[freertos] / Demo / Common / ethernet / lwIP / netif / ppp / ppp.c

/*****************************************************************************
* ppp.c - Network Point to Point Protocol program file.
*
* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
* portions Copyright (c) 1997 by Global Election Systems Inc.
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice and the following disclaimer are included verbatim in any 
* distributions. No written agreement, license, or royalty fee is required
* for any of the authorized uses.
*
* THIS SOFTWARE IS PROVIDED BY THE 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 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.
*
******************************************************************************
* REVISION HISTORY
*
* 03-01-01 Marc Boucher <marc@mbsi.ca>
*   Ported to lwIP.
* 97-11-05 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
*   Original.
*****************************************************************************/

/*
 * ppp_defs.h - PPP definitions.
 *
 * if_pppvar.h - private structures and declarations for PPP.
 *
 * Copyright (c) 1994 The Australian National University.
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation is hereby granted, provided that the above copyright
 * notice appears in all copies.  This software is provided without any
 * warranty, express or implied. The Australian National University
 * makes no representations about the suitability of this software for
 * any purpose.
 *
 * IN NO EVENT SHALL THE AUSTRALIAN NATIONAL UNIVERSITY BE LIABLE TO ANY
 * PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
 * THE AUSTRALIAN NATIONAL UNIVERSITY HAVE BEEN ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * THE AUSTRALIAN NATIONAL UNIVERSITY SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE AUSTRALIAN NATIONAL UNIVERSITY HAS NO
 * OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS,
 * OR MODIFICATIONS.
 */

/*
 * if_ppp.h - Point-to-Point Protocol definitions.
 *
 * Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
 
#include <string.h>
 
#include "ppp.h"
#if PPP_SUPPORT > 0
#include "randm.h"
#include "fsm.h"
#if PAP_SUPPORT > 0
#include "pap.h"
#endif
#if CHAP_SUPPORT > 0
#include "chap.h"
#endif
#include "ipcp.h"
#include "lcp.h"
#include "magic.h"
#include "auth.h"
#if VJ_SUPPORT > 0
#include "vj.h"
#endif

#include "pppdebug.h"

/*************************/
/*** LOCAL DEFINITIONS ***/
/*************************/

/*
 * The basic PPP frame.
 */
#define PPP_ADDRESS(p)  (((u_char *)(p))[0])
#define PPP_CONTROL(p)  (((u_char *)(p))[1])
#define PPP_PROTOCOL(p) ((((u_char *)(p))[2] << 8) + ((u_char *)(p))[3])

/* PPP packet parser states.  Current state indicates operation yet to be
 * completed. */
typedef enum {
    PDIDLE = 0,                 /* Idle state - waiting. */
    PDSTART,                    /* Process start flag. */
    PDADDRESS,                  /* Process address field. */
    PDCONTROL,                  /* Process control field. */
    PDPROTOCOL1,                /* Process protocol field 1. */
    PDPROTOCOL2,                /* Process protocol field 2. */
    PDDATA                      /* Process data byte. */
} PPPDevStates;

#define ESCAPE_P(accm, c) ((accm)[(c) >> 3] & pppACCMMask[c & 0x07])

/************************/
/*** LOCAL DATA TYPES ***/
/************************/
/*
 * PPP interface control block.
 */
typedef struct PPPControl_s {
    char openFlag;                      /* True when in use. */
    char oldFrame;                      /* Old framing character for fd. */
    sio_fd_t fd;                    /* File device ID of port. */
    int  kill_link;                     /* Shut the link down. */
    int  sig_hup;                       /* Carrier lost. */
    int  if_up;                         /* True when the interface is up. */
    int  errCode;                       /* Code indicating why interface is down. */
    struct pbuf *inHead, *inTail;       /* The input packet. */
    PPPDevStates inState;               /* The input process state. */
    char inEscaped;                     /* Escape next character. */
    u16_t inProtocol;                   /* The input protocol code. */
    u16_t inFCS;                        /* Input Frame Check Sequence value. */
    int  mtu;                           /* Peer's mru */
    int  pcomp;                         /* Does peer accept protocol compression? */
    int  accomp;                        /* Does peer accept addr/ctl compression? */
    u_long lastXMit;                    /* Time of last transmission. */
    ext_accm inACCM;                    /* Async-Ctl-Char-Map for input. */
    ext_accm outACCM;                   /* Async-Ctl-Char-Map for output. */
#if VJ_SUPPORT > 0
    int  vjEnabled;                     /* Flag indicating VJ compression enabled. */
    struct vjcompress vjComp;           /* Van Jabobsen compression header. */
#endif

    struct netif netif;

    struct ppp_addrs addrs;

    void (*linkStatusCB)(void *ctx, int errCode, void *arg);
    void *linkStatusCtx;

} PPPControl;


/*
 * Ioctl definitions.
 */

struct npioctl {
    int     protocol;           /* PPP procotol, e.g. PPP_IP */
    enum NPmode mode;
};



/***********************************/
/*** LOCAL FUNCTION DECLARATIONS ***/
/***********************************/
static void pppMain(void *pd);
static void pppDrop(PPPControl *pc);
static void pppInProc(int pd, u_char *s, int l);


/******************************/
/*** PUBLIC DATA STRUCTURES ***/
/******************************/
u_long subnetMask;

static PPPControl pppControl[NUM_PPP]; /* The PPP interface control blocks. */

/*
 * PPP Data Link Layer "protocol" table.
 * One entry per supported protocol.
 * The last entry must be NULL.
 */
struct protent *ppp_protocols[] = {
    &lcp_protent,
#if PAP_SUPPORT > 0
    &pap_protent,
#endif
#if CHAP_SUPPORT > 0
    &chap_protent,
#endif
#if CBCP_SUPPORT > 0
    &cbcp_protent,
#endif
    &ipcp_protent,
#if CCP_SUPPORT > 0
    &ccp_protent,
#endif
    NULL
};


/*
 * Buffers for outgoing packets.  This must be accessed only from the appropriate
 * PPP task so that it doesn't need to be protected to avoid collisions.
 */
u_char outpacket_buf[NUM_PPP][PPP_MRU+PPP_HDRLEN];  


/*****************************/
/*** LOCAL DATA STRUCTURES ***/
/*****************************/

/*
 * FCS lookup table as calculated by genfcstab.
 */
static const u_short fcstab[256] = {
    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
    0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
    0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
    0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
    0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
    0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
    0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
    0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
    0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
    0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
    0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
    0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
    0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
    0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
    0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
    0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
    0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
    0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
    0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
    0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
    0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
    0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
    0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
    0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
    0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
    0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
    0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
    0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
    0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};

