pre-2.3.4..

[davej-history.git] / drivers / net / strip.c

/*
 * Copyright 1996 The Board of Trustees of The Leland Stanford
 * Junior University. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  Stanford University
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 *
 * strip.c      This module implements Starmode Radio IP (STRIP)
 *              for kernel-based devices like TTY.  It interfaces between a
 *              raw TTY, and the kernel's INET protocol layers (via DDI).
 *
 * Version:     @(#)strip.c     1.3     July 1997
 *
 * Author:      Stuart Cheshire <cheshire@cs.stanford.edu>
 *
 * Fixes:       v0.9 12th Feb 1996 (SC)
 *              New byte stuffing (2+6 run-length encoding)
 *              New watchdog timer task
 *              New Protocol key (SIP0)
 *              
 *              v0.9.1 3rd March 1996 (SC)
 *              Changed to dynamic device allocation -- no more compile
 *              time (or boot time) limit on the number of STRIP devices.
 *              
 *              v0.9.2 13th March 1996 (SC)
 *              Uses arp cache lookups (but doesn't send arp packets yet)
 *              
 *              v0.9.3 17th April 1996 (SC)
 *              Fixed bug where STR_ERROR flag was getting set unneccessarily
 *              (causing otherwise good packets to be unneccessarily dropped)
 *              
 *              v0.9.4 27th April 1996 (SC)
 *              First attempt at using "&COMMAND" Starmode AT commands
 *              
 *              v0.9.5 29th May 1996 (SC)
 *              First attempt at sending (unicast) ARP packets
 *              
 *              v0.9.6 5th June 1996 (Elliot)
 *              Put "message level" tags in every "printk" statement
 *              
 *              v0.9.7 13th June 1996 (laik)
 *              Added support for the /proc fs
 *
 *              v0.9.8 July 1996 (Mema)
 *              Added packet logging
 *
 *              v1.0 November 1996 (SC)
 *              Fixed (severe) memory leaks in the /proc fs code
 *              Fixed race conditions in the logging code
 *
 *              v1.1 January 1997 (SC)
 *              Deleted packet logging (use tcpdump instead)
 *              Added support for Metricom Firmware v204 features
 *              (like message checksums)
 *
 *              v1.2 January 1997 (SC)
 *              Put portables list back in
 *
 *              v1.3 July 1997 (SC)
 *              Made STRIP driver set the radio's baud rate automatically.
 *              It is no longer necessarily to manually set the radio's
 *              rate permanently to 115200 -- the driver handles setting
 *              the rate automatically.
 */

#ifdef MODULE
static const char StripVersion[] = "1.3-STUART.CHESHIRE-MODULAR";
#else
static const char StripVersion[] = "1.3-STUART.CHESHIRE";
#endif

#define TICKLE_TIMERS 0
#define EXT_COUNTERS 1


/************************************************************************/
/* Header files                                                         */

#include <linux/config.h>

#ifdef MODULE
#include <linux/module.h>
#include <linux/version.h>
#endif

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/segment.h>
#include <asm/bitops.h>

/*
 * isdigit() and isspace() use the ctype[] array, which is not available
 * to kernel modules.  If compiling as a module,  use  a local definition
 * of isdigit() and isspace() until  _ctype is added to ksyms.
 */
#ifdef MODULE
# define isdigit(c) ('0' <= (c) && (c)  <= '9')
# define isspace(c) ((c) == ' ' || (c)  == '\t')
#else
# include <linux/ctype.h>
#endif

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/if_strip.h>
#include <linux/proc_fs.h>
#include <linux/serial.h>
#include <net/arp.h>

#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/time.h>


/************************************************************************/
/* Useful structures and definitions                                    */

/*
 * A MetricomKey identifies the protocol being carried inside a Metricom
 * Starmode packet.
 */

typedef union
{
    __u8 c[4];
    __u32 l;
} MetricomKey;

/*
 * An IP address can be viewed as four bytes in memory (which is what it is) or as
 * a single 32-bit long (which is convenient for assignment, equality testing etc.)
 */

typedef union
{
    __u8 b[4];
    __u32 l;
} IPaddr;

/*
 * A MetricomAddressString is used to hold a printable representation of
 * a Metricom address.
 */

typedef struct
{
    __u8 c[24];
} MetricomAddressString;

/* Encapsulation can expand packet of size x to 65/64x + 1
 * Sent packet looks like "<CR>*<address>*<key><encaps payload><CR>"
 *                           1 1   1-18  1  4         ?         1
 * eg.                     <CR>*0000-1234*SIP0<encaps payload><CR>
 * We allow 31 bytes for the stars, the key, the address and the <CR>s
 */
#define STRIP_ENCAP_SIZE(X) (32 + (X)*65L/64L)

/*
 * A STRIP_Header is never really sent over the radio, but making a dummy
 * header for internal use within the kernel that looks like an Ethernet
 * header makes certain other software happier. For example, tcpdump
 * already understands Ethernet headers.
 */

typedef struct
{
    MetricomAddress dst_addr;           /* Destination address, e.g. "0000-1234"   */
    MetricomAddress src_addr;           /* Source address, e.g. "0000-5678"        */
    unsigned short  protocol;           /* The protocol type, using Ethernet codes */
} STRIP_Header;

typedef struct
{
    char c[60];
} MetricomNode;

#define NODE_TABLE_SIZE 32
typedef struct
{
    struct timeval timestamp;
    int            num_nodes;
    MetricomNode   node[NODE_TABLE_SIZE];
} MetricomNodeTable;

enum { FALSE = 0, TRUE = 1 };

/*
 * Holds the radio's firmware version.
 */
typedef struct
{
    char c[50];
} FirmwareVersion;

/*
 * Holds the radio's serial number.
 */
typedef struct
{
    char c[18];
} SerialNumber;

/*
 * Holds the radio's battery voltage.
 */
typedef struct
{
    char c[11];
} BatteryVoltage;

typedef struct
{
    char c[8];
} char8;

enum
{
    NoStructure = 0,            /* Really old firmware */
    StructuredMessages = 1,     /* Parsable AT response msgs */
    ChecksummedMessages = 2     /* Parsable AT response msgs with checksums */
} FirmwareLevel;

struct strip
{
    int magic;
    /*
     * These are pointers to the malloc()ed frame buffers.
     */

    unsigned char     *rx_buff;                 /* buffer for received IP packet*/
    unsigned char     *sx_buff;                 /* buffer for received serial data*/
    int                sx_count;                /* received serial data counter */
    int                sx_size;                 /* Serial buffer size           */
    unsigned char     *tx_buff;                 /* transmitter buffer           */
    unsigned char     *tx_head;                 /* pointer to next byte to XMIT */
    int                tx_left;                 /* bytes left in XMIT queue     */
    int                tx_size;                 /* Serial buffer size           */

    /*
     * STRIP interface statistics.
     */

    unsigned long      rx_packets;              /* inbound frames counter       */
    unsigned long      tx_packets;              /* outbound frames counter      */
    unsigned long      rx_errors;               /* Parity, etc. errors          */
    unsigned long      tx_errors;               /* Planned stuff                */
    unsigned long      rx_dropped;              /* No memory for skb            */
    unsigned long      tx_dropped;              /* When MTU change              */
    unsigned long      rx_over_errors;          /* Frame bigger then STRIP buf. */

    unsigned long      pps_timer;               /* Timer to determine pps       */
    unsigned long      rx_pps_count;            /* Counter to determine pps     */
    unsigned long      tx_pps_count;            /* Counter to determine pps     */
    unsigned long      sx_pps_count;            /* Counter to determine pps     */
    unsigned long      rx_average_pps;          /* rx packets per second * 8    */
    unsigned long      tx_average_pps;          /* tx packets per second * 8    */
    unsigned long      sx_average_pps;          /* sent packets per second * 8  */

#ifdef EXT_COUNTERS
    unsigned long      rx_bytes;                /* total received bytes */
    unsigned long      tx_bytes;                /* total received bytes */
    unsigned long      rx_rbytes;               /* bytes thru radio i/f */
    unsigned long      tx_rbytes;               /* bytes thru radio i/f */
    unsigned long      rx_sbytes;               /* tot bytes thru serial i/f */
    unsigned long      tx_sbytes;               /* tot bytes thru serial i/f */
    unsigned long      rx_ebytes;               /* tot stat/err bytes */
    unsigned long      tx_ebytes;               /* tot stat/err bytes */
#endif

    /*
     * Internal variables.
     */

    struct strip      *next;                    /* The next struct in the list  */
    struct strip     **referrer;                /* The pointer that points to us*/
    int                discard;                 /* Set if serial error          */
    int                working;                 /* Is radio working correctly?  */
    int                firmware_level;          /* Message structuring level    */
    int                next_command;            /* Next periodic command        */
    unsigned int       user_baud;               /* The user-selected baud rate  */
    int                mtu;                     /* Our mtu (to spot changes!)   */
    long               watchdog_doprobe;        /* Next time to test the radio  */
    long               watchdog_doreset;        /* Time to do next reset        */
    long               gratuitous_arp;          /* Time to send next ARP refresh*/
    long               arp_interval;            /* Next ARP interval            */
    struct timer_list  idle_timer;              /* For periodic wakeup calls    */
    MetricomAddress    true_dev_addr;           /* True address of radio        */
    int                manual_dev_addr;         /* Hack: See note below         */

    FirmwareVersion    firmware_version;        /* The radio's firmware version */
    SerialNumber       serial_number;           /* The radio's serial number    */
    BatteryVoltage     battery_voltage;         /* The radio's battery voltage  */

    /*
     * Other useful structures.
     */

    struct tty_struct *tty;                     /* ptr to TTY structure         */
    char8              if_name;                 /* Dynamically generated name   */
    struct device      dev;                     /* Our device structure         */

    /*
     * Neighbour radio records
     */

    MetricomNodeTable  portables;
    MetricomNodeTable  poletops;
};

