text: /*
   * lcp.c - PPP Link Control Protocol.
   *
   * Copyright (c) 1984-2000 Carnegie Mellon University. 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. The name "Carnegie Mellon University" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For permission or any legal
   *    details, please contact
   *      Office of Technology Transfer
   *      Carnegie Mellon University
   *      5000 Forbes Avenue
   *      Pittsburgh, PA  15213-3890
   *      (412) 268-4387, fax: (412) 268-7395
   *      tech-transfer@andrew.cmu.edu
   *
   * 4. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by Computing Services
   *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
   *
   * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
   * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
   * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
   * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
   * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
   * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <netif/ppp/ppp_opts.h>
  #if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
  
  /*
   * @todo:
   */
  
  #if 0 /* UNUSED */
  #include <stdio.h>
  #include <string.h>
  #include <stdlib.h>
  #endif /* UNUSED */
  
  #include "netif/ppp/ppp_impl.h"
  
  #include "netif/ppp/fsm.h"
  #include "netif/ppp/lcp.h"
  #if CHAP_SUPPORT
  #include "netif/ppp/chap-new.h"
  #endif /* CHAP_SUPPORT */
  #include "netif/ppp/magic.h"
  
  /*
   * When the link comes up we want to be able to wait for a short while,
   * or until seeing some input from the peer, before starting to send
   * configure-requests.  We do this by delaying the fsm_lowerup call.
   */
  /* steal a bit in fsm flags word */
  #define DELAYED_UP	0x80
  
  static void lcp_delayed_up(void *arg);
  
  /*
   * LCP-related command-line options.
   */
  #if 0 /* UNUSED */
  int	lcp_echo_interval = 0; 	/* Interval between LCP echo-requests */
  int	lcp_echo_fails = 0;	/* Tolerance to unanswered echo-requests */
  #endif /* UNUSED */
  
  #if 0 /* UNUSED */
  /* options */
  static u_int lcp_echo_interval      = LCP_ECHOINTERVAL; /* Interval between LCP echo-requests */
  static u_int lcp_echo_fails         = LCP_MAXECHOFAILS; /* Tolerance to unanswered echo-requests */
  #endif /* UNUSED */
  
  #if 0 /* UNUSED */
  #if PPP_LCP_ADAPTIVE
  bool	lcp_echo_adaptive = 0;	/* request echo only if the link was idle */
  #endif
  bool	lax_recv = 0;		/* accept control chars in asyncmap */
  bool	noendpoint = 0;		/* don't send/accept endpoint discriminator */
  #endif /* UNUSED */
  
  #if PPP_OPTIONS
  static int noopt (char **);
  #endif /* PPP_OPTIONS */
  
  #ifdef HAVE_MULTILINK
  static int setendpoint (char **);
  static void printendpoint (option_t *, void (*)(void *, char *, ...),
  			       void *);
  #endif /* HAVE_MULTILINK */
  
  #if PPP_OPTIONS
  static option_t lcp_option_list[] = {
      /* LCP options */
      { "-all", o_special_noarg, (void *)noopt,
        "Don't request/allow any LCP options" },
  
      { "noaccomp", o_bool, &lcp_wantoptions[0].neg_accompression,
        "Disable address/control compression",
        OPT_A2CLR, &lcp_allowoptions[0].neg_accompression },
      { "-ac", o_bool, &lcp_wantoptions[0].neg_accompression,
        "Disable address/control compression",
        OPT_ALIAS | OPT_A2CLR, &lcp_allowoptions[0].neg_accompression },
  
      { "asyncmap", o_uint32, &lcp_wantoptions[0].asyncmap,
        "Set asyncmap (for received packets)",
        OPT_OR, &lcp_wantoptions[0].neg_asyncmap },
      { "-as", o_uint32, &lcp_wantoptions[0].asyncmap,
        "Set asyncmap (for received packets)",
        OPT_ALIAS | OPT_OR, &lcp_wantoptions[0].neg_asyncmap },
      { "default-asyncmap", o_uint32, &lcp_wantoptions[0].asyncmap,
        "Disable asyncmap negotiation",
        OPT_OR | OPT_NOARG | OPT_VAL(~0U) | OPT_A2CLR,
        &lcp_allowoptions[0].neg_asyncmap },
      { "-am", o_uint32, &lcp_wantoptions[0].asyncmap,
        "Disable asyncmap negotiation",
        OPT_ALIAS | OPT_OR | OPT_NOARG | OPT_VAL(~0U) | OPT_A2CLR,
        &lcp_allowoptions[0].neg_asyncmap },
  
      { "nomagic", o_bool, &lcp_wantoptions[0].neg_magicnumber,
        "Disable magic number negotiation (looped-back line detection)",
        OPT_A2CLR, &lcp_allowoptions[0].neg_magicnumber },
      { "-mn", o_bool, &lcp_wantoptions[0].neg_magicnumber,
        "Disable magic number negotiation (looped-back line detection)",
        OPT_ALIAS | OPT_A2CLR, &lcp_allowoptions[0].neg_magicnumber },
  
      { "mru", o_int, &lcp_wantoptions[0].mru,
        "Set MRU (maximum received packet size) for negotiation",
        OPT_PRIO, &lcp_wantoptions[0].neg_mru },
      { "default-mru", o_bool, &lcp_wantoptions[0].neg_mru,
        "Disable MRU negotiation (use default 1500)",
        OPT_PRIOSUB | OPT_A2CLR, &lcp_allowoptions[0].neg_mru },
      { "-mru", o_bool, &lcp_wantoptions[0].neg_mru,
        "Disable MRU negotiation (use default 1500)",
        OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLR, &lcp_allowoptions[0].neg_mru },
  
      { "mtu", o_int, &lcp_allowoptions[0].mru,
        "Set our MTU", OPT_LIMITS, NULL, MAXMRU, MINMRU },
  
      { "nopcomp", o_bool, &lcp_wantoptions[0].neg_pcompression,
        "Disable protocol field compression",
        OPT_A2CLR, &lcp_allowoptions[0].neg_pcompression },
      { "-pc", o_bool, &lcp_wantoptions[0].neg_pcompression,
        "Disable protocol field compression",
        OPT_ALIAS | OPT_A2CLR, &lcp_allowoptions[0].neg_pcompression },
  
      { "passive", o_bool, &lcp_wantoptions[0].passive,
        "Set passive mode", 1 },
      { "-p", o_bool, &lcp_wantoptions[0].passive,
        "Set passive mode", OPT_ALIAS | 1 },
  
      { "silent", o_bool, &lcp_wantoptions[0].silent,
        "Set silent mode", 1 },
  
      { "lcp-echo-failure", o_int, &lcp_echo_fails,
        "Set number of consecutive echo failures to indicate link failure",
        OPT_PRIO },
      { "lcp-echo-interval", o_int, &lcp_echo_interval,
        "Set time in seconds between LCP echo requests", OPT_PRIO },
  #if PPP_LCP_ADAPTIVE
      { "lcp-echo-adaptive", o_bool, &lcp_echo_adaptive,
        "Suppress LCP echo requests if traffic was received", 1 },
  #endif
      { "lcp-restart", o_int, &lcp_fsm[0].timeouttime,
        "Set time in seconds between LCP retransmissions", OPT_PRIO },
      { "lcp-max-terminate", o_int, &lcp_fsm[0].maxtermtransmits,
        "Set maximum number of LCP terminate-request transmissions", OPT_PRIO },
      { "lcp-max-configure", o_int, &lcp_fsm[0].maxconfreqtransmits,
        "Set maximum number of LCP configure-request transmissions", OPT_PRIO },
      { "lcp-max-failure", o_int, &lcp_fsm[0].maxnakloops,
        "Set limit on number of LCP configure-naks", OPT_PRIO },
  
      { "receive-all", o_bool, &lax_recv,
        "Accept all received control characters", 1 },
  
  #ifdef HAVE_MULTILINK
      { "mrru", o_int, &lcp_wantoptions[0].mrru,
        "Maximum received packet size for multilink bundle",
        OPT_PRIO, &lcp_wantoptions[0].neg_mrru },
  
      { "mpshortseq", o_bool, &lcp_wantoptions[0].neg_ssnhf,
        "Use short sequence numbers in multilink headers",
        OPT_PRIO | 1, &lcp_allowoptions[0].neg_ssnhf },
      { "nompshortseq", o_bool, &lcp_wantoptions[0].neg_ssnhf,
        "Don't use short sequence numbers in multilink headers",
        OPT_PRIOSUB | OPT_A2CLR, &lcp_allowoptions[0].neg_ssnhf },
  
      { "endpoint", o_special, (void *) setendpoint,
        "Endpoint discriminator for multilink",
        OPT_PRIO | OPT_A2PRINTER, (void *) printendpoint },
  #endif /* HAVE_MULTILINK */
  
      { "noendpoint", o_bool, &noendpoint,
        "Don't send or accept multilink endpoint discriminator", 1 },
  
      {NULL}
  };
  #endif /* PPP_OPTIONS */
  
  /*
   * Callbacks for fsm code.  (CI = Configuration Information)
   */
  static void lcp_resetci(fsm *f);	/* Reset our CI */
  static int  lcp_cilen(fsm *f);		/* Return length of our CI */
  static void lcp_addci(fsm *f, u_char *ucp, int *lenp); /* Add our CI to pkt */
  static int  lcp_ackci(fsm *f, u_char *p, int len); /* Peer ack'd our CI */
  static int  lcp_nakci(fsm *f, u_char *p, int len, int treat_as_reject); /* Peer nak'd our CI */
  static int  lcp_rejci(fsm *f, u_char *p, int len); /* Peer rej'd our CI */
  static int  lcp_reqci(fsm *f, u_char *inp, int *lenp, int reject_if_disagree); /* Rcv peer CI */
  static void lcp_up(fsm *f);		/* We're UP */
  static void lcp_down(fsm *f);		/* We're DOWN */
  static void lcp_starting (fsm *);	/* We need lower layer up */
  static void lcp_finished (fsm *);	/* We need lower layer down */
  static int  lcp_extcode(fsm *f, int code, int id, u_char *inp, int len);
  static void lcp_rprotrej(fsm *f, u_char *inp, int len);
  
  /*
   * routines to send LCP echos to peer
   */
  
  static void lcp_echo_lowerup(ppp_pcb *pcb);
  static void lcp_echo_lowerdown(ppp_pcb *pcb);
  static void LcpEchoTimeout(void *arg);
  static void lcp_received_echo_reply(fsm *f, int id, u_char *inp, int len);
  static void LcpSendEchoRequest(fsm *f);
  static void LcpLinkFailure(fsm *f);
  static void LcpEchoCheck(fsm *f);
  
  static const fsm_callbacks lcp_callbacks = {	/* LCP callback routines */
      lcp_resetci,		/* Reset our Configuration Information */
      lcp_cilen,			/* Length of our Configuration Information */
      lcp_addci,			/* Add our Configuration Information */
      lcp_ackci,			/* ACK our Configuration Information */
      lcp_nakci,			/* NAK our Configuration Information */
      lcp_rejci,			/* Reject our Configuration Information */
      lcp_reqci,			/* Request peer's Configuration Information */
      lcp_up,			/* Called when fsm reaches OPENED state */
      lcp_down,			/* Called when fsm leaves OPENED state */
      lcp_starting,		/* Called when we want the lower layer up */
      lcp_finished,		/* Called when we want the lower layer down */
      NULL,			/* Called when Protocol-Reject received */
      NULL,			/* Retransmission is necessary */
      lcp_extcode,		/* Called to handle LCP-specific codes */
      "LCP"			/* String name of protocol */
  };
  
  /*
   * Protocol entry points.
   * Some of these are called directly.
   */
  
  static void lcp_init(ppp_pcb *pcb);
  static void lcp_input(ppp_pcb *pcb, u_char *p, int len);
  static void lcp_protrej(ppp_pcb *pcb);
  #if PRINTPKT_SUPPORT
  static int lcp_printpkt(const u_char *p, int plen,
  		void (*printer) (void *, const char *, ...), void *arg);
  #endif /* PRINTPKT_SUPPORT */
  
  const struct protent lcp_protent = {
      PPP_LCP,
      lcp_init,
      lcp_input,
      lcp_protrej,
      lcp_lowerup,
      lcp_lowerdown,
      lcp_open,
      lcp_close,
  #if PRINTPKT_SUPPORT
      lcp_printpkt,
  #endif /* PRINTPKT_SUPPORT */
  #if PPP_DATAINPUT
      NULL,
  #endif /* PPP_DATAINPUT */
  #if PRINTPKT_SUPPORT
      "LCP",
      NULL,
  #endif /* PRINTPKT_SUPPORT */
  #if PPP_OPTIONS
      lcp_option_list,
      NULL,
  #endif /* PPP_OPTIONS */
  #if DEMAND_SUPPORT
      NULL,
      NULL
  #endif /* DEMAND_SUPPORT */
  };
  
