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slc.c

/*
 * 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 1.1.1.1 2004-10-14 13:19:53 ianb 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 */

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