where it is anyway in a closed state
afterwards. This prevents event/stack recursions.
We also flush QSslSocket/QTcpSocket receive buffers when receiving a disconnect
so that the developer always gets the full decrypted data from the buffers.

[ChangeLog][QtNetwork] Fix HTTP issues with "Unknown Error" and "Connection Closed"
[ChangeLog][QtNetwork][Sockets] Read OS/encrypted read buffers when connection
closed by server.

Change-Id: Ib4d6a2d0d988317e3a5356f36e8dbcee4590beed
Task-number: QTBUG-47048
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Reviewed-by: Richard J. Moore <rich@kde.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index 26667715be..0e82d4ab66 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -768,6 +768,7 @@ bool QAbstractSocketPrivate::canReadNotification()
 void QAbstractSocketPrivate::canCloseNotification()
 {
     Q_Q(QAbstractSocket);
+    // Note that this method is only called on Windows. Other platforms close in the canReadNotification()
 
 #if defined (QABSTRACTSOCKET_DEBUG)
     qDebug("QAbstractSocketPrivate::canCloseNotification()");
@@ -777,7 +778,11 @@ void QAbstractSocketPrivate::canCloseNotification()
     if (isBuffered) {
         // Try to read to the buffer, if the read fail we can close the socket.
         newBytes = buffer.size();
-        if (!readFromSocket()) {
+        qint64 oldReadBufferMaxSize = readBufferMaxSize;
+        readBufferMaxSize = 0; // temporarily disable max read buffer, we want to empty the OS buffer
+        bool hadReadFromSocket = readFromSocket();
+        readBufferMaxSize = oldReadBufferMaxSize;
+        if (!hadReadFromSocket) {
             q->disconnectFromHost();
             return;
         }