• Contact: tech-userlevel, tech-kern
• Duration estimate: 3 months

The existing puffs protocol gives a way to forward kernel-level file system actions to a userspace process. This project generalizes that protocol to allow forwarding file system actions arbitrarily across a network. This will make it possible to mount any kernel file system type from any location on the network, given a suitable arrangement of components.

The file system components to be used are puffs and rump. puffs is used to forward local file system requests from the kernel to userspace and rump is used to facilitate running the kernel file system in userspace as a service daemon.

The milestones are the following:

• Write the necessary code to be able to forward requests from one source to another. This involves most likely reworking a bit of the libpuffs option parsing code and creating a puffs client (say, mount_puffs) to be able to forward requests from one location to another. The puffs protocol should be extended to include the necessary new features or a new protocol invented.

  Proof-of-concept code for this has already been written. (Where is it?)

• Currently the puffs protocol used for communication between the kernel and userland is machine dependent. To facilitate forwarding the protocol to remote hosts, a machine independent version must be specified.

• To be able to handle multiple clients, the file systems must be converted to daemons instead of being utilities. This will also, in the case of kernel file system servers, include adding locking to the communication protocol.

The end result will look something like this:

# start serving ffs from /dev/wd0a on port 12675
onehost> ffs_serv -p 12675 /dev/wd0a
# start serving cd9660 from /dev/cd0a on port 12676
onehost> cd9660_serv -p 12675 /dev/cd0a

# meanwhile in outer space, mount anotherhost from port 12675
anotherhost> mount_puffs -t tcp onehost:12675 /mnt
anotherhost> mount
...
anotherhost:12675 on /mnt type <negotiated>
...
anotherhost> cd /mnt
anotherhost> ls
  ... etc

The implementor should have some familiarity with file systems and network services.

Any proposal should include answers to at least the following questions:

• How is this different from NFS?

• How is the protocol different from 9p?

• How is this scheme going to handle the hard things that NFS doesn't do very well, such as distributed cache consistency?

• Given industry trends, why is this project proposing a new protocol instead of conforming to the SOA model?