slc.c

这是关于远程登陆TELNET 的源代码 已经测试过的。

/*
 * Copyright (c) 1989 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * From: @(#)slc.c	5.7 (Berkeley) 3/1/91
 */
char slc_rcsid[] = 
  "$Id: slc.c,v 1.5 1999/12/12 14:59:44 dholland Exp $";

#include "telnetd.h"

#ifdef LINEMODE
/*
 * local varibles
 */
static unsigned char *def_slcbuf = (unsigned char *)0;
static int def_slclen = 0;
static int slcchange;	/* change to slc is requested */
static int slcoff;                      /* offset into slc buffer */
static unsigned char slcbuf[NSLC*6];	/* buffer for slc negotiation */

static void add_slcbuf_raw_char(unsigned char ch) {
   if (slcoff < sizeof(slcbuf)) {
      slcbuf[slcoff++] = ch;
   }
}

static void add_slcbuf_char(unsigned char ch) {
   add_slcbuf_raw_char(ch);
   if (ch==0xff) {
      add_slcbuf_raw_char(0xff);
   }
}

/*
 * send_slc
 *
 * Write out the current special characters to the client.
 */
void send_slc(void) {
    int i;

    /*
     * Send out list of triplets of special characters
     * to client.  We only send info on the characters
     * that are currently supported.
     */
    for (i = 1; i <= NSLC; i++) {
	if ((slctab[i].defset.flag & SLC_LEVELBITS) == SLC_NOSUPPORT)
	    continue;
	add_slc((unsigned char)i, slctab[i].current.flag,
		slctab[i].current.val);
    }
}

/*
 * default_slc
 *
 * Set pty special characters to all the defaults.
 */
void default_slc(void) {
    int i;
    for (i = 1; i <= NSLC; i++) {
	slctab[i].current.val = slctab[i].defset.val;
	if (slctab[i].current.val == (cc_t)(_POSIX_VDISABLE)) {
	    slctab[i].current.flag = SLC_NOSUPPORT;
	}
	else {
	    slctab[i].current.flag = slctab[i].defset.flag;
	}
	if (slctab[i].sptr) {
	    *(slctab[i].sptr) = slctab[i].defset.val;
	}
    }
    slcchange = 1;
}

#endif	/* LINEMODE */

/*
 * get_slc_defaults
 *
 * Initialize the slc mapping table.
 */
void get_slc_defaults(void) {
    int i;
    init_termbuf();
    for (i = 1; i <= NSLC; i++) {
	slctab[i].defset.flag = spcset(i, &slctab[i].defset.val, 
				       &slctab[i].sptr);
	slctab[i].current.flag = SLC_NOSUPPORT; 
	slctab[i].current.val = 0; 
    }
}

#ifdef LINEMODE
/*
 * add_slc
 *
 * Add an slc triplet to the slc buffer.
 */
void add_slc(char func, char flag, cc_t val) {
    add_slcbuf_char(func);
    add_slcbuf_char(flag);
    add_slcbuf_char(val);
}

/*
 * start_slc
 *
 * Get ready to process incoming slc's and respond to them.
 *
 * The parameter getit is non-zero if it is necessary to grab a copy
 * of the terminal control structures.
 */
void start_slc(int getit) {
    slcchange = 0;
    if (getit) init_termbuf();
    snprintf(slcbuf, sizeof(slcbuf), "%c%c%c%c", 
	     IAC, SB, TELOPT_LINEMODE, LM_SLC);
    slcoff = 4;
}

/*
 * end_slc
 *
 * Finish up the slc negotiation.  If something to send, then send it.
 */
int end_slc(unsigned char **bufp) {
    /*
     * If a change has occured, store the new terminal control
     * structures back to the terminal driver.
     */
    if (slcchange) {
	set_termbuf();
    }

