avoid compiler warning

[ppp.git] / linux / ppp.c

/*  PPP for Linux
 *
 *  Michael Callahan <callahan@maths.ox.ac.uk>
 *  Al Longyear <longyear@netcom.com>
 *
 *  Dynamic PPP devices by Jim Freeman <jfree@caldera.com>.
 *  ppp_tty_receive ``noisy-raise-bug'' fixed by Ove Ewerlid <ewerlid@syscon.uu.se>
 *
 *  ==FILEVERSION 960528==
 *
 *  NOTE TO MAINTAINERS:
 *     If you modify this file at all, please set the number above to the
 *     date of the modification as YYMMDD (year month day).
 *     ppp.c is shipped with a PPP distribution as well as with the kernel;
 *     if everyone increases the FILEVERSION number above, then scripts
 *     can do the right thing when deciding whether to install a new ppp.c
 *     file.  Don't change the format of that line otherwise, so the
 *     installation script can recognize it.
 */

/*
   Sources:

   slip.c

   RFC1331: The Point-to-Point Protocol (PPP) for the Transmission of
   Multi-protocol Datagrams over Point-to-Point Links

   RFC1332: IPCP

   ppp-2.0

   Flags for this module (any combination is acceptable for testing.):

   OPTIMIZE_FLAG_TIME - Number of jiffies to force sending of leading flag
                        character. This is normally set to ((HZ * 3) / 2).
                        This is 1.5 seconds. If zero then the leading
                        flag is always sent.

   CHECK_CHARACTERS   - Enable the checking on all received characters for
                        8 data bits, no parity. This adds a small amount of
                        processing for each received character.
*/

#define OPTIMIZE_FLAG_TIME      ((HZ * 3)/2)

#define CHECK_CHARACTERS        1
#define PPP_COMPRESS            1

#ifndef PPP_MAX_DEV
#define PPP_MAX_DEV     256
#endif

/* $Id: ppp.c,v 1.8 1996/09/14 05:37:07 paulus Exp $
 * Added dynamic allocation of channels to eliminate
 *   compiled-in limits on the number of channels.
 *
 * Dynamic channel allocation code Copyright 1995 Caldera, Inc.,
 *   released under the GNU General Public License Version 2.
 */

#include <linux/module.h>
#include <endian.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/interrupt.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/in.h>
#include <linux/malloc.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/sched.h>        /* to get the struct task_struct */
#include <linux/string.h>       /* used in new tty drivers */
#include <linux/signal.h>       /* used in new tty drivers */
#include <asm/system.h>
#include <asm/bitops.h>
#include <asm/segment.h>
#include <linux/if.h>
#include <linux/if_ether.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/inet.h>
#include <linux/ioctl.h>

typedef struct sk_buff       sk_buff;
#define skb_data(skb)        ((__u8 *) (skb)->data)

#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/if_arp.h>
#include <net/slhc_vj.h>

#define fcstab  ppp_crc16_table         /* Name of the table in the kernel */
#include <linux/ppp_defs.h>

#include <linux/socket.h>
#include <linux/if_ppp.h>
#include <linux/if_pppvar.h>

#undef   PACKETPTR
#define  PACKETPTR 1
#include <linux/ppp-comp.h>
#undef   PACKETPTR

#define bsd_decompress  (*ppp->sc_rcomp->decompress)
#define bsd_compress    (*ppp->sc_xcomp->compress)

#ifndef PPP_IPX
#define PPP_IPX 0x2b  /* IPX protocol over PPP */
#endif

#ifndef PPP_LQR
#define PPP_LQR 0xc025  /* Link Quality Reporting Protocol */
#endif

static int ppp_register_compressor (struct compressor *cp);
static void ppp_unregister_compressor (struct compressor *cp);

/*
 * Local functions
 */

static struct compressor *find_compressor (int type);
static void ppp_init_ctrl_blk (register struct ppp *);
static void ppp_kick_tty (struct ppp *, struct ppp_buffer *bfr);
static int ppp_doframe (struct ppp *);
static struct ppp *ppp_alloc (void);
static struct ppp *ppp_find (int pid_value);
static void ppp_print_buffer (const __u8 *, const __u8 *, int);
extern inline void ppp_stuff_char (struct ppp *ppp,
                                   register struct ppp_buffer *buf,
                                   register __u8 chr);
extern inline int lock_buffer (register struct ppp_buffer *buf);

static int rcv_proto_ip         (struct ppp *, __u16, __u8 *, int);
static int rcv_proto_ipx        (struct ppp *, __u16, __u8 *, int);
static int rcv_proto_vjc_comp   (struct ppp *, __u16, __u8 *, int);
static int rcv_proto_vjc_uncomp (struct ppp *, __u16, __u8 *, int);
static int rcv_proto_unknown    (struct ppp *, __u16, __u8 *, int);
static int rcv_proto_lqr        (struct ppp *, __u16, __u8 *, int);
static void ppp_doframe_lower   (struct ppp *, __u8 *, int);
static int ppp_doframe          (struct ppp *);

extern int  ppp_bsd_compressor_init(void);
static void ppp_proto_ccp (struct ppp *ppp, __u8 *dp, int len, int rcvd);
static int  rcv_proto_ccp (struct ppp *, __u16, __u8 *, int);

#define ins_char(pbuf,c) (buf_base(pbuf) [(pbuf)->count++] = (__u8)(c))

#ifndef OPTIMIZE_FLAG_TIME
#define OPTIMIZE_FLAG_TIME      0
#endif

#ifndef PPP_MAX_DEV
#define PPP_MAX_DEV 256
#endif

/*
 * Parameters which may be changed via insmod.
 */

static int  flag_time = OPTIMIZE_FLAG_TIME;
static int  max_dev   = PPP_MAX_DEV;

/*
 * The "main" procedure to the ppp device
 */

int ppp_init (struct device *);

/*
 * Network device driver callback routines
 */

static int ppp_dev_open (struct device *);
static int ppp_dev_ioctl (struct device *dev, struct ifreq *ifr, int cmd);
static int ppp_dev_close (struct device *);
static int ppp_dev_xmit (sk_buff *, struct device *);
static struct enet_statistics *ppp_dev_stats (struct device *);
static int ppp_dev_header (sk_buff *, struct device *, __u16,
                           void *, void *, unsigned int);
static int ppp_dev_rebuild (void *eth, struct device *dev,
                            unsigned long raddr, struct sk_buff *skb);
/*
 * TTY callbacks
 */

static int ppp_tty_read (struct tty_struct *, struct file *, __u8 *,
                         unsigned int);
static int ppp_tty_write (struct tty_struct *, struct file *, const __u8 *,
                          unsigned int);
static int ppp_tty_ioctl (struct tty_struct *, struct file *, unsigned int,
                          unsigned long);
static int ppp_tty_select (struct tty_struct *tty, struct inode *inode,
                      struct file *filp, int sel_type, select_table * wait);
static int ppp_tty_open (struct tty_struct *);
static void ppp_tty_close (struct tty_struct *);
static int ppp_tty_room (struct tty_struct *tty);
static void ppp_tty_receive (struct tty_struct *tty, const __u8 * cp,
                             char *fp, int count);
static void ppp_tty_wakeup (struct tty_struct *tty);

#define CHECK_PPP(a)  if (!ppp->inuse) { printk (ppp_warning, __LINE__); return a;}
#define CHECK_PPP_VOID()  if (!ppp->inuse) { printk (ppp_warning, __LINE__); return;}

#define in_xmap(ppp,c)  (ppp->xmit_async_map[(c) >> 5] & (1 << ((c) & 0x1f)))
#define in_rmap(ppp,c)  ((((unsigned int) (__u8) (c)) < 0x20) && \
                        ppp->recv_async_map & (1 << (c)))

#define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))

#define tty2ppp(tty)    ((struct ppp *) (tty->disc_data))
#define dev2ppp(dev)    ((struct ppp *) (dev->priv))
#define ppp2tty(ppp)    ((struct tty_struct *) ppp->tty)
#define ppp2dev(ppp)    ((struct device *) ppp->dev)

struct ppp_hdr {
        __u8 address;
        __u8 control;
        __u8 protocol[2];
};

#define PPP_HARD_HDR_LEN        (sizeof (struct ppp_hdr))

typedef struct  ppp_ctrl {
        struct ppp_ctrl *next;          /* Next structure in the list   */
        char            name [8];       /* Name of the device           */
        struct ppp      ppp;            /* PPP control table            */
        struct device   dev;            /* Device information table     */
} ppp_ctrl_t;

static ppp_ctrl_t *ppp_list = NULL;

#define ctl2ppp(ctl) (struct ppp *)    &ctl->ppp
#define ctl2dev(ctl) (struct device *) &ctl->dev
#undef  PPP_NRUNIT

/* Buffer types */
#define BUFFER_TYPE_DEV_RD      0  /* ppp read buffer       */
#define BUFFER_TYPE_TTY_WR      1  /* tty write buffer      */
#define BUFFER_TYPE_DEV_WR      2  /* ppp write buffer      */
#define BUFFER_TYPE_TTY_RD      3  /* tty read buffer       */
#define BUFFER_TYPE_VJ          4  /* vj compression buffer */

/* Define this string only once for all macro invocations */
static char ppp_warning[] = KERN_WARNING "PPP: ALERT! not INUSE! %d\n";

static char szVersion[]         = PPP_VERSION;
 
/*
 * Information for the protocol decoder
 */

typedef int (*pfn_proto)  (struct ppp *, __u16, __u8 *, int);

typedef struct ppp_proto_struct {
        int             proto;
        pfn_proto       func;
} ppp_proto_type;

static
ppp_proto_type proto_list[] = {
        { PPP_IP,         rcv_proto_ip         },
        { PPP_IPX,        rcv_proto_ipx        },
        { PPP_VJC_COMP,   rcv_proto_vjc_comp   },
        { PPP_VJC_UNCOMP, rcv_proto_vjc_uncomp },
        { PPP_LQR,        rcv_proto_lqr        },
        { PPP_CCP,        rcv_proto_ccp        },
        { 0,              rcv_proto_unknown    }  /* !!! MUST BE LAST !!! */
};

__u16 ppp_crc16_table[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
};

#ifdef CHECK_CHARACTERS
static __u32 paritytab[8] =
{
        0x96696996, 0x69969669, 0x69969669, 0x96696996,
        0x69969669, 0x96696996, 0x96696996, 0x69969669
};
#endif

/* local function to store a value into the LQR frame */
extern inline __u8 * store_long (register __u8 *p, register int value) {
        *p++ = (__u8) (value >> 24);
        *p++ = (__u8) (value >> 16);
        *p++ = (__u8) (value >>  8);
        *p++ = (__u8) value;
        return p;
}

/*************************************************************
 * INITIALIZATION
 *************************************************************/

/* This procedure is called once and once only to define who we are to
 * the operating system and the various procedures that it may use in
 * accessing the ppp protocol.
 */

static int
ppp_first_time (void)
{
        static struct tty_ldisc ppp_ldisc;
        int    status;

        printk (KERN_INFO
                "PPP: version %s (dynamic channel allocation)"
                "\n", szVersion);

#ifndef MODULE /* slhc module logic has its own copyright announcement */
        printk (KERN_INFO
                "TCP compression code copyright 1989 Regents of the "
                "University of California\n");
#endif
        
        printk (KERN_INFO
                "PPP Dynamic channel allocation code copyright 1995 "
                "Caldera, Inc.\n");
/*
 * Register the tty discipline
 */     
        (void) memset (&ppp_ldisc, 0, sizeof (ppp_ldisc));
        ppp_ldisc.magic         = TTY_LDISC_MAGIC;
        ppp_ldisc.open          = ppp_tty_open;
        ppp_ldisc.close         = ppp_tty_close;
        ppp_ldisc.read          = ppp_tty_read;
        ppp_ldisc.write         = ppp_tty_write;
        ppp_ldisc.ioctl         = ppp_tty_ioctl;
        ppp_ldisc.select        = ppp_tty_select;
        ppp_ldisc.receive_room  = ppp_tty_room;
        ppp_ldisc.receive_buf   = ppp_tty_receive;
        ppp_ldisc.write_wakeup  = ppp_tty_wakeup;
        
        status = tty_register_ldisc (N_PPP, &ppp_ldisc);
        if (status == 0)
                printk (KERN_INFO "PPP line discipline registered.\n");
        else
                printk (KERN_ERR "error registering line discipline: %d\n",
                        status);
        return status;
}

/*************************************************************
 * INITIALIZATION
 *************************************************************/

