Re: Simplified protocol?

[Wouter Verhelst <w@uter.be>]

This discussion died out a bit, mostly because I have been busy
preparing for a move to Cape Town.

I'm on the plane now \o/

I've committed (but not pushed yet -- no Internet on this flight) all
the suggestions that were made. Once I remember to do so after landing,
I'll push them to github.

Feel free to remind me if you see this mail and it's not there yet ;-)

We really should finish this...

On Thu, Nov 15, 2018 at 06:03:53PM +0000, Richard W.M. Jones wrote:
> On Thu, Nov 15, 2018 at 03:41:08PM +0100, Wouter Verhelst wrote:
> > +### Baseline
> > +
> > +The following MUST be implemented by all implementations, and should be
> > +considered a baseline:
> > +
> > +- NOTLS mode
> > +- The fixed newstyle handshake
> > +- During the handshake:
> > +
> > +    - the `NBD_OPT_INFO` and `NBD_OPT_GO` messages, with the
> > +      `NBD_INFO_EXPORT` response.
> > +    - Servers that receive messages which they do not implement MUST
> > +      reply to them with `NBD_OPT_UNSUP`, and MUST NOT fail to parse
> > +      the next message received.
> > +    - the `NBD_OPT_ABORT` message, and its response.
> > +    - the `NBD_OPT_LIST` message and its response.
> > +
> > +- During the transmission phase:
> > +
> > +    - Simple replies
> > +    - the `NBD_CMD_READ` message (and its response)
> > +    - the `NBD_CMD_WRITE` message (and its response)
> 
> Could drop this, or note that it's only necessary for read/write
> exports.
> 
> > +Clients and servers that desire maximum interoperability SHOULD
> > +implement the following features:
> > +
> > +- TLS-encrypted communication, which may be required by some
> > +  implementations or configurations;
> > +- Servers that implement block constraints through `NBD_INFO_BLOCK_SIZE`
> > +  and desire maximum interoperability SHOULD NOT require them.
> > +  Similarly, clients that desire maximum interoperability SHOULD
> > +  implement querying for block size constraints. Since some older
> > +  clients default to a block size of 1024 bytes, implementations
> > +  desiring maximum interoperability MAY default to that size.
> > +- Clients or servers that desire interoperability with older
> > +  implementations SHOULD implement the `NBD_OPT_EXPORT_NAME` message in
> > +  addition to `NBD_OPT_INFO` and `NBD_OPT_GO`.
> > +- For data safety, implementing `NBD_CMD_FLUSH` and the
> > +  `NBD_CMD_FLAG_FUA` flag to `NBD_CMD_WRITE` is strongly recommended.
> 
> This section mixes clients and servers, and I wonder if it would be
> better to separate them out?
> 
> Rich.
> 
> -- 
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
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> 

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