This is a distribution of both client and server telnet. These programs
SunOs 3.5 X X (no linemode in server)
SunOs 4.1 X X (no linemode in server)
DYNIX V3.0.17.9 X X (no linemode in server)
Ultrix 3.1 X X (no linemode in server)
Ultrix 4.0 X X (no linemode in server)
In addition, previous versions have been compiled on the following
machines, but were not available for testing this version.
SunOs 4.0.3c X X (no linemode in server)
BSD 4.3 X X (no linemode in server)
DYNIX V3.0.12 X X (no linemode in server)
This version of telnet/telnetd has support for both
the AUTHENTICATION and ENCRYPTION options. The
AUTHENTICATION option is fairly well defined, and
an option number has been assigned to it. The
ENCRYPTION option is still in a state of flux; an
option number has NOT been assigned to it yet.
The code is provided in this release for experimental
The telnet "send" command can now be used to send
do/dont/will/wont commands, with any telnet option
name. The rules for when do/dont/will/wont are sent
are still followed, so just because the user requests
that one of these be sent doesn't mean that it will
The telnet "getstatus" command no longer requires
that option printing be enabled to see the response
to the "DO STATUS" command.
A -n flag has been added to telnetd to disable
A new telnet command, "auth" has been added (if
AUTHENTICATE is defined). It has four sub-commands,
"status", "debug", "disable", "enable" and "help".
A new telnet command, "encrypt" has been added (if
ENCRYPT is defined). It has many sub-commands:
"enable", "type", "start", "stop", "input",
"-input", "output", "-output", "status", "auto",
"verbose", "debug", and "help".
An "rlogin" interface has been added. If the program
is named "rlogin", or the "-r" flag is given, then
an rlogin type of interface will be used.
~. Terminates the session
~<susp> Suspend the session
~^] Escape to telnet command mode
BUG: If you type the rlogin escape character
in the middle of a line while in rlogin
mode, you cannot erase it or any characters
before it. Hopefully this can be fixed
A "libtelnet.a" has now been created. This libraray
contains code that is common to both telnet and
telnetd. This is also where library routines that
are needed, but are not in the standard C library,
The makefiles have been re-done. All of the site
specific configuration information has now been put
into a single "Config.generic" file, in the top level
directory. Changing this one file will take care of
all three subdirectories. Also, to add a new/local
definition, a "Config.local" file may be created
at the top level; if that file exists, the subdirectories
will use that file instead of "Config.generic".
Many 1-2 line functions in commands.c have been
removed, and just inserted in-line, or replaced
The non-termio code in both telnet and telnetd was
setting/clearing CTLECH in the sg_flags word. This
was incorrect, and has been changed to set/clear the
LCTLECH bit in the local mode word.
The SRCRT #define has been removed. If IP_OPTIONS
and IPPROTO_IP are defined on the system, then the
source route code is automatically enabled.
The NO_GETTYTAB #define has been removed; there
is a compatability routine that can be built into
libtelnet to achive the same results.
The server, telnetd, has been switched to use getopt()
for parsing the argument list.
The code for getting the input/output speeds via
cfgetispeed()/cfgetospeed() was still not quite
right in telnet. Posix says if the ispeed is 0,
then it is really equal to the ospeed.
The suboption processing code in telnet now has
explicit checks to make sure that we received
the entire suboption (telnetd was already doing this).
The telnet code for processing the terminal type
could cause a core dump if an existing connection
was closed, and a new connection opened without
Telnetd was doing a TCSADRAIN when setting the new
terminal settings; This is not good, because it means
that the tcsetattr() will hang waiting for output to
drain, and telnetd is the only one that will drain
the output... The fix is to use TCSANOW which does
Telnetd was improperly setting/clearing the ISTRIP
flag in the c_lflag field, it should be using the
When the child process of telnetd was opening the
slave side of the pty, it was re-setting the EXTPROC
bit too early, and some of the other initialization
code was wiping it out. This would cause telnetd
to go out of linemode and into single character mode.