/* called when the device is actually created */

static int
ppp_init_dev (struct device *dev)
{
        int    indx;

        dev->hard_header      = ppp_dev_header;
        dev->rebuild_header   = ppp_dev_rebuild;
        dev->hard_header_len  = PPP_HARD_HDR_LEN;

        /* device INFO */
        dev->mtu              = PPP_MTU;
        dev->hard_start_xmit  = ppp_dev_xmit;
        dev->open             = ppp_dev_open;
        dev->stop             = ppp_dev_close;
        dev->get_stats        = ppp_dev_stats;
        dev->do_ioctl         = ppp_dev_ioctl;
        dev->addr_len         = 0;
        dev->tx_queue_len     = 10;
        dev->type             = ARPHRD_PPP;

        for (indx = 0; indx < DEV_NUMBUFFS; indx++)
                skb_queue_head_init (&dev->buffs[indx]);

        /* New-style flags */
        dev->flags      = IFF_POINTOPOINT;
        dev->family     = AF_INET;
        dev->pa_addr    = 0;
        dev->pa_brdaddr = 0;
        dev->pa_mask    = 0;
        dev->pa_alen    = 4; /* sizeof (__u32) */

        return 0;
}

/*
 * Local procedure to initialize the ppp structure
 */

static void
ppp_init_ctrl_blk (register struct ppp *ppp)
{
        ppp->magic  = PPP_MAGIC;
        ppp->toss   = 0xE0;
        ppp->escape = 0;

        ppp->flags  = 0;
        ppp->mtu    = PPP_MTU;
        ppp->mru    = PPP_MRU;

        memset (ppp->xmit_async_map, 0, sizeof (ppp->xmit_async_map));
        ppp->xmit_async_map[0] = 0xffffffff;
        ppp->xmit_async_map[3] = 0x60000000;
        ppp->recv_async_map    = 0x00000000;

        ppp->rbuf       = NULL;
        ppp->wbuf       = NULL;
        ppp->ubuf       = NULL;
        ppp->cbuf       = NULL;
        ppp->slcomp     = NULL;
        ppp->read_wait  = NULL;
        ppp->write_wait = NULL;
        ppp->last_xmit  = jiffies - flag_time;

        /* clear statistics */
        memset (&ppp->stats, '\0', sizeof (struct pppstat));

        /* Reset the demand dial information */
        ppp->ddinfo.xmit_idle=         /* time since last NP packet sent */
        ppp->ddinfo.recv_idle=jiffies; /* time since last NP packet received */

        /* PPP compression data */
        ppp->sc_xc_state =
        ppp->sc_rc_state = NULL;
}

static struct symbol_table ppp_syms = {
#include <linux/symtab_begin.h>
        X(ppp_register_compressor),
        X(ppp_unregister_compressor),
        X(ppp_crc16_table),
#include <linux/symtab_end.h>
};

/* called at boot/load time for each ppp device defined in the kernel */

#ifndef MODULE
int
ppp_init (struct device *dev)
{
        static int first_time = 1;
        int    answer = 0;

        if (first_time) {
                first_time = 0;
                answer     = ppp_first_time();
                if (answer == 0)
                        (void) register_symtab (&ppp_syms);
        }
        if (answer == 0)
                answer = -ENODEV;
        return answer;
}
#endif

/*
 * Routine to allocate a buffer for later use by the driver.
 */

static struct ppp_buffer *
ppp_alloc_buf (int size, int type)
{
        struct ppp_buffer *buf;

        buf = (struct ppp_buffer *) kmalloc (size + sizeof (struct ppp_buffer),
                                             GFP_ATOMIC);

        if (buf != NULL) {
                buf->size   = size - 1; /* Mask for the buffer size */
                buf->type   = type;
                buf->locked = 0;
                buf->count  = 0;
                buf->head   = 0;
                buf->tail   = 0;
                buf->fcs    = PPP_INITFCS;

        }
        return (buf);
}

/*
 * Routine to release the allocated buffer.
 */

static void
ppp_free_buf (struct ppp_buffer *ptr)
{
        if (ptr != NULL)
                kfree (ptr);
}

/*
 * Lock the indicated transmit buffer
 */

extern inline int
lock_buffer (register struct ppp_buffer *buf)
{
        register int state;
        unsigned long flags;
/*
 * Save the current state and if free then set it to the "busy" state
 */
        save_flags (flags);
        cli ();
        state = buf->locked;
        if (state == 0)
                buf->locked = 2;

        restore_flags (flags);
        return (state);
}

/*
 * MTU has been changed by the IP layer. Unfortunately we are not told
 * about this, but we spot it ourselves and fix things up. We could be
 * in an upcall from the tty driver, or in an ip packet queue.
 */

static int
ppp_changedmtu (struct ppp *ppp, int new_mtu, int new_mru)
{
        struct device *dev;

        struct ppp_buffer *new_rbuf;
        struct ppp_buffer *new_wbuf;
        struct ppp_buffer *new_cbuf;
        struct ppp_buffer *new_tbuf;

        struct ppp_buffer *old_rbuf;
        struct ppp_buffer *old_wbuf;
        struct ppp_buffer *old_cbuf;
        struct ppp_buffer *old_tbuf;

        int mtu, mru;
/*
 *  Allocate the buffer from the kernel for the data
 */
        dev = ppp2dev (ppp);
        mru = new_mru;
        /* allow for possible escaping of every character */
        mtu = (new_mtu * 2) + 20;

        /* RFC 1331, section 7.2 says the minimum value is 1500 bytes */
        if (mru < PPP_MRU)
                mru = PPP_MRU;

        mru += 10;
        
        if (ppp->flags & SC_DEBUG)
                printk (KERN_INFO "ppp: channel %s mtu = %d, mru = %d\n",
                        dev->name, new_mtu, new_mru);

        new_wbuf = ppp_alloc_buf (mtu+PPP_HARD_HDR_LEN, BUFFER_TYPE_DEV_WR);
        new_tbuf = ppp_alloc_buf ((PPP_MTU * 2) + 24,   BUFFER_TYPE_TTY_WR);
        new_rbuf = ppp_alloc_buf (mru + 84,             BUFFER_TYPE_DEV_RD);
        new_cbuf = ppp_alloc_buf (mru+PPP_HARD_HDR_LEN, BUFFER_TYPE_VJ);
/*
 *  If the buffers failed to allocate then complain and release the partial
 *  allocations.
 */
        if (new_wbuf == NULL || new_tbuf == NULL ||
            new_rbuf == NULL || new_cbuf == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                                "ppp: failed to allocate new buffers\n");

                ppp_free_buf (new_wbuf);
                ppp_free_buf (new_tbuf);
                ppp_free_buf (new_rbuf);
                ppp_free_buf (new_cbuf);
                return 0;
        }
/*
 *  Update the pointers to the new buffer structures.
 */
        cli ();
        old_wbuf = ppp->wbuf;
        old_rbuf = ppp->rbuf;
        old_cbuf = ppp->cbuf;
        old_tbuf = ppp->tbuf;

        ppp->wbuf = new_wbuf;
        ppp->rbuf = new_rbuf;
        ppp->cbuf = new_cbuf;
        ppp->tbuf = new_tbuf;

        ppp->rbuf->size -= 80;  /* reserve space for vj header expansion */

        dev->mem_start  = (unsigned long) buf_base (new_wbuf);
        dev->mem_end    = (unsigned long) (dev->mem_start + mtu);
        dev->rmem_start = (unsigned long) buf_base (new_rbuf);
        dev->rmem_end   = (unsigned long) (dev->rmem_start + mru);
/*
 *  Update the parameters for the new buffer sizes
 */
        ppp->toss   = 0xE0;     /* To ignore characters until new FLAG */
        ppp->escape = 0;        /* No pending escape character */

        dev->mtu    =
        ppp->mtu    = new_mtu;
        ppp->mru    = new_mru;

        ppp->s1buf  = NULL;
        ppp->s2buf  = NULL;
        ppp->xbuf   = NULL;

        ppp->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
        ppp->flags      &= ~SC_XMIT_BUSY;

        sti ();
/*
 *  Release old buffer pointers
 */
        ppp_free_buf (old_rbuf);
        ppp_free_buf (old_wbuf);
        ppp_free_buf (old_cbuf);
        ppp_free_buf (old_tbuf);
        return 1;
}

/*
 * CCP is down; free (de)compressor state if necessary.
 */

static void
ppp_ccp_closed (struct ppp *ppp)
{
        if (ppp->sc_xc_state) {
                (*ppp->sc_xcomp->comp_free) (ppp->sc_xc_state);
                ppp->sc_xc_state = NULL;
        }

        if (ppp->sc_rc_state) {
                (*ppp->sc_rcomp->decomp_free) (ppp->sc_rc_state);
                ppp->sc_rc_state = NULL;
        }
}

/*
 * Called to release all of the information in the current PPP structure.
 *
 * It is called when the ppp device goes down or if it is unable to go
 * up.
 */

static void
ppp_release (struct ppp *ppp)
{
        struct tty_struct *tty;
        struct device *dev;

        tty = ppp2tty (ppp);
        dev = ppp2dev (ppp);

        ppp_ccp_closed (ppp);

        /* Ensure that the pppd process is not hanging on select() */
        wake_up_interruptible (&ppp->read_wait);
        wake_up_interruptible (&ppp->write_wait);

        if (tty != NULL && tty->disc_data == ppp)
                tty->disc_data = NULL;  /* Break the tty->ppp link */

        if (dev && dev->flags & IFF_UP) {
                dev_close (dev); /* close the device properly */
                dev->flags = 0;  /* prevent recursion */
        }

        ppp_free_buf (ppp->rbuf);
        ppp_free_buf (ppp->wbuf);
        ppp_free_buf (ppp->cbuf);
        ppp_free_buf (ppp->ubuf);
        ppp_free_buf (ppp->tbuf);

        ppp->rbuf  =
        ppp->wbuf  =
        ppp->cbuf  =
        ppp->tbuf  =
        ppp->xbuf  =
        ppp->s1buf =
        ppp->s2buf =
        ppp->ubuf  = NULL;

        if (ppp->slcomp) {
                slhc_free (ppp->slcomp);
                ppp->slcomp = NULL;
        }

        ppp->inuse = 0;
        ppp->tty   = NULL;
}

/*
 * Device callback.
 *
 * Called when the PPP device goes down in response to an ifconfig request.
 */

static void
ppp_tty_close_local (struct tty_struct *tty, int sc_xfer)
{
        struct ppp *ppp = tty2ppp (tty);

        if (ppp != NULL) {
                if (ppp->magic != PPP_MAGIC) {
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_WARNING
                                       "ppp: trying to close unopened tty!\n");
                } else {
                        CHECK_PPP_VOID();
                        ppp->sc_xfer = sc_xfer;
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO "ppp: channel %s closing.\n",
                                        ppp2dev(ppp) -> name);
                        ppp_release (ppp);
                        MOD_DEC_USE_COUNT;
                }
        }
}

static void
ppp_tty_close (struct tty_struct *tty)
{
        ppp_tty_close_local (tty, 0);
}

/*
 * TTY callback.
 *
 * Called when the tty discipline is switched to PPP.
 */

static int
ppp_tty_open (struct tty_struct *tty)
{
        struct ppp *ppp = tty2ppp (tty);
        int indx;
/*
 * There should not be an existing table for this slot.
 */
        if (ppp) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                        "ppp_tty_open: gack! tty already associated to %s!\n",
                        ppp->magic == PPP_MAGIC ? ppp2dev(ppp)->name
                                                : "unknown");
                return -EEXIST;
        }
/*
 * Allocate the structure from the system
 */
        ppp = ppp_find(current->pid);
        if (ppp == NULL) {
                ppp = ppp_find(0);
                if (ppp == NULL)
                        ppp = ppp_alloc();
        }

        if (ppp == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                        "ppp_tty_open: couldn't allocate ppp channel\n");
                return -ENFILE;
        }
/*
 * Initialize the control block
 */
        ppp_init_ctrl_blk (ppp);
        ppp->tty       = tty;
        tty->disc_data = ppp;
/*
 * Flush any pending characters in the driver and discipline.
 */
        if (tty->ldisc.flush_buffer)
                tty->ldisc.flush_buffer (tty);

        if (tty->driver.flush_buffer)
                tty->driver.flush_buffer (tty);
/*
 * Allocate space for the default VJ header compression slots
 */
        ppp->slcomp = slhc_init (16, 16);
        if (ppp->slcomp == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                        "ppp_tty_open: no space for compression buffers!\n");
                ppp_release (ppp);
                return -ENOMEM;
        }
/*
 * Allocate space for the MTU and MRU buffers
 */
        if (ppp_changedmtu (ppp, ppp2dev(ppp)->mtu, ppp->mru) == 0) {
                ppp_release (ppp);
                return -ENOMEM;
        }
/*
 * Allocate space for a user level buffer
 */
        ppp->ubuf = ppp_alloc_buf (RBUFSIZE, BUFFER_TYPE_TTY_RD);
        if (ppp->ubuf == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                       "ppp_tty_open: no space for user receive buffer\n");
                ppp_release (ppp);
                return -ENOMEM;
        }

        if (ppp->flags & SC_DEBUG)
                printk (KERN_INFO "ppp: channel %s open\n",
                        ppp2dev(ppp)->name);

        for (indx = 0; indx < NUM_NP; ++indx)
                ppp->sc_npmode[indx] = NPMODE_PASS;

