readme.old

里面包含了telnet的客户端和服务器端

This is a distribution of both client and server telnet.  These programs
have been compiled on:
			telnet	telnetd
	BSD 4.3 Reno	  X	  X
	UNICOS 5.1	  X	  X
	UNICOS 6.0	  X	  X
	UNICOS 6.1	  X	  X
	UNICOS 7.0	  X	  X
	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.
			telnet	telnetd
	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)

Februrary 22, 1991:

    Features:

	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
	and testing purposes.

	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
	be sent...

	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
	keepalives.

	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
		~~	Pass through the ~.
	    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
		 in a future release...

    General changes:

	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,
	are placed.

	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
	with a macro.

    Bug Fixes:

	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
	exiting telnet.

	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
	not wait.

	Telnetd was improperly setting/clearing the ISTRIP
	flag in the c_lflag field, it should be using the
	c_iflag field. 

	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
	echo.

	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.

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.