  /*
   * Length of each type of configuration option (in octets)
   */
  #define CILEN_VOID	2
  #define CILEN_CHAR	3
  #define CILEN_SHORT	4	/* CILEN_VOID + 2 */
  #if CHAP_SUPPORT
  #define CILEN_CHAP	5	/* CILEN_VOID + 2 + 1 */
  #endif /* CHAP_SUPPORT */
  #define CILEN_LONG	6	/* CILEN_VOID + 4 */
  #if LQR_SUPPORT
  #define CILEN_LQR	8	/* CILEN_VOID + 2 + 4 */
  #endif /* LQR_SUPPORT */
  #define CILEN_CBCP	3
  
  #define CODENAME(x)	((x) == CONFACK ? "ACK" : \
  			 (x) == CONFNAK ? "NAK" : "REJ")
  
  #if PPP_OPTIONS
  /*
   * noopt - Disable all options (why?).
   */
  static int
  noopt(argv)
      char **argv;
  {
      BZERO((char *) &lcp_wantoptions[0], sizeof (struct lcp_options));
      BZERO((char *) &lcp_allowoptions[0], sizeof (struct lcp_options));
  
      return (1);
  }
  #endif /* PPP_OPTIONS */
  
  #ifdef HAVE_MULTILINK
  static int
  setendpoint(argv)
      char **argv;
  {
      if (str_to_epdisc(&lcp_wantoptions[0].endpoint, *argv)) {
  	lcp_wantoptions[0].neg_endpoint = 1;
  	return 1;
      }
      option_error("Can't parse '%s' as an endpoint discriminator", *argv);
      return 0;
  }
  
  static void
  printendpoint(opt, printer, arg)
      option_t *opt;
      void (*printer) (void *, char *, ...);
      void *arg;
  {
  	printer(arg, "%s", epdisc_to_str(&lcp_wantoptions[0].endpoint));
  }
  #endif /* HAVE_MULTILINK */
  
  /*
   * lcp_init - Initialize LCP.
   */
  static void lcp_init(ppp_pcb *pcb) {
      fsm *f = &pcb->lcp_fsm;
      lcp_options *wo = &pcb->lcp_wantoptions;
      lcp_options *ao = &pcb->lcp_allowoptions;
  
      f->pcb = pcb;
      f->protocol = PPP_LCP;
      f->callbacks = &lcp_callbacks;
  
      fsm_init(f);
  
      BZERO(wo, sizeof(*wo));
      wo->neg_mru = 1;
      wo->mru = PPP_DEFMRU;
      wo->neg_asyncmap = 1;
      wo->neg_magicnumber = 1;
      wo->neg_pcompression = 1;
      wo->neg_accompression = 1;
  
      BZERO(ao, sizeof(*ao));
      ao->neg_mru = 1;
      ao->mru = PPP_MAXMRU;
      ao->neg_asyncmap = 1;
  #if CHAP_SUPPORT
      ao->neg_chap = 1;
      ao->chap_mdtype = CHAP_MDTYPE_SUPPORTED;
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
      ao->neg_upap = 1;
  #endif /* PAP_SUPPORT */
  #if EAP_SUPPORT
      ao->neg_eap = 1;
  #endif /* EAP_SUPPORT */
      ao->neg_magicnumber = 1;
      ao->neg_pcompression = 1;
      ao->neg_accompression = 1;
      ao->neg_endpoint = 1;
  }
  
  
  /*
   * lcp_open - LCP is allowed to come up.
   */
  void lcp_open(ppp_pcb *pcb) {
      fsm *f = &pcb->lcp_fsm;
      lcp_options *wo = &pcb->lcp_wantoptions;
  
      f->flags &= ~(OPT_PASSIVE | OPT_SILENT);
      if (wo->passive)
  	f->flags |= OPT_PASSIVE;
      if (wo->silent)
  	f->flags |= OPT_SILENT;
      fsm_open(f);
  }
  
  
  /*
   * lcp_close - Take LCP down.
   */
  void lcp_close(ppp_pcb *pcb, const char *reason) {
      fsm *f = &pcb->lcp_fsm;
      int oldstate;
  
      if (pcb->phase != PPP_PHASE_DEAD
  #ifdef HAVE_MULTILINK
      && pcb->phase != PPP_PHASE_MASTER
  #endif /* HAVE_MULTILINK */
      )
  	new_phase(pcb, PPP_PHASE_TERMINATE);
  
      if (f->flags & DELAYED_UP) {
  	UNTIMEOUT(lcp_delayed_up, f);
  	f->state = PPP_FSM_STOPPED;
      }
      oldstate = f->state;
  
      fsm_close(f, reason);
      if (oldstate == PPP_FSM_STOPPED && (f->flags & (OPT_PASSIVE|OPT_SILENT|DELAYED_UP))) {
  	/*
  	 * This action is not strictly according to the FSM in RFC1548,
  	 * but it does mean that the program terminates if you do a
  	 * lcp_close() when a connection hasn't been established
  	 * because we are in passive/silent mode or because we have
  	 * delayed the fsm_lowerup() call and it hasn't happened yet.
  	 */
  	f->flags &= ~DELAYED_UP;
  	lcp_finished(f);
      }
  }
  
  
  /*
   * lcp_lowerup - The lower layer is up.
   */
  void lcp_lowerup(ppp_pcb *pcb) {
      lcp_options *wo = &pcb->lcp_wantoptions;
      fsm *f = &pcb->lcp_fsm;
      /*
       * Don't use A/C or protocol compression on transmission,
       * but accept A/C and protocol compressed packets
       * if we are going to ask for A/C and protocol compression.
       */
      if (ppp_send_config(pcb, PPP_MRU, 0xffffffff, 0, 0) < 0
  	|| ppp_recv_config(pcb, PPP_MRU, (pcb->settings.lax_recv? 0: 0xffffffff),
  			   wo->neg_pcompression, wo->neg_accompression) < 0)
  	    return;
      pcb->peer_mru = PPP_MRU;
  
      if (pcb->settings.listen_time != 0) {
  	f->flags |= DELAYED_UP;
  	TIMEOUTMS(lcp_delayed_up, f, pcb->settings.listen_time);
      } else
  	fsm_lowerup(f);
  }
  
  
  /*
   * lcp_lowerdown - The lower layer is down.
   */
  void lcp_lowerdown(ppp_pcb *pcb) {
      fsm *f = &pcb->lcp_fsm;
  
      if (f->flags & DELAYED_UP) {
  	f->flags &= ~DELAYED_UP;
  	UNTIMEOUT(lcp_delayed_up, f);
      } else
  	fsm_lowerdown(f);
  }
  
  
  /*
   * lcp_delayed_up - Bring the lower layer up now.
   */
  static void lcp_delayed_up(void *arg) {
      fsm *f = (fsm*)arg;
  
      if (f->flags & DELAYED_UP) {
  	f->flags &= ~DELAYED_UP;
  	fsm_lowerup(f);
      }
  }
  
  
  /*
   * lcp_input - Input LCP packet.
   */
  static void lcp_input(ppp_pcb *pcb, u_char *p, int len) {
      fsm *f = &pcb->lcp_fsm;
  
      if (f->flags & DELAYED_UP) {
  	f->flags &= ~DELAYED_UP;
  	UNTIMEOUT(lcp_delayed_up, f);
  	fsm_lowerup(f);
      }
      fsm_input(f, p, len);
  }
  
  /*
   * lcp_extcode - Handle a LCP-specific code.
   */
  static int lcp_extcode(fsm *f, int code, int id, u_char *inp, int len) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      u_char *magp;
  
      switch( code ){
      case PROTREJ:
  	lcp_rprotrej(f, inp, len);
  	break;
      
      case ECHOREQ:
  	if (f->state != PPP_FSM_OPENED)
  	    break;
  	magp = inp;
  	PUTLONG(go->magicnumber, magp);
  	fsm_sdata(f, ECHOREP, id, inp, len);
  	break;
      
      case ECHOREP:
  	lcp_received_echo_reply(f, id, inp, len);
  	break;
  
      case DISCREQ:
      case IDENTIF:
      case TIMEREM:
  	break;
  
      default:
  	return 0;
      }
      return 1;
  }
  
      
  /*
   * lcp_rprotrej - Receive an Protocol-Reject.
   *
   * Figure out which protocol is rejected and inform it.
   */
  static void lcp_rprotrej(fsm *f, u_char *inp, int len) {
      int i;
      const struct protent *protp;
      u_short prot;
  #if PPP_PROTOCOLNAME
      const char *pname;
  #endif /* PPP_PROTOCOLNAME */
  
      if (len < 2) {
  	LCPDEBUG(("lcp_rprotrej: Rcvd short Protocol-Reject packet!"));
  	return;
      }
  
      GETSHORT(prot, inp);
  
      /*
       * Protocol-Reject packets received in any state other than the LCP
       * OPENED state SHOULD be silently discarded.
       */
      if( f->state != PPP_FSM_OPENED ){
  	LCPDEBUG(("Protocol-Reject discarded: LCP in state %d", f->state));
  	return;
      }
  
  #if PPP_PROTOCOLNAME
      pname = protocol_name(prot);
  #endif /* PPP_PROTOCOLNAME */
  
      /*
       * Upcall the proper Protocol-Reject routine.
       */
      for (i = 0; (protp = protocols[i]) != NULL; ++i)
  	if (protp->protocol == prot) {
  #if PPP_PROTOCOLNAME
  	    if (pname != NULL)
  		ppp_dbglog("Protocol-Reject for '%s' (0x%x) received", pname,
  		       prot);
  	    else
  #endif /* PPP_PROTOCOLNAME */
  		ppp_dbglog("Protocol-Reject for 0x%x received", prot);
  	    (*protp->protrej)(f->pcb);
  	    return;
  	}
  
  #if PPP_PROTOCOLNAME
      if (pname != NULL)
  	ppp_warn("Protocol-Reject for unsupported protocol '%s' (0x%x)", pname,
  	     prot);
      else
  #endif /* #if PPP_PROTOCOLNAME */
  	ppp_warn("Protocol-Reject for unsupported protocol 0x%x", prot);
  }
  
  
  /*
   * lcp_protrej - A Protocol-Reject was received.
   */
  /*ARGSUSED*/
  static void lcp_protrej(ppp_pcb *pcb) {
      /*
       * Can't reject LCP!
       */
      ppp_error("Received Protocol-Reject for LCP!");
      fsm_protreject(&pcb->lcp_fsm);
  }
  
  
  /*
   * lcp_sprotrej - Send a Protocol-Reject for some protocol.
   */
  void lcp_sprotrej(ppp_pcb *pcb, u_char *p, int len) {
      fsm *f = &pcb->lcp_fsm;
      /*
       * Send back the protocol and the information field of the
       * rejected packet.  We only get here if LCP is in the OPENED state.
       */
  #if 0
      p += 2;
      len -= 2;
  #endif
  
      fsm_sdata(f, PROTREJ, ++f->id,
  	      p, len);
  }
  
  
  /*
   * lcp_resetci - Reset our CI.
   */
  static void lcp_resetci(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *wo = &pcb->lcp_wantoptions;
      lcp_options *go = &pcb->lcp_gotoptions;
      lcp_options *ao = &pcb->lcp_allowoptions;
  
  #if PPP_AUTH_SUPPORT
  
      /* note: default value is true for allow options */
      if (pcb->settings.user && pcb->settings.passwd) {
  #if PAP_SUPPORT
        if (pcb->settings.refuse_pap) {
          ao->neg_upap = 0;
        }
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
        if (pcb->settings.refuse_chap) {
          ao->chap_mdtype &= ~MDTYPE_MD5;
        }
  #if MSCHAP_SUPPORT
        if (pcb->settings.refuse_mschap) {
          ao->chap_mdtype &= ~MDTYPE_MICROSOFT;
        }
        if (pcb->settings.refuse_mschap_v2) {
          ao->chap_mdtype &= ~MDTYPE_MICROSOFT_V2;
        }
  #endif /* MSCHAP_SUPPORT */
        ao->neg_chap = (ao->chap_mdtype != MDTYPE_NONE);
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
        if (pcb->settings.refuse_eap) {
          ao->neg_eap = 0;
        }
  #endif /* EAP_SUPPORT */
  