/* PPP's Asynchronous-Control-Character-Map.  The mask array is used
 * to select the specific bit for a character. */
static u_char pppACCMMask[] = {
    0x01,
    0x02,
    0x04,
    0x08,
    0x10,
    0x20,
    0x40,
    0x80
};


/***********************************/
/*** PUBLIC FUNCTION DEFINITIONS ***/
/***********************************/
/* Initialize the PPP subsystem. */

struct ppp_settings ppp_settings;

void pppInit(void)
{
    struct protent *protp;
    int i, j;
    
        memset(&ppp_settings, 0, sizeof(ppp_settings));
        ppp_settings.usepeerdns = 1;
        pppSetAuth(PPPAUTHTYPE_NONE, NULL, NULL);

        magicInit();

    for (i = 0; i < NUM_PPP; i++) {
        pppControl[i].openFlag = 0;

                subnetMask = htonl(0xffffff00);
    
        /*
         * Initialize to the standard option set.
         */
        for (j = 0; (protp = ppp_protocols[j]) != NULL; ++j)
            (*protp->init)(i);
    }

#if LINK_STATS
    /* Clear the statistics. */
    memset(&lwip_stats.link, 0, sizeof(lwip_stats.link));
#endif
}

void pppSetAuth(enum pppAuthType authType, const char *user, const char *passwd)
{
    switch(authType) {
        case PPPAUTHTYPE_NONE:
        default:
#ifdef LWIP_PPP_STRICT_PAP_REJECT
            ppp_settings.refuse_pap = 1;
#else
            /* some providers request pap and accept an empty login/pw */
            ppp_settings.refuse_pap = 0;
#endif
            ppp_settings.refuse_chap = 1;
            break;
        case PPPAUTHTYPE_ANY:
/* Warning: Using PPPAUTHTYPE_ANY might have security consequences.
 * RFC 1994 says:
 *
 * In practice, within or associated with each PPP server, there is a
 * database which associates "user" names with authentication
 * information ("secrets").  It is not anticipated that a particular
 * named user would be authenticated by multiple methods.  This would
 * make the user vulnerable to attacks which negotiate the least secure
 * method from among a set (such as PAP rather than CHAP).  If the same
 * secret was used, PAP would reveal the secret to be used later with
 * CHAP.
 *
 * Instead, for each user name there should be an indication of exactly
 * one method used to authenticate that user name.  If a user needs to
 * make use of different authentication methods under different
 * circumstances, then distinct user names SHOULD be employed, each of
 * which identifies exactly one authentication method.
 *
 */
            ppp_settings.refuse_pap = 0;
            ppp_settings.refuse_chap = 0;
            break;
        case PPPAUTHTYPE_PAP:
            ppp_settings.refuse_pap = 0;
            ppp_settings.refuse_chap = 1;
            break;
        case PPPAUTHTYPE_CHAP:
            ppp_settings.refuse_pap = 1;
            ppp_settings.refuse_chap = 0;
            break;
    }

    if(user) {
        strncpy(ppp_settings.user, user, sizeof(ppp_settings.user)-1);
        ppp_settings.user[sizeof(ppp_settings.user)-1] = '\0';
    } else
        ppp_settings.user[0] = '\0';

    if(passwd) {
        strncpy(ppp_settings.passwd, passwd, sizeof(ppp_settings.passwd)-1);
        ppp_settings.passwd[sizeof(ppp_settings.passwd)-1] = '\0';
    } else
        ppp_settings.passwd[0] = '\0';
}

/* Open a new PPP connection using the given I/O device.
 * This initializes the PPP control block but does not
 * attempt to negotiate the LCP session.  If this port
 * connects to a modem, the modem connection must be
 * established before calling this.
 * Return a new PPP connection descriptor on success or
 * an error code (negative) on failure. */
int pppOpen(sio_fd_t fd, void (*linkStatusCB)(void *ctx, int errCode, void *arg), void *linkStatusCtx)
{
    PPPControl *pc;
    int pd;

    /* Find a free PPP session descriptor. Critical region? */
    for (pd = 0; pd < NUM_PPP && pppControl[pd].openFlag != 0; pd++);
    if (pd >= NUM_PPP)
        pd = PPPERR_OPEN;
    else
        pppControl[pd].openFlag = !0;

    /* Launch a deamon thread. */
    if (pd >= 0) {

        pppControl[pd].openFlag = 1;

        lcp_init(pd);
        pc = &pppControl[pd];
        pc->fd = fd;
        pc->kill_link = 0;
        pc->sig_hup = 0;
        pc->if_up = 0;
        pc->errCode = 0;
        pc->inState = PDIDLE;
        pc->inHead = NULL;
        pc->inTail = NULL;
        pc->inEscaped = 0;
        pc->lastXMit = 0;

#if VJ_SUPPORT > 0
        pc->vjEnabled = 0;
        vj_compress_init(&pc->vjComp);
#endif

        /* 
         * Default the in and out accm so that escape and flag characters
         * are always escaped. 
         */
        memset(pc->inACCM, 0, sizeof(ext_accm));
        pc->inACCM[15] = 0x60;
        memset(pc->outACCM, 0, sizeof(ext_accm));
        pc->outACCM[15] = 0x60;

        pc->linkStatusCB = linkStatusCB;
        pc->linkStatusCtx = linkStatusCtx;

        sys_thread_new(pppMain, (void*)pd, PPP_THREAD_PRIO);
        if(!linkStatusCB) {
                while(pd >= 0 && !pc->if_up) {
                        sys_msleep(500);
                        if (lcp_phase[pd] == PHASE_DEAD) {
                                pppClose(pd);
                                if (pc->errCode)
                                        pd = pc->errCode;
                                else
                                        pd = PPPERR_CONNECT;
                        }
                }
        }
    }
    return pd;
}

/* Close a PPP connection and release the descriptor. 
 * Any outstanding packets in the queues are dropped.
 * Return 0 on success, an error code on failure. */
int pppClose(int pd)
{
    PPPControl *pc = &pppControl[pd];
    int st = 0;

    /* Disconnect */
    pc->kill_link = !0;
    pppMainWakeup(pd);
    
    if(!pc->linkStatusCB) {
            while(st >= 0 && lcp_phase[pd] != PHASE_DEAD) {
                    sys_msleep(500);
                    break;
            }
    }
    return st;
}

