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Refcount redirection close #106

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Refcount redirection close #106

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kvojacheck
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Proposed reference counting workaround to issue #105
Please kindly review, since I'm quite new to Windows driver developement.

@kvojacheck
Cleanup warnings
a30a1f4
@kvojacheck
Add ability to pass process ID to OnClose()
a58993c 
Refactor CUsbDkFilterStrategy::OnClose() in a way that the process id
can be passed from the beginning of the call-chain.
This is just a technical change needed for the next commit.
@kvojacheck
Stop redirection upon closing the last reference
bc6cae1 
Add reference counting, since the previously used 'PID-based' method
might not work reliably: for example, if the program doing redirection
is forcefully closed from the task manager, the USB redirection could
remain stuck.
After this commit, we are always stopping redirection if the reference
count drops to zero.
@ybendito
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@kvojacheck What happens in following flow: app1 redirects the device and uses it, app2 opens the device and closes it?
as pid == 0 means 'match all' will this stop the redirection?

@ybendito
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Probably the proper thing is to use file context (WDFFILECONTEXT) instead of process identifier

@kvojacheck
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@kvojacheck What happens in following flow: app1 redirects the device and uses it, app2 opens the device and closes it? as pid == 0 means 'match all' will this stop the redirection?

At the time app2 closes the device, the refcount is still 1 (since app1 is still using the device), therefore we would go to the PID-based identification as before: as the returned PID value by PsGetCurrentProcessId is likely corresponds to app2 (and most likely not app1), the closure of app2 wouldn't cause the removal of the redirection.

@kvojacheck
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Probably the proper thing is to use file context (WDFFILECONTEXT) instead of process identifier

Thank you for the tip, I will definitely look into this!

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@kvojacheck @ybendito