RedirFS and Dazuko Filter

Hi,

it has been a while since my last post to this mailing list about RedirFS.
In spite of that John Ogness did not like the idea of replacing(hooking) VFS object operations
I kept on working on RedirFS and I started the RedirFS project. Because I have made some progress
and the first testing version is available for public I would like to tell you few things about
the RedirFS project and about the Dazuko Filter.

RedirFS stands for Redirecting FileSystem. It is implemented as a Linux Kernel Module(LKM) and creates a new
layer between Linux Virtual Filesystem Switch(VFS) and native filesystem drivers(EXT2, NFS, etc.). It is based
on replacing VFS object operations and its main purpose is to make native filesystem calls accessible
to 3rd-party LKM.

Here is a list of RedirFS's basic features:
* Implemented as a LKM that does not need to modify Linux kernel source code.
* For now it works only with 2.6.x kernels. Back-port to 2.4.x kernels should be not difficult.
* Allows to manage one or more Filters(3rd-party LKMs) and call them in specific order based on their priorities.
* Allows Filters to select pre and post callback function for selected native filesystem call.
* Allows Filters to include or exclude directories over which their callback function will be called or not.
* It redirects only operations which are required by Filters. All other calls goes directly to native filesystem
  drivers with absolutely no overhead. If redirected operation is no longer used by any Filter it is set back to original
  operation.
* Only VFS objects which belong to directories selected by Filters are affected.
* Allows Filters on-the-fly to set, reset and remove callback functions.
* Allows Filters on-the-fly to include and exclude directories.
* Filters can be dynamically added and removed.
* For now only selected operations for regular files, directories and dentries can be redirected.
* For now it ignores sub-mounts, so you have to explicitly include them.

Notes:
- RedirFS was tested on x86(i386) and x86_64 architectures.
- Do NOT try to include /proc directory(/proc directory has different operations then its subdirs)
- It is strongly recommended to use RedirFS only on testing machines where filesystem violation is acceptable.



Dazuko Filter uses the RedirFS Framework to get necessary events from Linux kernel.

Dazuko Filter features:
* available as a patch for Dazuko 2.1.0
* allows Dazuko to generate ON_OPEN, ON_EXEC, ON_CLOSE, ON_RMDIR and ON_UNLINK events.

For more information please see the RedirFS project site at www.redirfs.org.

RedirFS INSTALL file - http://www.redirfs.org/svn/redirfs/trunk/src/redirfs/INSTALL
Dazuko Filter INSTALL file - http://www.redirfs.org/svn/redirfs/trunk/src/dazukoflt/INSTALL

RedirFS is intended as a general framework which will allow to redirect all operations in VFS objects.
I think that a lot of interesting Filters can be written using the RedirFS Framework(e.g. UnionFS, 
CompressFS, CryptographicFS, ACLs etc.)

I will be thankful for all your feedbacks.

Frantisek Hrbata