        MOD_INC_USE_COUNT;
        return (ppp->line);
}

/*
 * Local function to send the next portion of the buffer.
 *
 * Called by the tty driver's tty_wakeup function should it be entered
 * because the partial buffer was transmitted.
 *
 * Called by kick_tty to send the initial portion of the buffer.
 *
 * Completion processing of the buffer transmission is handled here.
 */

static void
ppp_tty_wakeup_code (struct ppp *ppp, struct tty_struct *tty,
                     struct ppp_buffer *xbuf)
{
        register int count, actual;
/*
 * Prevent re-entrancy by ensuring that this routine is called only once.
 */
        cli ();
        if (ppp->flags & SC_XMIT_BUSY) {
                sti ();
                return;
        }
        ppp->flags |= SC_XMIT_BUSY;
        sti ();
/*
 * Send the next block of data to the modem
 */
        count = xbuf->count - xbuf->tail;
        actual = tty->driver.write (tty, 0,
                                    buf_base (xbuf) + xbuf->tail, count);
/*
 * Terminate transmission of any block which may have an error.
 * This could occur should the carrier drop.
 */
        if (actual < 0) {
                ppp->stats.ppp_oerrors++;
                actual = count;
        } else
                ppp->bytes_sent += actual;
/*
 * If the buffer has been transmitted then clear the indicators.
 */
        xbuf->tail += actual;
        if (actual == count) {
                xbuf = NULL;
                ppp->flags &= ~SC_XMIT_BUSY;
/*
 * Complete the transmission on the current buffer.
 */
                xbuf = ppp->xbuf;
                if (xbuf != NULL) {
                        tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
                        xbuf->locked = 0;
                        ppp->xbuf    = NULL;
/*
 * If the completed buffer came from the device write, then complete the
 * transmission block.
 */
                        if (ppp2dev (ppp) -> flags & IFF_UP) {
                                if (xbuf->type == BUFFER_TYPE_DEV_WR)
                                        ppp2dev (ppp)->tbusy = 0;
                                mark_bh (NET_BH);
                        }
/*
 * Wake up the transmission queue for all completion events.
 */
                        wake_up_interruptible (&ppp->write_wait);
/*
 * Look at the priorities. Choose a daemon write over the device driver.
 */
                        cli();
                        xbuf = ppp->s1buf;
                        ppp->s1buf = NULL;
                        if (xbuf == NULL) {
                                xbuf = ppp->s2buf;
                                ppp->s2buf = NULL;
                        }
                        sti();
/*
 * If there is a pending buffer then transmit it now.
 */
                        if (xbuf != NULL) {
                                ppp->flags &= ~SC_XMIT_BUSY;
                                ppp_kick_tty (ppp, xbuf);
                                return;
                        }
                }
        }
/*
 * Clear the re-entry flag
 */
        ppp->flags &= ~SC_XMIT_BUSY;
}

/*
 * This function is called by the tty driver when the transmit buffer has
 * additional space. It is used by the ppp code to continue to transmit
 * the current buffer should the buffer have been partially sent.
 *
 * In addition, it is used to send the first part of the buffer since the
 * logic and the inter-locking would be identical.
 */

static void
ppp_tty_wakeup (struct tty_struct *tty)
{
        struct ppp_buffer *xbuf;
        struct ppp *ppp = tty2ppp (tty);

        if (!ppp)
                return;

        if (ppp->magic != PPP_MAGIC)
                return;
/*
 * Ensure that there is a transmission pending. Clear the re-entry flag if
 * there is no pending buffer. Otherwise, send the buffer.
 */
        xbuf = ppp->xbuf;
        if (xbuf == NULL)
                tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
        else
                ppp_tty_wakeup_code (ppp, tty, xbuf);
}

/*
 * This function is called to transmit a buffer to the remote. The buffer
 * is placed on the pending queue if there is presently a buffer being
 * sent or it is transmitted with the aid of ppp_tty_wakeup.
 */

static void
ppp_kick_tty (struct ppp *ppp, struct ppp_buffer *xbuf)
{
        unsigned long flags;
/*
 * Hold interrupts.
 */
        save_flags (flags);
        cli ();
/*
 * Control the flags which are best performed with the interrupts masked.
 */
        xbuf->locked     = 1;
        xbuf->tail       = 0;
/*
 * If the transmitter is busy then place the buffer on the appropriate
 * priority queue.
 */
        if (ppp->xbuf != NULL) {
                if (xbuf->type == BUFFER_TYPE_TTY_WR)
                        ppp->s1buf = xbuf;
                else
                        ppp->s2buf = xbuf;
                restore_flags (flags);
                return;
        }
/*
 * If the transmitter is not busy then this is the highest priority frame
 */
        ppp->flags      &= ~SC_XMIT_BUSY;
        ppp->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
        ppp->xbuf        = xbuf;
        restore_flags (flags);
/*
 * Do the "tty wakeup_code" to actually send this buffer.
 */
        ppp_tty_wakeup_code (ppp, ppp2tty (ppp), xbuf);
}

/*************************************************************
 * TTY INPUT
 *    The following functions handle input that arrives from
 *    the TTY.  It recognizes PPP frames and either hands them
 *    to the network layer or queues them for delivery to a
 *    user process reading this TTY.
 *************************************************************/

/*
 * Callback function from tty driver. Return the amount of space left
 * in the receiver's buffer to decide if remote transmitter is to be
 * throttled.
 */

static int
ppp_tty_room (struct tty_struct *tty)
{
        return 65536;       /* We can handle an infinite amount of data. :-) */
}

/*
 * Callback function when data is available at the tty driver.
 */
static void
ppp_tty_receive (struct tty_struct *tty, const __u8 * data,
                 char *flags, int count)
{
        register struct ppp *ppp = tty2ppp (tty);
        register struct ppp_buffer *buf = NULL;
        __u8 chr;

        if (count >= TTY_FLIPBUF_SIZE)
                printk(KERN_WARNING "ppp_tty_receive: got %d chars\n", count);

/*
 * Fetch the pointer to the buffer. Be careful about race conditions.
 */
        if (ppp != NULL)
                buf = ppp->rbuf;

        if (buf == NULL)
                return;
/*
 * Verify the table pointer and ensure that the line is
 * still in PPP discipline.
 */
        if (ppp->magic != PPP_MAGIC) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_DEBUG
                                "PPP: handler called but couldn't find "
                                "PPP struct.\n");
                return;
        }
        CHECK_PPP_VOID ();
/*
 * Print the buffer if desired
 */
        if (ppp->flags & SC_LOG_RAWIN)
                ppp_print_buffer ("receive buffer", data, count);
/*
 * Collect the character and error condition for the character. Set the toss
 * flag for the first character error.
 */
        while (count-- > 0) {
                ppp->bytes_rcvd++;
                chr = *data++;
                if (flags) {
                        if (*flags && ppp->toss == 0)
                                ppp->toss = *flags;
                        ++flags;
                }
/*
 * Set the flags for 8 data bits and no parity.
 *
 * Actually, it sets the flags for d7 being 0/1 and parity being even/odd
 * so that the normal processing would have all flags set at the end of the
 * session. A missing flag bit would denote an error condition.
 */

#ifdef CHECK_CHARACTERS
                if (chr & 0x80)
                        ppp->flags |= SC_RCV_B7_1;
                else
                        ppp->flags |= SC_RCV_B7_0;

                if (paritytab[chr >> 5] & (1 << (chr & 0x1F)))
                        ppp->flags |= SC_RCV_ODDP;
                else
                        ppp->flags |= SC_RCV_EVNP;
#endif
/*
 * Branch on the character.
 */
                switch (chr) {
/*
 * FLAG. This is the end of the block. If the block terminated by ESC FLAG,
 * then the block is to be ignored. In addition, characters before the very
 * first FLAG are also tossed by this procedure.
 */
                case PPP_FLAG:  /* PPP_FLAG: end of frame */
                        ppp->stats.ppp_ibytes += ppp->rbuf->count;
                        if (ppp->escape)
                                ppp->toss |= 0x80;
/*
 * Process frames which are not to be ignored. If the processing failed,
 * then clean up the VJ tables.
 */
                        if (ppp_doframe (ppp) == 0) {
                                slhc_toss (ppp->slcomp);
                        }
/*
 * Reset all indicators for the new frame to follow.
 */
                        buf->count  = 0;
                        buf->fcs    = PPP_INITFCS;
                        ppp->escape = 0;
                        ppp->toss   = 0;
                        break;
/*
 * All other characters in the data come here. If the character is in the
 * receive mask then ignore the character.
 */
                default:
                        /* If we're tossing, look no further. */
                        if (ppp->toss != 0)
                                break;

                        /* If this is a control char to be ignored, do so */
                        if (in_rmap (ppp, chr)) {
                                if (ppp->flags & SC_DEBUG)
                                        printk(KERN_DEBUG "ignoring control char %x\n", chr);
                                break;
                        }

                        /*
                         * Modify the next character if preceded by escape.
                         * The escape character (0x7d) could be an escaped
                         * 0x5d, if it follows an escape :-)
                         */
                        if (ppp->escape) {
                                chr ^= ppp->escape;
                                ppp->escape = 0;
                        } else if (chr == PPP_ESCAPE) {
                                ppp->escape = PPP_TRANS;
                                break;
                        }

/*
 * If the count sent is within reason then store the character, bump the
 * count, and update the FCS for the character.
 */
                        if (buf->count < buf->size) {
                                buf_base (buf)[buf->count++] = chr;
                                buf->fcs = PPP_FCS (buf->fcs, chr);
                                break;
                        }
/*
 * The peer sent too much data. Set the flags to discard the current frame
 * and wait for the re-synchronization FLAG to be sent.
 */
                        ppp->stats.ppp_ierrors++;
                        ppp->toss |= 0xC0;
                        break;
                }
        }
}

/*
 * Put the input frame into the networking system for the indicated protocol
 */

static int
ppp_rcv_rx (struct ppp *ppp, __u16 proto, __u8 * data, int count)
{
        sk_buff *skb = dev_alloc_skb (count);
/*
 * Generate a skb buffer for the new frame.
 */
        if (skb == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                         "ppp_do_ip: packet dropped on %s (no memory)!\n",
                         ppp2dev (ppp)->name);
                return 0;
        }
/*
 * Move the received data from the input buffer to the skb buffer.
 */
        skb->dev      = ppp2dev (ppp);  /* We are the device */
        skb->protocol = proto;
        skb->mac.raw  = skb_data(skb);
        memcpy (skb_put(skb,count), data, count);       /* move data */
/*
 * Tag the frame and kick it to the proper receive routine
 */
        skb->free = 1;
        ppp->ddinfo.recv_idle = jiffies;
        netif_rx (skb);
        return 1;
}

/*
 * Process the receipt of an IP frame
 */

static int
rcv_proto_ip (struct ppp *ppp, __u16 proto, __u8 * data, int count)
{
        if ((ppp2dev (ppp)->flags & IFF_UP) && (count > 0))
                if (ppp->sc_npmode[NP_IP] == NPMODE_PASS)
                        return ppp_rcv_rx (ppp, htons (ETH_P_IP), data, count);
        return 0;
}

/*
 * Process the receipt of an IPX frame
 */

static int
rcv_proto_ipx (struct ppp *ppp, __u16 proto, __u8 * data, int count)
{
        if (((ppp2dev (ppp)->flags & IFF_UP) != 0) && (count > 0))
                return ppp_rcv_rx (ppp, htons (ETH_P_IPX), data, count);
        return 0;
}

