[unix-history] / usr / src / usr.bin / telnet / README



This is a distribution of both client and server telnet.  These programs
have been compiled on:
			telnet	telnetd
	BSD 4.4		  X	  X
	UNICOS 5.1	  X	  X
	UNICOS 6.0	  X	  X
	SunOs 3.5	  X	  X (no linemode in server)
	SunOs 4.0.3c	  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	    (server compiles, but doesn't
					work with /bin/csh)

In addition, previous versions have been compiled on the following
machines, but were not available for testing this version.
			telnet	telnetd
	BSD 4.3		  X  	  X (no linemode in server)
	DYNIX V3.0.12	  X	  X (no linemode in server)

September 14, 1990:

	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
	and DO BINARY reversed.

	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
	switch value with 0xff.

	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
	"options" is on.

	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
	"Password:" prompt.)

	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
	is fork()ed.

	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
	to work properly:

	> *** tty_pty.c.ORG	Tue Sep 11 09:41:53 1990
	> --- tty_pty.c	Tue Sep 11 17:48:03 1990
	> ***************
	> *** 609,613 ****
	> 			if ((tp->t_lflag&NOFLSH) == 0)
	> 				ttyflush(tp, FREAD|FWRITE);
	> ! 			pgsignal(tp->t_pgrp, *(unsigned int *)data);
	> 			return(0);
	> 		}
	> --- 609,616 ----
	> 			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))
	> ! 				ttyinfo(tp);
	> 			return(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.

June 20, 1990:
	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:
		make 4.4bsd WHAT=clean
	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
	character.

	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
	debugging ability.

	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
	variables.

	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
	option turned back off!

	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)
		recv DO ECHO	0

		recv DONT ECHO	0
		send WONT ECHO	1
		recv DONT ECHO	0
		recv DO ECHO	1
		send WILL ECHO	0
		(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
	example become:

		send will ECHO	1
		send wont ECHO	2
		recv do ECHO	1
		send will ECHO	2
		recv dont ECHO	1
		recv dont ECHO	0
		recv do ECHO	1
		send will ECHO	0

	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
	lint happier.

	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.


March 1, 1990:
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
	is only in UNICOS 6.0).

	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...

Questions/comments go to
		David Borman
		Cray Research, Inc.
		655F Lone Oak Drive
		Eagan, MN 55123
		dab@cray.com.

README:	You are reading it.

kern.diff:
	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
	your particular system.

	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.

	New ioctl()s:

		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:
		struct xx {
			struct sgttyb a;
			struct tchars b;
			struct ltchars c;
			int t_state;
			int t_flags;
		}
	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
	state is.

	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.

stty.diff:
	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.

telnet.state:
	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.

telnet:
	This directory contains the client code.  No kernel changes are
	needed to use this code.

telnetd:
	This directory contains the server code.  If LINEMODE or KLUDGELINEMODE
	are defined, then the kernel modifications listed above are needed.

arpa:
	This directory has a new <arpa/telnet.h>


The following TELNET options are supported:
	
	LINEMODE:
		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.

	TERMINAL-TYPE:
		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.

	TERMINAL-SPEED:
		Implemented as per RFC 1079

	TOGGLE-FLOW-CONTROL:
		Implemented as per RFC 1080

	TIMING-MARK:
		As per RFC 860

	SGA:	As per RFC 858

	ECHO:	As per RFC 857

	STATUS:
		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.

	ENVIRON:
		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...

	X-DISPLAY-LOCATION:
		This functionality can be done through the ENVIRON
		option, it is added here for completeness.

