18.104.22.168.8 UID Generation
User IDs (UIDs) are generated on CIFS servers. The generation of UIDs MUST satisfy the following constraints:
The UID MUST be a 16-bit opaque value.
The UID MUST be unique for a specified client/server SMB connection.
The UID MUST remain valid for the lifetime of the SMB connection on which the authentication is performed, or until the client sends a request to the server to close the UID (to log off the user).
Once a UID has been closed, the value can be reused in the response to another authentication request.
The value 0xFFFE was declared reserved in the LAN Manager 1.0 documentation, so a value of 0xFFFE SHOULD NOT be used as a valid UID.<21> All other possible values for a UID, excluding zero (0x0000), are valid.