/*
 * Process the receipt of an VJ Compressed frame
 */

static int
rcv_proto_vjc_comp (struct ppp *ppp, __u16 proto,
                    __u8 *data, int count)
{
        if ((ppp->flags & SC_REJ_COMP_TCP) == 0) {
                int new_count = slhc_uncompress (ppp->slcomp, data, count);
                if (new_count >= 0) {
                        return rcv_proto_ip (ppp, PPP_IP, data, new_count);
                }
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_NOTICE
                                "ppp: error in VJ decompression\n");
        }
        return 0;
}

/*
 * Process the receipt of an VJ Un-compressed frame
 */

static int
rcv_proto_vjc_uncomp (struct ppp *ppp, __u16 proto,
                      __u8 *data, int count)
{
        if ((ppp->flags & SC_REJ_COMP_TCP) == 0) {
                if (slhc_remember (ppp->slcomp, data, count) > 0) {
                        return rcv_proto_ip (ppp, PPP_IP, data, count);
                }
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_NOTICE
                                "ppp: error in VJ memorizing\n");
        }
        return 0;
}

/*
 * Receive all unclassified protocols.
 */

static int
rcv_proto_unknown (struct ppp *ppp, __u16 proto,
                   __u8 *data, int len)
{
        int totlen;
        register int current_idx;

#define PUTC(c)                                          \
{                                                        \
    buf_base (ppp->ubuf) [current_idx++] = (__u8) (c); \
    current_idx &= ppp->ubuf->size;                      \
    if (current_idx == ppp->ubuf->tail)                  \
            goto failure;                                \
}

/*
 * The total length includes the protocol data.
 * Lock the user information buffer.
 */
        if (set_bit (0, &ppp->ubuf->locked)) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_DEBUG
                                "ppp_us_queue: can't get lock\n");
        } else {
                current_idx = ppp->ubuf->head;
/*
 * Insert the buffer length (not counted), the protocol, and the data
 */
                totlen = len + 2;
                PUTC (totlen >> 8);
                PUTC (totlen);

                PUTC (proto >> 8);
                PUTC (proto);

                totlen -= 2;
                while (totlen-- > 0) {
                        PUTC (*data++);
                }
#undef PUTC
/*
 * The frame is complete. Update the head pointer and wakeup the pppd
 * process.
 */
                ppp->ubuf->head = current_idx;

                clear_bit (0, &ppp->ubuf->locked);
                wake_up_interruptible (&ppp->read_wait);
                if (ppp->tty->fasync != NULL)
                        kill_fasync (ppp->tty->fasync, SIGIO);

                if (ppp->flags & SC_DEBUG)
                        printk (KERN_INFO
                                "ppp: successfully queued %d bytes, flags = %x\n",
                                len + 2, ppp->flags);

                return 1;
/*
 * The buffer is full. Unlock the header
 */
failure:
                clear_bit (0, &ppp->ubuf->locked);
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_INFO
                                "ppp_us_queue: ran out of buffer space.\n");
        }
/*
 * Discard the frame. There are no takers for this protocol.
 */
        if (ppp->flags & SC_DEBUG)
                printk (KERN_WARNING
                        "ppp: dropping packet on the floor.\n");
        slhc_toss (ppp->slcomp);
        return 0;
}

/*
 * Handle a CCP packet.
 *
 * The CCP packet is passed along to the pppd process just like any
 * other PPP frame. The difference is that some processing needs to be
 * immediate or the compressors will become confused on the peer.
 */

static void ppp_proto_ccp (struct ppp *ppp, __u8 *dp, int len, int rcvd)
{
        int slen    = CCP_LENGTH(dp);
        __u8 *opt = dp   + CCP_HDRLEN;
        int opt_len = slen - CCP_HDRLEN;

        if (slen > len)
                return;

        switch (CCP_CODE(dp)) {
        case CCP_CONFREQ:
        case CCP_TERMREQ:
        case CCP_TERMACK:
/*
 * CCP must be going down - disable compression
 */
                if (ppp->flags & SC_CCP_UP) {
                        ppp->flags &= ~(SC_CCP_UP   |
                                        SC_COMP_RUN |
                                        SC_DECOMP_RUN);
                }
                break;

        case CCP_CONFACK:
                if ((ppp->flags & SC_CCP_OPEN) == 0)
                        break;
                if (ppp->flags & SC_CCP_UP)
                        break;
                if (slen < (CCP_HDRLEN + CCP_OPT_MINLEN))
                        break;
                if (slen < (CCP_OPT_LENGTH (opt) + CCP_HDRLEN))
                        break;
/*
 * we're agreeing to send compressed packets.
 */
                if (!rcvd) {
                        if (ppp->sc_xc_state == NULL)
                                break;

                        if ((*ppp->sc_xcomp->comp_init)
                            (ppp->sc_xc_state,
                             opt,
                             opt_len,
                             ppp2dev (ppp)->base_addr,
                             0,
                             ppp->flags))
                                ppp->flags |= SC_COMP_RUN;
                        break;
                }
/*
 * peer is agreeing to send compressed packets.
 */
                if (ppp->sc_rc_state == NULL)
                        break;

                if ((*ppp->sc_rcomp->decomp_init)
                    (ppp->sc_rc_state,
                     opt,
                     opt_len,
                     ppp2dev (ppp)->base_addr,
                     0,
                     ppp->mru,
                     ppp->flags)) {
                        ppp->flags |= SC_DECOMP_RUN;
                        ppp->flags &= ~(SC_DC_ERROR | SC_DC_FERROR);
                }
                break;
/*
 * The protocol sequence is complete at this end
 */
        case CCP_RESETACK:
                if ((ppp->flags & SC_CCP_UP) == 0)
                        break;

                if (!rcvd) {
                        if (ppp->sc_xc_state && (ppp->flags & SC_COMP_RUN))
                                (*ppp->sc_xcomp->comp_reset)(ppp->sc_xc_state);
                } else {
                        if (ppp->sc_rc_state && (ppp->flags & SC_DECOMP_RUN)) {
                              (*ppp->sc_rcomp->decomp_reset)(ppp->sc_rc_state);
                                ppp->flags &= ~SC_DC_ERROR;
                        }
                }
                break;
        }
}

static int
rcv_proto_ccp (struct ppp *ppp, __u16 proto, __u8 *dp, int len)
{
        ppp_proto_ccp (ppp, dp, len, 1);
        return rcv_proto_unknown (ppp, proto, dp, len);
}

/*
 * Handle a LQR packet.
 */

static int
rcv_proto_lqr (struct ppp *ppp, __u16 proto, __u8 * data, int len)
{
        return rcv_proto_unknown (ppp, proto, data, len);
}

/* on entry, a received frame is in ppp->rbuf.bufr
   check it and dispose as appropriate */

static void ppp_doframe_lower (struct ppp *ppp, __u8 *data, int count)
{
        __u16           proto = PPP_PROTOCOL (data);
        ppp_proto_type  *proto_ptr;
/*
 * Ignore empty frames
 */
        if (count <= 4)
                return;
/*
 * Count the frame and print it
 */
        ++ppp->stats.ppp_ipackets;
        if (ppp->flags & SC_LOG_INPKT)
                ppp_print_buffer ("receive frame", data, count);
/*
 * Find the procedure to handle this protocol. The last one is marked
 * as a protocol 0 which is the 'catch-all' to feed it to the pppd daemon.
 */
        proto_ptr = proto_list;
        while (proto_ptr->proto != 0 && proto_ptr->proto != proto)
                ++proto_ptr;
/*
 * Update the appropriate statistic counter.
 */
        if ((*proto_ptr->func) (ppp, proto,
                                &data[PPP_HARD_HDR_LEN],
                                count - PPP_HARD_HDR_LEN))
                ppp->stats.ppp_ioctects += count;
        else
                ++ppp->stats.ppp_discards;
}

/* on entry, a received frame is in ppp->rbuf.bufr
   check it and dispose as appropriate */

static int
ppp_doframe (struct ppp *ppp)
{
        __u8    *data = buf_base (ppp->rbuf);
        int     count = ppp->rbuf->count;
        int     addr, ctrl, proto;
        int     new_count;
        __u8 *new_data;
/*
 * If there is a pending error from the receiver then log it and discard
 * the damaged frame.
 */
        if (ppp->toss) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_DEBUG
                                "ppp_toss: tossing frame, reason = %x\n",
                                ppp->toss);
                ppp->stats.ppp_ierrors++;
                return 0;
        }
/*
 * An empty frame is ignored. This occurs if the FLAG sequence precedes and
 * follows each frame.
 */
        if (count == 0)
                return 1;
/*
 * Generate an error if the frame is too small.
 */
        if (count < PPP_HARD_HDR_LEN) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp: got runt ppp frame, %d chars\n", count);
                slhc_toss (ppp->slcomp);
                ppp->stats.ppp_ierrors++;
                return 1;
        }
/*
 * Verify the CRC of the frame and discard the CRC characters from the
 * end of the buffer.
 */
        if (ppp->rbuf->fcs != PPP_GOODFCS) {
                if (ppp->flags & SC_DEBUG) {
                        printk (KERN_WARNING
                                "ppp: frame with bad fcs, excess = %x, length = %d\n",
                                ppp->rbuf->fcs ^ PPP_GOODFCS, count);
                        ppp_print_buffer("bad frame", data, count);
                }
                ppp->stats.ppp_ierrors++;
                return 0;
        }
        count -= 2;             /* ignore the fcs characters */
/*
 * Ignore the leading ADDRESS and CONTROL fields in the frame.
 */
        addr   = PPP_ALLSTATIONS;
        ctrl   = PPP_UI;

        if ((data[0] == PPP_ALLSTATIONS) && (data[1] == PPP_UI)) {
                data  += 2;
                count -= 2;
        }
/*
 * Obtain the protocol from the frame
 */
        proto = (__u16) *data++;
        if ((proto & 1) == 0) {
                proto = (proto << 8) | (__u16) *data++;
                --count;
        }
/*
 * Rewrite the header with the full information. This may encroach upon
 * the 'filler' area in the buffer header. This is the purpose for the
 * filler.
 */
        *(--data) = proto;
        *(--data) = proto >> 8;
        *(--data) = ctrl;
        *(--data) = addr;
        count    += 3;
/*
 * Process the active decompressor.
 */
        if ((ppp->sc_rc_state != (void *) 0) &&
            (ppp->flags & SC_DECOMP_RUN)     &&
            ((ppp->flags & (SC_DC_FERROR | SC_DC_ERROR)) == 0)) {
                if (proto == PPP_COMP) {
/*
 * If the frame is compressed then decompress it.
 */
                        new_data = kmalloc (ppp->mru + 4, GFP_ATOMIC);
                        if (new_data == NULL) {
                                if (ppp->flags & SC_DEBUG)
                                        printk (KERN_ERR
                                                "ppp_doframe: no memory\n");
                                slhc_toss (ppp->slcomp);
                                (*ppp->sc_rcomp->incomp) (ppp->sc_rc_state,
                                                          data,
                                                          count);
                                return 1;
                        }
/*
 * Decompress the frame
 */
                        new_count = bsd_decompress (ppp->sc_rc_state,
                                                    data,
                                                    count,
                                                    new_data,
                                                    ppp->mru + 4);
                        switch (new_count) {
                        default:
                                ppp_doframe_lower (ppp, new_data, new_count);
                                kfree (new_data);
                                return 1;

                        case DECOMP_OK:
                                break;

                        case DECOMP_ERROR:
                                ppp->flags |= SC_DC_ERROR;
                                break;

                        case DECOMP_FATALERROR:
                                ppp->flags |= SC_DC_FERROR;
                                break;
                        }
/*
 * Log the error condition and discard the frame.
 */
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_ERR
                                        "ppp_proto_comp: "
                                        "decompress err %d\n", new_count);
                        kfree (new_data);
                        slhc_toss (ppp->slcomp);
                        return 1;
                }
/*
 * The frame is not special. Pass it through the compressor without
 * actually compressing the data
 */
                (*ppp->sc_rcomp->incomp) (ppp->sc_rc_state,
                                          data,
                                          count);
        }
/*
 * Process the uncompressed frame.
 */
        ppp_doframe_lower (ppp, data, count);
        return 1;
}

/*************************************************************
 * LINE DISCIPLINE SUPPORT
 *    The following functions form support user programs
 *    which read and write data on a TTY with the PPP line
 *    discipline.  Reading is done from a circular queue,
 *    filled by the lower TTY levels.
 *************************************************************/