Look at the Makefile for comments about #define paramaters that need
to be set up for your individual site.  There are also several Makefiles
for various systems that these have been compiled on.
Commit	Line	Data
bd994ff1 PB	1
	2
	3	This is a distribution of both client and server telnet. These programs
	4	have been compiled on:
	5	telnet telnetd
	6	BSD 4.4 X X
	7	UNICOS 5.1 X X
	8	UNICOS 6.0 X X
	9	SunOs 3.5 X X (no linemode in server)
	10	SunOs 4.0.3c X X (no linemode in server)
	11	SunOs 4.1 X X (no linemode in server)
	12	DYNIX V3.0.17.9 X X (no linemode in server)
	13	Ultrix 3.1 X X (no linemode in server)
	14	Ultrix 4.0 X (server compiles, but doesn't
	15	work with /bin/csh)
	16
	17	In addition, previous versions have been compiled on the following
	18	machines, but were not available for testing this version.
	19	telnet telnetd
	20	BSD 4.3 X X (no linemode in server)
	21	DYNIX V3.0.12 X X (no linemode in server)
	22
	23	September 14, 1990:
	24
	25	Switch the client to use getopt() for parsing the
	26	argument list. The 4.3Reno getopt.c is included for
	27	systems that don't have getopt().
	28
	29	Use the posix _POSIX_VDISABLE value for what value
	30	to use when disabling special characters. If this
	31	is undefined, it defaults to 0x3ff.
	32
	33	For non-termio systems, TIOCSETP was being used to
	34	change the state of the terminal. This causes the
	35	input queue to be flushed, which we don't want. This
	36	is now changed to TIOCSETN.
	37
	38	Take out the "#ifdef notdef" around the code in the
	39	server that generates a "sync" when the pty oputput
	40	is flushed. The potential problem is that some older
	41	telnet clients may go into an infinate loop when they
	42	receive a "sync", if so, the server can be compiled
	43	with "NO_URGENT" defined.
	44
	45	Fix the client where it was setting/clearing the OPOST
	46	bit in the c_lflag field, not the c_oflag field.
	47
	48	Fix the client where it was setting/clearing the ISTRIP
	49	bit in the c_lflag field, not the c_iflag field. (On
	50	4.3Reno, this is the ECHOPRT bit in the c_lflag field.)
	51	The client also had its interpretation of WILL BINARY
	52	and DO BINARY reversed.
	53
	54	Fix a bug in client that would cause a core dump when
	55	attempting to remove the last environment variable.
	56
	57	In the client, there were a few places were switch()
	58	was being passed a character, and if it was a negative
	59	value, it could get sign extended, and not match
	60	the 8 bit case statements. The fix is to and the
	61	switch value with 0xff.
	62
	63	Add a couple more printoption() calls in the client, I
	64	don't think there are any more places were a telnet
65	command can be received and not printed out when
66	"options" is on.
67
68	A new flag has been added to the client, "-a". Currently,
69	this just causes the USER name to be sent across, in
70	the future this may be used to signify that automatic
71	authentication is requested.
72
73	The USER variable is now only sent by the client if
74	the "-a" or "-l user" options are explicity used, or
75	if the user explicitly asks for the "USER" environment
76	variable to be exported. In the server, if it receives
77	the "USER" environment variable, it won't print out the
78	banner message, so that only "Password:" will be printed.
79	This makes the symantics more like rlogin, and should be
80	more familiar to the user. (People are not used to
81	getting a banner message, and then getting just a
82	"Password:" prompt.)
83
84	Re-vamp the code for starting up the child login
85	process. The code was getting ugly, and it was
86	hard to tell what was really going on. What we
87	do now is after the fork(), in the child:
88	1) make sure we have no controlling tty
89	2) open and initialize the tty
90	3) do a setsid()/setpgrp()
91	4) makes the tty our controlling tty.
92	On some systems, #2 makes the tty our controlling
93	tty, and #4 is a no-op. The parent process does
94	a gets rid of any controlling tty after the child
95	is fork()ed.
96
97	Use the strdup() library routine in telnet, instead
98	of the local savestr() routine. If you don't have
99	strdup(), you need to define NO_STRDUP.
100
101	Add support for ^T (SIGINFO/VSTATUS), found in the
102	4.3Reno distribution. This maps to the AYT character.
103	You need a 4-line bugfix in the kernel to get this
104	to work properly:
105
106	> *** tty_pty.c.ORG Tue Sep 11 09:41:53 1990
107	> --- tty_pty.c Tue Sep 11 17:48:03 1990
108	> ***************
109	> * 609,613 **
110	> if ((tp->t_lflag&NOFLSH) == 0)
111	> ttyflush(tp, FREAD\|FWRITE);
112	> ! pgsignal(tp->t_pgrp, (unsigned int )data);
113	> return(0);
114	> }
115	> --- 609,616 ----
116	> if ((tp->t_lflag&NOFLSH) == 0)
117	> ttyflush(tp, FREAD\|FWRITE);
118	> ! pgsignal(tp->t_pgrp, (unsigned int )data, 1);
119	> ! if (((unsigned int )data == SIGINFO) &&
120	> ! ((tp->t_lflag&NOKERNINFO) == 0))
121	> ! ttyinfo(tp);
122	> return(0);
123	> }
124
125	The client is now smarter when setting the telnet escape
126	character; it only sets it to one of VEOL and VEOL2 if
127	one of them is undefined, and the other one is not already
128	defined to the telnet escape character.
129
130	Handle TERMIOS systems that have seperate input and output