/* This function is called when carrier is lost on the PPP channel. */
void pppSigHUP(int pd)
{
    PPPControl *pc = &pppControl[pd];

    pc->sig_hup = 1;
    pppMainWakeup(pd);
}

static void nPut(PPPControl *pc, struct pbuf *nb)
{
        struct pbuf *b;
        int c;

        for(b = nb; b != NULL; b = b->next) {
            if((c = sio_write(pc->fd, b->payload, b->len)) != b->len) {
                PPPDEBUG((LOG_WARNING,
                            "PPP nPut: incomplete sio_write(%d,, %u) = %d\n", pc->fd, b->len, c));
#if LINK_STATS
                lwip_stats.link.err++;
#endif /* LINK_STATS */
                pc->lastXMit = 0; /* prepend PPP_FLAG to next packet */
                break;
            }
        }
        pbuf_free(nb);

#if LINK_STATS
        lwip_stats.link.xmit++;
#endif /* LINK_STATS */
}

/* 
 * pppAppend - append given character to end of given pbuf.  If outACCM
 * is not NULL and the character needs to be escaped, do so.
 * If pbuf is full, append another.
 * Return the current pbuf.
 */
static struct pbuf *pppAppend(u_char c, struct pbuf *nb, ext_accm *outACCM)
{
    struct pbuf *tb = nb;
    
    /* Make sure there is room for the character and an escape code.
     * Sure we don't quite fill the buffer if the character doesn't
     * get escaped but is one character worth complicating this? */
    /* Note: We assume no packet header. */
    if (nb && (PBUF_POOL_BUFSIZE - nb->len) < 2) {
        tb = pbuf_alloc(PBUF_RAW, 0, PBUF_POOL);
        if (tb) {
            nb->next = tb;
        }
#if LINK_STATS
        else {
            lwip_stats.link.memerr++;
        }
#endif /* LINK_STATS */
        nb = tb;
    }
    if (nb) {
        if (outACCM && ESCAPE_P(*outACCM, c)) {
            *((u_char*)nb->payload + nb->len++) = PPP_ESCAPE;
            *((u_char*)nb->payload + nb->len++) = c ^ PPP_TRANS;
        }
        else
            *((u_char*)nb->payload + nb->len++) = c;
    }
        
    return tb;
}

/* Send a packet on the given connection. */
static err_t pppifOutput(struct netif *netif, struct pbuf *pb, struct ip_addr *ipaddr)
{
    int pd = (int)netif->state;
    u_short protocol = PPP_IP;
    PPPControl *pc = &pppControl[pd];
    u_int fcsOut = PPP_INITFCS;
    struct pbuf *headMB = NULL, *tailMB = NULL, *p;
    u_char c;

    (void)ipaddr;

    /* Validate parameters. */
    /* We let any protocol value go through - it can't hurt us
     * and the peer will just drop it if it's not accepting it. */
        if (pd < 0 || pd >= NUM_PPP || !pc->openFlag || !pb) {
        PPPDEBUG((LOG_WARNING, "pppifOutput[%d]: bad parms prot=%d pb=%p\n",
                    pd, protocol, pb));
#if LINK_STATS
                lwip_stats.link.opterr++;
                lwip_stats.link.drop++;
#endif
                return ERR_ARG;
        }

    /* Check that the link is up. */
        if (lcp_phase[pd] == PHASE_DEAD) {
        PPPDEBUG((LOG_ERR, "pppifOutput[%d]: link not up\n", pd));
#if LINK_STATS
                lwip_stats.link.rterr++;
                lwip_stats.link.drop++;
#endif
                return ERR_RTE;
        }

    /* Grab an output buffer. */
        headMB = pbuf_alloc(PBUF_RAW, 0, PBUF_POOL);
    if (headMB == NULL) {
        PPPDEBUG((LOG_WARNING, "pppifOutput[%d]: first alloc fail\n", pd));
#if LINK_STATS
                lwip_stats.link.memerr++;
                lwip_stats.link.drop++;
#endif /* LINK_STATS */
        return ERR_MEM;
    }
        
#if VJ_SUPPORT > 0
    /* 
     * Attempt Van Jacobson header compression if VJ is configured and
     * this is an IP packet. 
     */
    if (protocol == PPP_IP && pc->vjEnabled) {
        switch (vj_compress_tcp(&pc->vjComp, pb)) {
        case TYPE_IP:
            /* No change...
            protocol = PPP_IP_PROTOCOL;
             */
            break;
        case TYPE_COMPRESSED_TCP:
            protocol = PPP_VJC_COMP;
            break;
        case TYPE_UNCOMPRESSED_TCP:
            protocol = PPP_VJC_UNCOMP;
            break;
        default:
            PPPDEBUG((LOG_WARNING, "pppifOutput[%d]: bad IP packet\n", pd));
#if LINK_STATS
                        lwip_stats.link.proterr++;
                        lwip_stats.link.drop++;
#endif
                pbuf_free(headMB);
            return ERR_VAL;
        }
    }
#endif
        
    tailMB = headMB;
        
    /* Build the PPP header. */
    if ((sys_jiffies() - pc->lastXMit) >= PPP_MAXIDLEFLAG)
        tailMB = pppAppend(PPP_FLAG, tailMB, NULL);
    pc->lastXMit = sys_jiffies();
    if (!pc->accomp) {
        fcsOut = PPP_FCS(fcsOut, PPP_ALLSTATIONS);
        tailMB = pppAppend(PPP_ALLSTATIONS, tailMB, &pc->outACCM);
        fcsOut = PPP_FCS(fcsOut, PPP_UI);
        tailMB = pppAppend(PPP_UI, tailMB, &pc->outACCM);
    }
    if (!pc->pcomp || protocol > 0xFF) {
        c = (protocol >> 8) & 0xFF;
        fcsOut = PPP_FCS(fcsOut, c);
        tailMB = pppAppend(c, tailMB, &pc->outACCM);
    }
    c = protocol & 0xFF;
    fcsOut = PPP_FCS(fcsOut, c);
    tailMB = pppAppend(c, tailMB, &pc->outACCM);
    
    /* Load packet. */
        for(p = pb; p; p = p->next) {
        int n;
        u_char *sPtr;

        sPtr = (u_char*)p->payload;
        n = p->len;
        while (n-- > 0) {
            c = *sPtr++;
            
            /* Update FCS before checking for special characters. */
            fcsOut = PPP_FCS(fcsOut, c);
            
            /* Copy to output buffer escaping special characters. */
            tailMB = pppAppend(c, tailMB, &pc->outACCM);
        }
    }