One instance of leaving linemode in telnetd forgot
to send a WILL ECHO to the client, the net result
would be that the user would see double character
If the MODE was being changed several times very
quickly, telnetd could get out of sync with the
state changes and the returning acks; and wind up
being left in the wrong state.
Switch the client to use getopt() for parsing the
argument list. The 4.3Reno getopt.c is included for
systems that don't have getopt().
Use the posix _POSIX_VDISABLE value for what value
to use when disabling special characters. If this
is undefined, it defaults to 0x3ff.
For non-termio systems, TIOCSETP was being used to
change the state of the terminal. This causes the
input queue to be flushed, which we don't want. This
is now changed to TIOCSETN.
Take out the "#ifdef notdef" around the code in the
server that generates a "sync" when the pty oputput
is flushed. The potential problem is that some older
telnet clients may go into an infinate loop when they
receive a "sync", if so, the server can be compiled
with "NO_URGENT" defined.
Fix the client where it was setting/clearing the OPOST
bit in the c_lflag field, not the c_oflag field.
Fix the client where it was setting/clearing the ISTRIP
bit in the c_lflag field, not the c_iflag field. (On
4.3Reno, this is the ECHOPRT bit in the c_lflag field.)
The client also had its interpretation of WILL BINARY
Fix a bug in client that would cause a core dump when
attempting to remove the last environment variable.
In the client, there were a few places were switch()
was being passed a character, and if it was a negative
value, it could get sign extended, and not match
the 8 bit case statements. The fix is to and the
Add a couple more printoption() calls in the client, I
don't think there are any more places were a telnet
command can be received and not printed out when
A new flag has been added to the client, "-a". Currently,
this just causes the USER name to be sent across, in
the future this may be used to signify that automatic
authentication is requested.
The USER variable is now only sent by the client if
the "-a" or "-l user" options are explicity used, or
if the user explicitly asks for the "USER" environment
variable to be exported. In the server, if it receives
the "USER" environment variable, it won't print out the
banner message, so that only "Password:" will be printed.
This makes the symantics more like rlogin, and should be
more familiar to the user. (People are not used to
getting a banner message, and then getting just a
Re-vamp the code for starting up the child login
process. The code was getting ugly, and it was
hard to tell what was really going on. What we
do now is after the fork(), in the child:
1) make sure we have no controlling tty
2) open and initialize the tty
3) do a setsid()/setpgrp()
4) makes the tty our controlling tty.
On some systems, #2 makes the tty our controlling
tty, and #4 is a no-op. The parent process does
a gets rid of any controlling tty after the child
Use the strdup() library routine in telnet, instead
of the local savestr() routine. If you don't have
strdup(), you need to define NO_STRDUP.
Add support for ^T (SIGINFO/VSTATUS), found in the
4.3Reno distribution. This maps to the AYT character.
You need a 4-line bugfix in the kernel to get this
> *** tty_pty.c.ORG Tue Sep 11 09:41:53 1990
> --- tty_pty.c Tue Sep 11 17:48:03 1990
> if ((tp->t_lflag&NOFLSH) == 0)
> ttyflush(tp, FREAD|FWRITE);
> ! pgsignal(tp->t_pgrp, *(unsigned int *)data);
> if ((tp->t_lflag&NOFLSH) == 0)
> ttyflush(tp, FREAD|FWRITE);
> ! pgsignal(tp->t_pgrp, *(unsigned int *)data, 1);
> ! if ((*(unsigned int *)data == SIGINFO) &&
> ! ((tp->t_lflag&NOKERNINFO) == 0))
The client is now smarter when setting the telnet escape
character; it only sets it to one of VEOL and VEOL2 if
one of them is undefined, and the other one is not already
defined to the telnet escape character.
Handle TERMIOS systems that have seperate input and output
line speed settings imbedded in the flags.
Many other minor bug fixes.
