In message <Pine.NEB.4.33.0211011033400.20030-100000@vespasia.home-net.internet
connect.net>, Bill Studenmund writes:
>

>
>> 2.  If I enable DSR/DTR handshaking, whenever the terminal tries to handshak
>e,
>> it ends up causing getty to respawn - I suspect NetBSD is seeing it as a
>> break.
>
>That actually would be good. That means that DTR is getting mapped to CD,
>which is what mdmbuf wants. Mark the port local, and go for it.
>
I don't think so.  The "break" key on a terminal sends a "long space" 
signal, i.e., an in-band "bit" that is stretched long enough that it 
causes a framing error because there's no stop bit.  (We're getting far 
afield here of NetBSD, but...  An RS-232 line in idle state is sending 
a constant voltage equivalent to a 1-bit.  A start bit is one bit-time 
worth of a 0-bit, followed by some number (usually 8) bit-times of 0 or 
1 bits, as needed.  That's followed by one (sometimes more) "stop bits" 
-- idle time, really, when the signal value *must* be 1.  If it isn't, 
a framing error is signaled.  The break key sends about 1/4 second of 
0-bit, enough to cause a framing error at any baud rate.  It's thus a 
speed-independent signal of *something*.  It has nothing to do with DTR 
or CD, and in fact can be sent on 3-wire interfaces with no control 
leads.)

		--Steve Bellovin, http://www.research.att.com/~smb (me)
		http://www.wilyhacker.com ("Firewalls" book)