    /* Add FCS and trailing flag. */
    c = ~fcsOut & 0xFF;
    tailMB = pppAppend(c, tailMB, &pc->outACCM);
    c = (~fcsOut >> 8) & 0xFF;
    tailMB = pppAppend(c, tailMB, &pc->outACCM);
    tailMB = pppAppend(PPP_FLAG, tailMB, NULL);
        
    /* If we failed to complete the packet, throw it away. */
    if (!tailMB) {
        PPPDEBUG((LOG_WARNING,
                    "pppifOutput[%d]: Alloc err - dropping proto=%d\n", 
                    pd, protocol));
        pbuf_free(headMB);
#if LINK_STATS
                lwip_stats.link.memerr++;
                lwip_stats.link.drop++;
#endif
        return ERR_MEM;
    }

        /* Send it. */
    PPPDEBUG((LOG_INFO, "pppifOutput[%d]: proto=0x%04X\n", pd, protocol));

    nPut(pc, headMB);

    return ERR_OK;
}

/* Get and set parameters for the given connection.
 * Return 0 on success, an error code on failure. */
int  pppIOCtl(int pd, int cmd, void *arg)
{
    PPPControl *pc = &pppControl[pd];
    int st = 0;

    if (pd < 0 || pd >= NUM_PPP)
        st = PPPERR_PARAM;
    else {
        switch(cmd) {
        case PPPCTLG_UPSTATUS:      /* Get the PPP up status. */
            if (arg) 
                *(int *)arg = (int)(pc->if_up);
            else
                st = PPPERR_PARAM;
            break;
        case PPPCTLS_ERRCODE:       /* Set the PPP error code. */
            if (arg) 
                pc->errCode = *(int *)arg;
            else
                st = PPPERR_PARAM;
            break;
        case PPPCTLG_ERRCODE:       /* Get the PPP error code. */
            if (arg) 
                *(int *)arg = (int)(pc->errCode);
            else
                st = PPPERR_PARAM;
            break;
        case PPPCTLG_FD:
            if (arg) 
                *(sio_fd_t *)arg = pc->fd;
            else
                st = PPPERR_PARAM;
            break;
        default:
            st = PPPERR_PARAM;
            break;
        }
    }
    
    return st;
}

/*
 * Return the Maximum Transmission Unit for the given PPP connection.
 */
u_int pppMTU(int pd)
{
    PPPControl *pc = &pppControl[pd];
    u_int st;
    
    /* Validate parameters. */
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag)
        st = 0;
    else
        st = pc->mtu;
        
    return st;
}

/*
 * Write n characters to a ppp link.
 *  RETURN: >= 0 Number of characters written
 *           -1 Failed to write to device
 */
int pppWrite(int pd, const u_char *s, int n)
{
    PPPControl *pc = &pppControl[pd];
    u_char c;
    u_int fcsOut = PPP_INITFCS;
    struct pbuf *headMB = NULL, *tailMB;
        headMB = pbuf_alloc(PBUF_RAW, 0, PBUF_POOL);
    if (headMB == NULL) {
#if LINK_STATS
                lwip_stats.link.memerr++;
                lwip_stats.link.proterr++;
#endif /* LINK_STATS */
                return PPPERR_ALLOC;
    }

    tailMB = headMB;
        
    /* If the link has been idle, we'll send a fresh flag character to
     * flush any noise. */
    if ((sys_jiffies() - pc->lastXMit) >= PPP_MAXIDLEFLAG)
        tailMB = pppAppend(PPP_FLAG, tailMB, NULL);
    pc->lastXMit = sys_jiffies();
     
    /* Load output buffer. */
    while (n-- > 0) {
        c = *s++;
        
        /* Update FCS before checking for special characters. */
        fcsOut = PPP_FCS(fcsOut, c);
        
        /* Copy to output buffer escaping special characters. */
        tailMB = pppAppend(c, tailMB, &pc->outACCM);
    }
    
    /* Add FCS and trailing flag. */
    c = ~fcsOut & 0xFF;
    tailMB = pppAppend(c, tailMB, &pc->outACCM);
    c = (~fcsOut >> 8) & 0xFF;
    tailMB = pppAppend(c, tailMB, &pc->outACCM);
    tailMB = pppAppend(PPP_FLAG, tailMB, NULL);
        
    /* If we failed to complete the packet, throw it away.
     * Otherwise send it. */
    if (!tailMB) {
                PPPDEBUG((LOG_WARNING,
                "pppWrite[%d]: Alloc err - dropping pbuf len=%d\n", pd, headMB->len));
/*                "pppWrite[%d]: Alloc err - dropping %d:%.*H", pd, headMB->len, LWIP_MIN(headMB->len * 2, 40), headMB->payload)); */
                pbuf_free(headMB);
#if LINK_STATS
                lwip_stats.link.memerr++;
                lwip_stats.link.proterr++;
#endif /* LINK_STATS */
                return PPPERR_ALLOC;
        }

    PPPDEBUG((LOG_INFO, "pppWrite[%d]: len=%d\n", pd, headMB->len));
/*     "pppWrite[%d]: %d:%.*H", pd, headMB->len, LWIP_MIN(headMB->len * 2, 40), headMB->payload)); */
    nPut(pc, headMB);

    return PPPERR_NONE;
}

/*
 * ppp_send_config - configure the transmit characteristics of
 * the ppp interface.
 */
void ppp_send_config(
    int unit, 
    int mtu,
    u32_t asyncmap,
    int pcomp, 
    int accomp
)
{
    PPPControl *pc = &pppControl[unit];
    int i;
    
    pc->mtu = mtu;
    pc->pcomp = pcomp;
    pc->accomp = accomp;
    
    /* Load the ACCM bits for the 32 control codes. */
    for (i = 0; i < 32/8; i++)
        pc->outACCM[i] = (u_char)((asyncmap >> (8 * i)) & 0xFF);
    PPPDEBUG((LOG_INFO, "ppp_send_config[%d]: outACCM=%X %X %X %X\n",
                unit,
                pc->outACCM[0], pc->outACCM[1], pc->outACCM[2], pc->outACCM[3]));
}


/*
 * ppp_set_xaccm - set the extended transmit ACCM for the interface.
 */
void ppp_set_xaccm(int unit, ext_accm *accm)
{
    memcpy(pppControl[unit].outACCM, accm, sizeof(ext_accm));
    PPPDEBUG((LOG_INFO, "ppp_set_xaccm[%d]: outACCM=%X %X %X %X\n",
                unit,
                pppControl[unit].outACCM[0],
                pppControl[unit].outACCM[1],
                pppControl[unit].outACCM[2],
                pppControl[unit].outACCM[3]));
}


