IFWXExternalIOCompletion::CompleteAsyncIO is the
I/O completion notification used with asynchronous I/O for
operating system files. If the Microsoft Firewall service has a
handle for an operating system file, and needs to read the file or
write to it, this operation will be asynchronous, so that it can
take place in the background. An example of an asynchronous I/O
operation for operating system files is writing to or reading from
There are four sequential steps to this process:
- The Firewall service calls IFWXFirewall::HookToCompletionPort,
which connects the file handle to the service completion port. This
step takes place once per connection.
- The Firewall service calls IFWXFirewall::CreateOverlapped
to create the overlapped object, which implements the IFWXOverlapped interface.
- The Firewall service uses IFWXOverlapped::GetOverlapped
to get a pointer to the Winsock OVERLAPPED structure, and IFWXOverlapped::SetNotificationInterface
to send notification when the I/O operation is completed.
receives the notification, including a succeed or fail message,
information regarding the user, and the number of bytes
The following figure summarizes the process of asynchronous I/O
for operating system files.
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