All four of the other network-protocol backends (Raw, Telnet, rlogin
and SUPDUP) now have a 'socket_connected' flag, which starts off false
and is set to true when (if) their Socket signals that the connection
attempt has succeeded.
This field is used to tell backend_socket_log whether the session has
started yet (hence, whether it should still be logging messages from
the proxy). This replaces various ad-hoc answers to that question in
each backend, which were the best I could do when sockets didn't
notify connection success. Now they do, we can do it properly.
Also, the new flag controls the answer to each backend's sendok()
method, which makes them all satisfy a new policy rule: no backend
shall return true from sendok() while its network connection attempt
is still ongoing.
(Rationale: the network connection attempt may in future involve a
proxy implementation interacting with the user via the terminal, and
it can't do that if the backend is already consuming all the terminal
input.)
It looks as if Ben put that in when he originally wrote the file,
since it refers to a C file style called 'simon', which isn't what I
call my preferred style in _my_ Emacs preferences, but might plausibly
be what he called it in his.
It causes an annoying error every time I load the source file into
Emacs, because it refers to a nonexistent style name. And surely it
will do the same to almost all other Emacs users. Get rid of it.
On a similar theme of separating the query operation from the
attempted change, backend_send() now no longer has the side effect of
returning the current size of the send buffer. Instead, you have to
call backend_sendbuffer() every time you want to know that.
This is used to notify the Seat that some data has been cleared from
the backend's outgoing data buffer. In other words, it notifies the
Seat that it might be worth calling backend_sendbuffer() again.
We've never needed this before, because until now, Seats have always
been the 'main program' part of the application, meaning they were
also in control of the event loop. So they've been able to call
backend_sendbuffer() proactively, every time they go round the event
loop, instead of having to wait for a callback.
But now, the SSH proxy is the first example of a Seat without
privileged access to the event loop, so it has no way to find out that
the backend's sendbuffer has got smaller. And without that, it can't
pass that notification on to plug_sent, to unblock in turn whatever
the proxied connection might have been waiting to send.
In fact, before this commit, sshproxy.c never called plug_sent at all.
As a result, large data uploads over an SSH jump host would hang
forever as soon as the outgoing buffer filled up for the first time:
the main backend (to which sshproxy.c was acting as a Socket) would
carefully stop filling up the buffer, and then never receive the call
to plug_sent that would cause it to start again.
The new callback is ignored everywhere except in sshproxy.c. It might
be a good idea to remove backend_sendbuffer() entirely and convert all
previous uses of it into non-empty implementations of this callback,
so that we've only got one system; but for the moment, I haven't done
that.
This notifies the Seat that the entire backend session has finished
and closed its network connection - or rather, that it _might_ have
done, and that the frontend should check backend_connected() if it
wasn't planning to do so already.
The existing Seat implementations haven't needed this: the GUI ones
don't actually need to do anything specific when the network
connection goes away, and the CLI ones deal with it by being in charge
of their own event loop so that they can easily check
backend_connected() at every possible opportunity in any case. But I'm
about to introduce a new Seat implementation that does need to know
this, and doesn't have any other way to get notified of it.
This is the last of the subdirectory creations I had planned. This one
is almost too footling to bother with (it hardly declutters the top
level very much).
One useful side effect is that I've included testback.c (containing
the null and loopback backends) in the otherbackends library, which
means it will now actually be _compiled_ even when nothing's using it,
and we'll spot bit-rot promptly when internal APIs change.
(And, to prove the point, I've immediately had to fix some bit-rot.)