/*
 * Note: manual_dev_addr hack
 * 
 * It is not possible to change the hardware address of a Metricom radio,
 * or to send packets with a user-specified hardware source address, thus
 * trying to manually set a hardware source address is a questionable
 * thing to do.  However, if the user *does* manually set the hardware
 * source address of a STRIP interface, then the kernel will believe it,
 * and use it in certain places. For example, the hardware address listed
 * by ifconfig will be the manual address, not the true one.
 * (Both addresses are listed in /proc/net/strip.)
 * Also, ARP packets will be sent out giving the user-specified address as
 * the source address, not the real address. This is dangerous, because
 * it means you won't receive any replies -- the ARP replies will go to
 * the specified address, which will be some other radio. The case where
 * this is useful is when that other radio is also connected to the same
 * machine. This allows you to connect a pair of radios to one machine,
 * and to use one exclusively for inbound traffic, and the other
 * exclusively for outbound traffic. Pretty neat, huh?
 * 
 * Here's the full procedure to set this up:
 * 
 * 1. "slattach" two interfaces, e.g. st0 for outgoing packets,
 *    and st1 for incoming packets
 * 
 * 2. "ifconfig" st0 (outbound radio) to have the hardware address
 *    which is the real hardware address of st1 (inbound radio).
 *    Now when it sends out packets, it will masquerade as st1, and
 *    replies will be sent to that radio, which is exactly what we want.
 * 
 * 3. Set the route table entry ("route add default ..." or
 *    "route add -net ...", as appropriate) to send packets via the st0
 *    interface (outbound radio). Do not add any route which sends packets
 *    out via the st1 interface -- that radio is for inbound traffic only.
 * 
 * 4. "ifconfig" st1 (inbound radio) to have hardware address zero.
 *    This tells the STRIP driver to "shut down" that interface and not
 *    send any packets through it. In particular, it stops sending the
 *    periodic gratuitous ARP packets that a STRIP interface normally sends.
 *    Also, when packets arrive on that interface, it will search the
 *    interface list to see if there is another interface who's manual
 *    hardware address matches its own real address (i.e. st0 in this
 *    example) and if so it will transfer ownership of the skbuff to
 *    that interface, so that it looks to the kernel as if the packet
 *    arrived on that interface. This is necessary because when the
 *    kernel sends an ARP packet on st0, it expects to get a reply on
 *    st0, and if it sees the reply come from st1 then it will ignore
 *    it (to be accurate, it puts the entry in the ARP table, but
 *    labelled in such a way that st0 can't use it).
 * 
 * Thanks to Petros Maniatis for coming up with the idea of splitting
 * inbound and outbound traffic between two interfaces, which turned
 * out to be really easy to implement, even if it is a bit of a hack.
 * 
 * Having set a manual address on an interface, you can restore it
 * to automatic operation (where the address is automatically kept
 * consistent with the real address of the radio) by setting a manual
 * address of all ones, e.g. "ifconfig st0 hw strip FFFFFFFFFFFF"
 * This 'turns off' manual override mode for the device address.
 * 
 * Note: The IEEE 802 headers reported in tcpdump will show the *real*
 * radio addresses the packets were sent and received from, so that you
 * can see what is really going on with packets, and which interfaces
 * they are really going through.
 */


/************************************************************************/
/* Constants                                                            */

/*
 * CommandString1 works on all radios
 * Other CommandStrings are only used with firmware that provides structured responses.
 * 
 * ats319=1 Enables Info message for node additions and deletions
 * ats319=2 Enables Info message for a new best node
 * ats319=4 Enables checksums
 * ats319=8 Enables ACK messages
 */

static const int MaxCommandStringLength = 32;
static const int CompatibilityCommand = 1;

static const char CommandString0[] = "*&COMMAND*ATS319=7";      /* Turn on checksums & info messages */
static const char CommandString1[] = "*&COMMAND*ATS305?";       /* Query radio name */
static const char CommandString2[] = "*&COMMAND*ATS325?";       /* Query battery voltage */
static const char CommandString3[] = "*&COMMAND*ATS300?";       /* Query version information */
static const char CommandString4[] = "*&COMMAND*ATS311?";       /* Query poletop list */
static const char CommandString5[] = "*&COMMAND*AT~LA";         /* Query portables list */
typedef struct { const char *string; long length; } StringDescriptor;

static const StringDescriptor CommandString[] =
    {
    { CommandString0, sizeof(CommandString0)-1 },
    { CommandString1, sizeof(CommandString1)-1 },
    { CommandString2, sizeof(CommandString2)-1 },
    { CommandString3, sizeof(CommandString3)-1 },
    { CommandString4, sizeof(CommandString4)-1 },
    { CommandString5, sizeof(CommandString5)-1 }
    };

#define GOT_ALL_RADIO_INFO(S)      \
    ((S)->firmware_version.c[0] && \
     (S)->battery_voltage.c[0]  && \
     memcmp(&(S)->true_dev_addr, zero_address.c, sizeof(zero_address)))

static const char            hextable[16]      = "0123456789ABCDEF";

static const MetricomAddress zero_address;
static const MetricomAddress broadcast_address = { { 0xFF,0xFF,0xFF,0xFF,0xFF,0xFF } };

static const MetricomKey     SIP0Key           = { { "SIP0" } };
static const MetricomKey     ARP0Key           = { { "ARP0" } };
static const MetricomKey     ATR_Key           = { { "ATR " } };
static const MetricomKey     ACK_Key           = { { "ACK_" } };
static const MetricomKey     INF_Key           = { { "INF_" } };
static const MetricomKey     ERR_Key           = { { "ERR_" } };

static const long            MaxARPInterval    = 60 * HZ;          /* One minute */

/*
 * Maximum Starmode packet length is 1183 bytes. Allowing 4 bytes for
 * protocol key, 4 bytes for checksum, one byte for CR, and 65/64 expansion
 * for STRIP encoding, that translates to a maximum payload MTU of 1155.
 * Note: A standard NFS 1K data packet is a total of 0x480 (1152) bytes
 * long, including IP header, UDP header, and NFS header. Setting the STRIP
 * MTU to 1152 allows us to send default sized NFS packets without fragmentation.
 */
static const unsigned short  MAX_SEND_MTU          = 1152;
static const unsigned short  MAX_RECV_MTU          = 1500; /* Hoping for Ethernet sized packets in the future! */
static const unsigned short  DEFAULT_STRIP_MTU      = 1152;
static const int             STRIP_MAGIC            = 0x5303;
static const long            LongTime               = 0x7FFFFFFF;


/************************************************************************/
/* Global variables                                                     */

static struct strip *struct_strip_list = NULL;


/************************************************************************/
/* Macros                                                               */

/* Returns TRUE if text T begins with prefix P */
#define has_prefix(T,L,P) (((L) >= sizeof(P)-1) && !strncmp((T), (P), sizeof(P)-1))

/* Returns TRUE if text T of length L is equal to string S */
#define text_equal(T,L,S) (((L) == sizeof(S)-1) && !strncmp((T), (S), sizeof(S)-1))

#define READHEX(X) ((X)>='0' && (X)<='9' ? (X)-'0' :      \
                    (X)>='a' && (X)<='f' ? (X)-'a'+10 :   \
                    (X)>='A' && (X)<='F' ? (X)-'A'+10 : 0 )

#define READHEX16(X) ((__u16)(READHEX(X)))

#define READDEC(X) ((X)>='0' && (X)<='9' ? (X)-'0' : 0)

#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
#define MAX(X, Y) ((X) > (Y) ? (X) : (Y))
#define ELEMENTS_OF(X) (sizeof(X) / sizeof((X)[0]))
#define ARRAY_END(X) (&((X)[ELEMENTS_OF(X)]))

#define JIFFIE_TO_SEC(X) ((X) / HZ)


/************************************************************************/
/* Utility routines                                                     */

typedef unsigned long InterruptStatus;

extern __inline__ InterruptStatus DisableInterrupts(void)
{
    InterruptStatus x;
    save_flags(x);
    cli();
    return(x);
}

extern __inline__ void RestoreInterrupts(InterruptStatus x)
{
    restore_flags(x);
}

static int arp_query(unsigned char *haddr, u32 paddr, struct device * dev)
{
    struct neighbour *neighbor_entry;

    neighbor_entry = neigh_lookup(&arp_tbl, &paddr, dev);

    if (neighbor_entry != NULL)
    {
        neighbor_entry->used = jiffies;
        if (neighbor_entry->nud_state & NUD_VALID)
        {
            memcpy(haddr, neighbor_entry->ha, dev->addr_len);
            return 1;
        }
    }
    return 0;
}

static void DumpData(char *msg, struct strip *strip_info, __u8 *ptr, __u8 *end)
{
    static const int MAX_DumpData = 80;
    __u8 pkt_text[MAX_DumpData], *p = pkt_text;

    *p++ = '\"';

    while (ptr<end && p < &pkt_text[MAX_DumpData-4])
    {
        if (*ptr == '\\')
        {
            *p++ = '\\';
            *p++ = '\\';
        }
        else
        {
            if (*ptr >= 32 && *ptr <= 126)
            {
                *p++ = *ptr;
            }
            else
            {
                sprintf(p, "\\%02X", *ptr);
                p+= 3;
            }
        }
        ptr++;
    }

    if (ptr == end)
    {
        *p++ = '\"';
    }

    *p++ = 0;

    printk(KERN_INFO "%s: %-13s%s\n", strip_info->dev.name, msg, pkt_text);
}

#if 0
static void HexDump(char *msg, struct strip *strip_info, __u8 *start, __u8 *end)
{
    __u8 *ptr = start;
    printk(KERN_INFO "%s: %s: %d bytes\n", strip_info->dev.name, msg, end-ptr);

    while (ptr < end)
    {
        long offset = ptr - start;
        __u8 text[80], *p = text;
        while (ptr < end && p < &text[16*3])
        {
            *p++ = hextable[*ptr >> 4];
            *p++ = hextable[*ptr++ & 0xF];
            *p++ = ' ';
        }
        p[-1] = 0;
        printk(KERN_INFO "%s: %4lX %s\n", strip_info->dev.name, offset, text);
    }
}
#endif


/************************************************************************/
/* Byte stuffing/unstuffing routines                                    */

/* Stuffing scheme:
 * 00    Unused (reserved character)
 * 01-3F Run of 2-64 different characters
 * 40-7F Run of 1-64 different characters plus a single zero at the end
 * 80-BF Run of 1-64 of the same character
 * C0-FF Run of 1-64 zeroes (ASCII 0)
 */

typedef enum
{
    Stuff_Diff      = 0x00,
    Stuff_DiffZero  = 0x40,
    Stuff_Same      = 0x80,
    Stuff_Zero      = 0xC0,
    Stuff_NoCode    = 0xFF,     /* Special code, meaning no code selected */

    Stuff_CodeMask  = 0xC0,
    Stuff_CountMask = 0x3F,
    Stuff_MaxCount  = 0x3F,
    Stuff_Magic     = 0x0D      /* The value we are eliminating */
} StuffingCode;

/* StuffData encodes the data starting at "src" for "length" bytes.
 * It writes it to the buffer pointed to by "dst" (which must be at least
 * as long as 1 + 65/64 of the input length). The output may be up to 1.6%
 * larger than the input for pathological input, but will usually be smaller.
 * StuffData returns the new value of the dst pointer as its result.
 * "code_ptr_ptr" points to a "__u8 *" which is used to hold encoding state
 * between calls, allowing an encoded packet to be incrementally built up
 * from small parts. On the first call, the "__u8 *" pointed to should be
 * initialized to NULL; between subsequent calls the calling routine should
 * leave the value alone and simply pass it back unchanged so that the
 * encoder can recover its current state.
 */

#define StuffData_FinishBlock(X) \
(*code_ptr = (X) ^ Stuff_Magic, code = Stuff_NoCode)

static __u8 *StuffData(__u8 *src, __u32 length, __u8 *dst, __u8 **code_ptr_ptr)
{
    __u8 *end = src + length;
    __u8 *code_ptr = *code_ptr_ptr;
     __u8 code = Stuff_NoCode, count = 0;

    if (!length)
        return(dst);

    if (code_ptr)
    {
        /*
         * Recover state from last call, if applicable
         */
        code  = (*code_ptr ^ Stuff_Magic) & Stuff_CodeMask;
        count = (*code_ptr ^ Stuff_Magic) & Stuff_CountMask;
    }

    while (src < end)
    {
        switch (code)
        {
            /* Stuff_NoCode: If no current code, select one */
            case Stuff_NoCode:
                /* Record where we're going to put this code */
                code_ptr = dst++;
                count = 0;    /* Reset the count (zero means one instance) */
                /* Tentatively start a new block */
                if (*src == 0)
                {
                    code = Stuff_Zero;
                    src++;
                }
                else
                {
                    code = Stuff_Same;
                    *dst++ = *src++ ^ Stuff_Magic;
                }
                /* Note: We optimistically assume run of same -- */
                /* which will be fixed later in Stuff_Same */
                /* if it turns out not to be true. */
                break;