131	line speed settings imbedded in the flags.
132
133	Many other minor bug fixes.
134
135	June 20, 1990:
136	Re-organize makefiles and source tree. The telnet/Source
137	directory is now gone, and all the source that was in
138	telnet/Source is now just in the telnet directory.
139
140	Seperate makefile for each system are now gone. There
141	are two makefiles, Makefile and Makefile.generic.
142	The "Makefile" has the definitions for the various
143	system, and "Makefile.generic" does all the work.
144	There is a variable called "WHAT" that is used to
145	specify what to make. For example, in the telnet
146	directory, you might say:
147	make 4.4bsd WHAT=clean
148	to clean out the directory.
149
150	Add support for the ENVIRON and XDISPLOC options.
151	In order for the server to work, login has to have
152	the "-p" option to preserve environment variables.
153
154	Add the SOFT_TAB and LIT_ECHO modes in the LINEMODE support.
155
156	Add the "-l user" option to command line and open command
157	(This is passed through the ENVIRON option).
158
159	Add the "-e" command line option, for setting the escape
160	character.
161
162	Add the "-D", diagnostic, option to the server. This allows
163	the server to print out debug information, which is very
164	useful when trying to debug a telnet that doesn't have any
165	debugging ability.
166
167	Turn off the literal next character when not in LINEMODE.
168
169	Don't recognize ^Y locally, just pass it through.
170
171	Make minor modifications for Sun4.0 and Sun4.1
172
173	Add support for both FORW1 and FORW2 characters. The
174	telnet escpape character is set to whichever of the
175	two is not being used. If both are in use, the escape
176	character is not set, so when in linemode the user will
177	have to follow the escape character with a <CR> or <EOF)
178	to get it passed through.
179
180	Commands can now be put in single and double quotes, and
181	a backslash is now an escape character. This is needed
182	for allowing arbitrary strings to be assigned to environment
183	variables.
184
185	Switch telnetd to use macros like telnet for keeping
186	track of the state of all the options.
187
188	Fix telnetd's processing of options so that we always do
189	the right processing of the LINEMODE option, regardless
190	of who initiates the request to turn it on. Also, make
191	sure that if the other side went "WILL ECHO" in response
192	to our "DO ECHO", that we send a "DONT ECHO" to get the
193	option turned back off!
194
195	Fix the TERMIOS setting of the terminal speed to handle both
196	BSD's seperate fields, and the SYSV method of CBAUD bits.
197
198	Change how we deal with the other side refusing to enable
199	an option. The sequence used to be: send DO option; receive
200	WONT option; send DONT option. Now, the sequence is: send
201	DO option; receive WONT option. Both should be valid
202	according to the spec, but there has been at least one
203	client implementation of telnet identified that can get
204	really confused by this. (The exact sequence, from a trace
205	on the server side, is (numbers are number of responses that
206	we expect to get after that line...):
207
208	send WILL ECHO 1 (initial request)
209	send WONT ECHO 2 (server is changing state)
210	recv DO ECHO 1 (first reply, ok. expect DONT ECHO next)
211	send WILL ECHO 2 (server changes state again)
212	recv DONT ECHO 1 (second reply, ok. expect DO ECHO next)
213	recv DONT ECHO 0 (third reply, wrong answer. got DONT!!!)
214	*** send WONT ECHO (send WONT to acknowledge the DONT)
215	send WILL ECHO 1 (ask again to enable option)
216	recv DO ECHO 0
217
218	recv DONT ECHO 0
219	send WONT ECHO 1
220	recv DONT ECHO 0
221	recv DO ECHO 1
222	send WILL ECHO 0
223	(and the last 5 lines loop forever)
224
225	The line with the "***" is last of the WILL/DONT/WONT sequence.
226	The change to the server to not generate that makes this same
227	example become:
228
229	send will ECHO 1
230	send wont ECHO 2
231	recv do ECHO 1
232	send will ECHO 2
233	recv dont ECHO 1
234	recv dont ECHO 0
235	recv do ECHO 1
236	send will ECHO 0
237
238	There is other option negotiation going on, and not sending
239	the third part changes some of the timings, but this specific
240	example no longer gets stuck in a loop. The "telnet.state"
241	file has been modified to reflect this change to the algorithm.
242
243	A bunch of miscellaneous bug fixes and changes to make
244	lint happier.
245
246	This version of telnet also has some KERBEROS stuff in
247	it. This has not been tested, it uses an un-authorized
248	telnet option number, and uses an out-of-date version
249	of the (still being defined) AUTHENTICATION option.
250	There is no support for this code, do not enable it.
251
252
253	March 1, 1990:
254	CHANGES/BUGFIXES SINCE LAST RELEASE:
255	Some support for IP TOS has been added. Requires that the
256	kernel support the IP_TOS socket option (currently this
257	is only in UNICOS 6.0).
258
259	Both telnet and telnetd now use the cc_t typedef. typedefs are
260	included for systems that don't have it (in termios.h).
261
262	SLC_SUSP was not supported properly before. It is now.
263
264	IAC EOF was not translated properly in telnetd for SYSV_TERMIO