  #if PPP_SERVER
        /* note: default value is false for wanted options */
        if (pcb->settings.auth_required) {
  #if PAP_SUPPORT
          if (!pcb->settings.refuse_pap) {
            wo->neg_upap = 1;
          }
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
          if (!pcb->settings.refuse_chap) {
            wo->chap_mdtype |= MDTYPE_MD5;
          }
  #if MSCHAP_SUPPORT
          if (!pcb->settings.refuse_mschap) {
            wo->chap_mdtype |= MDTYPE_MICROSOFT;
          }
          if (!pcb->settings.refuse_mschap_v2) {
            wo->chap_mdtype |= MDTYPE_MICROSOFT_V2;
          }
  #endif /* MSCHAP_SUPPORT */
          wo->neg_chap = (wo->chap_mdtype != MDTYPE_NONE);
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
          if (!pcb->settings.refuse_eap) {
            wo->neg_eap = 1;
          }
  #endif /* EAP_SUPPORT */
        }
  #endif /* PPP_SERVER */
  
      } else {
  #if PAP_SUPPORT
        ao->neg_upap = 0;
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
        ao->neg_chap = 0;
        ao->chap_mdtype = MDTYPE_NONE;
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
        ao->neg_eap = 0;
  #endif /* EAP_SUPPORT */
      }
  
      PPPDEBUG(LOG_DEBUG, ("ppp: auth protocols:"));
  #if PAP_SUPPORT
      PPPDEBUG(LOG_DEBUG, (" PAP=%d", ao->neg_upap));
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
      PPPDEBUG(LOG_DEBUG, (" CHAP=%d CHAP_MD5=%d", ao->neg_chap, !!(ao->chap_mdtype&MDTYPE_MD5)));
  #if MSCHAP_SUPPORT
      PPPDEBUG(LOG_DEBUG, (" CHAP_MS=%d CHAP_MS2=%d", !!(ao->chap_mdtype&MDTYPE_MICROSOFT), !!(ao->chap_mdtype&MDTYPE_MICROSOFT_V2)));
  #endif /* MSCHAP_SUPPORT */
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
      PPPDEBUG(LOG_DEBUG, (" EAP=%d", ao->neg_eap));
  #endif /* EAP_SUPPORT */
      PPPDEBUG(LOG_DEBUG, ("\n"));
  
  #endif /* PPP_AUTH_SUPPORT */
  
      wo->magicnumber = magic();
      wo->numloops = 0;
      *go = *wo;
  #ifdef HAVE_MULTILINK
      if (!multilink) {
  	go->neg_mrru = 0;
  #endif /* HAVE_MULTILINK */
  	go->neg_ssnhf = 0;
  	go->neg_endpoint = 0;
  #ifdef HAVE_MULTILINK
      }
  #endif /* HAVE_MULTILINK */
      if (pcb->settings.noendpoint)
  	ao->neg_endpoint = 0;
      pcb->peer_mru = PPP_MRU;
  #if 0 /* UNUSED */
      auth_reset(pcb);
  #endif /* UNUSED */
  }
  
  
  /*
   * lcp_cilen - Return length of our CI.
   */
  static int lcp_cilen(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
  
  #define LENCIVOID(neg)	((neg) ? CILEN_VOID : 0)
  #if CHAP_SUPPORT
  #define LENCICHAP(neg)	((neg) ? CILEN_CHAP : 0)
  #endif /* CHAP_SUPPORT */
  #define LENCISHORT(neg)	((neg) ? CILEN_SHORT : 0)
  #define LENCILONG(neg)	((neg) ? CILEN_LONG : 0)
  #if LQR_SUPPORT
  #define LENCILQR(neg)	((neg) ? CILEN_LQR: 0)
  #endif /* LQR_SUPPORT */
  #define LENCICBCP(neg)	((neg) ? CILEN_CBCP: 0)
      /*
       * NB: we only ask for one of CHAP, UPAP, or EAP, even if we will
       * accept more than one.  We prefer EAP first, then CHAP, then
       * PAP.
       */
      return (LENCISHORT(go->neg_mru && go->mru != PPP_DEFMRU) +
  	    LENCILONG(go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF) +
  #if EAP_SUPPORT
  	    LENCISHORT(go->neg_eap) +
  #endif /* EAP_SUPPORT */
  #if CHAP_SUPPORT /* cannot be improved, embedding a directive within macro arguments is not portable */
  #if EAP_SUPPORT
  	    LENCICHAP(!go->neg_eap && go->neg_chap) +
  #endif /* EAP_SUPPORT */
  #if !EAP_SUPPORT
  	    LENCICHAP(go->neg_chap) +
  #endif /* !EAP_SUPPORT */
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT /* cannot be improved, embedding a directive within macro arguments is not portable */
  #if EAP_SUPPORT && CHAP_SUPPORT
  	    LENCISHORT(!go->neg_eap && !go->neg_chap && go->neg_upap) +
  #endif /* EAP_SUPPORT && CHAP_SUPPORT */
  #if EAP_SUPPORT && !CHAP_SUPPORT
  	    LENCISHORT(!go->neg_eap && go->neg_upap) +
  #endif /* EAP_SUPPORT && !CHAP_SUPPORT */
  #if !EAP_SUPPORT && CHAP_SUPPORT
  	    LENCISHORT(!go->neg_chap && go->neg_upap) +
  #endif /* !EAP_SUPPORT && CHAP_SUPPORT */
  #if !EAP_SUPPORT && !CHAP_SUPPORT
  	    LENCISHORT(go->neg_upap) +
  #endif /* !EAP_SUPPORT && !CHAP_SUPPORT */
  #endif /* PAP_SUPPORT */
  #if LQR_SUPPORT
  	    LENCILQR(go->neg_lqr) +
  #endif /* LQR_SUPPORT */
  	    LENCICBCP(go->neg_cbcp) +
  	    LENCILONG(go->neg_magicnumber) +
  	    LENCIVOID(go->neg_pcompression) +
  	    LENCIVOID(go->neg_accompression) +
  #ifdef HAVE_MULTILINK
  	    LENCISHORT(go->neg_mrru) +
  #endif /* HAVE_MULTILINK */
  	    LENCIVOID(go->neg_ssnhf) +
  	    (go->neg_endpoint? CILEN_CHAR + go->endpoint.length: 0));
  }
  
  
  /*
   * lcp_addci - Add our desired CIs to a packet.
   */
  static void lcp_addci(fsm *f, u_char *ucp, int *lenp) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      u_char *start_ucp = ucp;
  
  #define ADDCIVOID(opt, neg) \
      if (neg) { \
  	PUTCHAR(opt, ucp); \
  	PUTCHAR(CILEN_VOID, ucp); \
      }
  #define ADDCISHORT(opt, neg, val) \
      if (neg) { \
  	PUTCHAR(opt, ucp); \
  	PUTCHAR(CILEN_SHORT, ucp); \
  	PUTSHORT(val, ucp); \
      }
  #if CHAP_SUPPORT
  #define ADDCICHAP(opt, neg, val) \
      if (neg) { \
  	PUTCHAR((opt), ucp); \
  	PUTCHAR(CILEN_CHAP, ucp); \
  	PUTSHORT(PPP_CHAP, ucp); \
  	PUTCHAR((CHAP_DIGEST(val)), ucp); \
      }
  #endif /* CHAP_SUPPORT */
  #define ADDCILONG(opt, neg, val) \
      if (neg) { \
  	PUTCHAR(opt, ucp); \
  	PUTCHAR(CILEN_LONG, ucp); \
  	PUTLONG(val, ucp); \
      }
  #if LQR_SUPPORT
  #define ADDCILQR(opt, neg, val) \
      if (neg) { \
  	PUTCHAR(opt, ucp); \
  	PUTCHAR(CILEN_LQR, ucp); \
  	PUTSHORT(PPP_LQR, ucp); \
  	PUTLONG(val, ucp); \
      }
  #endif /* LQR_SUPPORT */
  #define ADDCICHAR(opt, neg, val) \
      if (neg) { \
  	PUTCHAR(opt, ucp); \
  	PUTCHAR(CILEN_CHAR, ucp); \
  	PUTCHAR(val, ucp); \
      }
  #define ADDCIENDP(opt, neg, class, val, len) \
      if (neg) { \
  	int i; \
  	PUTCHAR(opt, ucp); \
  	PUTCHAR(CILEN_CHAR + len, ucp); \
  	PUTCHAR(class, ucp); \
  	for (i = 0; i < len; ++i) \
  	    PUTCHAR(val[i], ucp); \
      }
  
      ADDCISHORT(CI_MRU, go->neg_mru && go->mru != PPP_DEFMRU, go->mru);
      ADDCILONG(CI_ASYNCMAP, go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF,
  	      go->asyncmap);
  #if EAP_SUPPORT
      ADDCISHORT(CI_AUTHTYPE, go->neg_eap, PPP_EAP);
  #endif /* EAP_SUPPORT */
  #if CHAP_SUPPORT /* cannot be improved, embedding a directive within macro arguments is not portable */
  #if EAP_SUPPORT
      ADDCICHAP(CI_AUTHTYPE, !go->neg_eap && go->neg_chap, go->chap_mdtype);
  #endif /* EAP_SUPPORT */
  #if !EAP_SUPPORT
      ADDCICHAP(CI_AUTHTYPE, go->neg_chap, go->chap_mdtype);
  #endif /* !EAP_SUPPORT */
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT /* cannot be improved, embedding a directive within macro arguments is not portable */
  #if EAP_SUPPORT && CHAP_SUPPORT
      ADDCISHORT(CI_AUTHTYPE, !go->neg_eap && !go->neg_chap && go->neg_upap, PPP_PAP);
  #endif /* EAP_SUPPORT && CHAP_SUPPORT */
  #if EAP_SUPPORT && !CHAP_SUPPORT
      ADDCISHORT(CI_AUTHTYPE, !go->neg_eap && go->neg_upap, PPP_PAP);
  #endif /* EAP_SUPPORT && !CHAP_SUPPORT */
  #if !EAP_SUPPORT && CHAP_SUPPORT
      ADDCISHORT(CI_AUTHTYPE, !go->neg_chap && go->neg_upap, PPP_PAP);
  #endif /* !EAP_SUPPORT && CHAP_SUPPORT */
  #if !EAP_SUPPORT && !CHAP_SUPPORT
      ADDCISHORT(CI_AUTHTYPE, go->neg_upap, PPP_PAP);
  #endif /* !EAP_SUPPORT && !CHAP_SUPPORT */
  #endif /* PAP_SUPPORT */
  #if LQR_SUPPORT
      ADDCILQR(CI_QUALITY, go->neg_lqr, go->lqr_period);
  #endif /* LQR_SUPPORT */
      ADDCICHAR(CI_CALLBACK, go->neg_cbcp, CBCP_OPT);
      ADDCILONG(CI_MAGICNUMBER, go->neg_magicnumber, go->magicnumber);
      ADDCIVOID(CI_PCOMPRESSION, go->neg_pcompression);
      ADDCIVOID(CI_ACCOMPRESSION, go->neg_accompression);
  #ifdef HAVE_MULTILINK
      ADDCISHORT(CI_MRRU, go->neg_mrru, go->mrru);
  #endif
      ADDCIVOID(CI_SSNHF, go->neg_ssnhf);
      ADDCIENDP(CI_EPDISC, go->neg_endpoint, go->endpoint.class_,
  	      go->endpoint.value, go->endpoint.length);
  
      if (ucp - start_ucp != *lenp) {
  	/* this should never happen, because peer_mtu should be 1500 */
  	ppp_error("Bug in lcp_addci: wrong length");
      }
  }
  
  
  /*
   * lcp_ackci - Ack our CIs.
   * This should not modify any state if the Ack is bad.
   *
   * Returns:
   *	0 - Ack was bad.
   *	1 - Ack was good.
   */
  static int lcp_ackci(fsm *f, u_char *p, int len) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      u_char cilen, citype, cichar;
      u_short cishort;
      u32_t cilong;
  