            /* Stuff_Zero: We already have at least one zero encoded */
            case Stuff_Zero:
                /* If another zero, count it, else finish this code block */
                if (*src == 0)
                {
                    count++;
                    src++;
                }
                else
                {
                    StuffData_FinishBlock(Stuff_Zero + count);
                }
                break;

            /* Stuff_Same: We already have at least one byte encoded */
            case Stuff_Same:
                /* If another one the same, count it */
                if ((*src ^ Stuff_Magic) == code_ptr[1])
                {
                    count++;
                    src++;
                    break;
                }
                /* else, this byte does not match this block. */
                /* If we already have two or more bytes encoded, finish this code block */
                if (count)
                {
                    StuffData_FinishBlock(Stuff_Same + count);
                    break;
                }
                /* else, we only have one so far, so switch to Stuff_Diff code */
                code = Stuff_Diff;
                /* and fall through to Stuff_Diff case below
                 * Note cunning cleverness here: case Stuff_Diff compares 
                 * the current character with the previous two to see if it
                 * has a run of three the same. Won't this be an error if
                 * there aren't two previous characters stored to compare with?
                 * No. Because we know the current character is *not* the same
                 * as the previous one, the first test below will necessarily
                 * fail and the send half of the "if" won't be executed.
                 */

            /* Stuff_Diff: We have at least two *different* bytes encoded */
            case Stuff_Diff:
                /* If this is a zero, must encode a Stuff_DiffZero, and begin a new block */
                if (*src == 0)
                {
                    StuffData_FinishBlock(Stuff_DiffZero + count);
                }
                /* else, if we have three in a row, it is worth starting a Stuff_Same block */
                else if ((*src ^ Stuff_Magic)==dst[-1] && dst[-1]==dst[-2])
                {
                    /* Back off the last two characters we encoded */
                    code += count-2;
                    /* Note: "Stuff_Diff + 0" is an illegal code */
                    if (code == Stuff_Diff + 0)
                    {
                        code = Stuff_Same + 0;
                    }
                    StuffData_FinishBlock(code);
                    code_ptr = dst-2;
                    /* dst[-1] already holds the correct value */
                    count = 2;        /* 2 means three bytes encoded */
                    code = Stuff_Same;
                }
                /* else, another different byte, so add it to the block */
                else
                {
                    *dst++ = *src ^ Stuff_Magic;
                    count++;
                }
                src++;    /* Consume the byte */
                break;
        }
        if (count == Stuff_MaxCount)
        {
            StuffData_FinishBlock(code + count);
        }
    }
    if (code == Stuff_NoCode)
    {
        *code_ptr_ptr = NULL;
    }
    else
    {
        *code_ptr_ptr = code_ptr;
        StuffData_FinishBlock(code + count);
    }
    return(dst);
}

/*
 * UnStuffData decodes the data at "src", up to (but not including) "end".
 * It writes the decoded data into the buffer pointed to by "dst", up to a
 * maximum of "dst_length", and returns the new value of "src" so that a
 * follow-on call can read more data, continuing from where the first left off.
 * 
 * There are three types of results:
 * 1. The source data runs out before extracting "dst_length" bytes:
 *    UnStuffData returns NULL to indicate failure.
 * 2. The source data produces exactly "dst_length" bytes:
 *    UnStuffData returns new_src = end to indicate that all bytes were consumed.
 * 3. "dst_length" bytes are extracted, with more remaining.
 *    UnStuffData returns new_src < end to indicate that there are more bytes
 *    to be read.
 * 
 * Note: The decoding may be destructive, in that it may alter the source
 * data in the process of decoding it (this is necessary to allow a follow-on
 * call to resume correctly).
 */

static __u8 *UnStuffData(__u8 *src, __u8 *end, __u8 *dst, __u32 dst_length)
{
    __u8 *dst_end = dst + dst_length;
    /* Sanity check */
    if (!src || !end || !dst || !dst_length)
        return(NULL);
    while (src < end && dst < dst_end)
    {
        int count = (*src ^ Stuff_Magic) & Stuff_CountMask;
        switch ((*src ^ Stuff_Magic) & Stuff_CodeMask)
        {
            case Stuff_Diff:
                if (src+1+count >= end)
                    return(NULL);
                do
                {
                    *dst++ = *++src ^ Stuff_Magic;
                }
                while(--count >= 0 && dst < dst_end);
                if (count < 0)
                    src += 1;
                else
                {
                    if (count == 0)
                        *src = Stuff_Same ^ Stuff_Magic;
                    else
                        *src = (Stuff_Diff + count) ^ Stuff_Magic;
                }
                break;
            case Stuff_DiffZero:
                if (src+1+count >= end)
                    return(NULL);
                do
                {
                    *dst++ = *++src ^ Stuff_Magic;
                }
                while(--count >= 0 && dst < dst_end);
                if (count < 0)
                    *src = Stuff_Zero ^ Stuff_Magic;
                else
                    *src = (Stuff_DiffZero + count) ^ Stuff_Magic;
                break;
            case Stuff_Same:
                if (src+1 >= end)
                    return(NULL);
                do
                {
                    *dst++ = src[1] ^ Stuff_Magic;
                }
                while(--count >= 0 && dst < dst_end);
                if (count < 0)
                    src += 2;
                else
                    *src = (Stuff_Same + count) ^ Stuff_Magic;
                break;
            case Stuff_Zero:
                do
                {
                    *dst++ = 0;
                }
                while(--count >= 0 && dst < dst_end);
                if (count < 0)
                    src += 1;
                else
                    *src = (Stuff_Zero + count) ^ Stuff_Magic;
                break;
        }
    }
    if (dst < dst_end)
        return(NULL);
    else
        return(src);
}


/************************************************************************/
/* General routines for STRIP                                           */

/*
 * get_baud returns the current baud rate, as one of the constants defined in
 * termbits.h
 * If the user has issued a baud rate override using the 'setserial' command
 * and the logical current rate is set to 38.4, then the true baud rate
 * currently in effect (57.6 or 115.2) is returned.
 */
static unsigned int get_baud(struct tty_struct *tty)
    {
    if (!tty || !tty->termios) return(0);
    if ((tty->termios->c_cflag & CBAUD) == B38400 && tty->driver_data)
        {
        struct async_struct *info = (struct async_struct *)tty->driver_data;
        if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI ) return(B57600);
        if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI) return(B115200);
        }
    return(tty->termios->c_cflag & CBAUD);
    }

/*
 * set_baud sets the baud rate to the rate defined by baudcode
 * Note: The rate B38400 should be avoided, because the user may have
 * issued a 'setserial' speed override to map that to a different speed.
 * We could achieve a true rate of 38400 if we needed to by cancelling
 * any user speed override that is in place, but that might annoy the
 * user, so it is simplest to just avoid using 38400.
 */
static void set_baud(struct tty_struct *tty, unsigned int baudcode)
    {
    struct termios old_termios = *(tty->termios);
    tty->termios->c_cflag &= ~CBAUD; /* Clear the old baud setting */
    tty->termios->c_cflag |= baudcode; /* Set the new baud setting */
    tty->driver.set_termios(tty, &old_termios);
    }

/*
 * Convert a string to a Metricom Address.
 */

#define IS_RADIO_ADDRESS(p) (                                                 \
  isdigit((p)[0]) && isdigit((p)[1]) && isdigit((p)[2]) && isdigit((p)[3]) && \
  (p)[4] == '-' &&                                                            \
  isdigit((p)[5]) && isdigit((p)[6]) && isdigit((p)[7]) && isdigit((p)[8])    )

static int string_to_radio_address(MetricomAddress *addr, __u8 *p)
{
    if (!IS_RADIO_ADDRESS(p)) return(1);
    addr->c[0] = 0;
    addr->c[1] = 0;
    addr->c[2] = READHEX(p[0]) << 4 | READHEX(p[1]);
    addr->c[3] = READHEX(p[2]) << 4 | READHEX(p[3]);
    addr->c[4] = READHEX(p[5]) << 4 | READHEX(p[6]);
    addr->c[5] = READHEX(p[7]) << 4 | READHEX(p[8]);
    return(0);
}

/*
 * Convert a Metricom Address to a string.
 */

static __u8 *radio_address_to_string(const MetricomAddress *addr, MetricomAddressString *p)
{
    sprintf(p->c, "%02X%02X-%02X%02X", addr->c[2], addr->c[3], addr->c[4], addr->c[5]);
    return(p->c);
}

/*
 * Note: Must make sure sx_size is big enough to receive a stuffed
 * MAX_RECV_MTU packet. Additionally, we also want to ensure that it's
 * big enough to receive a large radio neighbour list (currently 4K).
 */

static int allocate_buffers(struct strip *strip_info)
{
    struct device *dev = &strip_info->dev;
    int sx_size    = MAX(STRIP_ENCAP_SIZE(MAX_RECV_MTU), 4096);
    int tx_size    = STRIP_ENCAP_SIZE(dev->mtu) + MaxCommandStringLength;
    __u8 *r = kmalloc(MAX_RECV_MTU, GFP_ATOMIC);
    __u8 *s = kmalloc(sx_size,      GFP_ATOMIC);
    __u8 *t = kmalloc(tx_size,      GFP_ATOMIC);
    if (r && s && t)
    {
        strip_info->rx_buff = r;
        strip_info->sx_buff = s;
        strip_info->tx_buff = t;
        strip_info->sx_size = sx_size;
        strip_info->tx_size = tx_size;
        strip_info->mtu     = dev->mtu;
        return(1);
    }
    if (r) kfree(r);
    if (s) kfree(s);
    if (t) kfree(t);
    return(0);
}

/*
 * 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 void strip_changedmtu(struct strip *strip_info)
{
    int old_mtu           = strip_info->mtu;
    struct device *dev    = &strip_info->dev;
    unsigned char *orbuff = strip_info->rx_buff;
    unsigned char *osbuff = strip_info->sx_buff;
    unsigned char *otbuff = strip_info->tx_buff;
    InterruptStatus intstat;

    if (dev->mtu > MAX_SEND_MTU)
    {
        printk(KERN_ERR "%s: MTU exceeds maximum allowable (%d), MTU change cancelled.\n",
            strip_info->dev.name, MAX_SEND_MTU);
        dev->mtu = old_mtu;
        return;
    }

