[4338] in Kerberos
krb4 telnetd prevents zmodem uploads
daemon@ATHENA.MIT.EDU (Bruce R. Lewis)
Wed Dec 14 14:28:14 1994
To: kerberos@MIT.EDU
Date: 14 Dec 1994 19:09:34 GMT
From: brlewis@joy.mit.edu (Bruce R. Lewis)
Since we switched to Kerberized telnetd on some Ultrix machines at MIT,
users have complained that zmodem uploads no longer work. Any insights
on this problem are welcome.
I investigated the zmodem problem by network snooping. Data gets passed
through the following chain (thanks Marc Horowitz):
pc comm program (zterm on the Mac)
pc comm driver
pc serial port
modem (MIT ISDN phone)
5ESS
CPT X.25
CPT telnet client
<-- snooping here
dialup telnet server
pty master side
kernel
pty slave side
application (rz)
When rz is ready to receive data, it outputs a ctrl-q (among other
chars). My snooping revealed that when the ctrl-q is transmitted to the
CPT telnet client, the upload works. When ctrl-q is not transmitted,
the upload fails. Uploads fail when Kerberized telnetd is running on
Ultrix or AIX, but succeed when it's running on Solaris. Uploads work
when stock Ultrix telnetd is running.
The ctrl-q is getting eaten somewhere below the "snooping here" line
above. It's probably getting eaten in the pty master side. In all
likelihood, if Kerberized telnetd configured the master side the same
way Ultrix telnetd does, the problem would go away.
--
, Bruce R. Lewis ___
(| Analyst Programmer =====
|) Distributed Computing and Network Services |||||||
MIT' Information Systems -=======-
