sgifford at suspectclass.com
Thu Jan 31 13:20:06 GMT 2002
David Lee <t.d.lee at durham.ac.uk> writes:
> On Thu, 31 Jan 2002, Andrew Bartlett wrote:
> > Scott Gifford wrote:
> > > I believe that I'm the one that started talking about pseudo
> > > terminals, and I actually did intend it as an implementation detail.
> [ sorry for any mis-representation there... ]
No, it's good you said what you thought I meant; otherwise we'd just
all go on with our own assumptions and never know what we were talking
> > > They are widely available, mostly portable, easily understood, and
> > > well-tested.
> > >
> > > You can pretty much copy a couple dozen lines out of Stevens' Advanced
> > > Programming in the UNIX Environment and have a quite portable
> > > implementation in an hour or so.
> > We already have most of this, becouse the 'unix password sync' occurs
> > over a tty.
> Could you briefly point us to a source file in Samba? (With a version
> number, because I seem to recall that some of the password handling has
> been substantially changing in recent months/weeks.)
Look at findpty at chgpasswd.c:45 in the today's CVS.
> So it seems entirely reasonable to migrate. No longer use a fictitious
> "/dev/smb/<n>", but rather a real "/dev/pts/<n>" (or whatever is the
> natural name for that particular host OS).
> Then smbd can grab (or at least allocate) that 'real' pseudo-tty, and use
> its name in the utmp/connection stuff.
> Then, if "smb.conf" directs, it can also open it and listen on it for real
> "wall", "write", etc., and translate these into WinPopup messages.
> There we are. Mission accomplished, absolutely cleanly. No run-time code
> anywhere doing "/dev/blah/"-creation. The real UNIX utilities "simply
I think this is absolutely the solution.
> As an incidental benefit, we also now have a subroutine interface within
> smbd, so smbd internals (e.g. vfs modules) can message the user.
> What does it need?
> 1. Connection/utmp code to use names consistent with ttys on the OS,
> and whose name is allocated "live" in co-operation with the OS.
And I think most of this is in findpty().
> 2. If smb.conf option directs to enable wall/write-like support then
> smbd opens that same tty and adds it to the select list for reading.
> 3. If input arrives on that tty, it is sent as a WinPopup, using code
> from libsmb and friends. (Detail: that code needs some adjustment for
> this use, but this can be retro-fitted cleanly and transparently
> into the libsmb library.)
It's a little trickier than that, since there aren't clear message
delimiters, but it should still be do-able. I wrote a little
proof-of-concept program that read from a TTY, then packaged up a
message when it hadn't received anything new for 5 seconds. That
should work well enough for what we need; it did the write thing for
"echo message |write samba" and "wall message", which is what's
Unfortunately, when I tried to port it to use Samba's more portable
findpty and utmp code, I got into Dependency Hell and couldn't get it
to build. Somebody with more knowledge of Samba would probably be
able to throw something together relatively quickly.
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