/*
 * ppp_recv_config - configure the receive-side characteristics of
 * the ppp interface.
 */
void ppp_recv_config(
    int unit, 
    int mru,
    u32_t asyncmap,
    int pcomp, 
    int accomp
)
{
    PPPControl *pc = &pppControl[unit];
    int i;
    
        (void)accomp;
        (void)pcomp;
        (void)mru;

    /* Load the ACCM bits for the 32 control codes. */
    for (i = 0; i < 32 / 8; i++)
        pc->inACCM[i] = (u_char)(asyncmap >> (i * 8));
    PPPDEBUG((LOG_INFO, "ppp_recv_config[%d]: inACCM=%X %X %X %X\n",
                unit,
                pc->inACCM[0], pc->inACCM[1], pc->inACCM[2], pc->inACCM[3]));
}

#if 0
/*
 * ccp_test - ask kernel whether a given compression method
 * is acceptable for use.  Returns 1 if the method and parameters
 * are OK, 0 if the method is known but the parameters are not OK
 * (e.g. code size should be reduced), or -1 if the method is unknown.
 */
int ccp_test(
    int unit, 
    int opt_len, 
    int for_transmit,
    u_char *opt_ptr
)
{
    return 0;   /* XXX Currently no compression. */
}

/*
 * ccp_flags_set - inform kernel about the current state of CCP.
 */
void ccp_flags_set(int unit, int isopen, int isup)
{
    /* XXX */
}

/*
 * ccp_fatal_error - returns 1 if decompression was disabled as a
 * result of an error detected after decompression of a packet,
 * 0 otherwise.  This is necessary because of patent nonsense.
 */
int ccp_fatal_error(int unit)
{
    /* XXX */
    return 0;
}
#endif

/*
 * get_idle_time - return how long the link has been idle.
 */
int get_idle_time(int u, struct ppp_idle *ip)
{   
    /* XXX */
        (void)u;
        (void)ip;

    return 0;
}


/*
 * Return user specified netmask, modified by any mask we might determine
 * for address `addr' (in network byte order).
 * Here we scan through the system's list of interfaces, looking for
 * any non-point-to-point interfaces which might appear to be on the same
 * network as `addr'.  If we find any, we OR in their netmask to the
 * user-specified netmask.
 */
u32_t GetMask(u32_t addr)
{
    u32_t mask, nmask;
    
    htonl(addr);
    if (IN_CLASSA(addr))    /* determine network mask for address class */
        nmask = IN_CLASSA_NET;
    else if (IN_CLASSB(addr))
        nmask = IN_CLASSB_NET;
    else
        nmask = IN_CLASSC_NET;
    /* class D nets are disallowed by bad_ip_adrs */
    mask = subnetMask | htonl(nmask);
    
    /* XXX
     * Scan through the system's network interfaces.
     * Get each netmask and OR them into our mask.
     */
    
    return mask;
}

/*
 * sifvjcomp - config tcp header compression
 */
int sifvjcomp(
    int pd, 
    int vjcomp, 
    int cidcomp, 
    int maxcid
)
{
#if VJ_SUPPORT > 0
    PPPControl *pc = &pppControl[pd];
    
    pc->vjEnabled = vjcomp;
    pc->vjComp.compressSlot = cidcomp;
    pc->vjComp.maxSlotIndex = maxcid;
    PPPDEBUG((LOG_INFO, "sifvjcomp: VJ compress enable=%d slot=%d max slot=%d\n",
                vjcomp, cidcomp, maxcid));
#endif

    return 0;
}

/*
 * pppifNetifInit - netif init callback
 */
static err_t pppifNetifInit(struct netif *netif)
{
        netif->name[0] = 'p';
        netif->name[1] = 'p';
        netif->output = pppifOutput;
        netif->mtu = pppMTU((int)netif->state);
        return ERR_OK;
}


/*
 * sifup - Config the interface up and enable IP packets to pass.
 */
int sifup(int pd)
{
    PPPControl *pc = &pppControl[pd];
    int st = 1;
    
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag) {
        st = 0;
        PPPDEBUG((LOG_WARNING, "sifup[%d]: bad parms\n", pd));
    } else {
                netif_remove(&pc->netif);
                if (netif_add(&pc->netif, &pc->addrs.our_ipaddr, &pc->addrs.netmask, &pc->addrs.his_ipaddr, (void *)pd, pppifNetifInit, ip_input)) {
                
                netif_set_up(&pc->netif);
                pc->if_up = 1;
                pc->errCode = PPPERR_NONE;

                        PPPDEBUG((LOG_DEBUG, "sifup: unit %d: linkStatusCB=%lx errCode=%d\n", pd, pc->linkStatusCB, pc->errCode));
                        if(pc->linkStatusCB)
                                pc->linkStatusCB(pc->linkStatusCtx, pc->errCode, &pc->addrs);
                } else {
                st = 0;
                PPPDEBUG((LOG_ERR, "sifup[%d]: netif_add failed\n", pd));
                }
    }

    return st;
}

/*
 * sifnpmode - Set the mode for handling packets for a given NP.
 */
int sifnpmode(int u, int proto, enum NPmode mode)
{
        (void)u;
        (void)proto;
        (void)mode;
    return 0;
}

/*
 * sifdown - Config the interface down and disable IP.
 */
int sifdown(int pd)
{
    PPPControl *pc = &pppControl[pd];
    int st = 1;
    
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag) {
        st = 0;
        PPPDEBUG((LOG_WARNING, "sifdown[%d]: bad parms\n", pd));
    } else {
        pc->if_up = 0;
        netif_remove(&pc->netif);
        PPPDEBUG((LOG_DEBUG, "sifdown: unit %d: linkStatusCB=%lx errCode=%d\n", pd, pc->linkStatusCB, pc->errCode));
        if(pc->linkStatusCB)
                pc->linkStatusCB(pc->linkStatusCtx, PPPERR_CONNECT, NULL);
        }
    return st;
}

/*
 * sifaddr - Config the interface IP addresses and netmask.
 */
int sifaddr(
    int pd,             /* Interface unit ??? */
    u32_t o,        /* Our IP address ??? */
    u32_t h,        /* His IP address ??? */
    u32_t m,        /* IP subnet mask ??? */
    u32_t ns1,      /* Primary DNS */
    u32_t ns2       /* Secondary DNS */
)
{
    PPPControl *pc = &pppControl[pd];
    int st = 1;
    