    /*
     * Have to disable interrupts here because we're reallocating and resizing
     * the serial buffers, and we can't have data arriving in them while we're
     * moving them around in memory. This may cause data to be lost on the serial
     * port, but hopefully people won't change MTU that often.
     * Also note, this may not work on a symmetric multi-processor system.
     */
    intstat = DisableInterrupts();

    if (!allocate_buffers(strip_info))
    {
        RestoreInterrupts(intstat);
        printk(KERN_ERR "%s: unable to grow strip buffers, MTU change cancelled.\n",
            strip_info->dev.name);
        dev->mtu = old_mtu;
        return;
    }

    if (strip_info->sx_count)
    {
        if (strip_info->sx_count <= strip_info->sx_size)
            memcpy(strip_info->sx_buff, osbuff, strip_info->sx_count);
        else
        {
            strip_info->discard = strip_info->sx_count;
            strip_info->rx_over_errors++;
        }
    }

    if (strip_info->tx_left)
    {
        if (strip_info->tx_left <= strip_info->tx_size)
            memcpy(strip_info->tx_buff, strip_info->tx_head, strip_info->tx_left);
        else
        {
            strip_info->tx_left = 0;
            strip_info->tx_dropped++;
        }
    }
    strip_info->tx_head = strip_info->tx_buff;

    RestoreInterrupts(intstat);

    printk(KERN_NOTICE "%s: strip MTU changed fom %d to %d.\n",
        strip_info->dev.name, old_mtu, strip_info->mtu);

    if (orbuff) kfree(orbuff);
    if (osbuff) kfree(osbuff);
    if (otbuff) kfree(otbuff);
}

static void strip_unlock(struct strip *strip_info)
{
    /*
     * Set the timer to go off in one second.
     */
    strip_info->idle_timer.expires = jiffies + 1*HZ;
    add_timer(&strip_info->idle_timer);
    if (!test_and_clear_bit(0, (void *)&strip_info->dev.tbusy))
        printk(KERN_ERR "%s: trying to unlock already unlocked device!\n",
            strip_info->dev.name);
}


/************************************************************************/
/* Callback routines for exporting information through /proc            */

/*
 * This function updates the total amount of data printed so far. It then
 * determines if the amount of data printed into a buffer  has reached the
 * offset requested. If it hasn't, then the buffer is shifted over so that
 * the next bit of data can be printed over the old bit. If the total
 * amount printed so far exceeds the total amount requested, then this
 * function returns 1, otherwise 0.
 */
static int 
shift_buffer(char *buffer, int requested_offset, int requested_len,
             int *total, int *slop, char **buf)
{
    int printed;

    /* printk(KERN_DEBUG "shift: buffer: %d o: %d l: %d t: %d buf: %d\n",
           (int) buffer, requested_offset, requested_len, *total,
           (int) *buf); */
    printed = *buf - buffer;
    if (*total + printed <= requested_offset) {
        *total += printed;
        *buf = buffer;
    }
    else {
        if (*total < requested_offset) {
            *slop = requested_offset - *total;
        }
        *total = requested_offset + printed - *slop;
    }
    if (*total > requested_offset + requested_len) {
        return 1;
    }
    else {
        return 0;
    }
}

/*
 * This function calculates the actual start of the requested data
 * in the buffer. It also calculates actual length of data returned,
 * which could be less that the amount of data requested.
 */
static int
calc_start_len(char *buffer, char **start, int requested_offset,
               int requested_len, int total, char *buf)
{
    int return_len, buffer_len;

    buffer_len = buf - buffer;
    if (buffer_len >= 4095) {
        printk(KERN_ERR "STRIP: exceeded /proc buffer size\n");
    }

    /*
     * There may be bytes before and after the
     * chunk that was actually requested.
     */
    return_len = total - requested_offset;
    if (return_len < 0) {
        return_len = 0;
    }
    *start = buf - return_len;
    if (return_len > requested_len) {
        return_len = requested_len;
    }
    /* printk(KERN_DEBUG "return_len: %d\n", return_len); */
    return return_len;
}

/*
 * If the time is in the near future, time_delta prints the number of
 * seconds to go into the buffer and returns the address of the buffer.
 * If the time is not in the near future, it returns the address of the
 * string "Not scheduled" The buffer must be long enough to contain the
 * ascii representation of the number plus 9 charactes for the " seconds"
 * and the null character.
 */
static char *time_delta(char buffer[], long time)
{
    time -= jiffies;
    if (time > LongTime / 2) return("Not scheduled");
    if(time < 0) time = 0;  /* Don't print negative times */
    sprintf(buffer, "%ld seconds", time / HZ);
    return(buffer);
}

static int sprintf_neighbours(char *buffer, MetricomNodeTable *table, char *title)
{
    /* We wrap this in a do/while loop, so if the table changes */
    /* while we're reading it, we just go around and try again. */
    struct timeval t;
    char *ptr;
    do
        {
        int i;
        t = table->timestamp;
        ptr = buffer;
        if (table->num_nodes) ptr += sprintf(ptr, "\n %s\n", title);
        for (i=0; i<table->num_nodes; i++)
            {
            InterruptStatus intstat = DisableInterrupts();
            MetricomNode node = table->node[i];
            RestoreInterrupts(intstat);
            ptr += sprintf(ptr, "  %s\n", node.c);
            }
        } while (table->timestamp.tv_sec != t.tv_sec || table->timestamp.tv_usec != t.tv_usec);
    return ptr - buffer;
}

/*
 * This function prints radio status information into the specified buffer.
 * I think the buffer size is 4K, so this routine should never print more
 * than 4K of data into it. With the maximum of 32 portables and 32 poletops
 * reported, the routine outputs 3107 bytes into the buffer.
 */
static int
sprintf_status_info(char *buffer, struct strip *strip_info)
{
    char temp[32];
    char *p = buffer;
    MetricomAddressString addr_string;

    /* First, we must copy all of our data to a safe place, */
    /* in case a serial interrupt comes in and changes it.  */
    InterruptStatus intstat = DisableInterrupts();
    int                tx_left             = strip_info->tx_left;
    unsigned long      rx_average_pps      = strip_info->rx_average_pps;
    unsigned long      tx_average_pps      = strip_info->tx_average_pps;
    unsigned long      sx_average_pps      = strip_info->sx_average_pps;
    int                working             = strip_info->working;
    int                firmware_level      = strip_info->firmware_level;
    long               watchdog_doprobe    = strip_info->watchdog_doprobe;
    long               watchdog_doreset    = strip_info->watchdog_doreset;
    long               gratuitous_arp      = strip_info->gratuitous_arp;
    long               arp_interval        = strip_info->arp_interval;
    FirmwareVersion    firmware_version    = strip_info->firmware_version;
    SerialNumber       serial_number       = strip_info->serial_number;
    BatteryVoltage     battery_voltage     = strip_info->battery_voltage;
    char8              if_name             = strip_info->if_name;
    MetricomAddress    true_dev_addr       = strip_info->true_dev_addr;
    MetricomAddress    dev_dev_addr        = *(MetricomAddress*)strip_info->dev.dev_addr;
    int                manual_dev_addr     = strip_info->manual_dev_addr;
#ifdef EXT_COUNTERS
    unsigned long      rx_bytes            = strip_info->rx_bytes;
    unsigned long      tx_bytes            = strip_info->tx_bytes;
    unsigned long      rx_rbytes           = strip_info->rx_rbytes;
    unsigned long      tx_rbytes           = strip_info->tx_rbytes;
    unsigned long      rx_sbytes           = strip_info->rx_sbytes;
    unsigned long      tx_sbytes           = strip_info->tx_sbytes;
    unsigned long      rx_ebytes           = strip_info->rx_ebytes;
    unsigned long      tx_ebytes           = strip_info->tx_ebytes;
#endif
    RestoreInterrupts(intstat);

    p += sprintf(p, "\nInterface name\t\t%s\n", if_name.c);
    p += sprintf(p, " Radio working:\t\t%s\n", working ? "Yes" : "No");
    radio_address_to_string(&true_dev_addr, &addr_string);
    p += sprintf(p, " Radio address:\t\t%s\n", addr_string.c);
    if (manual_dev_addr)
    {
        radio_address_to_string(&dev_dev_addr, &addr_string);
        p += sprintf(p, " Device address:\t%s\n", addr_string.c);
    }
    p += sprintf(p, " Firmware version:\t%s", !working        ? "Unknown" :
                                              !firmware_level ? "Should be upgraded" :
                                              firmware_version.c);
    if (firmware_level >= ChecksummedMessages) p += sprintf(p, " (Checksums Enabled)");
    p += sprintf(p, "\n");
    p += sprintf(p, " Serial number:\t\t%s\n", serial_number.c);
    p += sprintf(p, " Battery voltage:\t%s\n", battery_voltage.c);
    p += sprintf(p, " Transmit queue (bytes):%d\n", tx_left);
    p += sprintf(p, " Receive packet rate:   %ld packets per second\n", rx_average_pps / 8);
    p += sprintf(p, " Transmit packet rate:  %ld packets per second\n", tx_average_pps / 8);
    p += sprintf(p, " Sent packet rate:      %ld packets per second\n", sx_average_pps / 8);
    p += sprintf(p, " Next watchdog probe:\t%s\n", time_delta(temp, watchdog_doprobe));
    p += sprintf(p, " Next watchdog reset:\t%s\n", time_delta(temp, watchdog_doreset));
    p += sprintf(p, " Next gratuitous ARP:\t");

    if (!memcmp(strip_info->dev.dev_addr, zero_address.c, sizeof(zero_address)))
        p += sprintf(p, "Disabled\n");
    else
    {
        p += sprintf(p, "%s\n", time_delta(temp, gratuitous_arp));
        p += sprintf(p, " Next ARP interval:\t%ld seconds\n", JIFFIE_TO_SEC(arp_interval));
    }

    if (working)
        {
#ifdef EXT_COUNTERS
          p += sprintf(p, "\n");
          p += sprintf(p, " Total bytes:         \trx:\t%lu\ttx:\t%lu\n", rx_bytes, tx_bytes);
          p += sprintf(p, "  thru radio:         \trx:\t%lu\ttx:\t%lu\n", rx_rbytes, tx_rbytes);
          p += sprintf(p, "  thru serial port:   \trx:\t%lu\ttx:\t%lu\n", rx_sbytes, tx_sbytes);
          p += sprintf(p, " Total stat/err bytes:\trx:\t%lu\ttx:\t%lu\n", rx_ebytes, tx_ebytes);
#endif
        p += sprintf_neighbours(p, &strip_info->poletops, "Poletops:");
        p += sprintf_neighbours(p, &strip_info->portables, "Portables:");
        }

    return p - buffer;
}

/*
 * This function is exports status information from the STRIP driver through
 * the /proc file system.
 */

static int get_status_info(char *buffer, char **start, off_t req_offset, int req_len, int dummy)
{
    int           total = 0, slop = 0;
    struct strip *strip_info = struct_strip_list;
    char         *buf = buffer;

    buf += sprintf(buf, "strip_version: %s\n", StripVersion);
    if (shift_buffer(buffer, req_offset, req_len, &total, &slop, &buf)) goto exit;

    while (strip_info != NULL)
        {
        buf += sprintf_status_info(buf, strip_info);
        if (shift_buffer(buffer, req_offset, req_len, &total, &slop, &buf)) break;
        strip_info = strip_info->next;
        }
    exit:
    return(calc_start_len(buffer, start, req_offset, req_len, total, buf));
}

static const char proc_strip_status_name[] = "strip";

