Do not discard WSAECONNRESET error code from UDP under Windows

When a datagram is sent to a closed host/port combination, the host will
likely send back an ICMP error message. In the regular socket API, there
isn't a good way of actually receiving this error, so some Windows kernels
wired that message back up to the call to WSARecvFrom() as a synthetic
datagram. Reading this datagram results in a WSAECONNRESET error code,
which should reported to the user as a refused connection attempt.

To make the errors a bit more informative, the native error strings for
WSAECONNRESET and WSAENETRESET were also added.

Task-number: QTBUG-49301
Change-Id: If659be54ba1b39965b5f481f0c0cb9eeea0a06d2
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Markus Goetz (Woboq GmbH) <markus@woboq.com>

3 files changed, 19 insertions, 1 deletions

diff --git a/src/network/socket/qnativesocketengine.cpp b/src/network/socket/qnativesocketengine.cpp
index 386e0e2cc7..dfece60036 100644
--- a/src/network/socket/qnativesocketengine.cpp
+++ b/src/network/socket/qnativesocketengine.cpp
@@ -275,6 +275,12 @@ void QNativeSocketEnginePrivate::setError(QAbstractSocket::SocketError error, Er
     case TemporaryErrorString:
         socketErrorString = QNativeSocketEngine::tr("Temporary error");
         break;
+    case NetworkDroppedConnectionErrorString:
+        socketErrorString = QNativeSocketEngine::tr("Network dropped connection on reset");
+        break;
+    case ConnectionResetErrorString:
+        socketErrorString = QNativeSocketEngine::tr("Connection reset by peer");
+        break;
     case UnknownSocketErrorString:
         socketErrorString = QNativeSocketEngine::tr("Unknown error");
         break;
diff --git a/src/network/socket/qnativesocketengine_p.h b/src/network/socket/qnativesocketengine_p.h
index c49ef2c3ad..e540b47069 100644
--- a/src/network/socket/qnativesocketengine_p.h
+++ b/src/network/socket/qnativesocketengine_p.h
@@ -229,6 +229,8 @@ public:
         NotSocketErrorString,
         InvalidProxyTypeString,
         TemporaryErrorString,
+        NetworkDroppedConnectionErrorString,
+        ConnectionResetErrorString,
 
         UnknownSocketErrorString = -1
     };
diff --git a/src/network/socket/qnativesocketengine_win.cpp b/src/network/socket/qnativesocketengine_win.cpp
index 708be2dea7..d673d3a15e 100644
--- a/src/network/socket/qnativesocketengine_win.cpp
+++ b/src/network/socket/qnativesocketengine_win.cpp
@@ -1250,7 +1250,17 @@ qint64 QNativeSocketEnginePrivate::nativeReceiveDatagram(char *data, qint64 maxL
             ret = qint64(bytesRead) > maxLength ? maxLength : qint64(bytesRead);
         } else {
             WS_ERROR_DEBUG(err);
-            setError(QAbstractSocket::NetworkError, ReceiveDatagramErrorString);
+            switch (err) {
+            case WSAENETRESET:
+                setError(QAbstractSocket::NetworkError, NetworkDroppedConnectionErrorString);
+                break;
+            case WSAECONNRESET:
+                setError(QAbstractSocket::ConnectionRefusedError, ConnectionResetErrorString);
+                break;
+            default:
+                setError(QAbstractSocket::NetworkError, ReceiveDatagramErrorString);
+                break;
+            }
             ret = -1;
         }
     } else {