    /*
     * If the pty state has not yet been fully processed and there is a
     * deferred slc request from the client, then do not send any
     * sort of slc negotiation now.  We will respond to the client's
     * request very soon.
     */
    if (def_slcbuf && (terminit() == 0)) {
	return 0;
    }

    if (slcoff > 4) {
	if (bufp) {
	    *bufp = &slcbuf[4];
	    return(slcoff - 4);
	} 
	else {
	    snprintf(slcbuf+slcoff, sizeof(slcbuf)-slcoff, "%c%c", IAC, SE);
	    slcoff += 2;
	    writenet(slcbuf, slcoff);
	    netflush();  /* force it out immediately */
	}
    }
    return 0;
}

/*
 * process_slc
 *
 * Figure out what to do about the client's slc
 */
void process_slc(unsigned char func, unsigned char flag, cc_t val) {
    register int hislevel, mylevel, ack;

    /*
     * Ensure that we know something about this function
     */
    if (func > NSLC) {
	add_slc(func, SLC_NOSUPPORT, 0);
	return;
    }

    /*
     * Process the special case requests of 0 SLC_DEFAULT 0
     * and 0 SLC_VARIABLE 0.  Be a little forgiving here, don't
     * worry about whether the value is actually 0 or not.
     */
    if (func == 0) {
	if ((flag = flag & SLC_LEVELBITS) == SLC_DEFAULT) {
	    default_slc();
	    send_slc();
	} 
	else if (flag == SLC_VARIABLE) {
	    send_slc();
	}
	return;
    }

    /*
     * Appears to be a function that we know something about.  So
     * get on with it and see what we know.
     */
    
    hislevel = flag & SLC_LEVELBITS;
    mylevel = slctab[func].current.flag & SLC_LEVELBITS;
    ack = flag & SLC_ACK;
    /*
     * ignore the command if:
     * the function value and level are the same as what we already have;
     * or the level is the same and the ack bit is set
     */
    if (hislevel == mylevel && (val == slctab[func].current.val || ack)) {
	return;
    } 
    else if (ack) {
	/*
	 * If we get here, we got an ack, but the levels don't match.
	 * This shouldn't happen.  If it does, it is probably because
	 * we have sent two requests to set a variable without getting
	 * a response between them, and this is the first response.
	 * So, ignore it, and wait for the next response.
	 */
	return;
    } 
    else {
	change_slc(func, flag, val);
    }
}

/*
 * change_slc
 *
 * Process a request to change one of our special characters.
 * Compare client's request with what we are capable of supporting.
 */
void change_slc(char func, char flag, cc_t val) {
    register int hislevel, mylevel;
    
    hislevel = flag & SLC_LEVELBITS;
    mylevel = slctab[func].defset.flag & SLC_LEVELBITS;
    /*
     * If client is setting a function to NOSUPPORT
     * or DEFAULT, then we can easily and directly
     * accomodate the request.
     */
    if (hislevel == SLC_NOSUPPORT) {
	slctab[func].current.flag = flag;
	slctab[func].current.val = (cc_t)_POSIX_VDISABLE;
	flag |= SLC_ACK;
	add_slc(func, flag, val);
	return;
    }
    if (hislevel == SLC_DEFAULT) {
	/*
	 * Special case here.  If client tells us to use
	 * the default on a function we don't support, then
	 * return NOSUPPORT instead of what we may have as a
	 * default level of DEFAULT.
	 */
	if (mylevel == SLC_DEFAULT) {
	    slctab[func].current.flag = SLC_NOSUPPORT;
	} 
	else {
	    slctab[func].current.flag = slctab[func].defset.flag;
	}
	slctab[func].current.val = slctab[func].defset.val;
	add_slc(func, slctab[func].current.flag,
		slctab[func].current.val);
	return;
    }
    