#ifdef CONFIG_PROC_FS
static struct proc_dir_entry proc_strip_get_status_info =
{
    PROC_NET_STRIP_STATUS,              /* unsigned short low_ino */
    sizeof(proc_strip_status_name)-1,   /* unsigned short namelen */
    proc_strip_status_name,             /* const char *name */
    S_IFREG | S_IRUGO,                  /* mode_t mode */
    1,                                  /* nlink_t nlink */
    0, 0, 0,                            /* uid_t uid, gid_t gid, unsigned long size */
    &proc_net_inode_operations,         /* struct inode_operations * ops */
    &get_status_info,                   /* int (*get_info)(...) */
    NULL,                               /* void (*fill_inode)(struct inode *); */
    NULL, NULL, NULL,                   /* struct proc_dir_entry *next, *parent, *subdir; */
    NULL                                /* void *data; */
};
#endif /* CONFIG_PROC_FS */

/************************************************************************/
/* Sending routines                                                     */

static void ResetRadio(struct strip *strip_info)
{
    struct tty_struct *tty = strip_info->tty;
    static const char init[] = "ate0q1dt**starmode\r**";
    StringDescriptor s = { init, sizeof(init)-1 };

    /* 
     * If the radio isn't working anymore,
     * we should clear the old status information.
     */
    if (strip_info->working)
    {
        printk(KERN_INFO "%s: No response: Resetting radio.\n", strip_info->dev.name);
        strip_info->firmware_version.c[0] = '\0';
        strip_info->serial_number.c[0] = '\0';
        strip_info->battery_voltage.c[0] = '\0';
        strip_info->portables.num_nodes = 0;
        do_gettimeofday(&strip_info->portables.timestamp);
        strip_info->poletops.num_nodes = 0;
        do_gettimeofday(&strip_info->poletops.timestamp);
    }

    strip_info->pps_timer      = jiffies;
    strip_info->rx_pps_count   = 0;
    strip_info->tx_pps_count   = 0;
    strip_info->sx_pps_count   = 0;
    strip_info->rx_average_pps = 0;
    strip_info->tx_average_pps = 0;
    strip_info->sx_average_pps = 0;

    /* Mark radio address as unknown */
    *(MetricomAddress*)&strip_info->true_dev_addr = zero_address;
    if (!strip_info->manual_dev_addr)
        *(MetricomAddress*)strip_info->dev.dev_addr = zero_address;
    strip_info->working = FALSE;
    strip_info->firmware_level = NoStructure;
    strip_info->next_command   = CompatibilityCommand;
    strip_info->watchdog_doprobe = jiffies + 10 * HZ;
    strip_info->watchdog_doreset = jiffies + 1 * HZ;

    /* If the user has selected a baud rate above 38.4 see what magic we have to do */
    if (strip_info->user_baud > B38400)
        {
        /*
         * Subtle stuff: Pay attention :-)
         * If the serial port is currently at the user's selected (>38.4) rate,
         * then we temporarily switch to 19.2 and issue the ATS304 command
         * to tell the radio to switch to the user's selected rate.
         * If the serial port is not currently at that rate, that means we just
         * issued the ATS304 command last time through, so this time we restore
         * the user's selected rate and issue the normal starmode reset string.
         */
        if (strip_info->user_baud == get_baud(tty))
            {
            static const char b0[] = "ate0q1s304=57600\r";
            static const char b1[] = "ate0q1s304=115200\r";
            static const StringDescriptor baudstring[2] =
                { { b0, sizeof(b0)-1 }, { b1, sizeof(b1)-1 } };
            set_baud(tty, B19200);
            if      (strip_info->user_baud == B57600 ) s = baudstring[0];
            else if (strip_info->user_baud == B115200) s = baudstring[1];
            else s = baudstring[1]; /* For now */
            }
        else set_baud(tty, strip_info->user_baud);
        }

    tty->driver.write(tty, 0, s.string, s.length);
#ifdef EXT_COUNTERS
    strip_info->tx_ebytes += s.length;
#endif
}

/*
 * Called by the driver when there's room for more data.  If we have
 * more packets to send, we send them here.
 */

static void strip_write_some_more(struct tty_struct *tty)
{
    struct strip *strip_info = (struct strip *) tty->disc_data;

    /* First make sure we're connected. */
    if (!strip_info || strip_info->magic != STRIP_MAGIC || !strip_info->dev.start)
        return;

    if (strip_info->tx_left > 0)
    {
        /*
         * If some data left, send it
         * Note: There's a kernel design bug here. The write_wakeup routine has to
         * know how many bytes were written in the previous call, but the number of
         * bytes written is returned as the result of the tty->driver.write call,
         * and there's no guarantee that the tty->driver.write routine will have
         * returned before the write_wakeup routine is invoked. If the PC has fast
         * Serial DMA hardware, then it's quite possible that the write could complete
         * almost instantaneously, meaning that my write_wakeup routine could be
         * called immediately, before tty->driver.write has had a chance to return
         * the number of bytes that it wrote. In an attempt to guard against this,
         * I disable interrupts around the call to tty->driver.write, although even
         * this might not work on a symmetric multi-processor system.
         */
        InterruptStatus intstat = DisableInterrupts();
        int num_written = tty->driver.write(tty, 0, strip_info->tx_head, strip_info->tx_left);
        strip_info->tx_left -= num_written;
        strip_info->tx_head += num_written;
#ifdef EXT_COUNTERS
        strip_info->tx_sbytes += num_written;
#endif
        RestoreInterrupts(intstat);
    }
    else            /* Else start transmission of another packet */
    {
        tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
        strip_unlock(strip_info);
        mark_bh(NET_BH);
    }
}

static __u8 *add_checksum(__u8 *buffer, __u8 *end)
{
    __u16 sum = 0;
    __u8 *p = buffer;
    while (p < end) sum += *p++;
    end[3] = hextable[sum & 0xF]; sum >>= 4;
    end[2] = hextable[sum & 0xF]; sum >>= 4;
    end[1] = hextable[sum & 0xF]; sum >>= 4;
    end[0] = hextable[sum & 0xF];
    return(end+4);
}

static unsigned char *strip_make_packet(unsigned char *buffer, struct strip *strip_info, struct sk_buff *skb)
{
    __u8           *ptr = buffer;
    __u8           *stuffstate = NULL;
    STRIP_Header   *header     = (STRIP_Header *)skb->data;
    MetricomAddress haddr      = header->dst_addr;
    int             len        = skb->len - sizeof(STRIP_Header);
    MetricomKey     key;

    /*HexDump("strip_make_packet", strip_info, skb->data, skb->data + skb->len);*/

    if      (header->protocol == htons(ETH_P_IP))  key = SIP0Key;
    else if (header->protocol == htons(ETH_P_ARP)) key = ARP0Key;
    else
    {
        printk(KERN_ERR "%s: strip_make_packet: Unknown packet type 0x%04X\n",
            strip_info->dev.name, ntohs(header->protocol));
        return(NULL);
    }

    if (len > strip_info->mtu)
    {
        printk(KERN_ERR "%s: Dropping oversized transmit packet: %d bytes\n",
            strip_info->dev.name, len);
        return(NULL);
    }

    /*
     * If we're sending to ourselves, discard the packet.
     * (Metricom radios choke if they try to send a packet to their own address.)
     */
    if (!memcmp(haddr.c, strip_info->true_dev_addr.c, sizeof(haddr)))
    {
        printk(KERN_ERR "%s: Dropping packet addressed to self\n", strip_info->dev.name);
        return(NULL);
    }

    /*
     * If this is a broadcast packet, send it to our designated Metricom
     * 'broadcast hub' radio (First byte of address being 0xFF means broadcast)
     */
    if (haddr.c[0] == 0xFF)
    {
        struct in_device *in_dev = strip_info->dev.ip_ptr;
        /* arp_query returns 1 if it succeeds in looking up the address, 0 if it fails */
        if (!arp_query(haddr.c, in_dev->ifa_list->ifa_broadcast, &strip_info->dev))
        {
            printk(KERN_ERR "%s: Unable to send packet (no broadcast hub configured)\n",
                strip_info->dev.name);
            return(NULL);
        }
        /*
         * If we are the broadcast hub, don't bother sending to ourselves.
         * (Metricom radios choke if they try to send a packet to their own address.)
         */
        if (!memcmp(haddr.c, strip_info->true_dev_addr.c, sizeof(haddr))) return(NULL);
    }

    *ptr++ = 0x0D;
    *ptr++ = '*';
    *ptr++ = hextable[haddr.c[2] >> 4];
    *ptr++ = hextable[haddr.c[2] & 0xF];
    *ptr++ = hextable[haddr.c[3] >> 4];
    *ptr++ = hextable[haddr.c[3] & 0xF];
    *ptr++ = '-';
    *ptr++ = hextable[haddr.c[4] >> 4];
    *ptr++ = hextable[haddr.c[4] & 0xF];
    *ptr++ = hextable[haddr.c[5] >> 4];
    *ptr++ = hextable[haddr.c[5] & 0xF];
    *ptr++ = '*';
    *ptr++ = key.c[0];
    *ptr++ = key.c[1];
    *ptr++ = key.c[2];
    *ptr++ = key.c[3];

    ptr = StuffData(skb->data + sizeof(STRIP_Header), len, ptr, &stuffstate);

    if (strip_info->firmware_level >= ChecksummedMessages) ptr = add_checksum(buffer+1, ptr);

    *ptr++ = 0x0D;
    return(ptr);
}

static void strip_send(struct strip *strip_info, struct sk_buff *skb)
{
    MetricomAddress haddr;
    unsigned char *ptr = strip_info->tx_buff;
    int doreset = (long)jiffies - strip_info->watchdog_doreset >= 0;
    int doprobe = (long)jiffies - strip_info->watchdog_doprobe >= 0 && !doreset;
    struct in_device *in_dev = strip_info->dev.ip_ptr;

    /*
     * 1. If we have a packet, encapsulate it and put it in the buffer
     */
    if (skb)
    {
        char *newptr = strip_make_packet(ptr, strip_info, skb);
        strip_info->tx_pps_count++;
        if (!newptr) strip_info->tx_dropped++;
        else
        {
            ptr = newptr;
            strip_info->sx_pps_count++;
            strip_info->tx_packets++;        /* Count another successful packet */
#ifdef EXT_COUNTERS
            strip_info->tx_bytes += skb->len;
            strip_info->tx_rbytes += ptr - strip_info->tx_buff;
#endif
            /*DumpData("Sending:", strip_info, strip_info->tx_buff, ptr);*/
            /*HexDump("Sending", strip_info, strip_info->tx_buff, ptr);*/
        }
    }

    /*
     * 2. If it is time for another tickle, tack it on, after the packet
     */
    if (doprobe)
    {
        StringDescriptor ts = CommandString[strip_info->next_command];
#if TICKLE_TIMERS
        {
        struct timeval tv;
        do_gettimeofday(&tv);
        printk(KERN_INFO "**** Sending tickle string %d      at %02d.%06d\n",
            strip_info->next_command, tv.tv_sec % 100, tv.tv_usec);
        }
#endif
        if (ptr == strip_info->tx_buff) *ptr++ = 0x0D;

        *ptr++ = '*'; /* First send "**" to provoke an error message */
        *ptr++ = '*';

        /* Then add the command */
        memcpy(ptr, ts.string, ts.length);

        /* Add a checksum ? */
        if (strip_info->firmware_level < ChecksummedMessages) ptr += ts.length;
        else ptr = add_checksum(ptr, ptr + ts.length);

