IRP_NOCACHE problem with lanmanredirector

NTFSD
1

Hi,

i want to realize a mini filter to encrypt/decrypt files in a particular shared folder.
I started with swapbuffer and i add a stream file context to know file name during read/write operation. I read that for a filter encryption only IRP_NOCACHE must be processed. It is correct?
Everythings work ok on local file.
When i attach filter to lanmanredirector and i drag a file to shared folder, filter receive operation with no IRP_NOCACHE. I don’t know if this way is the correct way to archive my goal.
Any suggestion?

Thanks

2

The SMB client implementation can (and does) change caching protocol internally, so that sometimes cached I/O is treated as non-cached I/O (based upon oplock state.) Depending upon the cache/no-cache behavior does not work reliably in my experience, and you should not build your solution to assume that you can know the caching behavior of the underlying file system.

Others on the list may have other experiences to share, but that’s been my experience in doing this.

Tony
OSR