      /*
       * CIs must be in exactly the same order that we sent.
       * Check packet length and CI length at each step.
       * If we find any deviations, then this packet is bad.
       */
  #define ACKCIVOID(opt, neg) \
      if (neg) { \
  	if ((len -= CILEN_VOID) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_VOID || \
  	    citype != opt) \
  	    goto bad; \
      }
  #define ACKCISHORT(opt, neg, val) \
      if (neg) { \
  	if ((len -= CILEN_SHORT) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_SHORT || \
  	    citype != opt) \
  	    goto bad; \
  	GETSHORT(cishort, p); \
  	if (cishort != val) \
  	    goto bad; \
      }
  #define ACKCICHAR(opt, neg, val) \
      if (neg) { \
  	if ((len -= CILEN_CHAR) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_CHAR || \
  	    citype != opt) \
  	    goto bad; \
  	GETCHAR(cichar, p); \
  	if (cichar != val) \
  	    goto bad; \
      }
  #if CHAP_SUPPORT
  #define ACKCICHAP(opt, neg, val) \
      if (neg) { \
  	if ((len -= CILEN_CHAP) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_CHAP || \
  	    citype != (opt)) \
  	    goto bad; \
  	GETSHORT(cishort, p); \
  	if (cishort != PPP_CHAP) \
  	    goto bad; \
  	GETCHAR(cichar, p); \
  	if (cichar != (CHAP_DIGEST(val))) \
  	  goto bad; \
      }
  #endif /* CHAP_SUPPORT */
  #define ACKCILONG(opt, neg, val) \
      if (neg) { \
  	if ((len -= CILEN_LONG) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_LONG || \
  	    citype != opt) \
  	    goto bad; \
  	GETLONG(cilong, p); \
  	if (cilong != val) \
  	    goto bad; \
      }
  #if LQR_SUPPORT
  #define ACKCILQR(opt, neg, val) \
      if (neg) { \
  	if ((len -= CILEN_LQR) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_LQR || \
  	    citype != opt) \
  	    goto bad; \
  	GETSHORT(cishort, p); \
  	if (cishort != PPP_LQR) \
  	    goto bad; \
  	GETLONG(cilong, p); \
  	if (cilong != val) \
  	  goto bad; \
      }
  #endif /* LQR_SUPPORT */
  #define ACKCIENDP(opt, neg, class, val, vlen) \
      if (neg) { \
  	int i; \
  	if ((len -= CILEN_CHAR + vlen) < 0) \
  	    goto bad; \
  	GETCHAR(citype, p); \
  	GETCHAR(cilen, p); \
  	if (cilen != CILEN_CHAR + vlen || \
  	    citype != opt) \
  	    goto bad; \
  	GETCHAR(cichar, p); \
  	if (cichar != class) \
  	    goto bad; \
  	for (i = 0; i < vlen; ++i) { \
  	    GETCHAR(cichar, p); \
  	    if (cichar != val[i]) \
  		goto bad; \
  	} \
      }
  
      ACKCISHORT(CI_MRU, go->neg_mru && go->mru != PPP_DEFMRU, go->mru);
      ACKCILONG(CI_ASYNCMAP, go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF,
  	      go->asyncmap);
  #if EAP_SUPPORT
      ACKCISHORT(CI_AUTHTYPE, go->neg_eap, PPP_EAP);
  #endif /* EAP_SUPPORT */
  #if CHAP_SUPPORT /* cannot be improved, embedding a directive within macro arguments is not portable */
  #if EAP_SUPPORT
      ACKCICHAP(CI_AUTHTYPE, !go->neg_eap && go->neg_chap, go->chap_mdtype);
  #endif /* EAP_SUPPORT */
  #if !EAP_SUPPORT
      ACKCICHAP(CI_AUTHTYPE, go->neg_chap, go->chap_mdtype);
  #endif /* !EAP_SUPPORT */
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT /* cannot be improved, embedding a directive within macro arguments is not portable */
  #if EAP_SUPPORT && CHAP_SUPPORT
      ACKCISHORT(CI_AUTHTYPE, !go->neg_eap && !go->neg_chap && go->neg_upap, PPP_PAP);
  #endif /* EAP_SUPPORT && CHAP_SUPPORT */
  #if EAP_SUPPORT && !CHAP_SUPPORT
      ACKCISHORT(CI_AUTHTYPE, !go->neg_eap && go->neg_upap, PPP_PAP);
  #endif /* EAP_SUPPORT && !CHAP_SUPPORT */
  #if !EAP_SUPPORT && CHAP_SUPPORT
      ACKCISHORT(CI_AUTHTYPE, !go->neg_chap && go->neg_upap, PPP_PAP);
  #endif /* !EAP_SUPPORT && CHAP_SUPPORT */
  #if !EAP_SUPPORT && !CHAP_SUPPORT
      ACKCISHORT(CI_AUTHTYPE, go->neg_upap, PPP_PAP);
  #endif /* !EAP_SUPPORT && !CHAP_SUPPORT */
  #endif /* PAP_SUPPORT */
  #if LQR_SUPPORT
      ACKCILQR(CI_QUALITY, go->neg_lqr, go->lqr_period);
  #endif /* LQR_SUPPORT */
      ACKCICHAR(CI_CALLBACK, go->neg_cbcp, CBCP_OPT);
      ACKCILONG(CI_MAGICNUMBER, go->neg_magicnumber, go->magicnumber);
      ACKCIVOID(CI_PCOMPRESSION, go->neg_pcompression);
      ACKCIVOID(CI_ACCOMPRESSION, go->neg_accompression);
  #ifdef HAVE_MULTILINK
      ACKCISHORT(CI_MRRU, go->neg_mrru, go->mrru);
  #endif /* HAVE_MULTILINK */
      ACKCIVOID(CI_SSNHF, go->neg_ssnhf);
      ACKCIENDP(CI_EPDISC, go->neg_endpoint, go->endpoint.class_,
  	      go->endpoint.value, go->endpoint.length);
  
      /*
       * If there are any remaining CIs, then this packet is bad.
       */
      if (len != 0)
  	goto bad;
      return (1);
  bad:
      LCPDEBUG(("lcp_acki: received bad Ack!"));
      return (0);
  }
  
  
  /*
   * lcp_nakci - Peer has sent a NAK for some of our CIs.
   * This should not modify any state if the Nak is bad
   * or if LCP is in the OPENED state.
   *
   * Returns:
   *	0 - Nak was bad.
   *	1 - Nak was good.
   */
  static int lcp_nakci(fsm *f, u_char *p, int len, int treat_as_reject) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      lcp_options *wo = &pcb->lcp_wantoptions;
      u_char citype, cichar, *next;
      u_short cishort;
      u32_t cilong;
      lcp_options no;		/* options we've seen Naks for */
      lcp_options try_;		/* options to request next time */
      int looped_back = 0;
      int cilen;
  
      BZERO(&no, sizeof(no));
      try_ = *go;
  
      /*
       * Any Nak'd CIs must be in exactly the same order that we sent.
       * Check packet length and CI length at each step.
       * If we find any deviations, then this packet is bad.
       */
  #define NAKCIVOID(opt, neg) \
      if (go->neg && \
  	len >= CILEN_VOID && \
  	p[1] == CILEN_VOID && \
  	p[0] == opt) { \
  	len -= CILEN_VOID; \
  	INCPTR(CILEN_VOID, p); \
  	no.neg = 1; \
  	try_.neg = 0; \
      }
  #if CHAP_SUPPORT
  #define NAKCICHAP(opt, neg, code) \
      if (go->neg && \
  	len >= CILEN_CHAP && \
  	p[1] == CILEN_CHAP && \
  	p[0] == opt) { \
  	len -= CILEN_CHAP; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETCHAR(cichar, p); \
  	no.neg = 1; \
  	code \
      }
  #endif /* CHAP_SUPPORT */
  #define NAKCICHAR(opt, neg, code) \
      if (go->neg && \
  	len >= CILEN_CHAR && \
  	p[1] == CILEN_CHAR && \
  	p[0] == opt) { \
  	len -= CILEN_CHAR; \
  	INCPTR(2, p); \
  	GETCHAR(cichar, p); \
  	no.neg = 1; \
  	code \
      }
  #define NAKCISHORT(opt, neg, code) \
      if (go->neg && \
  	len >= CILEN_SHORT && \
  	p[1] == CILEN_SHORT && \
  	p[0] == opt) { \
  	len -= CILEN_SHORT; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	no.neg = 1; \
  	code \
      }
  #define NAKCILONG(opt, neg, code) \
      if (go->neg && \
  	len >= CILEN_LONG && \
  	p[1] == CILEN_LONG && \
  	p[0] == opt) { \
  	len -= CILEN_LONG; \
  	INCPTR(2, p); \
  	GETLONG(cilong, p); \
  	no.neg = 1; \
  	code \
      }
  #if LQR_SUPPORT
  #define NAKCILQR(opt, neg, code) \
      if (go->neg && \
  	len >= CILEN_LQR && \
  	p[1] == CILEN_LQR && \
  	p[0] == opt) { \
  	len -= CILEN_LQR; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETLONG(cilong, p); \
  	no.neg = 1; \
  	code \
      }
  #endif /* LQR_SUPPORT */
  #define NAKCIENDP(opt, neg) \
      if (go->neg && \
  	len >= CILEN_CHAR && \
  	p[0] == opt && \
  	p[1] >= CILEN_CHAR && \
  	p[1] <= len) { \
  	len -= p[1]; \
  	INCPTR(p[1], p); \
  	no.neg = 1; \
  	try_.neg = 0; \
      }
  
      /*
       * NOTE!  There must be no assignments to individual fields of *go in
       * the code below.  Any such assignment is a BUG!
       */
      /*
       * We don't care if they want to send us smaller packets than
       * we want.  Therefore, accept any MRU less than what we asked for,
       * but then ignore the new value when setting the MRU in the kernel.
       * If they send us a bigger MRU than what we asked, accept it, up to
       * the limit of the default MRU we'd get if we didn't negotiate.
       */
      if (go->neg_mru && go->mru != PPP_DEFMRU) {
  	NAKCISHORT(CI_MRU, neg_mru,
  		   if (cishort <= wo->mru || cishort <= PPP_DEFMRU)
  		       try_.mru = cishort;
  		   );
      }
  
      /*
       * Add any characters they want to our (receive-side) asyncmap.
       */
      if (go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF) {
  	NAKCILONG(CI_ASYNCMAP, neg_asyncmap,
  		  try_.asyncmap = go->asyncmap | cilong;
  		  );
      }
  
      /*
       * If they've nak'd our authentication-protocol, check whether
       * they are proposing a different protocol, or a different
       * hash algorithm for CHAP.
       */
      if ((0
  #if CHAP_SUPPORT
          || go->neg_chap
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
          || go->neg_upap
  #endif /* PAP_SUPPORT */
  #if EAP_SUPPORT
          || go->neg_eap
  #endif /* EAP_SUPPORT */
          )
  	&& len >= CILEN_SHORT
  	&& p[0] == CI_AUTHTYPE && p[1] >= CILEN_SHORT && p[1] <= len) {
  	cilen = p[1];
  	len -= cilen;
  #if CHAP_SUPPORT
  	no.neg_chap = go->neg_chap;
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
  	no.neg_upap = go->neg_upap;
  #endif /* PAP_SUPPORT */
  #if EAP_SUPPORT
  	no.neg_eap = go->neg_eap;
  #endif /* EAP_SUPPORT */
  	INCPTR(2, p);
  	GETSHORT(cishort, p);
  
  #if PAP_SUPPORT
  	if (cishort == PPP_PAP && cilen == CILEN_SHORT) {
  #if EAP_SUPPORT
  	    /* If we were asking for EAP, then we need to stop that. */
  	    if (go->neg_eap)
  		try_.neg_eap = 0;
  	    else
  #endif /* EAP_SUPPORT */
  
  #if CHAP_SUPPORT
  	    /* If we were asking for CHAP, then we need to stop that. */
  	    if (go->neg_chap)
  		try_.neg_chap = 0;
  	    else
  #endif /* CHAP_SUPPORT */
  
  	    /*
  	     * If we weren't asking for CHAP or EAP, then we were asking for
  	     * PAP, in which case this Nak is bad.
  	     */
  		goto bad;
  	} else
  #endif /* PAP_SUPPORT */
  
