Re: Transport I-D: KEXINIT reserved field needs description

[Markus Friedl <markus%openbsd.org@localhost>]

On Wed, Jul 23, 2003 at 08:00:37AM -0700, Nicolas Williams wrote:
> On Wed, Jul 23, 2003 at 09:57:24AM +0200, Markus Friedl wrote:
> > On Tue, Jul 22, 2003 at 03:44:42PM -0700, Nicolas Williams wrote:
> > > I think the fact that some implementations do not tolerate KEXINIT
> > > "extensions" should not precluse the proposed change.  Several
> > > implementations already map the peer's version string to compatibility
> > > notes and react accordingly.  While I hope that we can put stop adding
> > > to this database of compatibility notes I think that this particular
> > > issue (KEXINIT extensibility) is worth the trouble to fix.
> > 
> > I don't think it's a good idea to break the protocol at
> > this point.  This compatibility database is always a pain
> > and you always miss some implementations.
> > 
> > I think you could only assume that the peer is able to deal with
> > the extension if it sends a non-zero value in the reserved field,
> > but I doubt this helps for what you want.  On the other hand, you
> > could send the extension data in an extra packet if the reserved byte
> > is not zero.
> 
> Of all the things in the compat db, this would be amongst the most
> important things to have in there.

yes, that's why it's dangerous and it's likely that you miss versions
strings. you should not depend on this and break the protocol this late.