        *ptr++ = 0x0D; /* Terminate the command with a <CR> */

        /* Cycle to next periodic command? */
        if (strip_info->firmware_level >= StructuredMessages)
                if (++strip_info->next_command >= ELEMENTS_OF(CommandString))
                        strip_info->next_command = 0;
#ifdef EXT_COUNTERS
        strip_info->tx_ebytes += ts.length;
#endif
        strip_info->watchdog_doprobe = jiffies + 10 * HZ;
        strip_info->watchdog_doreset = jiffies + 1 * HZ;
        /*printk(KERN_INFO "%s: Routine radio test.\n", strip_info->dev.name);*/
    }

    /*
     * 3. Set up the strip_info ready to send the data (if any).
     */
    strip_info->tx_head = strip_info->tx_buff;
    strip_info->tx_left = ptr - strip_info->tx_buff;
    strip_info->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);

    /*
     * 4. Debugging check to make sure we're not overflowing the buffer.
     */
    if (strip_info->tx_size - strip_info->tx_left < 20)
        printk(KERN_ERR "%s: Sending%5d bytes;%5d bytes free.\n", strip_info->dev.name,
            strip_info->tx_left, strip_info->tx_size - strip_info->tx_left);

    /*
     * 5. If watchdog has expired, reset the radio. Note: if there's data waiting in
     * the buffer, strip_write_some_more will send it after the reset has finished
     */
    if (doreset) { ResetRadio(strip_info); return; }

    /*
     * 6. If it is time for a periodic ARP, queue one up to be sent.
     * We only do this if:
     *  1. The radio is working
     *  2. It's time to send another periodic ARP
     *  3. We really know what our address is (and it is not manually set to zero)
     *  4. We have a designated broadcast address configured
     * If we queue up an ARP packet when we don't have a designated broadcast
     * address configured, then the packet will just have to be discarded in
     * strip_make_packet. This is not fatal, but it causes misleading information
     * to be displayed in tcpdump. tcpdump will report that periodic APRs are
     * being sent, when in fact they are not, because they are all being dropped
     * in the strip_make_packet routine.
     */
    if (strip_info->working && (long)jiffies - strip_info->gratuitous_arp >= 0 &&
        memcmp(strip_info->dev.dev_addr, zero_address.c, sizeof(zero_address)) &&
        arp_query(haddr.c, in_dev->ifa_list->ifa_broadcast, &strip_info->dev))
    {
        /*printk(KERN_INFO "%s: Sending gratuitous ARP with interval %ld\n",
            strip_info->dev.name, strip_info->arp_interval / HZ);*/
        strip_info->gratuitous_arp = jiffies + strip_info->arp_interval;
        strip_info->arp_interval *= 2;
        if (strip_info->arp_interval > MaxARPInterval)
            strip_info->arp_interval = MaxARPInterval;
        if (in_dev && in_dev->ifa_list)
            arp_send(
                ARPOP_REPLY, ETH_P_ARP,
                in_dev->ifa_list->ifa_address, /* Target address of ARP packet is our address */
                &strip_info->dev,              /* Device to send packet on */
                in_dev->ifa_list->ifa_address, /* Source IP address this ARP packet comes from */
                NULL,                          /* Destination HW address is NULL (broadcast it) */
                strip_info->dev.dev_addr,      /* Source HW address is our HW address */
                strip_info->dev.dev_addr);     /* Target HW address is our HW address (redundant) */
    }

    /*
     * 7. All ready. Start the transmission
     */
    strip_write_some_more(strip_info->tty);
}

/* Encapsulate a datagram and kick it into a TTY queue. */
static int strip_xmit(struct sk_buff *skb, struct device *dev)
{
    struct strip *strip_info = (struct strip *)(dev->priv);

    if (!dev->start)
    {
        printk(KERN_ERR "%s: xmit call when iface is down\n", dev->name);
        return(1);
    }
    if (test_and_set_bit(0, (void *) &strip_info->dev.tbusy)) return(1);
    del_timer(&strip_info->idle_timer);

    /* See if someone has been ifconfigging */
    if (strip_info->mtu != strip_info->dev.mtu)
        strip_changedmtu(strip_info);

    if (jiffies - strip_info->pps_timer > HZ)
    {
        unsigned long t = jiffies - strip_info->pps_timer;
        unsigned long rx_pps_count = (strip_info->rx_pps_count * HZ * 8 + t/2) / t;
        unsigned long tx_pps_count = (strip_info->tx_pps_count * HZ * 8 + t/2) / t;
        unsigned long sx_pps_count = (strip_info->sx_pps_count * HZ * 8 + t/2) / t;

        strip_info->pps_timer = jiffies;
        strip_info->rx_pps_count = 0;
        strip_info->tx_pps_count = 0;
        strip_info->sx_pps_count = 0;

        strip_info->rx_average_pps = (strip_info->rx_average_pps + rx_pps_count + 1) / 2;
        strip_info->tx_average_pps = (strip_info->tx_average_pps + tx_pps_count + 1) / 2;
        strip_info->sx_average_pps = (strip_info->sx_average_pps + sx_pps_count + 1) / 2;

        if (rx_pps_count / 8 >= 10)
            printk(KERN_INFO "%s: WARNING: Receiving %ld packets per second.\n",
                strip_info->dev.name, rx_pps_count / 8);
        if (tx_pps_count / 8 >= 10)
            printk(KERN_INFO "%s: WARNING: Tx        %ld packets per second.\n",
                strip_info->dev.name, tx_pps_count / 8);
        if (sx_pps_count / 8 >= 10)
            printk(KERN_INFO "%s: WARNING: Sending   %ld packets per second.\n",
                strip_info->dev.name, sx_pps_count / 8);
    }

    strip_send(strip_info, skb);

    if (skb) dev_kfree_skb(skb);
    return(0);
}

/*
 * IdleTask periodically calls strip_xmit, so even when we have no IP packets
 * to send for an extended period of time, the watchdog processing still gets
 * done to ensure that the radio stays in Starmode
 */

static void strip_IdleTask(unsigned long parameter)
{
    strip_xmit(NULL, (struct device *)parameter);
}

/*
 * Create the MAC header for an arbitrary protocol layer
 *
 * saddr!=NULL        means use this specific address (n/a for Metricom)
 * saddr==NULL        means use default device source address
 * daddr!=NULL        means use this destination address
 * daddr==NULL        means leave destination address alone
 *                 (e.g. unresolved arp -- kernel will call
 *                 rebuild_header later to fill in the address)
 */

static int strip_header(struct sk_buff *skb, struct device *dev,
        unsigned short type, void *daddr, void *saddr, unsigned len)
{
    struct strip *strip_info = (struct strip *)(dev->priv);
    STRIP_Header *header = (STRIP_Header *)skb_push(skb, sizeof(STRIP_Header));

    /*printk(KERN_INFO "%s: strip_header 0x%04X %s\n", dev->name, type,
        type == ETH_P_IP ? "IP" : type == ETH_P_ARP ? "ARP" : "");*/

    header->src_addr = strip_info->true_dev_addr;
    header->protocol = htons(type);

    /*HexDump("strip_header", (struct strip *)(dev->priv), skb->data, skb->data + skb->len);*/

    if (!daddr) return(-dev->hard_header_len);

    header->dst_addr = *(MetricomAddress*)daddr;
    return(dev->hard_header_len);
}

/*
 * Rebuild the MAC header. This is called after an ARP
 * (or in future other address resolution) has completed on this
 * sk_buff. We now let ARP fill in the other fields.
 * I think this should return zero if packet is ready to send,
 * or non-zero if it needs more time to do an address lookup
 */

static int strip_rebuild_header(struct sk_buff *skb)
{
#ifdef CONFIG_INET
    STRIP_Header *header = (STRIP_Header *) skb->data;

    /* Arp find returns zero if if knows the address, */
    /* or if it doesn't know the address it sends an ARP packet and returns non-zero */
    return arp_find(header->dst_addr.c, skb)? 1 : 0;
#else
    return 0;
#endif
}


/************************************************************************/
/* Receiving routines                                                   */

static int strip_receive_room(struct tty_struct *tty)
{
    return 0x10000;  /* We can handle an infinite amount of data. :-) */
}

/*
 * This function parses the response to the ATS300? command,
 * extracting the radio version and serial number.
 */
static void get_radio_version(struct strip *strip_info, __u8 *ptr, __u8 *end)
{
    __u8 *p, *value_begin, *value_end;
    int len;
    
    /* Determine the beginning of the second line of the payload */
    p = ptr;
    while (p < end && *p != 10) p++;
    if (p >= end) return;
    p++;
    value_begin = p;
    
    /* Determine the end of line */
    while (p < end && *p != 10) p++;
    if (p >= end) return;
    value_end = p;
    p++;
     
    len = value_end - value_begin;
    len = MIN(len, sizeof(FirmwareVersion) - 1);
    if (strip_info->firmware_version.c[0] == 0)
        printk(KERN_INFO "%s: Radio Firmware: %.*s\n",
            strip_info->dev.name, len, value_begin);
    sprintf(strip_info->firmware_version.c, "%.*s", len, value_begin);
    
    /* Look for the first colon */
    while (p < end && *p != ':') p++;
    if (p >= end) return;
    /* Skip over the space */
    p += 2;
    len = sizeof(SerialNumber) - 1;
    if (p + len <= end) {
        sprintf(strip_info->serial_number.c, "%.*s", len, p);
    }
    else {
        printk(KERN_DEBUG "STRIP: radio serial number shorter (%d) than expected (%d)\n",
               end - p, len);
    }
}

/*
 * This function parses the response to the ATS325? command,
 * extracting the radio battery voltage.
 */
static void get_radio_voltage(struct strip *strip_info, __u8 *ptr, __u8 *end)
{
    int len;

    len = sizeof(BatteryVoltage) - 1;
    if (ptr + len <= end) {
        sprintf(strip_info->battery_voltage.c, "%.*s", len, ptr);
    }
    else {
        printk(KERN_DEBUG "STRIP: radio voltage string shorter (%d) than expected (%d)\n",
               end - ptr, len);
    }
}

/*
 * This function parses the responses to the AT~LA and ATS311 commands,
 * which list the radio's neighbours.
 */
static void get_radio_neighbours(MetricomNodeTable *table, __u8 *ptr, __u8 *end)
{
    table->num_nodes = 0;
    while (ptr < end && table->num_nodes < NODE_TABLE_SIZE)
        {
        MetricomNode *node = &table->node[table->num_nodes++];
        char *dst = node->c, *limit = dst + sizeof(*node) - 1;
        while (ptr < end && *ptr <= 32) ptr++;
        while (ptr < end && dst < limit && *ptr != 10) *dst++ = *ptr++;
        *dst++ = 0;
        while (ptr < end && ptr[-1] != 10) ptr++;
        }
    do_gettimeofday(&table->timestamp);
}

static int get_radio_address(struct strip *strip_info, __u8 *p)
{
    MetricomAddress addr;

    if (string_to_radio_address(&addr, p)) return(1);