/* read a PPP frame from the us_rbuff circular buffer,
   waiting if necessary
*/

static int
ppp_tty_read (struct tty_struct *tty, struct file *file, __u8 * buf,
              unsigned int nr)
{
        struct ppp *ppp = tty2ppp (tty);
        __u8 c;
        int len, indx;

#define GETC(c)                                         \
{                                                       \
        c = buf_base (ppp->ubuf) [ppp->ubuf->tail++];   \
        ppp->ubuf->tail &= ppp->ubuf->size;             \
}

/*
 * Validate the pointers
 */
        if (!ppp)
                return -EIO;

        if (ppp->magic != PPP_MAGIC)
                return -EIO;

        CHECK_PPP (-ENXIO);

        if (ppp->flags & SC_DEBUG)
                printk (KERN_DEBUG
                        "ppp_tty_read: called buf=%p nr=%u\n",
                        buf, nr);
/*
 * Acquire the read lock.
 */
        for (;;) {
                ppp = tty2ppp (tty);
                if (!ppp || ppp->magic != PPP_MAGIC || !ppp->inuse)
                        return 0;

                if (set_bit (0, &ppp->ubuf->locked) != 0) {
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_DEBUG
                                     "ppp_tty_read: sleeping(ubuf)\n");

                        current->timeout = 0;
                        current->state   = TASK_INTERRUPTIBLE;
                        schedule ();

                        if (current->signal & ~current->blocked)
                                return -EINTR;
                        continue;
                }
/*
 * Before we attempt to write the frame to the user, ensure that the
 * user has access to the pages for the total buffer length.
 */
                indx = verify_area (VERIFY_WRITE, buf, nr);
                if (indx != 0)
                        return (indx);
/*
 * Fetch the length of the buffer from the first two bytes.
 */
                if (ppp->ubuf->head == ppp->ubuf->tail)
                        len = 0;
                else {
                        GETC (c);
                        len = c << 8;
                        GETC (c);
                        len += c;
                }
/*
 * If there is no length then wait for the data to arrive.
 */
                if (len == 0) {
                        /* no data */
                        clear_bit (0, &ppp->ubuf->locked);
                        if (file->f_flags & O_NONBLOCK) {
                                if (ppp->flags & SC_DEBUG)
                                        printk (KERN_DEBUG
                                                "ppp_tty_read: no data "
                                                "(EAGAIN)\n");
                                return -EAGAIN;
                        }
                        current->timeout = 0;

                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_DEBUG
                                        "ppp_tty_read: sleeping(read_wait)\n");

                        interruptible_sleep_on (&ppp->read_wait);
                        if (current->signal & ~current->blocked)
                                return -EINTR;
                        continue;
                }
/*
 * Reset the time of the last read operation.
 */
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_DEBUG "ppp_tty_read: len = %d\n", len);
/*
 * Ensure that the frame will fit within the caller's buffer. If not, then
 * discard the frame from the input buffer.
 */
                if (len + 2 > nr) {
                        /* Can't copy it, update us_rbuff_head */

                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_DEBUG
                                "ppp: read of %u bytes too small for %d "
                                "frame\n", nr, len + 2);
                        ppp->ubuf->tail += len;
                        ppp->ubuf->tail &= ppp->ubuf->size;
                        clear_bit (0, &ppp->ubuf->locked);
                        ppp->stats.ppp_ierrors++;
                        return -EOVERFLOW;
                }
/*
 * Before we attempt to write the frame to the user, ensure that the
 * page tables are proper.
 */
                indx = verify_area (VERIFY_WRITE, buf, len + 2);
                if (indx != 0) {
                        ppp->ubuf->tail += len;
                        ppp->ubuf->tail &= ppp->ubuf->size;
                        clear_bit (0, &ppp->ubuf->locked);
                        return (indx);
                }
/*
 * Fake the insertion of the ADDRESS and CONTROL information because these
 * were not saved in the buffer.
 */
                put_user (PPP_ALLSTATIONS, buf++);
                put_user (PPP_UI,          buf++);

                indx = len;
/*
 * Copy the received data from the buffer to the caller's area.
 */
                while (indx-- > 0) {
                        GETC (c);
                        put_user (c, buf);
                        ++buf;
                }

                clear_bit (0, &ppp->ubuf->locked);
                len += 2; /* Account for ADDRESS and CONTROL bytes */
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_DEBUG
                                "ppp_tty_read: passing %d bytes up\n", len);
                return len;
        }
#undef GETC
}

/* stuff a character into the transmit buffer, using PPP's way of escaping
   special characters.
   also, update fcs to take account of new character */

extern inline void
ppp_stuff_char (struct ppp *ppp, register struct ppp_buffer *buf,
                register __u8 chr)
{
/*
 * The buffer should not be full.
 */
        if (ppp->flags & SC_DEBUG) {
                if ((buf->count < 0) || (buf->count > 3000))
                        printk (KERN_DEBUG "ppp_stuff_char: %x %d\n",
                                (unsigned int) buf->count,
                                (unsigned int) chr);
        }
/*
 * Update the FCS and if the character needs to be escaped, do it.
 */
        buf->fcs = PPP_FCS (buf->fcs, chr);
        if (in_xmap (ppp, chr)) {
                chr ^= PPP_TRANS;
                ins_char (buf, PPP_ESCAPE);
        }
/*
 * Add the character to the buffer.
 */
        ins_char (buf, chr);
}

/*
 * Procedure to encode the data with the proper escaping and send the
 * data to the remote system.
 */

static void
ppp_dev_xmit_lower (struct ppp *ppp, struct ppp_buffer *buf,
                    __u8 *data, int count, int non_ip)
{
        __u16   write_fcs;
        int     address, control;
        int     proto;
/*
 * Insert the leading FLAG character
 */
        buf->count = 0;

        if (non_ip || flag_time == 0)
                ins_char (buf, PPP_FLAG);
        else {
                if (jiffies - ppp->last_xmit > flag_time)
                        ins_char (buf, PPP_FLAG);
        }
        ppp->last_xmit = jiffies;
        buf->fcs       = PPP_INITFCS;
/*
 * Emit the address/control information if needed
 */
        address = PPP_ADDRESS  (data);
        control = PPP_CONTROL  (data);
        proto   = PPP_PROTOCOL (data);

        if (address != PPP_ALLSTATIONS ||
            control != PPP_UI ||
            (ppp->flags & SC_COMP_AC) == 0) {
                ppp_stuff_char (ppp, buf, address);
                ppp_stuff_char (ppp, buf, control);
        }
/*
 * Emit the protocol (compressed if possible)
 */
        if ((ppp->flags & SC_COMP_PROT) == 0 || (proto & 0xFF00))
                ppp_stuff_char (ppp, buf, proto >> 8);

        ppp_stuff_char (ppp, buf, proto);
/*
 * Insert the data
 */
        data  += 4;
        count -= 4;

        while (count-- > 0)
                ppp_stuff_char (ppp, buf, *data++);
/*
 * Add the trailing CRC and the final flag character
 */
        write_fcs = buf->fcs ^ 0xFFFF;
        ppp_stuff_char (ppp, buf, write_fcs);
        ppp_stuff_char (ppp, buf, write_fcs >> 8);
/*
 * Add the trailing flag character
 */
        ins_char (buf, PPP_FLAG);
/*
 * Print the buffer
 */
        if (ppp->flags & SC_LOG_FLUSH)
                ppp_print_buffer ("ppp flush", buf_base (buf),
                                  buf->count);
/*
 * Send the block to the tty driver.
 */
        ppp->stats.ppp_obytes += buf->count;
        ppp_kick_tty (ppp, buf);
}

/*
 * Send an frame to the remote with the proper bsd compression.
 *
 * Return 0 if frame was queued for transmission.
 *        1 if frame must be re-queued for later driver support.
 */

static int
ppp_dev_xmit_frame (struct ppp *ppp, struct ppp_buffer *buf,
                    __u8 *data, int count)
{
        int     proto;
        int     address, control;
        __u8 *new_data;
        int     new_count;
/*
 * Print the buffer
 */
        if (ppp->flags & SC_LOG_OUTPKT)
                ppp_print_buffer ("write frame", data, count);
/*
 * Determine if the frame may be compressed. Attempt to compress the
 * frame if possible.
 */
        proto   = PPP_PROTOCOL (data);
        address = PPP_ADDRESS  (data);
        control = PPP_CONTROL  (data);

        if (((ppp->flags & SC_COMP_RUN) != 0)   &&
            (ppp->sc_xc_state != (void *) 0)    &&
            (address == PPP_ALLSTATIONS)        &&
            (control == PPP_UI)                 &&
            (proto != PPP_LCP)                  &&
            (proto != PPP_CCP)) {
                new_data = kmalloc (count, GFP_ATOMIC);
                if (new_data == NULL) {
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_ERR
                                        "ppp_dev_xmit_frame: no memory\n");
                        return 1;
                }

                new_count = bsd_compress (ppp->sc_xc_state,
                                          data,
                                          new_data,
                                          count,
                                          count);

                if (new_count > 0) {
                        ++ppp->stats.ppp_opackets;
                        ppp->stats.ppp_ooctects += new_count;

                        ppp_dev_xmit_lower (ppp, buf, new_data,
                                            new_count, 0);
                        kfree (new_data);
                        return 0;
                }
/*
 * The frame could not be compressed.
 */
                kfree (new_data);
        }
/*
 * The frame may not be compressed. Update the statistics before the
 * count field is destroyed. The frame will be transmitted.
 */
        ++ppp->stats.ppp_opackets;
        ppp->stats.ppp_ooctects += count;
/*
 * Go to the escape encoding
 */
        ppp_dev_xmit_lower (ppp, buf, data, count, !!(proto & 0xFF00));
        return 0;
}

/*
 * Revise the tty frame for specific protocols.
 */

static int
send_revise_frame (register struct ppp *ppp, __u8 *data, int len)
{
        __u8 *p;

        switch (PPP_PROTOCOL (data)) {
/*
 * Update the LQR frame with the current MIB information. This saves having
 * the daemon read old MIB data from the driver.
 */
        case PPP_LQR:
                len = 48;                       /* total size of this frame */
                p   = (__u8 *) &data [40];      /* Point to last two items. */
                p   = store_long (p, ppp->stats.ppp_opackets + 1);
                p   = store_long (p, ppp->stats.ppp_ooctects + len);
                break;
/*
 * Outbound compression frames
 */
        case PPP_CCP:
                ppp_proto_ccp (ppp,
                               data + PPP_HARD_HDR_LEN,
                               len  - PPP_HARD_HDR_LEN,
                               0);
                break;

        default:
                break;
        }

        return len;
}

/*
 * write a frame with NR chars from BUF to TTY
 * we have to put the FCS field on ourselves
 */

static int
ppp_tty_write (struct tty_struct *tty, struct file *file, const __u8 * data,
               unsigned int count)
{
        struct ppp *ppp = tty2ppp (tty);
        __u8 *new_data;
        int status;
/*
 * Verify the pointers.
 */
        if (!ppp)
                return -EIO;

        if (ppp->magic != PPP_MAGIC)
                return -EIO;

        CHECK_PPP (-ENXIO);
/*
 * Ensure that the caller does not wish to send too much.
 */
        if (count > PPP_MTU) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp_tty_write: truncating user packet "
                                "from %u to mtu %d\n", count, PPP_MTU);
                count = PPP_MTU;
        }
/*
 * Allocate a buffer for the data and fetch it from the user space.
 */
        new_data = kmalloc (count, GFP_KERNEL);
        if (new_data == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                                "ppp_tty_write: no memory\n");
                return 0;
        }
/*
 * lock this PPP unit so we will be the only writer;
 * sleep if necessary
 */
        while (lock_buffer (ppp->tbuf) != 0) {
                current->timeout = 0;
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_DEBUG "ppp_tty_write: sleeping\n");
                interruptible_sleep_on (&ppp->write_wait);

                ppp = tty2ppp (tty);
                if (!ppp || ppp->magic != PPP_MAGIC || !ppp->inuse) {
                        kfree (new_data);
                        return 0;
                }

                if (current->signal & ~current->blocked) {
                        kfree (new_data);
                        return -EINTR;
                }
        }
/*
 * Ensure that the caller's buffer is valid.
 */
        status = verify_area (VERIFY_READ, data, count);
        if (status != 0) {
                kfree (new_data);
                ppp->tbuf->locked = 0;
                return status;
        }

        memcpy_fromfs (new_data, data, count);
/*
 * Change the LQR frame
 */
        count = send_revise_frame (ppp, new_data, count);
/*
 * Send the data
 */
        ppp_dev_xmit_frame (ppp, ppp->tbuf, new_data, count);
        kfree (new_data);
        return (int) count;
}

