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

[Simon Tatham <anakin%pobox.com@localhost>]

Joseph Galbraith  <galb-list%vandyke.com@localhost> wrote:
> 2. SSH_MSG_UNIMPLEMENTED has some drawbacks (in particular, it isn't
>    reasonably possible to identify which packet was unimplemented.)

Why not? You can remember the sequence number when you construct
your outgoing packets.

I admit I have no first-hand experience of actually trying this, but
I'd imagine that there aren't _many_ circumstances under which you
can recover from SSH_MSG_UNIMPLEMENTED and continue a useful
session. In other words, you'd be able to identify _specific_
outgoing packets on your side of the connection for which you'd be
interested in noticing SSH_MSG_UNIMPLEMENTED. Then you can remember
the sequence number of each of those specific packets until you
receive either the SSH_MSG_UNIMPLEMENTED or the expected response.
For any packet for which you _don't_ have a defined
SSH_MSG_UNIMPLEMENTED handler, there's nothing you can really do
except to terminate the session on the grounds that the other side
refused to deal with something you couldn't manage without.
-- 
Simon Tatham         "My heart bleeds.
<anakin%pobox.com@localhost>    (That's how it works.)"   -- Gareth Taylor