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag) {
        st = 0;
        PPPDEBUG((LOG_WARNING, "sifup[%d]: bad parms\n", pd));
    } else {
                memcpy(&pc->addrs.our_ipaddr, &o, sizeof(o));
                memcpy(&pc->addrs.his_ipaddr, &h, sizeof(h));
                memcpy(&pc->addrs.netmask, &m, sizeof(m));
                memcpy(&pc->addrs.dns1, &ns1, sizeof(ns1));
                memcpy(&pc->addrs.dns2, &ns2, sizeof(ns2));
    }
    return st;
}

/*
 * cifaddr - Clear the interface IP addresses, and delete routes
 * through the interface if possible.
 */
int cifaddr(
    int pd,         /* Interface unit ??? */
    u32_t o,    /* Our IP address ??? */
    u32_t h     /* IP broadcast address ??? */
)
{
    PPPControl *pc = &pppControl[pd];
    int st = 1;
    
        (void)o;
        (void)h;
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag) {
        st = 0;
        PPPDEBUG((LOG_WARNING, "sifup[%d]: bad parms\n", pd));
    } else {
                IP4_ADDR(&pc->addrs.our_ipaddr, 0,0,0,0);
                IP4_ADDR(&pc->addrs.his_ipaddr, 0,0,0,0);
                IP4_ADDR(&pc->addrs.netmask, 255,255,255,0);
                IP4_ADDR(&pc->addrs.dns1, 0,0,0,0);
                IP4_ADDR(&pc->addrs.dns2, 0,0,0,0);
    }
    return st;
}

/*
 * sifdefaultroute - assign a default route through the address given.
 */
int sifdefaultroute(int pd, u32_t l, u32_t g)
{
    PPPControl *pc = &pppControl[pd];
    int st = 1;
    
        (void)l;
        (void)g;
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag) {
        st = 0;
        PPPDEBUG((LOG_WARNING, "sifup[%d]: bad parms\n", pd));
    } else {
                netif_set_default(&pc->netif);
    }

    /* TODO: check how PPP handled the netMask, previously not set by ipSetDefault */

    return st;
}

/*
 * cifdefaultroute - delete a default route through the address given.
 */
int cifdefaultroute(int pd, u32_t l, u32_t g)
{
    PPPControl *pc = &pppControl[pd];
    int st = 1;
    
        (void)l;
        (void)g;
    if (pd < 0 || pd >= NUM_PPP || !pc->openFlag) {
        st = 0;
        PPPDEBUG((LOG_WARNING, "sifup[%d]: bad parms\n", pd));
    } else {
                netif_set_default(NULL);
    }

    return st;
}

void
pppMainWakeup(int pd)
{
        PPPDEBUG((LOG_DEBUG, "pppMainWakeup: unit %d\n", pd));
        sio_read_abort(pppControl[pd].fd);
}

/* these callbacks are necessary because lcp_* functions
   must be called in the same context as pppInput(),
   namely the tcpip_thread(), essentially because
   they manipulate timeouts which are thread-private
*/

static void
pppStartCB(void *arg)
{
    int pd = (int)arg;

        PPPDEBUG((LOG_DEBUG, "pppStartCB: unit %d\n", pd));
    lcp_lowerup(pd);
    lcp_open(pd);      /* Start protocol */
}

static void
pppStopCB(void *arg)
{
    int pd = (int)arg;

        PPPDEBUG((LOG_DEBUG, "pppStopCB: unit %d\n", pd));
    lcp_close(pd, "User request");
}

static void
pppHupCB(void *arg)
{
    int pd = (int)arg;

        PPPDEBUG((LOG_DEBUG, "pppHupCB: unit %d\n", pd));
    lcp_lowerdown(pd);
    link_terminated(pd);
}
/**********************************/
/*** LOCAL FUNCTION DEFINITIONS ***/
/**********************************/
/* The main PPP process function.  This implements the state machine according
 * to section 4 of RFC 1661: The Point-To-Point Protocol. */
static void pppMain(void *arg)
{
    int pd = (int)arg;
    struct pbuf *p;
    PPPControl* pc;

    pc = &pppControl[pd];

    p = pbuf_alloc(PBUF_RAW, PPP_MRU+PPP_HDRLEN, PBUF_RAM);
    if(!p) {
                LWIP_ASSERT("p != NULL", p);
                pc->errCode = PPPERR_ALLOC;
                goto out;
    }

    /*
     * Start the connection and handle incoming events (packet or timeout).
     */
        PPPDEBUG((LOG_INFO, "pppMain: unit %d: Connecting\n", pd));
    tcpip_callback(pppStartCB, arg);
    while (lcp_phase[pd] != PHASE_DEAD) {
        if (pc->kill_link) {
                PPPDEBUG((LOG_DEBUG, "pppMainWakeup: unit %d kill_link -> pppStopCB\n", pd));
                pc->errCode = PPPERR_USER;
                /* This will leave us at PHASE_DEAD. */
                tcpip_callback(pppStopCB, arg);
                pc->kill_link = 0;
        }
        else if (pc->sig_hup) {
                PPPDEBUG((LOG_DEBUG, "pppMainWakeup: unit %d sig_hup -> pppHupCB\n", pd));
                pc->sig_hup = 0;
                tcpip_callback(pppHupCB, arg);
        } else {
                int c = sio_read(pc->fd, p->payload, p->len);
                if(c > 0) {
                        pppInProc(pd, p->payload, c);
                } else {
                    PPPDEBUG((LOG_DEBUG, "pppMainWakeup: unit %d sio_read len=%d returned %d\n", pd, p->len, c));
                    sys_msleep(1); /* give other tasks a chance to run */
                }
        }
    }
        PPPDEBUG((LOG_INFO, "pppMain: unit %d: PHASE_DEAD\n", pd));
    pbuf_free(p);

out:
        PPPDEBUG((LOG_DEBUG, "pppMain: unit %d: linkStatusCB=%lx errCode=%d\n", pd, pc->linkStatusCB, pc->errCode));
    if(pc->linkStatusCB)
            pc->linkStatusCB(pc->linkStatusCtx, pc->errCode ? pc->errCode : PPPERR_PROTOCOL, NULL);

    pc->openFlag = 0;
}

static struct pbuf *pppSingleBuf(struct pbuf *p)
{
        struct pbuf *q, *b;
        u_char *pl;

        if(p->tot_len == p->len)
                return p;

        q = pbuf_alloc(PBUF_RAW, p->tot_len, PBUF_RAM);
        if(!q) {
                PPPDEBUG((LOG_ERR,
                        "pppSingleBuf: unable to alloc new buf (%d)\n", p->tot_len));
                return p; /* live dangerously */
        }

        for(b = p, pl = q->payload; b != NULL; b = b->next) {
                memcpy(pl, b->payload, b->len);
                pl += b->len;
        }

        pbuf_free(p);

        return q;
}

struct pppInputHeader {
        int unit;
        u16_t proto;
};