265	when not in linemode. It now saves a copy of the VEOF character,
266	so that when ICANON is turned off and we can't trust it anymore
267	(because it is now the VMIN character) we use the saved value.
268
269	There were two missing "break" commands in the linemode
270	processing code in telnetd.
271
272	Telnetd wasn't setting the kernel window size information
273	properly. It was using the rows for both rows and columns...
274
275	Questions/comments go to
276	David Borman
277	Cray Research, Inc.
278	655F Lone Oak Drive
279	Eagan, MN 55123
280	dab@cray.com.
281
282	README: You are reading it.
283
284	kern.diff:
285	This file contains the diffs for the changes needed for the
286	kernel to support LINEMODE is the server. These changes are
287	for a 4.3BSD system. You may need to make some changes for
288	your particular system.
289
290	There is a new bit in the terminal state word, TS_EXTPROC.
291	When this bit is set, several aspects of the terminal driver
292	are disabled. Input line editing, character echo, and
293	mapping of signals are all disabled. This allows the telnetd
294	to turn of these functions when in linemode, but still keep
295	track of what state the user wants the terminal to be in.
296
297	New ioctl()s:
298
299	TIOCEXT Turn on/off the TS_EXTPROC bit
300	TIOCGSTATE Get t_state of tty to look at TS_EXTPROC bit
301	TIOCSIG Generate a signal to processes in the
302	current process group of the pty.
303
304	There is a new mode for packet driver, the TIOCPKT_IOCTL bit.
305	When packet mode is turned on in the pty, and the TS_EXTPROC
306	bit is set, then whenever the state of the pty is changed, the
307	next read on the master side of the pty will have the TIOCPKT_IOCTL
308	bit set, and the data will contain the following:
309	struct xx {
310	struct sgttyb a;
311	struct tchars b;
312	struct ltchars c;
313	int t_state;
314	int t_flags;
315	}
316	This allows the process on the server side of the pty to know
317	when the state of the terminal has changed, and what the new
318	state is.
319
320	However, if you define USE_TERMIO or SYSV_TERMIO, the code will
321	expect that the structure returned in the TIOCPKT_IOCTL is
322	the termio/termios structure.
323
324	stty.diff:
325	This file contains the changes needed for the stty(1) program
326	to report on the current status of the TS_EXTPROC bit. It also
327	allows the user to turn on/off the TS_EXTPROC bit. This is useful
328	because it allows the user to say "stty -extproc", and the
329	LINEMODE option will be automatically disabled, and saying "stty
330	extproc" will re-enable the LINEMODE option.
331
332	telnet.state:
333	Both the client and server have code in them to deal
334	with option negotiation loops. The algorithm that is
335	used is described in this file.
336
337	telnet:
338	This directory contains the client code. No kernel changes are
339	needed to use this code.
340
341	telnetd:
342	This directory contains the server code. If LINEMODE or KLUDGELINEMODE
343	are defined, then the kernel modifications listed above are needed.
344
345	arpa:
346	This directory has a new <arpa/telnet.h>
347
348
349	The following TELNET options are supported:
350
351	LINEMODE:
352	The LINEMODE option is supported as per RFC1116. The
353	FORWARDMASK option is not currently supported.
354
355	BINARY: The client has the ability to turn on/off the BINARY
356	option in each direction. Turning on BINARY from
357	server to client causes the LITOUT bit to get set in
358	the terminal driver on both ends, turning on BINARY
359	from the client to the server causes the PASS8 bit
360	to get set in the terminal driver on both ends.
361
362	TERMINAL-TYPE:
363	This is supported as per RFC1091. On the server side,
364	when a terminal type is received, termcap/terminfo
365	is consulted to determine if it is a known terminal
366	type. It keeps requesting terminal types until it
367	gets one that it recongnizes, or hits the end of the
368	list. The server side looks up the entry in the
369	termcap/terminfo data base, and generates a list of
370	names which it then passes one at a time to each
371	request for a terminal type, duplicating the last
372	entry in the list before cycling back to the beginning.
373
374	NAWS: The Negotiate about Window Size, as per RFC 1073.
375
376	TERMINAL-SPEED:
377	Implemented as per RFC 1079
378
379	TOGGLE-FLOW-CONTROL:
380	Implemented as per RFC 1080
381
382	TIMING-MARK:
383	As per RFC 860
384
385	SGA: As per RFC 858
386
387	ECHO: As per RFC 857
388
389	STATUS:
390	The server will send its current status upon
391	request. It does not ask for the clients status.
392	The client will request the servers current status
393	from the "send getstatus" command.
394
395	ENVIRON:
396	This option is currently being defined by the IETF
397	Telnet Working Group, and an RFC has not yet been
398	issued, but should be in the near future...
399
400	X-DISPLAY-LOCATION:
401	This functionality can be done through the ENVIRON
402	option, it is added here for completeness.
403
404	Look at the Makefile for comments about #define paramaters that need
405	to be set up for your individual site. There are also several Makefiles
406	for various systems that these have been compiled on.