Re-organize makefiles and source tree. The telnet/Source
directory is now gone, and all the source that was in
telnet/Source is now just in the telnet directory.
Seperate makefile for each system are now gone. There
are two makefiles, Makefile and Makefile.generic.
The "Makefile" has the definitions for the various
system, and "Makefile.generic" does all the work.
There is a variable called "WHAT" that is used to
specify what to make. For example, in the telnet
directory, you might say:
to clean out the directory.
Add support for the ENVIRON and XDISPLOC options.
In order for the server to work, login has to have
the "-p" option to preserve environment variables.
Add the SOFT_TAB and LIT_ECHO modes in the LINEMODE support.
Add the "-l user" option to command line and open command
(This is passed through the ENVIRON option).
Add the "-e" command line option, for setting the escape
Add the "-D", diagnostic, option to the server. This allows
the server to print out debug information, which is very
useful when trying to debug a telnet that doesn't have any
Turn off the literal next character when not in LINEMODE.
Don't recognize ^Y locally, just pass it through.
Make minor modifications for Sun4.0 and Sun4.1
Add support for both FORW1 and FORW2 characters. The
telnet escpape character is set to whichever of the
two is not being used. If both are in use, the escape
character is not set, so when in linemode the user will
have to follow the escape character with a <CR> or <EOF)
to get it passed through.
Commands can now be put in single and double quotes, and
a backslash is now an escape character. This is needed
for allowing arbitrary strings to be assigned to environment
Switch telnetd to use macros like telnet for keeping
track of the state of all the options.
Fix telnetd's processing of options so that we always do
the right processing of the LINEMODE option, regardless
of who initiates the request to turn it on. Also, make
sure that if the other side went "WILL ECHO" in response
to our "DO ECHO", that we send a "DONT ECHO" to get the
Fix the TERMIOS setting of the terminal speed to handle both
BSD's seperate fields, and the SYSV method of CBAUD bits.
Change how we deal with the other side refusing to enable
an option. The sequence used to be: send DO option; receive
WONT option; send DONT option. Now, the sequence is: send
DO option; receive WONT option. Both should be valid
according to the spec, but there has been at least one
client implementation of telnet identified that can get
really confused by this. (The exact sequence, from a trace
on the server side, is (numbers are number of responses that
we expect to get after that line...):
send WILL ECHO 1 (initial request)
send WONT ECHO 2 (server is changing state)
recv DO ECHO 1 (first reply, ok. expect DONT ECHO next)
send WILL ECHO 2 (server changes state again)
recv DONT ECHO 1 (second reply, ok. expect DO ECHO next)
recv DONT ECHO 0 (third reply, wrong answer. got DONT!!!)
*** send WONT ECHO (send WONT to acknowledge the DONT)
send WILL ECHO 1 (ask again to enable option)
(and the last 5 lines loop forever)
The line with the "***" is last of the WILL/DONT/WONT sequence.
The change to the server to not generate that makes this same
There is other option negotiation going on, and not sending
the third part changes some of the timings, but this specific
example no longer gets stuck in a loop. The "telnet.state"
file has been modified to reflect this change to the algorithm.
A bunch of miscellaneous bug fixes and changes to make
This version of telnet also has some KERBEROS stuff in
it. This has not been tested, it uses an un-authorized
telnet option number, and uses an out-of-date version
of the (still being defined) AUTHENTICATION option.
There is no support for this code, do not enable it.
CHANGES/BUGFIXES SINCE LAST RELEASE:
Some support for IP TOS has been added. Requires that the
kernel support the IP_TOS socket option (currently this
Both telnet and telnetd now use the cc_t typedef. typedefs are
included for systems that don't have it (in termios.h).
SLC_SUSP was not supported properly before. It is now.
IAC EOF was not translated properly in telnetd for SYSV_TERMIO
when not in linemode. It now saves a copy of the VEOF character,
so that when ICANON is turned off and we can't trust it anymore
(because it is now the VMIN character) we use the saved value.
There were two missing "break" commands in the linemode
processing code in telnetd.