/*
 * Pass the processed input packet to the appropriate handler.
 * This function and all handlers run in the context of the tcpip_thread
 */
static void pppInput(void *arg)
{
        struct pbuf *nb = (struct pbuf *)arg;
    u16_t protocol;
    int pd;

        pd = ((struct pppInputHeader *)nb->payload)->unit;
        protocol = ((struct pppInputHeader *)nb->payload)->proto;

    pbuf_header(nb, -(int)sizeof(struct pppInputHeader));

#if LINK_STATS
    lwip_stats.link.recv++;
#endif /* LINK_STATS */

    /*
     * Toss all non-LCP packets unless LCP is OPEN.
     * Until we get past the authentication phase, toss all packets
     * except LCP, LQR and authentication packets.
     */
    if((lcp_phase[pd] <= PHASE_AUTHENTICATE) && (protocol != PPP_LCP)) {
            if(!((protocol == PPP_LQR) || (protocol == PPP_PAP) || (protocol == PPP_CHAP)) ||
                        (lcp_phase[pd] != PHASE_AUTHENTICATE)) {
                PPPDEBUG((LOG_INFO, "pppInput: discarding proto 0x%04X in phase %d\n", protocol, lcp_phase[pd]));
                goto drop;
            }
    }

    switch(protocol) {
    case PPP_VJC_COMP:      /* VJ compressed TCP */
#if VJ_SUPPORT > 0
        PPPDEBUG((LOG_INFO, "pppInput[%d]: vj_comp in pbuf len=%d\n", pd, nb->len));
        /*
         * Clip off the VJ header and prepend the rebuilt TCP/IP header and
         * pass the result to IP.
         */
        if (vj_uncompress_tcp(&nb, &pppControl[pd].vjComp) >= 0) {
            if (pppControl[pd].netif.input != NULL) {
              pppControl[pd].netif.input(nb, &pppControl[pd].netif);
            }
                        return;
        }
        /* Something's wrong so drop it. */
        PPPDEBUG((LOG_WARNING, "pppInput[%d]: Dropping VJ compressed\n", pd));
#else
        /* No handler for this protocol so drop the packet. */
        PPPDEBUG((LOG_INFO, "pppInput[%d]: drop VJ Comp in %d:%s\n", pd, nb->len, nb->payload));
#endif /* VJ_SUPPORT > 0 */
        break;
    case PPP_VJC_UNCOMP:    /* VJ uncompressed TCP */
#if VJ_SUPPORT > 0
        PPPDEBUG((LOG_INFO, "pppInput[%d]: vj_un in pbuf len=%d\n", pd, nb->len));
        /*
         * Process the TCP/IP header for VJ header compression and then pass
         * the packet to IP.
         */
        if (vj_uncompress_uncomp(nb, &pppControl[pd].vjComp) >= 0) {
            if (pppControl[pd].netif.input != NULL) {
              pppControl[pd].netif.input(nb, &pppControl[pd].netif);
            }
                        return;
        }
        /* Something's wrong so drop it. */
        PPPDEBUG((LOG_WARNING, "pppInput[%d]: Dropping VJ uncompressed\n", pd));
#else
        /* No handler for this protocol so drop the packet. */
        PPPDEBUG((LOG_INFO,
                    "pppInput[%d]: drop VJ UnComp in %d:.*H\n", 
                    pd, nb->len, LWIP_MIN(nb->len * 2, 40), nb->payload));
#endif /* VJ_SUPPORT > 0 */
        break;
    case PPP_IP:            /* Internet Protocol */
        PPPDEBUG((LOG_INFO, "pppInput[%d]: ip in pbuf len=%d\n", pd, nb->len));
        if (pppControl[pd].netif.input != NULL) {
          pppControl[pd].netif.input(nb, &pppControl[pd].netif);
        }
                return;
    default:
        {
                struct protent *protp;
                int i;

                /*
                 * Upcall the proper protocol input routine.
                 */
                for (i = 0; (protp = ppp_protocols[i]) != NULL; ++i) {
                        if (protp->protocol == protocol && protp->enabled_flag) {
                                PPPDEBUG((LOG_INFO, "pppInput[%d]: %s len=%d\n", pd, protp->name, nb->len));
                                nb = pppSingleBuf(nb);
                                (*protp->input)(pd, nb->payload, nb->len);
                                goto out;
                        }
                }

                /* No handler for this protocol so reject the packet. */
                PPPDEBUG((LOG_INFO, "pppInput[%d]: rejecting unsupported proto 0x%04X len=%d\n", pd, protocol, nb->len));
                pbuf_header(nb, sizeof(protocol));
#if BYTE_ORDER == LITTLE_ENDIAN
                protocol = htons(protocol);
                memcpy(nb->payload, &protocol, sizeof(protocol));
#endif
                lcp_sprotrej(pd, nb->payload, nb->len);
        }
        break;
    }

drop:
#if LINK_STATS
    lwip_stats.link.drop++;
#endif

out:
    pbuf_free(nb);
    return;
}


/*
 * Drop the input packet.
 */
static void pppDrop(PPPControl *pc)
{
    if (pc->inHead != NULL) {
#if 0       
        PPPDEBUG((LOG_INFO, "pppDrop: %d:%.*H\n", pc->inHead->len, min(60, pc->inHead->len * 2), pc->inHead->payload));
#endif  
        PPPDEBUG((LOG_INFO, "pppDrop: pbuf len=%d\n", pc->inHead->len));
        if (pc->inTail && (pc->inTail != pc->inHead))
            pbuf_free(pc->inTail);
        pbuf_free(pc->inHead);
        pc->inHead = NULL;
        pc->inTail = NULL;
    }
#if VJ_SUPPORT > 0
    vj_uncompress_err(&pc->vjComp);
#endif

#if LINK_STATS
    lwip_stats.link.drop++;
#endif /* LINK_STATS */
}


/*
 * Process a received octet string.
 */
static void pppInProc(int pd, u_char *s, int l)
{
    PPPControl *pc = &pppControl[pd];
    struct pbuf *nextNBuf;
    u_char curChar;

    PPPDEBUG((LOG_DEBUG, "pppInProc[%d]: got %d bytes\n", pd, l));
    while (l-- > 0) {
        curChar = *s++;
        