/*
 * Process the BSD compression IOCTL event for the tty device.
 */

static int
ppp_set_compression (struct ppp *ppp, struct ppp_option_data *odp)
{
        struct compressor *cp;
        struct ppp_option_data data;
        int error;
        int nb;
        __u8 *ptr;
        __u8 ccp_option[CCP_MAX_OPTION_LENGTH];
/*
 * Fetch the compression parameters
 */
        error = verify_area (VERIFY_READ, odp, sizeof (data));
        if (error == 0) {
                memcpy_fromfs (&data, odp, sizeof (data));
                nb  = data.length;
                ptr = data.ptr;
                if ((__u32) nb >= (__u32)CCP_MAX_OPTION_LENGTH)
                        nb = CCP_MAX_OPTION_LENGTH;
        
                error = verify_area (VERIFY_READ, ptr, nb);
        }

        if (error != 0)
                return error;

        memcpy_fromfs (ccp_option, ptr, nb);

        if (ccp_option[1] < 2)  /* preliminary check on the length byte */
                return (-EINVAL);

        cp = find_compressor ((int) (unsigned int) (__u8) ccp_option[0]);
        if (cp != (struct compressor *) 0) {
                /*
                 * Found a handler for the protocol - try to allocate
                 * a compressor or decompressor.
                 */
                error = 0;
                if (data.transmit) {
                        if (ppp->sc_xc_state != NULL)
                                (*ppp->sc_xcomp->comp_free)(ppp->sc_xc_state);

                        ppp->sc_xcomp    = cp;
                        ppp->sc_xc_state = cp->comp_alloc(ccp_option, nb);

                        if (ppp->sc_xc_state == NULL) {
                                if (ppp->flags & SC_DEBUG)
                                        printk("ppp%ld: comp_alloc failed\n",
                                               ppp2dev (ppp)->base_addr);
                                error = -ENOBUFS;
                        }
                        ppp->flags &= ~SC_COMP_RUN;
                } else {
                        if (ppp->sc_rc_state != NULL)
                                (*ppp->sc_rcomp->decomp_free)(ppp->sc_rc_state);
                        ppp->sc_rcomp    = cp;
                        ppp->sc_rc_state = cp->decomp_alloc(ccp_option, nb);
                        if (ppp->sc_rc_state == NULL) {
                                if (ppp->flags & SC_DEBUG)
                                        printk("ppp%ld: decomp_alloc failed\n",
                                               ppp2dev (ppp)->base_addr);
                                error = ENOBUFS;
                        }
                        ppp->flags &= ~SC_DECOMP_RUN;
                }
                return (error);
        }

        if (ppp->flags & SC_DEBUG)
                printk(KERN_DEBUG "ppp%ld: no compressor for [%x %x %x], %x\n",
                       ppp2dev (ppp)->base_addr, ccp_option[0], ccp_option[1],
                       ccp_option[2], nb);
        return (-EINVAL);       /* no handler found */
}

/*
 * Process the IOCTL event for the tty device.
 */

static int
ppp_tty_ioctl (struct tty_struct *tty, struct file * file,
               unsigned int param2, unsigned long param3)
{
        struct ppp *ppp = tty2ppp (tty);
        register int temp_i = 0;
        int error = 0;
/*
 * Verify the status of the PPP device.
 */
        if (!ppp)
                return -EBADF;

        if (ppp->magic != PPP_MAGIC)
                return -EBADF;

        CHECK_PPP (-ENXIO);
/*
 * The user must have an euid of root to do these requests.
 */
        if (!suser ())
                return -EPERM;
/*
 * Set the MRU value
 */
        switch (param2) {
        case PPPIOCSMRU:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        temp_i = get_user ((int *) param3);
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                 "ppp_tty_ioctl: set mru to %x\n", temp_i);

                        if (ppp->mru != temp_i)
                                ppp_changedmtu (ppp, ppp2dev (ppp)->mtu, temp_i);
                }
                break;
/*
 * Fetch the flags
 */
        case PPPIOCGFLAGS:
                error = verify_area (VERIFY_WRITE, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        temp_i = (ppp->flags & SC_MASK);
#ifndef CHECK_CHARACTERS /* Don't generate errors if we don't check chars. */
                        temp_i |= SC_RCV_B7_1 | SC_RCV_B7_0 |
                                  SC_RCV_ODDP | SC_RCV_EVNP;
#endif
                        put_user (temp_i, (int *) param3);
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_DEBUG
                                "ppp_tty_ioctl: get flags: addr %lx flags "
                                "%x\n", param3, temp_i);
                }
                break;
/*
 * Set the flags for the various options
 */
        case PPPIOCSFLAGS:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        temp_i  = get_user ((int *) param3) & SC_MASK;
                        temp_i |= (ppp->flags & ~SC_MASK);

                        if ((ppp->flags & SC_CCP_OPEN) &&
                            (temp_i & SC_CCP_OPEN) == 0)
                                ppp_ccp_closed (ppp);

                        if ((ppp->flags | temp_i) & SC_DEBUG)
                                printk (KERN_INFO
                               "ppp_tty_ioctl: set flags to %x\n", temp_i);
                        ppp->flags = temp_i;
                }
                break;
/*
 * Set the compression mode
 */
        case PPPIOCSCOMPRESS:
                error = ppp_set_compression (ppp,
                                            (struct ppp_option_data *) param3);
                break;
/*
 * Retrieve the transmit async map
 */
        case PPPIOCGASYNCMAP:
                error = verify_area (VERIFY_WRITE, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        put_user (ppp->xmit_async_map[0], (int *) param3);
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                     "ppp_tty_ioctl: get asyncmap: addr "
                                     "%lx asyncmap %x\n",
                                     param3,
                                     ppp->xmit_async_map[0]);
                }
                break;
/*
 * Set the transmit async map
 */
        case PPPIOCSASYNCMAP:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        ppp->xmit_async_map[0] = get_user ((int *) param3);
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                     "ppp_tty_ioctl: set xmit asyncmap %x\n",
                                     ppp->xmit_async_map[0]);
                }
                break;
/*
 * Set the receive async map
 */
        case PPPIOCSRASYNCMAP:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        ppp->recv_async_map = get_user ((int *) param3);
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                     "ppp_tty_ioctl: set rcv asyncmap %x\n",
                                     ppp->recv_async_map);
                }
                break;
/*
 * Obtain the unit number for this device.
 */
        case PPPIOCGUNIT:
                error = verify_area (VERIFY_WRITE, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        put_user (ppp2dev (ppp)->base_addr, (int *) param3);
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                        "ppp_tty_ioctl: get unit: %ld",
                                        ppp2dev (ppp)->base_addr);
                }
                break;
/*
 * Set the debug level
 */
        case PPPIOCSDEBUG:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        temp_i  = (get_user ((int *) param3) & 0x1F) << 16;
                        temp_i |= (ppp->flags & ~0x1F0000);

                        if ((ppp->flags | temp_i) & SC_DEBUG)
                                printk (KERN_INFO
                               "ppp_tty_ioctl: set flags to %x\n", temp_i);
                        ppp->flags = temp_i;
                }
                break;
/*
 * Get the debug level
 */
        case PPPIOCGDEBUG:
                error = verify_area (VERIFY_WRITE, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        temp_i = (ppp->flags >> 16) & 0x1F;
                        put_user (temp_i, (int *) param3);

                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                        "ppp_tty_ioctl: get debug level %d\n",
                                        temp_i);
                }
                break;
/*
 * Get the times since the last send/receive frame operation
 */
        case PPPIOCGIDLE:
                error = verify_area (VERIFY_WRITE, (void *) param3,
                                     sizeof (struct ppp_idle));
                if (error == 0) {
                        struct ppp_idle cur_ddinfo;
                        __u32 cur_jiffies = jiffies;

                        /* change absolute times to relative times. */
                        cur_ddinfo.xmit_idle = (cur_jiffies - ppp->ddinfo.xmit_idle) / HZ;
                        cur_ddinfo.recv_idle = (cur_jiffies - ppp->ddinfo.recv_idle) / HZ;
                        memcpy_tofs ((void *) param3, &cur_ddinfo,
                                     sizeof (cur_ddinfo));
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                "ppp_tty_ioctl: read demand dial info\n");
                }
                break;
/*
 * Retrieve the extended async map
 */
        case PPPIOCGXASYNCMAP:
                error = verify_area (VERIFY_WRITE,
                                     (void *) param3,
                                     sizeof (ppp->xmit_async_map));
                if (error == 0) {
                        memcpy_tofs ((void *) param3,
                                     ppp->xmit_async_map,
                                     sizeof (ppp->xmit_async_map));

                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                "ppp_tty_ioctl: get xasyncmap: addr %lx\n",
                                param3);
                }
                break;
/*
 * Set the async extended map
 */
        case PPPIOCSXASYNCMAP:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (ppp->xmit_async_map));
                if (error == 0) {
                        __u32 temp_tbl[8];

                        memcpy_fromfs (temp_tbl, (void *) param3,
                                       sizeof (ppp->xmit_async_map));
                        temp_tbl[1]  =  0x00000000;
                        temp_tbl[2] &= ~0x40000000;
                        temp_tbl[3] |=  0x60000000;

                        if ((temp_tbl[2] & temp_tbl[3]) != 0 ||
                            (temp_tbl[4] & temp_tbl[5]) != 0 ||
                            (temp_tbl[6] & temp_tbl[7]) != 0)
                                error = -EINVAL;
                        else {
                                memcpy (ppp->xmit_async_map, temp_tbl,
                                        sizeof (ppp->xmit_async_map));

                                if (ppp->flags & SC_DEBUG)
                                        printk (KERN_INFO
                                        "ppp_tty_ioctl: set xasyncmap\n");
                        }
                }
                break;
/*
 * Set the maximum VJ header compression slot number.
 */
        case PPPIOCSMAXCID:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (temp_i));
                if (error == 0) {
                        temp_i = get_user ((int *) param3) + 1;
                        if (ppp->flags & SC_DEBUG)
                                printk (KERN_INFO
                                     "ppp_tty_ioctl: set maxcid to %d\n",
                                     temp_i);
                        if (ppp->slcomp != NULL)
                                slhc_free (ppp->slcomp);
                        ppp->slcomp = slhc_init (16, temp_i);

                        if (ppp->slcomp == NULL) {
                                if (ppp->flags & SC_DEBUG)
                                        printk (KERN_ERR
                                        "ppp: no space for compression buffers!\n");
                                ppp_release (ppp);
                                error = -ENOMEM;
                        }
                }
                break;

    case PPPIOCXFERUNIT:
                ppp_tty_close_local (tty, current->pid);
                break;

    case PPPIOCGNPMODE:
    case PPPIOCSNPMODE:
                error = verify_area (VERIFY_READ, (void *) param3,
                                     sizeof (struct npioctl));
                if (error == 0) {
                        struct npioctl npi;
                        memcpy_fromfs (&npi,
                                       (void *) param3,
                                       sizeof (npi));

                        switch (npi.protocol) {
                        case PPP_IP:
                                npi.protocol = NP_IP;
                                break;
                        default:
                                error = -EINVAL;
                        }

                        if (error != 0)
                                break;

                        if (param2 == PPPIOCGNPMODE) {
                                npi.mode = ppp->sc_npmode[npi.protocol];
                                error = verify_area (VERIFY_WRITE,
                                                     (void *) param3,
                                                     sizeof (npi));
                                if (error != 0)
                                        break;

                                memcpy_tofs ((void *) param3,
                                             &npi,
                                             sizeof (npi));
                                break;
                        }

                        if (npi.mode != ppp->sc_npmode[npi.protocol]) {
                                ppp->sc_npmode[npi.protocol] = npi.mode;
                                if (npi.mode != NPMODE_QUEUE) {
                                        /* ppp_requeue(ppp); maybe needed */
                                        ppp_tty_wakeup (ppp2tty(ppp));
                                }
                        }
                }
                break;
/*
 * Allow users to read, but not set, the serial port parameters
 */
        case TCGETS:
        case TCGETA:
                error = n_tty_ioctl (tty, file, param2, param3);
                break;

        case FIONREAD:
                error = verify_area (VERIFY_WRITE,
                                     (void *) param3,
                                     sizeof (int));
                if (error == 0) {
                        int count = ppp->ubuf->tail - ppp->ubuf->head;
                        if (count < 0)
                                count += (ppp->ubuf->size + 1);