  #if CHAP_SUPPORT
  	if (cishort == PPP_CHAP && cilen == CILEN_CHAP) {
  	    GETCHAR(cichar, p);
  #if EAP_SUPPORT
  	    /* Stop asking for EAP, if we were. */
  	    if (go->neg_eap) {
  		try_.neg_eap = 0;
  		/* Try to set up to use their suggestion, if possible */
  		if (CHAP_CANDIGEST(go->chap_mdtype, cichar))
  		    try_.chap_mdtype = CHAP_MDTYPE_D(cichar);
  	    } else
  #endif /* EAP_SUPPORT */
  	    if (go->neg_chap) {
  		/*
  		 * We were asking for our preferred algorithm, they must
  		 * want something different.
  		 */
  		if (cichar != CHAP_DIGEST(go->chap_mdtype)) {
  		    if (CHAP_CANDIGEST(go->chap_mdtype, cichar)) {
  			/* Use their suggestion if we support it ... */
  			try_.chap_mdtype = CHAP_MDTYPE_D(cichar);
  		    } else {
  			/* ... otherwise, try our next-preferred algorithm. */
  			try_.chap_mdtype &= ~(CHAP_MDTYPE(try_.chap_mdtype));
  			if (try_.chap_mdtype == MDTYPE_NONE) /* out of algos */
  			    try_.neg_chap = 0;
  		    }
  		} else {
  		    /*
  		     * Whoops, they Nak'd our algorithm of choice
  		     * but then suggested it back to us.
  		     */
  		    goto bad;
  		}
  	    } else {
  		/*
  		 * Stop asking for PAP if we were asking for it.
  		 */
  #if PAP_SUPPORT
  		try_.neg_upap = 0;
  #endif /* PAP_SUPPORT */
  	    }
  
  	} else
  #endif /* CHAP_SUPPORT */
  	{
  
  #if EAP_SUPPORT
  	    /*
  	     * If we were asking for EAP, and they're Conf-Naking EAP,
  	     * well, that's just strange.  Nobody should do that.
  	     */
  	    if (cishort == PPP_EAP && cilen == CILEN_SHORT && go->neg_eap)
  		ppp_dbglog("Unexpected Conf-Nak for EAP");
  
  	    /*
  	     * We don't recognize what they're suggesting.
  	     * Stop asking for what we were asking for.
  	     */
  	    if (go->neg_eap)
  		try_.neg_eap = 0;
  	    else
  #endif /* EAP_SUPPORT */
  
  #if CHAP_SUPPORT
  	    if (go->neg_chap)
  		try_.neg_chap = 0;
  	    else
  #endif /* CHAP_SUPPORT */
  
  #if PAP_SUPPORT
  	    if(1)
  		try_.neg_upap = 0;
  	    else
  #endif /* PAP_SUPPORT */
  	    {}
  
  	    p += cilen - CILEN_SHORT;
  	}
      }
  
  #if LQR_SUPPORT
      /*
       * If they can't cope with our link quality protocol, we'll have
       * to stop asking for LQR.  We haven't got any other protocol.
       * If they Nak the reporting period, take their value XXX ?
       */
      NAKCILQR(CI_QUALITY, neg_lqr,
  	     if (cishort != PPP_LQR)
  		 try_.neg_lqr = 0;
  	     else
  		 try_.lqr_period = cilong;
  	     );
  #endif /* LQR_SUPPORT */
  
      /*
       * Only implementing CBCP...not the rest of the callback options
       */
      NAKCICHAR(CI_CALLBACK, neg_cbcp,
                try_.neg_cbcp = 0;
                (void)cichar; /* if CHAP support is not compiled, cichar is set but not used, which makes some compilers complaining */
                );
  
      /*
       * Check for a looped-back line.
       */
      NAKCILONG(CI_MAGICNUMBER, neg_magicnumber,
  	      try_.magicnumber = magic();
  	      looped_back = 1;
  	      );
  
      /*
       * Peer shouldn't send Nak for protocol compression or
       * address/control compression requests; they should send
       * a Reject instead.  If they send a Nak, treat it as a Reject.
       */
      NAKCIVOID(CI_PCOMPRESSION, neg_pcompression);
      NAKCIVOID(CI_ACCOMPRESSION, neg_accompression);
  
  #ifdef HAVE_MULTILINK
      /*
       * Nak for MRRU option - accept their value if it is smaller
       * than the one we want.
       */
      if (go->neg_mrru) {
  	NAKCISHORT(CI_MRRU, neg_mrru,
  		   if (treat_as_reject)
  		       try_.neg_mrru = 0;
  		   else if (cishort <= wo->mrru)
  		       try_.mrru = cishort;
  		   );
      }
  #else /* HAVE_MULTILINK */
      LWIP_UNUSED_ARG(treat_as_reject);
  #endif /* HAVE_MULTILINK */
  
      /*
       * Nak for short sequence numbers shouldn't be sent, treat it
       * like a reject.
       */
      NAKCIVOID(CI_SSNHF, neg_ssnhf);
  
      /*
       * Nak of the endpoint discriminator option is not permitted,
       * treat it like a reject.
       */
      NAKCIENDP(CI_EPDISC, neg_endpoint);
  
      /*
       * There may be remaining CIs, if the peer is requesting negotiation
       * on an option that we didn't include in our request packet.
       * If we see an option that we requested, or one we've already seen
       * in this packet, then this packet is bad.
       * If we wanted to respond by starting to negotiate on the requested
       * option(s), we could, but we don't, because except for the
       * authentication type and quality protocol, if we are not negotiating
       * an option, it is because we were told not to.
       * For the authentication type, the Nak from the peer means
       * `let me authenticate myself with you' which is a bit pointless.
       * For the quality protocol, the Nak means `ask me to send you quality
       * reports', but if we didn't ask for them, we don't want them.
       * An option we don't recognize represents the peer asking to
       * negotiate some option we don't support, so ignore it.
       */
      while (len >= CILEN_VOID) {
  	GETCHAR(citype, p);
  	GETCHAR(cilen, p);
  	if (cilen < CILEN_VOID || (len -= cilen) < 0)
  	    goto bad;
  	next = p + cilen - 2;
  
  	switch (citype) {
  	case CI_MRU:
  	    if ((go->neg_mru && go->mru != PPP_DEFMRU)
  		|| no.neg_mru || cilen != CILEN_SHORT)
  		goto bad;
  	    GETSHORT(cishort, p);
  	    if (cishort < PPP_DEFMRU) {
  		try_.neg_mru = 1;
  		try_.mru = cishort;
  	    }
  	    break;
  	case CI_ASYNCMAP:
  	    if ((go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF)
  		|| no.neg_asyncmap || cilen != CILEN_LONG)
  		goto bad;
  	    break;
  	case CI_AUTHTYPE:
  	    if (0
  #if CHAP_SUPPORT
                  || go->neg_chap || no.neg_chap
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
                  || go->neg_upap || no.neg_upap
  #endif /* PAP_SUPPORT */
  #if EAP_SUPPORT
  		|| go->neg_eap || no.neg_eap
  #endif /* EAP_SUPPORT */
  		)
  		goto bad;
  	    break;
  	case CI_MAGICNUMBER:
  	    if (go->neg_magicnumber || no.neg_magicnumber ||
  		cilen != CILEN_LONG)
  		goto bad;
  	    break;
  	case CI_PCOMPRESSION:
  	    if (go->neg_pcompression || no.neg_pcompression
  		|| cilen != CILEN_VOID)
  		goto bad;
  	    break;
  	case CI_ACCOMPRESSION:
  	    if (go->neg_accompression || no.neg_accompression
  		|| cilen != CILEN_VOID)
  		goto bad;
  	    break;
  #if LQR_SUPPORT
  	case CI_QUALITY:
  	    if (go->neg_lqr || no.neg_lqr || cilen != CILEN_LQR)
  		goto bad;
  	    break;
  #endif /* LQR_SUPPORT */
  #ifdef HAVE_MULTILINK
  	case CI_MRRU:
  	    if (go->neg_mrru || no.neg_mrru || cilen != CILEN_SHORT)
  		goto bad;
  	    break;
  #endif /* HAVE_MULTILINK */
  	case CI_SSNHF:
  	    if (go->neg_ssnhf || no.neg_ssnhf || cilen != CILEN_VOID)
  		goto bad;
  	    try_.neg_ssnhf = 1;
  	    break;
  	case CI_EPDISC:
  	    if (go->neg_endpoint || no.neg_endpoint || cilen < CILEN_CHAR)
  		goto bad;
  	    break;
  	default:
  	    break;
  	}
  	p = next;
      }
  
      /*
       * OK, the Nak is good.  Now we can update state.
       * If there are any options left we ignore them.
       */
      if (f->state != PPP_FSM_OPENED) {
  	if (looped_back) {
  	    if (++try_.numloops >= pcb->settings.lcp_loopbackfail) {
  		ppp_notice("Serial line is looped back.");
  		pcb->err_code = PPPERR_LOOPBACK;
  		lcp_close(f->pcb, "Loopback detected");
  	    }
  	} else
  	    try_.numloops = 0;
  	*go = try_;
      }
  
      return 1;
  
  bad:
      LCPDEBUG(("lcp_nakci: received bad Nak!"));
      return 0;
  }
  
  
  /*
   * lcp_rejci - Peer has Rejected some of our CIs.
   * This should not modify any state if the Reject is bad
   * or if LCP is in the OPENED state.
   *
   * Returns:
   *	0 - Reject was bad.
   *	1 - Reject was good.
   */
  static int lcp_rejci(fsm *f, u_char *p, int len) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      u_char cichar;
      u_short cishort;
      u32_t cilong;
      lcp_options try_;		/* options to request next time */
  
      try_ = *go;
  
      /*
       * Any Rejected CIs must be in exactly the same order that we sent.
       * Check packet length and CI length at each step.
       * If we find any deviations, then this packet is bad.
       */
  #define REJCIVOID(opt, neg) \
      if (go->neg && \
  	len >= CILEN_VOID && \
  	p[1] == CILEN_VOID && \
  	p[0] == opt) { \
  	len -= CILEN_VOID; \
  	INCPTR(CILEN_VOID, p); \
  	try_.neg = 0; \
      }
  #define REJCISHORT(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_SHORT && \
  	p[1] == CILEN_SHORT && \
  	p[0] == opt) { \
  	len -= CILEN_SHORT; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	/* Check rejected value. */ \
  	if (cishort != val) \
  	    goto bad; \
  	try_.neg = 0; \
      }
  
  #if CHAP_SUPPORT && EAP_SUPPORT && PAP_SUPPORT
  #define REJCICHAP(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_CHAP && \
  	p[1] == CILEN_CHAP && \
  	p[0] == opt) { \
  	len -= CILEN_CHAP; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETCHAR(cichar, p); \
  	/* Check rejected value. */ \
  	if ((cishort != PPP_CHAP) || (cichar != (CHAP_DIGEST(val)))) \
  	    goto bad; \
  	try_.neg = 0; \
  	try_.neg_eap = try_.neg_upap = 0; \
      }
  #endif /* CHAP_SUPPORT && EAP_SUPPORT && PAP_SUPPORT */
  
  #if CHAP_SUPPORT && !EAP_SUPPORT && PAP_SUPPORT
  #define REJCICHAP(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_CHAP && \
  	p[1] == CILEN_CHAP && \
  	p[0] == opt) { \
  	len -= CILEN_CHAP; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETCHAR(cichar, p); \
  	/* Check rejected value. */ \
  	if ((cishort != PPP_CHAP) || (cichar != (CHAP_DIGEST(val)))) \
  	    goto bad; \
  	try_.neg = 0; \
  	try_.neg_upap = 0; \
      }
  #endif /* CHAP_SUPPORT && !EAP_SUPPORT && PAP_SUPPORT */
  
  #if CHAP_SUPPORT && EAP_SUPPORT && !PAP_SUPPORT
  #define REJCICHAP(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_CHAP && \
  	p[1] == CILEN_CHAP && \
  	p[0] == opt) { \
  	len -= CILEN_CHAP; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETCHAR(cichar, p); \
  	/* Check rejected value. */ \
  	if ((cishort != PPP_CHAP) || (cichar != (CHAP_DIGEST(val)))) \
  	    goto bad; \
  	try_.neg = 0; \
  	try_.neg_eap = 0; \
      }
  #endif /* CHAP_SUPPORT && EAP_SUPPORT && !PAP_SUPPORT */
  