        /* Handle special characters. */
        if (ESCAPE_P(pc->inACCM, curChar)) {
            /* Check for escape sequences. */
            /* XXX Note that this does not handle an escaped 0x5d character which
             * would appear as an escape character.  Since this is an ASCII ']'
             * and there is no reason that I know of to escape it, I won't complicate
             * the code to handle this case. GLL */
            if (curChar == PPP_ESCAPE)
                pc->inEscaped = 1;
            /* Check for the flag character. */
            else if (curChar == PPP_FLAG) {
                /* If this is just an extra flag character, ignore it. */
                if (pc->inState <= PDADDRESS)
                    ;
                /* If we haven't received the packet header, drop what has come in. */
                else if (pc->inState < PDDATA) {
                    PPPDEBUG((LOG_WARNING,
                                "pppInProc[%d]: Dropping incomplete packet %d\n", 
                                pd, pc->inState));
#if LINK_STATS
                                        lwip_stats.link.lenerr++;
#endif
                    pppDrop(pc);
                }
                /* If the fcs is invalid, drop the packet. */
                else if (pc->inFCS != PPP_GOODFCS) {
                    PPPDEBUG((LOG_INFO,
                                "pppInProc[%d]: Dropping bad fcs 0x%04X proto=0x%04X\n", 
                                pd, pc->inFCS, pc->inProtocol));
#if LINK_STATS
                                        lwip_stats.link.chkerr++;
#endif
                    pppDrop(pc);
                }
                /* Otherwise it's a good packet so pass it on. */
                else {
                    
                    /* Trim off the checksum. */
                    if(pc->inTail->len >= 2) {
                        pc->inTail->len -= 2;

                        pc->inTail->tot_len = pc->inTail->len;
                        if (pc->inTail != pc->inHead) {
                            pbuf_cat(pc->inHead, pc->inTail);
                        }
                    } else {
                        pc->inTail->tot_len = pc->inTail->len;
                        if (pc->inTail != pc->inHead) {
                            pbuf_cat(pc->inHead, pc->inTail);
                        }

                        pbuf_realloc(pc->inHead, pc->inHead->tot_len - 2);
                    }

                    /* Dispatch the packet thereby consuming it. */
                    if(tcpip_callback(pppInput, pc->inHead) != ERR_OK) {
                        PPPDEBUG((LOG_ERR,
                                    "pppInProc[%d]: tcpip_callback() failed, dropping packet\n", pd));
                        pbuf_free(pc->inHead);
#if LINK_STATS
                        lwip_stats.link.drop++;
#endif
                    }
                    pc->inHead = NULL;
                    pc->inTail = NULL;
                }
                    
                /* Prepare for a new packet. */
                pc->inFCS = PPP_INITFCS;
                pc->inState = PDADDRESS;
                pc->inEscaped = 0;
            }
            /* Other characters are usually control characters that may have
             * been inserted by the physical layer so here we just drop them. */
            else {
                PPPDEBUG((LOG_WARNING,
                            "pppInProc[%d]: Dropping ACCM char <%d>\n", pd, curChar));
            }
        }
        /* Process other characters. */
        else {
            /* Unencode escaped characters. */
            if (pc->inEscaped) {
                pc->inEscaped = 0;
                curChar ^= PPP_TRANS;
            }
            
            /* Process character relative to current state. */
            switch(pc->inState) {
            case PDIDLE:                    /* Idle state - waiting. */
                /* Drop the character if it's not 0xff
                 * we would have processed a flag character above. */
                if (curChar != PPP_ALLSTATIONS) {
                        break;
                                }

                                /* Fall through */
            case PDSTART:                   /* Process start flag. */
                /* Prepare for a new packet. */
                pc->inFCS = PPP_INITFCS;

                                /* Fall through */
            case PDADDRESS:                 /* Process address field. */
                if (curChar == PPP_ALLSTATIONS) {
                    pc->inState = PDCONTROL;
                    break;
                }
                /* Else assume compressed address and control fields so
                 * fall through to get the protocol... */
            case PDCONTROL:                 /* Process control field. */
                /* If we don't get a valid control code, restart. */
                if (curChar == PPP_UI) {
                    pc->inState = PDPROTOCOL1;
                        break;
                }
#if 0
                else {
                    PPPDEBUG((LOG_WARNING,
                                "pppInProc[%d]: Invalid control <%d>\n", pd, curChar));
                    pc->inState = PDSTART;
                }
#endif
            case PDPROTOCOL1:               /* Process protocol field 1. */
                /* If the lower bit is set, this is the end of the protocol
                 * field. */
                if (curChar & 1) {
                    pc->inProtocol = curChar;
                    pc->inState = PDDATA;
                }
                else {
                    pc->inProtocol = (u_int)curChar << 8;
                    pc->inState = PDPROTOCOL2;
                }
                break;
            case PDPROTOCOL2:               /* Process protocol field 2. */
                pc->inProtocol |= curChar;
                pc->inState = PDDATA;
                break;
            case PDDATA:                    /* Process data byte. */
                /* Make space to receive processed data. */
                if (pc->inTail == NULL || pc->inTail->len == PBUF_POOL_BUFSIZE) {
                    if(pc->inTail) {
                        pc->inTail->tot_len = pc->inTail->len;
                        if (pc->inTail != pc->inHead) {
                            pbuf_cat(pc->inHead, pc->inTail);
                        }
                    }
                    /* If we haven't started a packet, we need a packet header. */
                    nextNBuf = pbuf_alloc(PBUF_RAW, 0, PBUF_POOL);
                    if (nextNBuf == NULL) {
                        /* No free buffers.  Drop the input packet and let the
                         * higher layers deal with it.  Continue processing
                         * the received pbuf chain in case a new packet starts. */
                        PPPDEBUG((LOG_ERR, "pppInProc[%d]: NO FREE MBUFS!\n", pd));
#if LINK_STATS
                                                lwip_stats.link.memerr++;
#endif /* LINK_STATS */
                        pppDrop(pc);
                        pc->inState = PDSTART;  /* Wait for flag sequence. */
                        break;
                    }
                    if (pc->inHead == NULL) {
                        struct pppInputHeader *pih = nextNBuf->payload;

                        pih->unit = pd;
                        pih->proto = pc->inProtocol;

                        nextNBuf->len += sizeof(*pih);

                        pc->inHead = nextNBuf;
                    }
                    pc->inTail = nextNBuf;
                }
                /* Load character into buffer. */
                ((u_char*)pc->inTail->payload)[pc->inTail->len++] = curChar;
                break;
            }

            /* update the frame check sequence number. */
            pc->inFCS = PPP_FCS(pc->inFCS, curChar);
        }
    }
        avRandomize();
}

#endif /* PPP_SUPPORT */