                        put_user (count, (int *) param3);
                }
                break;
/*
 *  All other ioctl() events will come here.
 */
        default:
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                                "ppp_tty_ioctl: invalid ioctl: %x, addr %lx\n",
                                param2,
                                param3);

                error = -ENOIOCTLCMD;
                break;
        }
        return error;
}

/*
 * TTY callback.
 *
 * Process the select() statement for the PPP device.
 */

static int
ppp_tty_select (struct tty_struct *tty, struct inode *inode,
                struct file *filp, int sel_type, select_table * wait)
{
        struct ppp *ppp = tty2ppp (tty);
        int result = 1;
/*
 * Verify the status of the PPP device.
 */
        if (!ppp)
                return -EBADF;

        if (ppp->magic != PPP_MAGIC)
                return -EBADF;

        CHECK_PPP (0);
/*
 * Branch on the type of select mode. A read request must lock the user
 * buffer area.
 */
        switch (sel_type) {
        case SEL_IN:
                if (set_bit (0, &ppp->ubuf->locked) == 0) {
                        /* Test for the presence of data in the queue */
                        if (ppp->ubuf->head != ppp->ubuf->tail) {
                                clear_bit (0, &ppp->ubuf->locked);
                                break;
                        }
                        clear_bit (0, &ppp->ubuf->locked);
                }               /* fall through */
/*
 * Exceptions or read errors.
 */
        case SEL_EX:
                /* Is this a pty link and the remote disconnected? */
                if (tty->flags & (1 << TTY_OTHER_CLOSED))
                        break;

                /* Is this a local link and the modem disconnected? */
                if (tty_hung_up_p (filp))
                        break;

                select_wait (&ppp->read_wait, wait);
                result = 0;
                break;
/*
 * Write mode. A write is allowed if there is no current transmission.
 */
        case SEL_OUT:
                if (ppp->tbuf->locked != 0) {
                        select_wait (&ppp->write_wait, wait);
                        result = 0;
                }
                break;
        }
        return result;
}

/*************************************************************
 * NETWORK OUTPUT
 *    This routine accepts requests from the network layer
 *    and attempts to deliver the packets.
 *    It also includes various routines we are compelled to
 *    have to make the network layer work (arp, etc...).
 *************************************************************/

/*
 * Callback from the network layer when the device goes up.
 */

static int
ppp_dev_open (struct device *dev)
{
        struct ppp *ppp = dev2ppp (dev);

        /* reset POINTOPOINT every time, since dev_close zaps it! */
        dev->flags |= IFF_POINTOPOINT;

        if (ppp2tty (ppp) == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                        "ppp: %s not connected to a TTY! can't go open!\n",
                        dev->name);
                return -ENXIO;
        }

        if (ppp->flags & SC_DEBUG)
                printk (KERN_INFO
                        "ppp: channel %s going up for IP packets!\n",
                        dev->name);

        CHECK_PPP (-ENXIO);
        return 0;
}

/*
 * Callback from the network layer when the ppp device goes down.
 */

static int
ppp_dev_close (struct device *dev)
{
        struct ppp *ppp = dev2ppp (dev);

        if (ppp2tty (ppp) == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                        "ppp: %s not connected to a TTY! can't go down!\n",
                        dev->name);
                return -ENXIO;
        }
/*
 * We don't do anything about the device going down. It is not important
 * for us.
 */
        if (ppp->flags & SC_DEBUG)
                printk (KERN_INFO
                        "ppp: channel %s going down for IP packets!\n",
                        dev->name);
        CHECK_PPP (-ENXIO);
        return 0;
}

/*
 * IOCTL operation to read the version of the driver.
 */

static int
ppp_dev_ioctl_version (struct ppp *ppp, struct ifreq *ifr)
{
        int error;
        int len;
        char *result;
/*
 * Must have write access to the buffer.
 */
        result = (char *) ifr->ifr_ifru.ifru_data;
        len    = strlen (szVersion) + 1;
        error  = verify_area (VERIFY_WRITE, result, len);
/*
 * Move the version data
 */
        if (error == 0)
                memcpy_tofs (result, szVersion, len);

        return error;
}

/*
 * IOCTL to read the statistics for the pppstats program.
 */

static int
ppp_dev_ioctl_stats (struct ppp *ppp, struct ifreq *ifr, struct device *dev)
{
        struct ppp_stats *result, temp;
        int    error;
/*
 * Must have write access to the buffer.
 */
        result = (struct ppp_stats *) ifr->ifr_ifru.ifru_data;
        error = verify_area (VERIFY_WRITE,
                             result,
                             sizeof (temp));
/*
 * Supply the information for the caller. First move the version data
 * then move the ppp stats; and finally the vj stats.
 */
        memset (&temp, 0, sizeof(temp));
        if (error == 0 && dev->flags & IFF_UP) {
                memcpy (&temp.p, &ppp->stats, sizeof (struct pppstat));
                if (ppp->slcomp != NULL) {
                        temp.vj.vjs_packets    = ppp->slcomp->sls_o_compressed+
                                                 ppp->slcomp->sls_o_uncompressed;
                        temp.vj.vjs_compressed = ppp->slcomp->sls_o_compressed;
                        temp.vj.vjs_searches   = ppp->slcomp->sls_o_searches;
                        temp.vj.vjs_misses     = ppp->slcomp->sls_o_misses;
                        temp.vj.vjs_errorin    = ppp->slcomp->sls_i_error;
                        temp.vj.vjs_tossed     = ppp->slcomp->sls_i_tossed;
                        temp.vj.vjs_uncompressedin = ppp->slcomp->sls_i_uncompressed;
                        temp.vj.vjs_compressedin   = ppp->slcomp->sls_i_compressed;
                }
        }

        if (error == 0)
                memcpy_tofs (result, &temp, sizeof (temp));
        return error;
}

/*
 * IOCTL to read the compression statistics for the pppstats program.
 */

static int
ppp_dev_ioctl_comp_stats (struct ppp *ppp, struct ifreq *ifr, struct device *dev)
{
        struct ppp_comp_stats *result, temp;
        int    error;
/*
 * Must have write access to the buffer.
 */
        result = (struct ppp_comp_stats *) ifr->ifr_ifru.ifru_data;
        error = verify_area (VERIFY_WRITE,
                             result,
                             sizeof (temp));
/*
 * Supply the information for the caller.
 */
        memset (&temp, 0, sizeof(temp));
        if (error == 0 && dev->flags & IFF_UP) {
                if (ppp->sc_xc_state != NULL)
                        (*ppp->sc_xcomp->comp_stat) (ppp->sc_xc_state,
                                                     &temp.c);

                if (ppp->sc_rc_state != NULL)
                        (*ppp->sc_rcomp->decomp_stat) (ppp->sc_rc_state,
                                                       &temp.d);
        }
/*
 * Move the data to the caller's buffer
 */
        if (error == 0)
                memcpy_tofs (result, &temp, sizeof (temp));
        return error;
}

/*
 * Callback from the network layer to process the sockioctl functions.
 */

static int
ppp_dev_ioctl (struct device *dev, struct ifreq *ifr, int cmd)
{
        struct ppp *ppp = dev2ppp (dev);
        int error;
/*
 * Process the requests
 */
        switch (cmd) {
        case SIOCGPPPSTATS:
                error = ppp_dev_ioctl_stats (ppp, ifr, dev);
                break;

        case SIOCGPPPCSTATS:
                error = ppp_dev_ioctl_comp_stats (ppp, ifr, dev);
                break;

        case SIOCGPPPVER:
                error = ppp_dev_ioctl_version (ppp, ifr);
                break;

        default:
                error = -EINVAL;
                break;
        }
        return error;
}

/*
 * Send an IP frame to the remote with vj header compression.
 *
 * Return 0 if frame was queued for transmission.
 *        1 if frame must be re-queued for later driver support.
 */

static int
ppp_dev_xmit_ip (struct device *dev, struct ppp *ppp, __u8 *data)
{
        int               proto = PPP_IP;
        int               len;
        struct ppp_hdr    *hdr;
        struct tty_struct *tty = ppp2tty (ppp);
/*
 * Obtain the length from the IP header.
 */
        len = ((struct iphdr *)data) -> tot_len;
        len = ntohs (len);
/*
 * Validate the tty interface
 */
        if (tty == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                                "ppp_dev_xmit: %s not connected to a TTY!\n",
                                dev->name);
                return 0;
        }
/*
 * Ensure that the PPP device is still up
 */
        if (!(dev->flags & IFF_UP)) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp_dev_xmit: packet sent on interface %s,"
                                " which is down for IP\n",
                                dev->name);
                return 0;
        }
/*
 * Branch on the type of processing for the IP frame.
 */
        switch (ppp->sc_npmode[NP_IP]) {
        case NPMODE_PASS:
                break;

        case NPMODE_ERROR:
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp_dev_xmit: npmode = NPMODE_ERROR on %s\n",
                                dev->name);
                return 0;

        case NPMODE_DROP:
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp_dev_xmit: npmode = NPMODE_DROP on %s\n",
                                dev->name);
                return 0;

        case NPMODE_QUEUE:
                break;

        default:
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp_dev_xmit: unknown npmode %d on %s\n",
                                ppp->sc_npmode[NP_IP],
                                dev->name);
                return 0;
        }
/*
 * Detect a change in the transfer size
 */
        if (ppp->mtu != ppp2dev (ppp)->mtu) {
                ppp_changedmtu (ppp,
                                ppp2dev (ppp)->mtu,
                                ppp->mru);
        }
/*
 * Acquire the lock on the transmission buffer. If the buffer was busy then
 * mark the device as busy.
 */
        if (lock_buffer (ppp->wbuf) != 0) {
                dev->tbusy = 1;
                return 1;
        }
/*
 * Print the frame being sent
 */
        if (ppp->flags & SC_LOG_OUTPKT)
                ppp_print_buffer ("ppp outpkt", data, len);
/*
 * At this point, the buffer will be transmitted. There is no other exit.
 *
 * Try to compress the header.
 */
        if (ppp->flags & SC_COMP_TCP) {
                len = slhc_compress (ppp->slcomp, data, len,
                                     buf_base (ppp->cbuf) + PPP_HARD_HDR_LEN,
                                     &data,
                                     (ppp->flags & SC_NO_TCP_CCID) == 0);

                if (data[0] & SL_TYPE_COMPRESSED_TCP) {
                        proto    = PPP_VJC_COMP;
                        data[0] ^= SL_TYPE_COMPRESSED_TCP;
                } else {
                        if (data[0] >= SL_TYPE_UNCOMPRESSED_TCP)
                                proto = PPP_VJC_UNCOMP;
                        data[0] = (data[0] & 0x0f) | 0x40;
                }
        }
/*
 * Send the frame
 */
        len  += PPP_HARD_HDR_LEN;
        hdr   = &((struct ppp_hdr *) data)[-1];

        hdr->address     = PPP_ALLSTATIONS;
        hdr->control     = PPP_UI;
        hdr->protocol[0] = 0;
        hdr->protocol[1] = proto;

        return ppp_dev_xmit_frame (ppp, ppp->wbuf, (__u8 *) hdr, len);
}

/*
 * Send an IPX (or any other non-IP) frame to the remote.
 *
 * Return 0 if frame was queued for transmission.
 *        1 if frame must be re-queued for later driver support.
 */
static int
ppp_dev_xmit_ipx (struct device *dev, struct ppp *ppp,
                  __u8 *data, int len, int proto)
{
        struct tty_struct *tty = ppp2tty (ppp);
        struct ppp_hdr    *hdr;
/*
 * Validate the tty interface
 */
        if (tty == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                                "ppp_dev_xmit: %s not connected to a TTY!\n",
                                dev->name);
                return 0;
        }
/*
 * Ensure that the PPP device is still up
 */
        if (!(dev->flags & IFF_UP)) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING
                                "ppp_dev_xmit: packet sent on interface %s,"
                                " which is down\n",
                                dev->name);
                return 0;
        }
/*
 * Detect a change in the transfer size
 */
        if (ppp->mtu != ppp2dev (ppp)->mtu) {
                ppp_changedmtu (ppp,
                                ppp2dev (ppp)->mtu,
                                ppp->mru);
        }
/*
 * Acquire the lock on the transmission buffer. If the buffer was busy then
 * mark the device as busy.
 */
        if (lock_buffer (ppp->wbuf) != 0) {
                dev->tbusy = 1;
                return 1;
        }
/*
 * Print the frame being sent
 */
        if (ppp->flags & SC_LOG_OUTPKT)
                ppp_print_buffer ("ppp outpkt", data, len);
/*
 * Send the frame
 */
        len  += PPP_HARD_HDR_LEN;
        hdr   = &((struct ppp_hdr *) data)[-1];