    /* See if our radio address has changed */
    if (memcmp(strip_info->true_dev_addr.c, addr.c, sizeof(addr)))
    {
        MetricomAddressString addr_string;
        radio_address_to_string(&addr, &addr_string);
        printk(KERN_INFO "%s: Radio address = %s\n", strip_info->dev.name, addr_string.c);
        strip_info->true_dev_addr = addr;
        if (!strip_info->manual_dev_addr) *(MetricomAddress*)strip_info->dev.dev_addr = addr;
        /* Give the radio a few seconds to get its head straight, then send an arp */
        strip_info->gratuitous_arp = jiffies + 15 * HZ;
        strip_info->arp_interval = 1 * HZ;
    }
    return(0);
}

static int verify_checksum(struct strip *strip_info)
{
    __u8 *p = strip_info->sx_buff;
    __u8 *end = strip_info->sx_buff + strip_info->sx_count - 4;
    u_short sum = (READHEX16(end[0]) << 12) | (READHEX16(end[1]) << 8) |
                  (READHEX16(end[2]) <<  4) | (READHEX16(end[3]));
    while (p < end) sum -= *p++;
    if (sum == 0 && strip_info->firmware_level == StructuredMessages)
    {
        strip_info->firmware_level = ChecksummedMessages;
        printk(KERN_INFO "%s: Radio provides message checksums\n", strip_info->dev.name);
    }
    return(sum == 0);
}

static void RecvErr(char *msg, struct strip *strip_info)
{
    __u8 *ptr = strip_info->sx_buff;
    __u8 *end = strip_info->sx_buff + strip_info->sx_count;
    DumpData(msg, strip_info, ptr, end);
    strip_info->rx_errors++;
}

static void RecvErr_Message(struct strip *strip_info, __u8 *sendername, const __u8 *msg, u_long len)
{
    if (has_prefix(msg, len, "001")) /* Not in StarMode! */
    {
        RecvErr("Error Msg:", strip_info);
        printk(KERN_INFO "%s: Radio %s is not in StarMode\n",
            strip_info->dev.name, sendername);
    }

    else if (has_prefix(msg, len, "002")) /* Remap handle */
    {
        /* We ignore "Remap handle" messages for now */
    }

    else if (has_prefix(msg, len, "003")) /* Can't resolve name */
    {
        RecvErr("Error Msg:", strip_info);
        printk(KERN_INFO "%s: Destination radio name is unknown\n",
            strip_info->dev.name);
    }

    else if (has_prefix(msg, len, "004")) /* Name too small or missing */
    {
        strip_info->watchdog_doreset = jiffies + LongTime;
#if TICKLE_TIMERS
        {
        struct timeval tv;
        do_gettimeofday(&tv);
        printk(KERN_INFO "**** Got ERR_004 response         at %02d.%06d\n",
            tv.tv_sec % 100, tv.tv_usec);
        }
#endif
        if (!strip_info->working)
        {
            strip_info->working = TRUE;
            printk(KERN_INFO "%s: Radio now in starmode\n", strip_info->dev.name);
            /*
             * If the radio has just entered a working state, we should do our first
             * probe ASAP, so that we find out our radio address etc. without delay.
             */
            strip_info->watchdog_doprobe = jiffies;
        }
        if (strip_info->firmware_level == NoStructure && sendername)
        {
            strip_info->firmware_level = StructuredMessages;
            strip_info->next_command   = 0; /* Try to enable checksums ASAP */
            printk(KERN_INFO "%s: Radio provides structured messages\n", strip_info->dev.name);
        }
        if (strip_info->firmware_level >= StructuredMessages)
        {
            /*
             * If this message has a valid checksum on the end, then the call to verify_checksum
             * will elevate the firmware_level to ChecksummedMessages for us. (The actual return
             * code from verify_checksum is ignored here.)
             */
            verify_checksum(strip_info);
            /*
             * If the radio has structured messages but we don't yet have all our information about it,
             * we should do probes without delay, until we have gathered all the information
             */
            if (!GOT_ALL_RADIO_INFO(strip_info)) strip_info->watchdog_doprobe = jiffies;
        }
    }

    else if (has_prefix(msg, len, "005")) /* Bad count specification */
        RecvErr("Error Msg:", strip_info);

    else if (has_prefix(msg, len, "006")) /* Header too big */
        RecvErr("Error Msg:", strip_info);

    else if (has_prefix(msg, len, "007")) /* Body too big */
    {
        RecvErr("Error Msg:", strip_info);
        printk(KERN_ERR "%s: Error! Packet size too big for radio.\n",
            strip_info->dev.name);
    }

    else if (has_prefix(msg, len, "008")) /* Bad character in name */
    {
        RecvErr("Error Msg:", strip_info);
        printk(KERN_ERR "%s: Radio name contains illegal character\n",
            strip_info->dev.name);
    }

    else if (has_prefix(msg, len, "009")) /* No count or line terminator */
        RecvErr("Error Msg:", strip_info);

    else if (has_prefix(msg, len, "010")) /* Invalid checksum */
        RecvErr("Error Msg:", strip_info);

    else if (has_prefix(msg, len, "011")) /* Checksum didn't match */
        RecvErr("Error Msg:", strip_info);

    else if (has_prefix(msg, len, "012")) /* Failed to transmit packet */
        RecvErr("Error Msg:", strip_info);

    else
        RecvErr("Error Msg:", strip_info);
}

static void process_AT_response(struct strip *strip_info, __u8 *ptr, __u8 *end)
{
    u_long len;
    __u8 *p = ptr;
    while (p < end && p[-1] != 10) p++; /* Skip past first newline character */
    /* Now ptr points to the AT command, and p points to the text of the response. */
    len = p-ptr;

#if TICKLE_TIMERS
    {
    struct timeval tv;
    do_gettimeofday(&tv);
    printk(KERN_INFO "**** Got AT response %.7s      at %02d.%06d\n",
        ptr, tv.tv_sec % 100, tv.tv_usec);
    }
#endif

    if      (has_prefix(ptr, len, "ATS300?" )) get_radio_version(strip_info, p, end);
    else if (has_prefix(ptr, len, "ATS305?" )) get_radio_address(strip_info, p);
    else if (has_prefix(ptr, len, "ATS311?" )) get_radio_neighbours(&strip_info->poletops, p, end);
    else if (has_prefix(ptr, len, "ATS319=7")) verify_checksum(strip_info);
    else if (has_prefix(ptr, len, "ATS325?" )) get_radio_voltage(strip_info, p, end);
    else if (has_prefix(ptr, len, "AT~LA"   )) get_radio_neighbours(&strip_info->portables, p, end);
    else                                       RecvErr("Unknown AT Response:", strip_info);
}

static void process_ACK(struct strip *strip_info, __u8 *ptr, __u8 *end)
{
    /* Currently we don't do anything with ACKs from the radio */
}

static void process_Info(struct strip *strip_info, __u8 *ptr, __u8 *end)
{
    if (ptr+16 > end) RecvErr("Bad Info Msg:", strip_info);
}

static struct device *get_strip_dev(struct strip *strip_info)
{
    /* If our hardware address is *manually set* to zero, and we know our */
    /* real radio hardware address, try to find another strip device that has been */
    /* manually set to that address that we can 'transfer ownership' of this packet to  */
    if (strip_info->manual_dev_addr &&
        !memcmp(strip_info->dev.dev_addr, zero_address.c, sizeof(zero_address)) &&
        memcmp(&strip_info->true_dev_addr, zero_address.c, sizeof(zero_address)))
    {
        struct device *dev;
        read_lock_bh(&dev_base_lock);
        dev = dev_base;
        while (dev)
        {
            if (dev->type == strip_info->dev.type &&
                !memcmp(dev->dev_addr, &strip_info->true_dev_addr, sizeof(MetricomAddress)))
            {
                printk(KERN_INFO "%s: Transferred packet ownership to %s.\n",
                    strip_info->dev.name, dev->name);
                read_unlock_bh(&dev_base_lock);
                return(dev);
            }
            dev = dev->next;
        }
        read_unlock_bh(&dev_base_lock);
    }
    return(&strip_info->dev);
}

/*
 * Send one completely decapsulated datagram to the next layer.
 */

static void deliver_packet(struct strip *strip_info, STRIP_Header *header, __u16 packetlen)
{
    struct sk_buff *skb = dev_alloc_skb(sizeof(STRIP_Header) + packetlen);
    if (!skb)
    {
        printk(KERN_ERR "%s: memory squeeze, dropping packet.\n", strip_info->dev.name);
        strip_info->rx_dropped++;
    }
    else
    {
        memcpy(skb_put(skb, sizeof(STRIP_Header)), header, sizeof(STRIP_Header));
        memcpy(skb_put(skb, packetlen), strip_info->rx_buff, packetlen);
        skb->dev      = get_strip_dev(strip_info);
        skb->protocol = header->protocol;
        skb->mac.raw  = skb->data;

        /* Having put a fake header on the front of the sk_buff for the */
        /* benefit of tools like tcpdump, skb_pull now 'consumes' that  */
        /* fake header before we hand the packet up to the next layer.  */
        skb_pull(skb, sizeof(STRIP_Header));

        /* Finally, hand the packet up to the next layer (e.g. IP or ARP, etc.) */
        strip_info->rx_packets++;
        strip_info->rx_pps_count++;
#ifdef EXT_COUNTERS
        strip_info->rx_bytes += packetlen;
#endif
        netif_rx(skb);
    }
}

static void process_IP_packet(struct strip *strip_info, STRIP_Header *header, __u8 *ptr, __u8 *end)
{
    __u16 packetlen;

    /* Decode start of the IP packet header */
    ptr = UnStuffData(ptr, end, strip_info->rx_buff, 4);
    if (!ptr)
    {
        RecvErr("IP Packet too short", strip_info);
        return;
    }

    packetlen = ((__u16)strip_info->rx_buff[2] << 8) | strip_info->rx_buff[3];

    if (packetlen > MAX_RECV_MTU)
    {
        printk(KERN_INFO "%s: Dropping oversized received IP packet: %d bytes\n",
            strip_info->dev.name, packetlen);
        strip_info->rx_dropped++;
        return;
    }

    /*printk(KERN_INFO "%s: Got %d byte IP packet\n", strip_info->dev.name, packetlen);*/

    /* Decode remainder of the IP packet */
    ptr = UnStuffData(ptr, end, strip_info->rx_buff+4, packetlen-4);
    if (!ptr)
    {
        RecvErr("IP Packet too short", strip_info);
        return;
    }

    if (ptr < end)
    {
        RecvErr("IP Packet too long", strip_info);
        return;
    }

    header->protocol = htons(ETH_P_IP);

    deliver_packet(strip_info, header, packetlen);
}

static void process_ARP_packet(struct strip *strip_info, STRIP_Header *header, __u8 *ptr, __u8 *end)
{
    __u16 packetlen;
    struct arphdr *arphdr = (struct arphdr *)strip_info->rx_buff;

    /* Decode start of the ARP packet */
    ptr = UnStuffData(ptr, end, strip_info->rx_buff, 8);
    if (!ptr)
    {
        RecvErr("ARP Packet too short", strip_info);
        return;
    }

    packetlen = 8 + (arphdr->ar_hln + arphdr->ar_pln) * 2;

    if (packetlen > MAX_RECV_MTU)
    {
        printk(KERN_INFO "%s: Dropping oversized received ARP packet: %d bytes\n",
            strip_info->dev.name, packetlen);
        strip_info->rx_dropped++;
        return;
    }