Telnetd wasn't setting the kernel window size information
properly. It was using the rows for both rows and columns...
README: You are reading it.
This file contains all the OS specific definitions. It
has pre-definitions for many common system types, and is
in standard makefile fromat. See the comments at the top
of the file for more information.
This is not part of the distribution, but if this file exists,
it is used instead of "Config.generic". This allows site
specific configuration without having to modify the distributed
This file contains the diffs for the changes needed for the
kernel to support LINEMODE is the server. These changes are
for a 4.3BSD system. You may need to make some changes for
There is a new bit in the terminal state word, TS_EXTPROC.
When this bit is set, several aspects of the terminal driver
are disabled. Input line editing, character echo, and
mapping of signals are all disabled. This allows the telnetd
to turn of these functions when in linemode, but still keep
track of what state the user wants the terminal to be in.
TIOCEXT Turn on/off the TS_EXTPROC bit
TIOCGSTATE Get t_state of tty to look at TS_EXTPROC bit
TIOCSIG Generate a signal to processes in the
current process group of the pty.
There is a new mode for packet driver, the TIOCPKT_IOCTL bit.
When packet mode is turned on in the pty, and the TS_EXTPROC
bit is set, then whenever the state of the pty is changed, the
next read on the master side of the pty will have the TIOCPKT_IOCTL
bit set, and the data will contain the following:
This allows the process on the server side of the pty to know
when the state of the terminal has changed, and what the new
However, if you define USE_TERMIO or SYSV_TERMIO, the code will
expect that the structure returned in the TIOCPKT_IOCTL is
the termio/termios structure.
This file contains the changes needed for the stty(1) program
to report on the current status of the TS_EXTPROC bit. It also
allows the user to turn on/off the TS_EXTPROC bit. This is useful
because it allows the user to say "stty -extproc", and the
LINEMODE option will be automatically disabled, and saying "stty
extproc" will re-enable the LINEMODE option.
Both the client and server have code in them to deal
with option negotiation loops. The algorithm that is
used is described in this file.
Macros for use in formatting the man pages on non-4.3Reno
This directory contains the client code. No kernel changes are
This directory contains the server code. If LINEMODE or KLUDGELINEMODE
are defined, then the kernel modifications listed above are needed.
This directory contains code that is common to both the client
This directory has a new <arpa/telnet.h>
The following TELNET options are supported:
The LINEMODE option is supported as per RFC1116. The
FORWARDMASK option is not currently supported.
BINARY: The client has the ability to turn on/off the BINARY
option in each direction. Turning on BINARY from
server to client causes the LITOUT bit to get set in
the terminal driver on both ends, turning on BINARY
from the client to the server causes the PASS8 bit
to get set in the terminal driver on both ends.
This is supported as per RFC1091. On the server side,
when a terminal type is received, termcap/terminfo
is consulted to determine if it is a known terminal
type. It keeps requesting terminal types until it
gets one that it recongnizes, or hits the end of the
list. The server side looks up the entry in the
termcap/terminfo data base, and generates a list of
names which it then passes one at a time to each
request for a terminal type, duplicating the last
entry in the list before cycling back to the beginning.
NAWS: The Negotiate about Window Size, as per RFC 1073.
Implemented as per RFC 1079
Implemented as per RFC 1080
The server will send its current status upon
request. It does not ask for the clients status.
The client will request the servers current status
from the "send getstatus" command.
This option is currently being defined by the IETF
Telnet Working Group, and an RFC has not yet been
issued, but should be in the near future...
This functionality can be done through the ENVIRON
option, it is added here for completeness.
This option is currently being defined by the IETF
Telnet Working Group, and an RFC has not yet been
issued. The basic framework is pretty much decided,
but the definitions for the specific authentication
schemes is still in a state of flux.
This option is currently being defined by the IETF
Telnet Working Group, and an RFC has not yet been
issued. The draft RFC is still in a state of flux,
so this code may change in the future.
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