1) Set the 'vc' ('virtual circuit') id to a non-zero value (if it's 0, the smb server will disconnect all hosts who are already connected)
2) Handle the authentication error NT_STATUS_REQUEST_NOT_ACCEPTED, which indicates that there are too many connected hosts (11 is the default on most versions of Windows, or 10 for the anonymous account). If we see the error, we wait and try again.
3) Handle the file creation error, NT_STATUS_PIPE_NOT_AVAILABLE, which appears to be caused by a race condition of some sort. It happens when a large number of connections are attempted simultaneously, and is fixed by a short backoff (50ms worked fine, but I'm using 100ms)
The end result is a significant speedup in our SMB checks without losing data.
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