  #if CHAP_SUPPORT && !EAP_SUPPORT && !PAP_SUPPORT
  #define REJCICHAP(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_CHAP && \
  	p[1] == CILEN_CHAP && \
  	p[0] == opt) { \
  	len -= CILEN_CHAP; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETCHAR(cichar, p); \
  	/* Check rejected value. */ \
  	if ((cishort != PPP_CHAP) || (cichar != (CHAP_DIGEST(val)))) \
  	    goto bad; \
  	try_.neg = 0; \
      }
  #endif /* CHAP_SUPPORT && !EAP_SUPPORT && !PAP_SUPPORT */
  
  #define REJCILONG(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_LONG && \
  	p[1] == CILEN_LONG && \
  	p[0] == opt) { \
  	len -= CILEN_LONG; \
  	INCPTR(2, p); \
  	GETLONG(cilong, p); \
  	/* Check rejected value. */ \
  	if (cilong != val) \
  	    goto bad; \
  	try_.neg = 0; \
      }
  #if LQR_SUPPORT
  #define REJCILQR(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_LQR && \
  	p[1] == CILEN_LQR && \
  	p[0] == opt) { \
  	len -= CILEN_LQR; \
  	INCPTR(2, p); \
  	GETSHORT(cishort, p); \
  	GETLONG(cilong, p); \
  	/* Check rejected value. */ \
  	if (cishort != PPP_LQR || cilong != val) \
  	    goto bad; \
  	try_.neg = 0; \
      }
  #endif /* LQR_SUPPORT */
  #define REJCICBCP(opt, neg, val) \
      if (go->neg && \
  	len >= CILEN_CBCP && \
  	p[1] == CILEN_CBCP && \
  	p[0] == opt) { \
  	len -= CILEN_CBCP; \
  	INCPTR(2, p); \
  	GETCHAR(cichar, p); \
  	/* Check rejected value. */ \
  	if (cichar != val) \
  	    goto bad; \
  	try_.neg = 0; \
      }
  #define REJCIENDP(opt, neg, class, val, vlen) \
      if (go->neg && \
  	len >= CILEN_CHAR + vlen && \
  	p[0] == opt && \
  	p[1] == CILEN_CHAR + vlen) { \
  	int i; \
  	len -= CILEN_CHAR + vlen; \
  	INCPTR(2, p); \
  	GETCHAR(cichar, p); \
  	if (cichar != class) \
  	    goto bad; \
  	for (i = 0; i < vlen; ++i) { \
  	    GETCHAR(cichar, p); \
  	    if (cichar != val[i]) \
  		goto bad; \
  	} \
  	try_.neg = 0; \
      }
  
      REJCISHORT(CI_MRU, neg_mru, go->mru);
      REJCILONG(CI_ASYNCMAP, neg_asyncmap, go->asyncmap);
  #if EAP_SUPPORT
      REJCISHORT(CI_AUTHTYPE, neg_eap, PPP_EAP);
      if (!go->neg_eap) {
  #endif /* EAP_SUPPORT */
  #if CHAP_SUPPORT
  	REJCICHAP(CI_AUTHTYPE, neg_chap, go->chap_mdtype);
  	if (!go->neg_chap) {
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
  	    REJCISHORT(CI_AUTHTYPE, neg_upap, PPP_PAP);
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
  	}
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
      }
  #endif /* EAP_SUPPORT */
  #if LQR_SUPPORT
      REJCILQR(CI_QUALITY, neg_lqr, go->lqr_period);
  #endif /* LQR_SUPPORT */
      REJCICBCP(CI_CALLBACK, neg_cbcp, CBCP_OPT);
      REJCILONG(CI_MAGICNUMBER, neg_magicnumber, go->magicnumber);
      REJCIVOID(CI_PCOMPRESSION, neg_pcompression);
      REJCIVOID(CI_ACCOMPRESSION, neg_accompression);
  #ifdef HAVE_MULTILINK
      REJCISHORT(CI_MRRU, neg_mrru, go->mrru);
  #endif /* HAVE_MULTILINK */
      REJCIVOID(CI_SSNHF, neg_ssnhf);
      REJCIENDP(CI_EPDISC, neg_endpoint, go->endpoint.class_,
  	      go->endpoint.value, go->endpoint.length);
  
      /*
       * If there are any remaining CIs, then this packet is bad.
       */
      if (len != 0)
  	goto bad;
      /*
       * Now we can update state.
       */
      if (f->state != PPP_FSM_OPENED)
  	*go = try_;
      return 1;
  
  bad:
      LCPDEBUG(("lcp_rejci: received bad Reject!"));
      return 0;
  }
  
  
  /*
   * lcp_reqci - Check the peer's requested CIs and send appropriate response.
   *
   * Returns: CONFACK, CONFNAK or CONFREJ and input packet modified
   * appropriately.  If reject_if_disagree is non-zero, doesn't return
   * CONFNAK; returns CONFREJ if it can't return CONFACK.
   *
   * inp = Requested CIs
   * lenp = Length of requested CIs
   */
  static int lcp_reqci(fsm *f, u_char *inp, int *lenp, int reject_if_disagree) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      lcp_options *ho = &pcb->lcp_hisoptions;
      lcp_options *ao = &pcb->lcp_allowoptions;
      u_char *cip, *next;		/* Pointer to current and next CIs */
      int cilen, citype, cichar;	/* Parsed len, type, char value */
      u_short cishort;		/* Parsed short value */
      u32_t cilong;		/* Parse long value */
      int rc = CONFACK;		/* Final packet return code */
      int orc;			/* Individual option return code */
      u_char *p;			/* Pointer to next char to parse */
      u_char *rejp;		/* Pointer to next char in reject frame */
      struct pbuf *nakp;          /* Nak buffer */
      u_char *nakoutp;		/* Pointer to next char in Nak frame */
      int l = *lenp;		/* Length left */
  
      /*
       * Reset all his options.
       */
      BZERO(ho, sizeof(*ho));
  
      /*
       * Process all his options.
       */
      next = inp;
      nakp = pbuf_alloc(PBUF_RAW, (u16_t)(PPP_CTRL_PBUF_MAX_SIZE), PPP_CTRL_PBUF_TYPE);
      if(NULL == nakp)
          return 0;
      if(nakp->tot_len != nakp->len) {
          pbuf_free(nakp);
          return 0;
      }
  
      nakoutp = (u_char*)nakp->payload;
      rejp = inp;
      while (l) {
  	orc = CONFACK;			/* Assume success */
  	cip = p = next;			/* Remember begining of CI */
  	if (l < 2 ||			/* Not enough data for CI header or */
  	    p[1] < 2 ||			/*  CI length too small or */
  	    p[1] > l) {			/*  CI length too big? */
  	    LCPDEBUG(("lcp_reqci: bad CI length!"));
  	    orc = CONFREJ;		/* Reject bad CI */
  	    cilen = l;			/* Reject till end of packet */
  	    l = 0;			/* Don't loop again */
  	    citype = 0;
  	    goto endswitch;
  	}
  	GETCHAR(citype, p);		/* Parse CI type */
  	GETCHAR(cilen, p);		/* Parse CI length */
  	l -= cilen;			/* Adjust remaining length */
  	next += cilen;			/* Step to next CI */
  
  	switch (citype) {		/* Check CI type */
  	case CI_MRU:
  	    if (!ao->neg_mru ||		/* Allow option? */
  		cilen != CILEN_SHORT) {	/* Check CI length */
  		orc = CONFREJ;		/* Reject CI */
  		break;
  	    }
  	    GETSHORT(cishort, p);	/* Parse MRU */
  
  	    /*
  	     * He must be able to receive at least our minimum.
  	     * No need to check a maximum.  If he sends a large number,
  	     * we'll just ignore it.
  	     */
  	    if (cishort < PPP_MINMRU) {
  		orc = CONFNAK;		/* Nak CI */
  		PUTCHAR(CI_MRU, nakoutp);
  		PUTCHAR(CILEN_SHORT, nakoutp);
  		PUTSHORT(PPP_MINMRU, nakoutp);	/* Give him a hint */
  		break;
  	    }
  	    ho->neg_mru = 1;		/* Remember he sent MRU */
  	    ho->mru = cishort;		/* And remember value */
  	    break;
  
  	case CI_ASYNCMAP:
  	    if (!ao->neg_asyncmap ||
  		cilen != CILEN_LONG) {
  		orc = CONFREJ;
  		break;
  	    }
  	    GETLONG(cilong, p);
  
  	    /*
  	     * Asyncmap must have set at least the bits
  	     * which are set in lcp_allowoptions[unit].asyncmap.
  	     */
  	    if ((ao->asyncmap & ~cilong) != 0) {
  		orc = CONFNAK;
  		PUTCHAR(CI_ASYNCMAP, nakoutp);
  		PUTCHAR(CILEN_LONG, nakoutp);
  		PUTLONG(ao->asyncmap | cilong, nakoutp);
  		break;
  	    }
  	    ho->neg_asyncmap = 1;
  	    ho->asyncmap = cilong;
  	    break;
  
  	case CI_AUTHTYPE:
  	    if (cilen < CILEN_SHORT ||
  		!(0
  #if PAP_SUPPORT
  		|| ao->neg_upap
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
  		|| ao->neg_chap
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
  		|| ao->neg_eap
  #endif /* EAP_SUPPORT */
  		)) {
  		/*
  		 * Reject the option if we're not willing to authenticate.
  		 */
  		ppp_dbglog("No auth is possible");
  		orc = CONFREJ;
  		break;
  	    }
  	    GETSHORT(cishort, p);
  
  	    /*
  	     * Authtype must be PAP, CHAP, or EAP.
  	     *
  	     * Note: if more than one of ao->neg_upap, ao->neg_chap, and
  	     * ao->neg_eap are set, and the peer sends a Configure-Request
  	     * with two or more authenticate-protocol requests, then we will
  	     * reject the second request.
  	     * Whether we end up doing CHAP, UPAP, or EAP depends then on
  	     * the ordering of the CIs in the peer's Configure-Request.
               */
  
