Revert "Fix for Flutter issue 11260 (https://github.com/flutter/flutter/issues/11260)"

runtime/bin/socket.cc

Index: runtime/bin/socket.cc
diff --git a/runtime/bin/socket.cc b/runtime/bin/socket.cc
index f6c01fba078a80fb8f36a6da967b7aba390a7128..e2e16778c3fb6179976d06a4e5ef4a384fbd1b0f 100644
--- a/runtime/bin/socket.cc
+++ b/runtime/bin/socket.cc
@@ -365,28 +365,18 @@ void FUNCTION_NAME(Socket_RecvFrom)(Dart_NativeArguments args) {
   Socket* socket =
       Socket::GetSocketIdNativeField(Dart_GetNativeArgument(args, 0));
 
-  const intptr_t available = SocketBase::Available(socket->fd());
-  if (available < 0) {
-    Dart_SetReturnValue(args, DartUtils::NewDartOSError());
-    return;
-  }
-  if (available == 0) {
-    Dart_SetReturnValue(args, Dart_Null());
-    return;
+  // TODO(sgjesse): Use a MTU value here. Only the loopback adapter can
+  // handle 64k datagrams.
+  IsolateData* isolate_data =
+      reinterpret_cast<IsolateData*>(Dart_CurrentIsolateData());
+  if (isolate_data->udp_receive_buffer == NULL) {
+    isolate_data->udp_receive_buffer =
+        reinterpret_cast<uint8_t*>(malloc(65536));
   }
-
-  // Allocate a buffer of the exact size into which data can be read.
-  uint8_t* data_buffer = NULL;
-  Dart_Handle data = IOBuffer::Allocate(available, &data_buffer);
-  if (Dart_IsError(data)) {
-    Dart_PropagateError(data);
-  }
-  ASSERT(data_buffer != NULL);
-
-  // Read data into the buffer.
   RawAddr addr;
-  const intptr_t bytes_read = SocketBase::RecvFrom(
-      socket->fd(), data_buffer, available, &addr, SocketBase::kAsync);
+  intptr_t bytes_read =
+      SocketBase::RecvFrom(socket->fd(), isolate_data->udp_receive_buffer,
+                           65536, &addr, SocketBase::kAsync);
   if (bytes_read == 0) {
     Dart_SetReturnValue(args, Dart_Null());
     return;
@@ -396,6 +386,15 @@ void FUNCTION_NAME(Socket_RecvFrom)(Dart_NativeArguments args) {
     Dart_SetReturnValue(args, DartUtils::NewDartOSError());
     return;
   }
+  // Datagram data read. Copy into buffer of the exact size,
+  ASSERT(bytes_read > 0);
+  uint8_t* data_buffer = NULL;
+  Dart_Handle data = IOBuffer::Allocate(bytes_read, &data_buffer);
+  if (Dart_IsError(data)) {
+    Dart_PropagateError(data);
+  }
+  ASSERT(data_buffer != NULL);
+  memmove(data_buffer, isolate_data->udp_receive_buffer, bytes_read);
 
   // Get the port and clear it in the sockaddr structure.
   int port = SocketAddress::GetAddrPort(addr);