        hdr->address     = PPP_ALLSTATIONS;
        hdr->control     = PPP_UI;
        hdr->protocol[0] = proto >> 8;
        hdr->protocol[1] = proto;

        return ppp_dev_xmit_frame (ppp, ppp->wbuf, (__u8 *) hdr, len);
}

/*
 * Send a frame to the remote.
 */

static int
ppp_dev_xmit (sk_buff *skb, struct device *dev)
{
        int answer, len;
        __u8              *data;
        struct ppp        *ppp = dev2ppp (dev);
        struct tty_struct *tty = ppp2tty (ppp);
/*
 * just a little sanity check.
 */
        if (skb == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_WARNING "ppp_dev_xmit: null packet!\n");
                return 0;
        }
/*
 * Avoid timing problem should tty hangup while data is queued to be sent
 */
        if (!ppp->inuse) {
                dev_kfree_skb (skb, FREE_WRITE);
                dev_close (dev);
                return 0;
        }
/*
 * Validate the tty interface
 */
        if (tty == NULL) {
                if (ppp->flags & SC_DEBUG)
                        printk (KERN_ERR
                                "ppp_dev_xmit: %s not connected to a TTY!\n",
                                dev->name);
                dev_kfree_skb (skb, FREE_WRITE);
                return 0;
        }
/*
 * Fetch the pointer to the data
 */
        len   = skb->len;
        data  = skb_data(skb);
/*
 * Look at the protocol in the skb to determine the difference between
 * an IP frame and an IPX frame.
 */
        switch (ntohs (skb->protocol)) {
        case ETH_P_IPX:
                answer = ppp_dev_xmit_ipx (dev, ppp, data, len, PPP_IPX);
                break;

        case ETH_P_IP:
                answer = ppp_dev_xmit_ip (dev, ppp, data);
                break;

        default: /* All others have no support at this time. */
                dev_kfree_skb (skb, FREE_WRITE);
                return 0;
        }
/*
 * This is the end of the transmission. Release the buffer if it was sent.
 */
        if (answer == 0) {
                dev_kfree_skb (skb, FREE_WRITE);
                ppp->ddinfo.xmit_idle = jiffies;
        }
        return answer;
}

/*
 * Generate the statistic information for the /proc/net/dev listing.
 */

static struct enet_statistics *
ppp_dev_stats (struct device *dev)
{
        struct ppp *ppp = dev2ppp (dev);
        static struct enet_statistics ppp_stats;

        ppp_stats.rx_packets          = ppp->stats.ppp_ipackets;
        ppp_stats.rx_errors           = ppp->stats.ppp_ierrors;
        ppp_stats.rx_dropped          = ppp->stats.ppp_ierrors;
        ppp_stats.rx_fifo_errors      = 0;
        ppp_stats.rx_length_errors    = 0;
        ppp_stats.rx_over_errors      = 0;
        ppp_stats.rx_crc_errors       = 0;
        ppp_stats.rx_frame_errors     = 0;
        ppp_stats.tx_packets          = ppp->stats.ppp_opackets;
        ppp_stats.tx_errors           = ppp->stats.ppp_oerrors;
        ppp_stats.tx_dropped          = 0;
        ppp_stats.tx_fifo_errors      = 0;
        ppp_stats.collisions          = 0;
        ppp_stats.tx_carrier_errors   = 0;
        ppp_stats.tx_aborted_errors   = 0;
        ppp_stats.tx_window_errors    = 0;
        ppp_stats.tx_heartbeat_errors = 0;

        if (ppp->flags & SC_DEBUG)
                printk (KERN_INFO "ppp_dev_stats called\n");
        return &ppp_stats;
}

static int ppp_dev_header (sk_buff *skb, struct device *dev,
                           __u16 type, void *daddr,
                           void *saddr, unsigned int len)
{
        return (0);
}

static int
ppp_dev_rebuild (void *eth, struct device *dev,
                 unsigned long raddr, struct sk_buff *skb)
{
        return (0);
}

/*************************************************************
 * UTILITIES
 *    Miscellany called by various functions above.
 *************************************************************/

/* Locate the previous instance of the PPP channel */
static struct ppp *
ppp_find (int pid_value)
{
        int             if_num;
        ppp_ctrl_t      *ctl;
        struct ppp      *ppp;

        /* try to find the exact same free device which we had before */
        ctl      = ppp_list;
        if_num   = 0;
  
        while (ctl) {
                ppp = ctl2ppp (ctl);
                if (!set_bit(0, &ppp->inuse)) {
                        if (ppp->sc_xfer == pid_value) {
                                ppp->sc_xfer = 0;
                                return (ppp);
                        }
                        clear_bit (0, &ppp->inuse);
                }
                ctl = ctl->next;
                if (++if_num == max_dev)
                        break;
        }
        return NULL;
}

/* allocate or create a PPP channel */
static struct ppp *
ppp_alloc (void)
{
        int             if_num;
        int             status;
        ppp_ctrl_t      *ctl;
        struct device   *dev;
        struct ppp      *ppp;

        /* try to find an free device */
        ctl      = ppp_list;
        if_num   = 0;
  
        while (ctl) {
                ppp = ctl2ppp (ctl);
                if (!set_bit(0, &ppp->inuse))
                        return (ppp);
                ctl = ctl->next;
                if (++if_num == max_dev)
                        return (NULL);
        }
/*
 * There are no available items. Allocate a device from the system pool
 */
        ctl = (ppp_ctrl_t *) kmalloc (sizeof(ppp_ctrl_t), GFP_KERNEL);
        if (ctl) {
                (void) memset(ctl, 0, sizeof(ppp_ctrl_t));
                ppp = ctl2ppp (ctl);
                dev = ctl2dev (ctl);

                /* initialize channel control data */
                set_bit(0, &ppp->inuse);

                ppp->line      = if_num;
                ppp->tty       = NULL;
                ppp->dev       = dev;
    
                dev->next      = NULL;
                dev->init      = ppp_init_dev;
                dev->name      = ctl->name;
                dev->base_addr = (__u32) if_num;
                dev->priv      = (void *) ppp;

                sprintf (dev->name, "ppp%d", if_num);
    
                /* link in the new channel */
                ctl->next      = ppp_list;
                ppp_list       = ctl;

                /* register device so that we can be ifconfig'd */
                /* ppp_init_dev() will be called as a side-effect */

                status = register_netdev (dev);
                if (status == 0) {
                        printk (KERN_INFO "registered device %s\n", dev->name);
                        return (ppp);
                }

                printk (KERN_ERR
                       "ppp_alloc - register_netdev(%s) = %d failure.\n",
                        dev->name, status);
                /* This one will forever be busy as it is not initialized */
        }
        return (NULL);
}

/*
 * Utility procedures to print a buffer in hex/ascii
 */

static void
ppp_print_hex (register __u8 * out, const __u8 * in, int count)
{
        register __u8 next_ch;
        static char hex[] = "0123456789ABCDEF";

        while (count-- > 0) {
                next_ch = *in++;
                *out++ = hex[(next_ch >> 4) & 0x0F];
                *out++ = hex[next_ch & 0x0F];
                ++out;
        }
}

static void
ppp_print_char (register __u8 * out, const __u8 * in, int count)
{
        register __u8 next_ch;

        while (count-- > 0) {
                next_ch = *in++;

                if (next_ch < 0x20 || next_ch > 0x7e)
                        *out++ = '.';
                else {
                        *out++ = next_ch;
                        if (next_ch == '%')   /* printk/syslogd has a bug !! */
                                *out++ = '%';
                }
        }
        *out = '\0';
}

static void
ppp_print_buffer (const __u8 * name, const __u8 * buf, int count)
{
        __u8 line[44];

        if (name != (__u8 *) NULL)
                printk (KERN_DEBUG "ppp: %s, count = %d\n", name, count);

        while (count > 8) {
                memset (line, 32, 44);
                ppp_print_hex (line, buf, 8);
                ppp_print_char (&line[8 * 3], buf, 8);
                printk (KERN_DEBUG "%s\n", line);
                count -= 8;
                buf += 8;
        }

        if (count > 0) {
                memset (line, 32, 44);
                ppp_print_hex (line, buf, count);
                ppp_print_char (&line[8 * 3], buf, count);
                printk (KERN_DEBUG "%s\n", line);
        }
}

/*************************************************************
 * Compressor module interface
 *************************************************************/

struct compressor_link {
        struct compressor_link  *next;
        struct compressor       *comp;
};

static struct compressor_link *ppp_compressors = (struct compressor_link *) 0;

static struct compressor *find_compressor (int type)
{
        struct compressor_link *lnk;
        unsigned long flags;

        save_flags(flags);
        cli();

        lnk = ppp_compressors;
        while (lnk != (struct compressor_link *) 0) {
                if ((int) (__u8) lnk->comp->compress_proto == type) {
                        restore_flags(flags);
                        return lnk->comp;
                }
                lnk = lnk->next;
        }

        restore_flags(flags);
        return (struct compressor *) 0;
}

static int ppp_register_compressor (struct compressor *cp)
{
        struct compressor_link *new;
        unsigned long flags;

        new = (struct compressor_link *) kmalloc (sizeof (struct compressor_link), GFP_KERNEL);

        if (new == (struct compressor_link *) 0)
                return 1;

        save_flags(flags);
        cli();

        if (find_compressor (cp->compress_proto)) {
                restore_flags(flags);
                kfree (new);
                return 0;
        }

        new->next       = ppp_compressors;
        new->comp       = cp;
        ppp_compressors = new;

        restore_flags(flags);
        return 0;
}

static void ppp_unregister_compressor (struct compressor *cp)
{
        struct compressor_link *prev = (struct compressor_link *) 0;
        struct compressor_link *lnk;
        unsigned long flags;

        save_flags(flags);
        cli();

        lnk  = ppp_compressors;
        while (lnk != (struct compressor_link *) 0) {
                if (lnk->comp == cp) {
                        if (prev)
                                prev->next = lnk->next;
                        else
                                ppp_compressors = lnk->next;
                        kfree (lnk);
                        break;
                }
                prev = lnk;
                lnk  = lnk->next;
        }
        restore_flags(flags);
}

/*************************************************************
 * Module support routines
 *************************************************************/

#ifdef MODULE
int
init_module(void)
{
        int status;

        /* register our line disciplines */
        status = ppp_first_time();
        if (status != 0)
                printk (KERN_INFO
                       "PPP: ppp_init() failure %d\n", status);
        else
                (void) register_symtab (&ppp_syms);
        return (status);
}

void
cleanup_module(void)
{
        int status;
        ppp_ctrl_t *ctl, *next_ctl;
        struct device *dev;
        struct ppp *ppp;
        int busy_flag = 0;
/*
 * Ensure that the devices are not in operation.
 */
        ctl = ppp_list;
        while (ctl) {
                ppp = ctl2ppp (ctl);
                if (ppp->inuse && ppp->tty != NULL) {
                        busy_flag = 1;
                        break;
                }

                dev = ctl2dev (ctl);
                if (dev->start || dev->flags & IFF_UP) {
                        busy_flag = 1;
                        break;
                }
                ctl = ctl->next;
        }
/*
 * Ensure that there are no compressor modules registered
 */
        if (ppp_compressors != NULL)
                busy_flag = 1;

        if (busy_flag) {
                printk (KERN_INFO
                        "PPP: device busy, remove delayed\n");
                return;
        }
/*
 * Release the tty registration of the line discipline so that no new entries
 * may be created.
 */
        status = tty_register_ldisc (N_PPP, NULL);
        if (status != 0)
                printk (KERN_INFO
                        "PPP: Unable to unregister ppp line discipline "
                        "(err = %d)\n", status);
        else
                printk (KERN_INFO
                       "PPP: ppp line discipline successfully unregistered\n");
/*
 * De-register the devices so that there is no problem with them
 */     
        next_ctl = ppp_list;
        while (next_ctl) {
                ctl      = next_ctl;
                next_ctl = ctl->next;
                ppp      = ctl2ppp (ctl);
                dev      = ctl2dev (ctl);

                ppp_release       (ppp);
                unregister_netdev (dev);
                kfree (ctl);
        }
}
#endif