On: NFS > FUSE: Why We Built Our Own NFS Server in Rus...

[mprovost]

NFSv4 is a completely different protocol and basically doesn't share anything with v2/v3. While technically it's still implemented using Sun RPC, it only has two procedures: NULL and COMPOUND. Version 3 is actually an RPC protocol, with a different procedure for each filesystem operation (READ, WRITE, CREATE, ...). One of the genius moves that Sun made with NFS was to distribute the protocol files (rpcgen) which autogenerate stubs (in C) making it easy to implement servers and clients. Nothing like that exists for v4.

[EdSchouten → mprovost]

Look at RFC 7531. XDR definitions for NFSv4 exists, and they can also be used to generate C bindings if you want.

[mprovost → EdSchouten]

Sure, running it through rpcgen generates bindings for both RPCs, NULL and COMPOUND:

    /// /*
    ///  * Remote file service routines
    ///  */
    /// program NFS4_PROGRAM {
    ///         version NFS_V4 {
    ///                 void
    ///                         NFSPROC4_NULL(void) = 0;
    ///
    ///                 COMPOUND4res
    ///                         NFSPROC4_COMPOUND(COMPOUND4args) = 1;
    ///
    ///         } = 4;
    /// } = 100003;

[EdSchouten → mprovost]

Which is also what you want, right? The issue is that with compound calls there is some state that’s carried over between operations (current/saved file handle), so you’d need to implement that yourself anyway.

[mprovost → EdSchouten]

Well yeah that's the difference, it doesn't generate the state machine for you so you "just" need to implement it yourself. For v3, rpcgen spits out a working function that you link into your program and you're done (on the client side anyway). Much easier.