  #if PAP_SUPPORT
  	    if (cishort == PPP_PAP) {
  		/* we've already accepted CHAP or EAP */
  		if (0
  #if CHAP_SUPPORT
  		    || ho->neg_chap
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
  		    || ho->neg_eap
  #endif /* EAP_SUPPORT */
  		    || cilen != CILEN_SHORT) {
  		    LCPDEBUG(("lcp_reqci: rcvd AUTHTYPE PAP, rejecting..."));
  		    orc = CONFREJ;
  		    break;
  		}
  		if (!ao->neg_upap) {	/* we don't want to do PAP */
  		    orc = CONFNAK;	/* NAK it and suggest CHAP or EAP */
  		    PUTCHAR(CI_AUTHTYPE, nakoutp);
  #if EAP_SUPPORT
  		    if (ao->neg_eap) {
  			PUTCHAR(CILEN_SHORT, nakoutp);
  			PUTSHORT(PPP_EAP, nakoutp);
  		    } else {
  #endif /* EAP_SUPPORT */
  #if CHAP_SUPPORT
  			PUTCHAR(CILEN_CHAP, nakoutp);
  			PUTSHORT(PPP_CHAP, nakoutp);
  			PUTCHAR(CHAP_DIGEST(ao->chap_mdtype), nakoutp);
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
  		    }
  #endif /* EAP_SUPPORT */
  		    break;
  		}
  		ho->neg_upap = 1;
  		break;
  	    }
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
  	    if (cishort == PPP_CHAP) {
  		/* we've already accepted PAP or EAP */
  		if (
  #if PAP_SUPPORT
  		    ho->neg_upap ||
  #endif /* PAP_SUPPORT */
  #if EAP_SUPPORT
  		    ho->neg_eap ||
  #endif /* EAP_SUPPORT */
  		    cilen != CILEN_CHAP) {
  		    LCPDEBUG(("lcp_reqci: rcvd AUTHTYPE CHAP, rejecting..."));
  		    orc = CONFREJ;
  		    break;
  		}
  		if (!ao->neg_chap) {	/* we don't want to do CHAP */
  		    orc = CONFNAK;	/* NAK it and suggest EAP or PAP */
  		    PUTCHAR(CI_AUTHTYPE, nakoutp);
  		    PUTCHAR(CILEN_SHORT, nakoutp);
  #if EAP_SUPPORT
  		    if (ao->neg_eap) {
  			PUTSHORT(PPP_EAP, nakoutp);
  		    } else
  #endif /* EAP_SUPPORT */
  #if PAP_SUPPORT
  		    if(1) {
  			PUTSHORT(PPP_PAP, nakoutp);
  		    }
  		    else
  #endif /* PAP_SUPPORT */
  		    {}
  		    break;
  		}
  		GETCHAR(cichar, p);	/* get digest type */
  		if (!(CHAP_CANDIGEST(ao->chap_mdtype, cichar))) {
  		    /*
  		     * We can't/won't do the requested type,
  		     * suggest something else.
  		     */
  		    orc = CONFNAK;
  		    PUTCHAR(CI_AUTHTYPE, nakoutp);
  		    PUTCHAR(CILEN_CHAP, nakoutp);
  		    PUTSHORT(PPP_CHAP, nakoutp);
  		    PUTCHAR(CHAP_DIGEST(ao->chap_mdtype), nakoutp);
  		    break;
  		}
  		ho->chap_mdtype = CHAP_MDTYPE_D(cichar); /* save md type */
  		ho->neg_chap = 1;
  		break;
  	    }
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
  	    if (cishort == PPP_EAP) {
  		/* we've already accepted CHAP or PAP */
  		if (
  #if CHAP_SUPPORT
  		    ho->neg_chap ||
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
  		    ho->neg_upap ||
  #endif /* PAP_SUPPORT */
  		    cilen != CILEN_SHORT) {
  		    LCPDEBUG(("lcp_reqci: rcvd AUTHTYPE EAP, rejecting..."));
  		    orc = CONFREJ;
  		    break;
  		}
  		if (!ao->neg_eap) {	/* we don't want to do EAP */
  		    orc = CONFNAK;	/* NAK it and suggest CHAP or PAP */
  		    PUTCHAR(CI_AUTHTYPE, nakoutp);
  #if CHAP_SUPPORT
  		    if (ao->neg_chap) {
  			PUTCHAR(CILEN_CHAP, nakoutp);
  			PUTSHORT(PPP_CHAP, nakoutp);
  			PUTCHAR(CHAP_DIGEST(ao->chap_mdtype), nakoutp);
  		    } else
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
  		    if(1) {
  			PUTCHAR(CILEN_SHORT, nakoutp);
  			PUTSHORT(PPP_PAP, nakoutp);
  		    } else
  #endif /* PAP_SUPPORT */
  		    {}
  		    break;
  		}
  		ho->neg_eap = 1;
  		break;
  	    }
  #endif /* EAP_SUPPORT */
  
  	    /*
  	     * We don't recognize the protocol they're asking for.
  	     * Nak it with something we're willing to do.
  	     * (At this point we know ao->neg_upap || ao->neg_chap ||
  	     * ao->neg_eap.)
  	     */
  	    orc = CONFNAK;
  	    PUTCHAR(CI_AUTHTYPE, nakoutp);
  
  #if EAP_SUPPORT
  	    if (ao->neg_eap) {
  		PUTCHAR(CILEN_SHORT, nakoutp);
  		PUTSHORT(PPP_EAP, nakoutp);
  	    } else
  #endif /* EAP_SUPPORT */
  #if CHAP_SUPPORT
  	    if (ao->neg_chap) {
  		PUTCHAR(CILEN_CHAP, nakoutp);
  		PUTSHORT(PPP_CHAP, nakoutp);
  		PUTCHAR(CHAP_DIGEST(ao->chap_mdtype), nakoutp);
  	    } else
  #endif /* CHAP_SUPPORT */
  #if PAP_SUPPORT
  	    if(1) {
  		PUTCHAR(CILEN_SHORT, nakoutp);
  		PUTSHORT(PPP_PAP, nakoutp);
  	    } else
  #endif /* PAP_SUPPORT */
  	    {}
  	    break;
  
  #if LQR_SUPPORT
  	case CI_QUALITY:
  	    if (!ao->neg_lqr ||
  		cilen != CILEN_LQR) {
  		orc = CONFREJ;
  		break;
  	    }
  
  	    GETSHORT(cishort, p);
  	    GETLONG(cilong, p);
  
  	    /*
  	     * Check the protocol and the reporting period.
  	     * XXX When should we Nak this, and what with?
  	     */
  	    if (cishort != PPP_LQR) {
  		orc = CONFNAK;
  		PUTCHAR(CI_QUALITY, nakoutp);
  		PUTCHAR(CILEN_LQR, nakoutp);
  		PUTSHORT(PPP_LQR, nakoutp);
  		PUTLONG(ao->lqr_period, nakoutp);
  		break;
  	    }
  	    break;
  #endif /* LQR_SUPPORT */
  
  	case CI_MAGICNUMBER:
  	    if (!(ao->neg_magicnumber || go->neg_magicnumber) ||
  		cilen != CILEN_LONG) {
  		orc = CONFREJ;
  		break;
  	    }
  	    GETLONG(cilong, p);
  
  	    /*
  	     * He must have a different magic number.
  	     */
  	    if (go->neg_magicnumber &&
  		cilong == go->magicnumber) {
  		cilong = magic();	/* Don't put magic() inside macro! */
  		orc = CONFNAK;
  		PUTCHAR(CI_MAGICNUMBER, nakoutp);
  		PUTCHAR(CILEN_LONG, nakoutp);
  		PUTLONG(cilong, nakoutp);
  		break;
  	    }
  	    ho->neg_magicnumber = 1;
  	    ho->magicnumber = cilong;
  	    break;
  
  
  	case CI_PCOMPRESSION:
  	    if (!ao->neg_pcompression ||
  		cilen != CILEN_VOID) {
  		orc = CONFREJ;
  		break;
  	    }
  	    ho->neg_pcompression = 1;
  	    break;
  
  	case CI_ACCOMPRESSION:
  	    if (!ao->neg_accompression ||
  		cilen != CILEN_VOID) {
  		orc = CONFREJ;
  		break;
  	    }
  	    ho->neg_accompression = 1;
  	    break;
  
  #ifdef HAVE_MULTILINK
  	case CI_MRRU:
  	    if (!ao->neg_mrru
  		|| !multilink
  		|| cilen != CILEN_SHORT) {
  		orc = CONFREJ;
  		break;
  	    }
  
  	    GETSHORT(cishort, p);
  	    /* possibly should insist on a minimum/maximum MRRU here */
  	    ho->neg_mrru = 1;
  	    ho->mrru = cishort;
  	    break;
  #endif /* HAVE_MULTILINK */
  
  	case CI_SSNHF:
  	    if (!ao->neg_ssnhf
  #ifdef HAVE_MULTILINK
  		|| !multilink
  #endif /* HAVE_MULTILINK */
  		|| cilen != CILEN_VOID) {
  		orc = CONFREJ;
  		break;
  	    }
  	    ho->neg_ssnhf = 1;
  	    break;
  
  	case CI_EPDISC:
  	    if (!ao->neg_endpoint ||
  		cilen < CILEN_CHAR ||
  		cilen > CILEN_CHAR + MAX_ENDP_LEN) {
  		orc = CONFREJ;
  		break;
  	    }
  	    GETCHAR(cichar, p);
  	    cilen -= CILEN_CHAR;
  	    ho->neg_endpoint = 1;
  	    ho->endpoint.class_ = cichar;
  	    ho->endpoint.length = cilen;
  	    MEMCPY(ho->endpoint.value, p, cilen);
  	    INCPTR(cilen, p);
  	    break;
  
  	default:
  	    LCPDEBUG(("lcp_reqci: rcvd unknown option %d", citype));
  	    orc = CONFREJ;
  	    break;
  	}
  
  endswitch:
  	if (orc == CONFACK &&		/* Good CI */
  	    rc != CONFACK)		/*  but prior CI wasnt? */
  	    continue;			/* Don't send this one */
  
  	if (orc == CONFNAK) {		/* Nak this CI? */
  	    if (reject_if_disagree	/* Getting fed up with sending NAKs? */
  		&& citype != CI_MAGICNUMBER) {
  		orc = CONFREJ;		/* Get tough if so */
  	    } else {
  		if (rc == CONFREJ)	/* Rejecting prior CI? */
  		    continue;		/* Don't send this one */
  		rc = CONFNAK;
  	    }
  	}
  	if (orc == CONFREJ) {		/* Reject this CI */
  	    rc = CONFREJ;
  	    if (cip != rejp)		/* Need to move rejected CI? */
  		MEMCPY(rejp, cip, cilen); /* Move it */
  	    INCPTR(cilen, rejp);	/* Update output pointer */
  	}
      }
  
      /*
       * If we wanted to send additional NAKs (for unsent CIs), the
       * code would go here.  The extra NAKs would go at *nakoutp.
       * At present there are no cases where we want to ask the
       * peer to negotiate an option.
       */
  
      switch (rc) {
      case CONFACK:
  	*lenp = next - inp;
  	break;
      case CONFNAK:
  	/*
  	 * Copy the Nak'd options from the nak buffer to the caller's buffer.
  	 */
  	*lenp = nakoutp - (u_char*)nakp->payload;
  	MEMCPY(inp, nakp->payload, *lenp);
  	break;
      case CONFREJ:
  	*lenp = rejp - inp;
  	break;
      default:
  	break;
      }
  
      pbuf_free(nakp);
      LCPDEBUG(("lcp_reqci: returning CONF%s.", CODENAME(rc)));
      return (rc);			/* Return final code */
  }
  
  
  /*
   * lcp_up - LCP has come UP.
   */
  static void lcp_up(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *wo = &pcb->lcp_wantoptions;
      lcp_options *ho = &pcb->lcp_hisoptions;
      lcp_options *go = &pcb->lcp_gotoptions;
      lcp_options *ao = &pcb->lcp_allowoptions;
      int mtu, mru;
  
      if (!go->neg_magicnumber)
  	go->magicnumber = 0;
      if (!ho->neg_magicnumber)
  	ho->magicnumber = 0;
  
      /*
       * Set our MTU to the smaller of the MTU we wanted and
       * the MRU our peer wanted.  If we negotiated an MRU,
       * set our MRU to the larger of value we wanted and
       * the value we got in the negotiation.
       * Note on the MTU: the link MTU can be the MRU the peer wanted,
       * the interface MTU is set to the lowest of that, the
       * MTU we want to use, and our link MRU.
       */
      mtu = ho->neg_mru? ho->mru: PPP_MRU;
      mru = go->neg_mru? LWIP_MAX(wo->mru, go->mru): PPP_MRU;
  #ifdef HAVE_MULTILINK
      if (!(multilink && go->neg_mrru && ho->neg_mrru))
  #endif /* HAVE_MULTILINK */
  	netif_set_mtu(pcb, LWIP_MIN(LWIP_MIN(mtu, mru), ao->mru));
      ppp_send_config(pcb, mtu,
  		    (ho->neg_asyncmap? ho->asyncmap: 0xffffffff),
  		    ho->neg_pcompression, ho->neg_accompression);
      ppp_recv_config(pcb, mru,
  		    (pcb->settings.lax_recv? 0: go->neg_asyncmap? go->asyncmap: 0xffffffff),
  		    go->neg_pcompression, go->neg_accompression);
  
      if (ho->neg_mru)
  	pcb->peer_mru = ho->mru;
  
      lcp_echo_lowerup(f->pcb);  /* Enable echo messages */
  
      link_established(pcb);
  }
  
  
  /*
   * lcp_down - LCP has gone DOWN.
   *
   * Alert other protocols.
   */
  static void lcp_down(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
  
      lcp_echo_lowerdown(f->pcb);
  
      link_down(pcb);
  
      ppp_send_config(pcb, PPP_MRU, 0xffffffff, 0, 0);
      ppp_recv_config(pcb, PPP_MRU,
  		    (go->neg_asyncmap? go->asyncmap: 0xffffffff),
  		    go->neg_pcompression, go->neg_accompression);
      pcb->peer_mru = PPP_MRU;
  }
  
  
  /*
   * lcp_starting - LCP needs the lower layer up.
   */
  static void lcp_starting(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      link_required(pcb);
  }
  
  
  /*
   * lcp_finished - LCP has finished with the lower layer.
   */
  static void lcp_finished(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      link_terminated(pcb);
  }
  