    /*
     * Client wants us to change to a new value or he
     * is telling us that he can't change to our value.
     * Some of the slc's we support and can change,
     * some we do support but can't change,
     * and others we don't support at all.
     * If we can change it then we have a pointer to
     * the place to put the new value, so change it,
     * otherwise, continue the negotiation.
     */
    if (slctab[func].sptr) {
	/*
	 * We can change this one.
	 */
	slctab[func].current.val = val;
	*(slctab[func].sptr) = val;
	slctab[func].current.flag = flag;
	flag |= SLC_ACK;
	slcchange = 1;
	add_slc(func, flag, val);
    } 
    else {
	/*
	 * It is not possible for us to support this
	 * request as he asks.
	 *
	 * If our level is DEFAULT, then just ack whatever was
	 * sent. 
	 *
	 * If he can't change and we can't change,
	 * then degenerate to NOSUPPORT.
	 *
	 * Otherwise we send our level back to him, (CANTCHANGE
	 * or NOSUPPORT) and if CANTCHANGE, send
	 * our value as well.
	 */
	if (mylevel == SLC_DEFAULT) {
	    slctab[func].current.flag = flag;
	    slctab[func].current.val = val;
	    flag |= SLC_ACK;
	} 
	else if (hislevel == SLC_CANTCHANGE && mylevel == SLC_CANTCHANGE) {
	    flag &= ~SLC_LEVELBITS;
	    flag |= SLC_NOSUPPORT;
	    slctab[func].current.flag = flag;
	} 
	else {
	    flag &= ~SLC_LEVELBITS;
	    flag |= mylevel;
	    slctab[func].current.flag = flag;
	    if (mylevel == SLC_CANTCHANGE) {
		slctab[func].current.val = slctab[func].defset.val;
		val = slctab[func].current.val;
	    }
	}
	add_slc(func, flag, val);
    }
}

#if (VEOF == VMIN)
cc_t oldeofc = '\004';
#endif

/*
 * check_slc
 *
 * Check the special characters in use and notify the client if any have
 * changed.  Only those characters that are capable of being changed are
 * likely to have changed.  If a local change occurs, kick the support level
 * and flags up to the defaults.
 */
void check_slc(void) {
    int i;
    for (i = 1; i <= NSLC; i++) {
#if (VEOF == VMIN)
	/*
	 * In a perfect world this would be a neat little
	 * function.  But in this world, we should not notify
	 * client of changes to the VEOF char when
	 * ICANON is off, because it is not representing
	 * a special character.
	 */
	if (i == SLC_EOF) {
	    if (!tty_isediting()) continue;
	    else if (slctab[i].sptr) oldeofc = *(slctab[i].sptr);
	}
#endif	/* VEOF==VMIN */

	if (slctab[i].sptr && (*(slctab[i].sptr) != slctab[i].current.val)) {
	    slctab[i].current.val = *(slctab[i].sptr);
	    if (*(slctab[i].sptr) == (cc_t)_POSIX_VDISABLE) {
		slctab[i].current.flag = SLC_NOSUPPORT;
	    }
	    else {
		slctab[i].current.flag = slctab[i].defset.flag;
	    }
	    add_slc((unsigned char)i, slctab[i].current.flag,
		    slctab[i].current.val);
	}
    }
}

/*
 * do_opt_slc
 *
 * Process an slc option buffer.  Defer processing of incoming slc's
 * until after the terminal state has been processed.  Save the first slc
 * request that comes along, but discard all others.
 *
 * ptr points to the beginning of the buffer, len is the length.
 */
void do_opt_slc(unsigned char  *ptr, int len) {
    unsigned char func, flag;
    cc_t val;
    unsigned char *end = ptr + len;

    if (terminit()) {  /* go ahead */
	while (ptr < end) {
	    func = *ptr++;
	    if (ptr >= end) break;
	    flag = *ptr++;
	    if (ptr >= end) break;
	    val = (cc_t)*ptr++;

	    process_slc(func, flag, val);
	    
	}
    } 
    else {
	/*
	 * save this slc buffer if it is the first, otherwise dump
	 * it.
	 */
	if (def_slcbuf == NULL) {
	    def_slclen = len;
	    def_slcbuf = malloc((unsigned)len);
	    if (def_slcbuf == NULL) return;  /* too bad */
	    bcopy(ptr, def_slcbuf, len);
	}
    }
}

/*
 * deferslc
 *
 * Do slc stuff that was deferred.
 */
void deferslc(void) {
    if (def_slcbuf) {
	start_slc(1);
	do_opt_slc(def_slcbuf, def_slclen);
	end_slc(0);
	free(def_slcbuf);
	def_slcbuf = (unsigned char *)0;
	def_slclen = 0;
    }
}

#endif	/* LINEMODE */