Re: draft-bjh21-ssh-transport-extension-01

[Joseph Galbraith <galb-list%vandyke.com@localhost>]

Ben Harris wrote:
> I've uploaded a new version of my transport extension draft which I 
> think addresses everyone's comments.  Any more before I wave it at the 
> IESG?  In particular, I'm wondering if I should extend it to allocate 
> similar message numbers for extensions to ssh-userauth and/or 
> ssh-connect.
> 
> <http://www.ietf.org/internet-drafts/draft-bjh21-ssh-transport-extension-01.txt>

I just read this through with an eye towards implementing it,
and have several comments:

1. Did I just miss it, or is the message number actually not yet
   defined?

2. SSH_MSG_UNIMPLEMENTED has some drawbacks (in particular, it isn't
   reasonably possible to identify which packet was unimplemented.)

   For unrecognized extensions, I'd rather see a predefined
   extension:

   byte      SSH_MSG_TRANSPORT_EXTENSION
   string    "unrecognized-extension"

   that should be sent in response to a extension the implementation
   doesn't recognize.

   This has the advantage that the sender can differentiate between
   implementations not implementing the draft and implementations
   not implementing the extension.

3. Do we need a nod to in-order vs. out-of-order processing:

   Much of the SSH protocol allows multiple requests to be
   made before receiving a response.  For any given extension
   requiring a response, the extension MUST define whether
   multiple outstanding requests are to be allowed, and if so,
   whether there are constraints on the ordering of the
   processing and responses.

Thanks,

Joseph