Increase the datagram receive buffer on Windows to 64k

runtime/bin/eventhandler_win.cc

Index: runtime/bin/eventhandler_win.cc
diff --git a/runtime/bin/eventhandler_win.cc b/runtime/bin/eventhandler_win.cc
index 6e27f821fb2a5fe603b02d80f04af957f6212f2c..5488e4d18fdb68c3c229fe07bb0a786a4017f98e 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -989,7 +989,8 @@ bool DatagramSocket::IssueRecvFrom() {
   ASSERT(completion_port_ != INVALID_HANDLE_VALUE);
   ASSERT(pending_read_ == NULL);
 
-  OverlappedBuffer* buffer = OverlappedBuffer::AllocateRecvFromBuffer(1024);
+  OverlappedBuffer* buffer =
+      OverlappedBuffer::AllocateRecvFromBuffer(64 * 1024);

[kustermann, 2015/10/02 15:36:58]

Maybe make a constant kMaxUDPPackageLength ?

[Theoretically they can actually be bigger: https://tools.ietf.org/html/rfc2675]

[Søren Gjesse, 2015/10/06 07:01:42]

Added a constant and mentioned the current limit in the dartdoc for receive.

 
   DWORD flags;
   flags = 0;
@@ -1212,16 +1213,21 @@ void EventHandlerImplementation::HandleRecvFrom(Handle* handle,
                                                 int bytes,
                                                 OverlappedBuffer* buffer) {
   ASSERT(handle->is_datagram_socket());
-  buffer->set_data_length(bytes);
-  handle->ReadComplete(buffer);
-  if (!handle->IsClosing()) {
-    int event_mask = 1 << kInEvent;
-    if ((handle->Mask() & event_mask) != 0) {
+  if (bytes >= 0) {
+    buffer->set_data_length(bytes);
+    handle->ReadComplete(buffer);
+    if (!handle->IsClosing()) {
+      int event_mask = 1 << kInEvent;
+      if ((handle->Mask() & event_mask) != 0) {
         Dart_Port port = handle->NextNotifyDartPort(event_mask);
-      DartUtils::PostInt32(port, event_mask);
+        DartUtils::PostInt32(port, event_mask);
+      }
     }
+  } else {
+    HandleError(handle);

[kustermann, 2015/10/02 15:36:58]

Is there a way to test that we report the error to Dart?

[Søren Gjesse, 2015/10/06 07:01:42]

I have not found one. I did a manual test with the small constant and received
the ERROR_MORE_DATA in Dart.

   }
 
+

[kustermann, 2015/10/02 15:36:58]

extra empty line

[Søren Gjesse, 2015/10/06 07:01:42]

Removed.

   DeleteIfClosed(handle);
 }
 
@@ -1413,6 +1419,11 @@ void EventHandlerImplementation::EventHandlerEntry(uword args) {
           last_error == ERROR_BROKEN_PIPE) {
         ASSERT(bytes == 0);
         handler_impl->HandleIOCompletion(bytes, key, overlapped);
+      } else if (last_error == ERROR_MORE_DATA) {
+        // Don't ASSERT no bytes in this case. This can happen if the receive
+        // buffer for datagram sockets is to small to contain a full datagram,
+        // and in this case bytes hold the bytes that was read.
+        handler_impl->HandleIOCompletion(-1, key, overlapped);
       } else {
         ASSERT(bytes == 0);
         handler_impl->HandleIOCompletion(-1, key, overlapped);