  
  #if PRINTPKT_SUPPORT
  /*
   * lcp_printpkt - print the contents of an LCP packet.
   */
  static const char* const lcp_codenames[] = {
      "ConfReq", "ConfAck", "ConfNak", "ConfRej",
      "TermReq", "TermAck", "CodeRej", "ProtRej",
      "EchoReq", "EchoRep", "DiscReq", "Ident",
      "TimeRem"
  };
  
  static int lcp_printpkt(const u_char *p, int plen,
  		void (*printer) (void *, const char *, ...), void *arg) {
      int code, id, len, olen, i;
      const u_char *pstart, *optend;
      u_short cishort;
      u32_t cilong;
  
      if (plen < HEADERLEN)
  	return 0;
      pstart = p;
      GETCHAR(code, p);
      GETCHAR(id, p);
      GETSHORT(len, p);
      if (len < HEADERLEN || len > plen)
  	return 0;
  
     if (code >= 1 && code <= (int)LWIP_ARRAYSIZE(lcp_codenames))
  	printer(arg, " %s", lcp_codenames[code-1]);
      else
  	printer(arg, " code=0x%x", code);
      printer(arg, " id=0x%x", id);
      len -= HEADERLEN;
      switch (code) {
      case CONFREQ:
      case CONFACK:
      case CONFNAK:
      case CONFREJ:
  	/* print option list */
  	while (len >= 2) {
  	    GETCHAR(code, p);
  	    GETCHAR(olen, p);
  	    p -= 2;
  	    if (olen < 2 || olen > len) {
  		break;
  	    }
  	    printer(arg, " <");
  	    len -= olen;
  	    optend = p + olen;
  	    switch (code) {
  	    case CI_MRU:
  		if (olen == CILEN_SHORT) {
  		    p += 2;
  		    GETSHORT(cishort, p);
  		    printer(arg, "mru %d", cishort);
  		}
  		break;
  	    case CI_ASYNCMAP:
  		if (olen == CILEN_LONG) {
  		    p += 2;
  		    GETLONG(cilong, p);
  		    printer(arg, "asyncmap 0x%x", cilong);
  		}
  		break;
  	    case CI_AUTHTYPE:
  		if (olen >= CILEN_SHORT) {
  		    p += 2;
  		    printer(arg, "auth ");
  		    GETSHORT(cishort, p);
  		    switch (cishort) {
  #if PAP_SUPPORT
  		    case PPP_PAP:
  			printer(arg, "pap");
  			break;
  #endif /* PAP_SUPPORT */
  #if CHAP_SUPPORT
  		    case PPP_CHAP:
  			printer(arg, "chap");
  			if (p < optend) {
  			    switch (*p) {
  			    case CHAP_MD5:
  				printer(arg, " MD5");
  				++p;
  				break;
  #if MSCHAP_SUPPORT
  			    case CHAP_MICROSOFT:
  				printer(arg, " MS");
  				++p;
  				break;
  
  			    case CHAP_MICROSOFT_V2:
  				printer(arg, " MS-v2");
  				++p;
  				break;
  #endif /* MSCHAP_SUPPORT */
  			    default:
  				break;
  			    }
  			}
  			break;
  #endif /* CHAP_SUPPORT */
  #if EAP_SUPPORT
  		    case PPP_EAP:
  			printer(arg, "eap");
  			break;
  #endif /* EAP_SUPPORT */
  		    default:
  			printer(arg, "0x%x", cishort);
  		    }
  		}
  		break;
  #if LQR_SUPPORT
  	    case CI_QUALITY:
  		if (olen >= CILEN_SHORT) {
  		    p += 2;
  		    printer(arg, "quality ");
  		    GETSHORT(cishort, p);
  		    switch (cishort) {
  		    case PPP_LQR:
  			printer(arg, "lqr");
  			break;
  		    default:
  			printer(arg, "0x%x", cishort);
  		    }
  		}
  		break;
  #endif /* LQR_SUPPORT */
  	    case CI_CALLBACK:
  		if (olen >= CILEN_CHAR) {
  		    p += 2;
  		    printer(arg, "callback ");
  		    GETCHAR(cishort, p);
  		    switch (cishort) {
  		    case CBCP_OPT:
  			printer(arg, "CBCP");
  			break;
  		    default:
  			printer(arg, "0x%x", cishort);
  		    }
  		}
  		break;
  	    case CI_MAGICNUMBER:
  		if (olen == CILEN_LONG) {
  		    p += 2;
  		    GETLONG(cilong, p);
  		    printer(arg, "magic 0x%x", cilong);
  		}
  		break;
  	    case CI_PCOMPRESSION:
  		if (olen == CILEN_VOID) {
  		    p += 2;
  		    printer(arg, "pcomp");
  		}
  		break;
  	    case CI_ACCOMPRESSION:
  		if (olen == CILEN_VOID) {
  		    p += 2;
  		    printer(arg, "accomp");
  		}
  		break;
  	    case CI_MRRU:
  		if (olen == CILEN_SHORT) {
  		    p += 2;
  		    GETSHORT(cishort, p);
  		    printer(arg, "mrru %d", cishort);
  		}
  		break;
  	    case CI_SSNHF:
  		if (olen == CILEN_VOID) {
  		    p += 2;
  		    printer(arg, "ssnhf");
  		}
  		break;
  	    case CI_EPDISC:
  #ifdef HAVE_MULTILINK
  		if (olen >= CILEN_CHAR) {
  		    struct epdisc epd;
  		    p += 2;
  		    GETCHAR(epd.class, p);
  		    epd.length = olen - CILEN_CHAR;
  		    if (epd.length > MAX_ENDP_LEN)
  			epd.length = MAX_ENDP_LEN;
  		    if (epd.length > 0) {
  			MEMCPY(epd.value, p, epd.length);
  			p += epd.length;
  		    }
  		    printer(arg, "endpoint [%s]", epdisc_to_str(&epd));
  		}
  #else
  		printer(arg, "endpoint");
  #endif
  		break;
  	    default:
  		break;
  	    }
  	    while (p < optend) {
  		GETCHAR(code, p);
  		printer(arg, " %.2x", code);
  	    }
  	    printer(arg, ">");
  	}
  	break;
  
      case TERMACK:
      case TERMREQ:
  	if (len > 0 && *p >= ' ' && *p < 0x7f) {
  	    printer(arg, " ");
  	    ppp_print_string(p, len, printer, arg);
  	    p += len;
  	    len = 0;
  	}
  	break;
  
      case ECHOREQ:
      case ECHOREP:
      case DISCREQ:
  	if (len >= 4) {
  	    GETLONG(cilong, p);
  	    printer(arg, " magic=0x%x", cilong);
  	    len -= 4;
  	}
  	break;
  
      case IDENTIF:
      case TIMEREM:
  	if (len >= 4) {
  	    GETLONG(cilong, p);
  	    printer(arg, " magic=0x%x", cilong);
  	    len -= 4;
  	}
  	if (code == TIMEREM) {
  	    if (len < 4)
  		break;
  	    GETLONG(cilong, p);
  	    printer(arg, " seconds=%u", cilong);
  	    len -= 4;
  	}
  	if (len > 0) {
  	    printer(arg, " ");
  	    ppp_print_string(p, len, printer, arg);
  	    p += len;
  	    len = 0;
  	}
  	break;
      default:
  	break;
      }
  
      /* print the rest of the bytes in the packet */
      for (i = 0; i < len && i < 32; ++i) {
  	GETCHAR(code, p);
  	printer(arg, " %.2x", code);
      }
      if (i < len) {
  	printer(arg, " ...");
  	p += len - i;
      }
  
      return p - pstart;
  }
  #endif /* PRINTPKT_SUPPORT */
  
  /*
   * Time to shut down the link because there is nothing out there.
   */
  
  static void LcpLinkFailure(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      if (f->state == PPP_FSM_OPENED) {
  	ppp_info("No response to %d echo-requests", pcb->lcp_echos_pending);
          ppp_notice("Serial link appears to be disconnected.");
  	pcb->err_code = PPPERR_PEERDEAD;
  	lcp_close(pcb, "Peer not responding");
      }
  }
  
  /*
   * Timer expired for the LCP echo requests from this process.
   */
  
  static void LcpEchoCheck(fsm *f) {
      ppp_pcb *pcb = f->pcb;
  
      LcpSendEchoRequest (f);
      if (f->state != PPP_FSM_OPENED)
  	return;
  
      /*
       * Start the timer for the next interval.
       */
      if (pcb->lcp_echo_timer_running)
  	ppp_warn("assertion lcp_echo_timer_running==0 failed");
      TIMEOUT (LcpEchoTimeout, f, pcb->settings.lcp_echo_interval);
      pcb->lcp_echo_timer_running = 1;
  }
  
  /*
   * LcpEchoTimeout - Timer expired on the LCP echo
   */
  
  static void LcpEchoTimeout(void *arg) {
      fsm *f = (fsm*)arg;
      ppp_pcb *pcb = f->pcb;
      if (pcb->lcp_echo_timer_running != 0) {
          pcb->lcp_echo_timer_running = 0;
          LcpEchoCheck ((fsm *) arg);
      }
  }
  
  /*
   * LcpEchoReply - LCP has received a reply to the echo
   */
  
  static void lcp_received_echo_reply(fsm *f, int id, u_char *inp, int len) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      u32_t magic_val;
      LWIP_UNUSED_ARG(id);
  
      /* Check the magic number - don't count replies from ourselves. */
      if (len < 4) {
  	ppp_dbglog("lcp: received short Echo-Reply, length %d", len);
  	return;
      }
      GETLONG(magic_val, inp);
      if (go->neg_magicnumber
  	&& magic_val == go->magicnumber) {
  	ppp_warn("appear to have received our own echo-reply!");
  	return;
      }
  
      /* Reset the number of outstanding echo frames */
      pcb->lcp_echos_pending = 0;
  }
  
  /*
   * LcpSendEchoRequest - Send an echo request frame to the peer
   */
  
  static void LcpSendEchoRequest(fsm *f) {
      ppp_pcb *pcb = f->pcb;
      lcp_options *go = &pcb->lcp_gotoptions;
      u32_t lcp_magic;
      u_char pkt[4], *pktp;
  
      /*
       * Detect the failure of the peer at this point.
       */
      if (pcb->settings.lcp_echo_fails != 0) {
          if (pcb->lcp_echos_pending >= pcb->settings.lcp_echo_fails) {
              LcpLinkFailure(f);
              pcb->lcp_echos_pending = 0;
  	}
      }
  
  #if PPP_LCP_ADAPTIVE
      /*
       * If adaptive echos have been enabled, only send the echo request if
       * no traffic was received since the last one.
       */
      if (pcb->settings.lcp_echo_adaptive) {
  	static unsigned int last_pkts_in = 0;
  
  #if PPP_STATS_SUPPORT
  	update_link_stats(f->unit);
  	link_stats_valid = 0;
  #endif /* PPP_STATS_SUPPORT */
  
  	if (link_stats.pkts_in != last_pkts_in) {
  	    last_pkts_in = link_stats.pkts_in;
  	    return;
  	}
      }
  #endif
  
      /*
       * Make and send the echo request frame.
       */
      if (f->state == PPP_FSM_OPENED) {
          lcp_magic = go->magicnumber;
  	pktp = pkt;
  	PUTLONG(lcp_magic, pktp);
          fsm_sdata(f, ECHOREQ, pcb->lcp_echo_number++, pkt, pktp - pkt);
  	++pcb->lcp_echos_pending;
      }
  }
  
  /*
   * lcp_echo_lowerup - Start the timer for the LCP frame
   */
  
  static void lcp_echo_lowerup(ppp_pcb *pcb) {
      fsm *f = &pcb->lcp_fsm;
  
      /* Clear the parameters for generating echo frames */
      pcb->lcp_echos_pending      = 0;
      pcb->lcp_echo_number        = 0;
      pcb->lcp_echo_timer_running = 0;
    
      /* If a timeout interval is specified then start the timer */
      if (pcb->settings.lcp_echo_interval != 0)
          LcpEchoCheck (f);
  }
  
  /*
   * lcp_echo_lowerdown - Stop the timer for the LCP frame
   */
  
  static void lcp_echo_lowerdown(ppp_pcb *pcb) {
      fsm *f = &pcb->lcp_fsm;
  
      if (pcb->lcp_echo_timer_running != 0) {
          UNTIMEOUT (LcpEchoTimeout, f);
          pcb->lcp_echo_timer_running = 0;
      }
  }
  
  #endif /* PPP_SUPPORT */
  