    /*printk(KERN_INFO "%s: Got %d byte ARP %s\n",
        strip_info->dev.name, packetlen,
        ntohs(arphdr->ar_op) == ARPOP_REQUEST ? "request" : "reply");*/

    /* Decode remainder of the ARP packet */
    ptr = UnStuffData(ptr, end, strip_info->rx_buff+8, packetlen-8);
    if (!ptr)
    {
        RecvErr("ARP Packet too short", strip_info);
        return;
    }

    if (ptr < end)
    {
        RecvErr("ARP Packet too long", strip_info);
        return;
    }

    header->protocol = htons(ETH_P_ARP);

    deliver_packet(strip_info, header, packetlen);
}

/*
 * process_text_message processes a <CR>-terminated block of data received
 * from the radio that doesn't begin with a '*' character. All normal
 * Starmode communication messages with the radio begin with a '*',
 * so any text that does not indicates a serial port error, a radio that
 * is in Hayes command mode instead of Starmode, or a radio with really
 * old firmware that doesn't frame its Starmode responses properly.
 */
static void process_text_message(struct strip *strip_info)
{
    __u8 *msg = strip_info->sx_buff;
    int len   = strip_info->sx_count;

    /* Check for anything that looks like it might be our radio name */
    /* (This is here for backwards compatibility with old firmware)  */
    if (len == 9 && get_radio_address(strip_info, msg) == 0) return;

    if (text_equal(msg, len, "OK"      )) return; /* Ignore 'OK' responses from prior commands */
    if (text_equal(msg, len, "ERROR"   )) return; /* Ignore 'ERROR' messages */
    if (has_prefix(msg, len, "ate0q1"  )) return; /* Ignore character echo back from the radio */

    /* Catch other error messages */
    /* (This is here for backwards compatibility with old firmware) */
    if (has_prefix(msg, len, "ERR_")) { RecvErr_Message(strip_info, NULL, &msg[4], len-4); return; }
    
    RecvErr("No initial *", strip_info);
}

/*
 * process_message processes a <CR>-terminated block of data received
 * from the radio. If the radio is not in Starmode or has old firmware,
 * it may be a line of text in response to an AT command. Ideally, with
 * a current radio that's properly in Starmode, all data received should
 * be properly framed and checksummed radio message blocks, containing
 * either a starmode packet, or a other communication from the radio
 * firmware, like "INF_" Info messages and &COMMAND responses.
 */
static void process_message(struct strip *strip_info)
{
    STRIP_Header header = { zero_address, zero_address, 0 };
    __u8 *ptr = strip_info->sx_buff;
    __u8 *end = strip_info->sx_buff + strip_info->sx_count;
    __u8 sendername[32], *sptr = sendername;
    MetricomKey key;

    /*HexDump("Receiving", strip_info, ptr, end);*/

    /* Check for start of address marker, and then skip over it */
    if (*ptr == '*') ptr++;
    else { process_text_message(strip_info); return; }

    /* Copy out the return address */
    while (ptr < end && *ptr != '*' && sptr < ARRAY_END(sendername)-1) *sptr++ = *ptr++;
    *sptr = 0;                /* Null terminate the sender name */

    /* Check for end of address marker, and skip over it */
    if (ptr >= end || *ptr != '*')
    {
        RecvErr("No second *", strip_info);
        return;
    }
    ptr++; /* Skip the second '*' */

    /* If the sender name is "&COMMAND", ignore this 'packet'       */
    /* (This is here for backwards compatibility with old firmware) */
    if (!strcmp(sendername, "&COMMAND"))
    {
        strip_info->firmware_level = NoStructure;
        strip_info->next_command   = CompatibilityCommand;
        return;
    }

    if (ptr+4 > end)
    {
        RecvErr("No proto key", strip_info);
        return;
    }

    /* Get the protocol key out of the buffer */
    key.c[0] = *ptr++;
    key.c[1] = *ptr++;
    key.c[2] = *ptr++;
    key.c[3] = *ptr++;

    /* If we're using checksums, verify the checksum at the end of the packet */
    if (strip_info->firmware_level >= ChecksummedMessages)
    {
        end -= 4;       /* Chop the last four bytes off the packet (they're the checksum) */
        if (ptr > end)
        {
            RecvErr("Missing Checksum", strip_info);
            return;
        }
        if (!verify_checksum(strip_info))
        {
            RecvErr("Bad Checksum", strip_info);
            return;
        }
    }

    /*printk(KERN_INFO "%s: Got packet from \"%s\".\n", strip_info->dev.name, sendername);*/

    /*
     * Fill in (pseudo) source and destination addresses in the packet.
     * We assume that the destination address was our address (the radio does not
     * tell us this). If the radio supplies a source address, then we use it.
     */
    header.dst_addr = strip_info->true_dev_addr;
    string_to_radio_address(&header.src_addr, sendername);

#ifdef EXT_COUNTERS
    if      (key.l == SIP0Key.l) {
      strip_info->rx_rbytes += (end - ptr);
      process_IP_packet(strip_info, &header, ptr, end);
    } else if (key.l == ARP0Key.l) {
      strip_info->rx_rbytes += (end - ptr);
      process_ARP_packet(strip_info, &header, ptr, end);
    } else if (key.l == ATR_Key.l) {
      strip_info->rx_ebytes += (end - ptr);
      process_AT_response(strip_info, ptr, end);
    } else if (key.l == ACK_Key.l) {
      strip_info->rx_ebytes += (end - ptr);
      process_ACK(strip_info, ptr, end);
    } else if (key.l == INF_Key.l) {
      strip_info->rx_ebytes += (end - ptr);
      process_Info(strip_info, ptr, end);
    } else if (key.l == ERR_Key.l) {
      strip_info->rx_ebytes += (end - ptr);
      RecvErr_Message(strip_info, sendername, ptr, end-ptr);
    } else RecvErr("Unrecognized protocol key", strip_info);
#else
    if      (key.l == SIP0Key.l) process_IP_packet  (strip_info, &header, ptr, end);
    else if (key.l == ARP0Key.l) process_ARP_packet (strip_info, &header, ptr, end);
    else if (key.l == ATR_Key.l) process_AT_response(strip_info, ptr, end);
    else if (key.l == ACK_Key.l) process_ACK        (strip_info, ptr, end);
    else if (key.l == INF_Key.l) process_Info       (strip_info, ptr, end);
    else if (key.l == ERR_Key.l) RecvErr_Message    (strip_info, sendername, ptr, end-ptr);
    else                         RecvErr("Unrecognized protocol key", strip_info);
#endif
}

#define TTYERROR(X) ((X) == TTY_BREAK   ? "Break"            : \
                     (X) == TTY_FRAME   ? "Framing Error"    : \
                     (X) == TTY_PARITY  ? "Parity Error"     : \
                     (X) == TTY_OVERRUN ? "Hardware Overrun" : "Unknown Error")

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of STRIP data has been received, which can now be decapsulated
 * and sent on to some IP layer for further processing.
 */

static void
strip_receive_buf(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
{
    struct strip *strip_info = (struct strip *) tty->disc_data;
    const unsigned char *end = cp + count;

    if (!strip_info || strip_info->magic != STRIP_MAGIC || !strip_info->dev.start)
        return;

    /* Argh! mtu change time! - costs us the packet part received at the change */
    if (strip_info->mtu != strip_info->dev.mtu)
        strip_changedmtu(strip_info);

#if 0
    {
    struct timeval tv;
    do_gettimeofday(&tv);
    printk(KERN_INFO "**** strip_receive_buf: %3d bytes at %02d.%06d\n",
        count, tv.tv_sec % 100, tv.tv_usec);
    }
#endif

#ifdef EXT_COUNTERS
    strip_info->rx_sbytes += count;
#endif

    /* Read the characters out of the buffer */
    while (cp < end)
    {
        if (fp && *fp) printk(KERN_INFO "%s: %s on serial port\n", strip_info->dev.name, TTYERROR(*fp));
        if (fp && *fp++ && !strip_info->discard) /* If there's a serial error, record it */
        {
            /* If we have some characters in the buffer, discard them */
            strip_info->discard = strip_info->sx_count;
            strip_info->rx_errors++;
        }

        /* Leading control characters (CR, NL, Tab, etc.) are ignored */
        if (strip_info->sx_count > 0 || *cp >= ' ')
        {
            if (*cp == 0x0D)                /* If end of packet, decide what to do with it */
            {
                if (strip_info->sx_count > 3000)
                    printk(KERN_INFO "%s: Cut a %d byte packet (%d bytes remaining)%s\n",
                        strip_info->dev.name, strip_info->sx_count, end-cp-1,
                        strip_info->discard ? " (discarded)" : "");
                if (strip_info->sx_count > strip_info->sx_size)
                {
                    strip_info->rx_over_errors++;
                    printk(KERN_INFO "%s: sx_buff overflow (%d bytes total)\n",
                           strip_info->dev.name, strip_info->sx_count);
                }
                else if (strip_info->discard)
                    printk(KERN_INFO "%s: Discarding bad packet (%d/%d)\n",
                        strip_info->dev.name, strip_info->discard, strip_info->sx_count);
                else process_message(strip_info);
                strip_info->discard = 0;
                strip_info->sx_count = 0;
            }
            else
            {
                /* Make sure we have space in the buffer */
                if (strip_info->sx_count < strip_info->sx_size)
                    strip_info->sx_buff[strip_info->sx_count] = *cp;
                strip_info->sx_count++;
            }
        }
        cp++;
    }
}


/************************************************************************/
/* General control routines                                             */

static int set_mac_address(struct strip *strip_info, MetricomAddress *addr)
{
    /*
     * We're using a manually specified address if the address is set
     * to anything other than all ones. Setting the address to all ones
     * disables manual mode and goes back to automatic address determination
     * (tracking the true address that the radio has).
     */
    strip_info->manual_dev_addr = memcmp(addr->c, broadcast_address.c, sizeof(broadcast_address));
    if (strip_info->manual_dev_addr)
         *(MetricomAddress*)strip_info->dev.dev_addr = *addr;
    else *(MetricomAddress*)strip_info->dev.dev_addr = strip_info->true_dev_addr;
    return 0;
}

static int dev_set_mac_address(struct device *dev, void *addr)
{
    struct strip *strip_info = (struct strip *)(dev->priv);
    struct sockaddr *sa = addr;
    printk(KERN_INFO "%s: strip_set_dev_mac_address called\n", dev->name);
    set_mac_address(strip_info, (MetricomAddress *)sa->sa_data);
    return 0;
}

static struct enet_statistics *strip_get_stats(struct device *dev)
{
    static struct enet_statistics stats;
    struct strip *strip_info = (struct strip *)(dev->priv);

    memset(&stats, 0, sizeof(struct enet_statistics));

    stats.rx_packets     = strip_info->rx_packets;
    stats.tx_packets     = strip_info->tx_packets;
    stats.rx_dropped     = strip_info->rx_dropped;
    stats.tx_dropped     = strip_info->tx_dropped;
    stats.tx_errors      = strip_info->tx_errors;
    stats.rx_errors      = strip_info->rx_errors;
    stats.rx_over_errors = strip_info->rx_over_errors;
    return(&stats);
}


/************************************************************************/
/* Opening and closing                                                  */

/*
 * Here's the order things happen:
 * When the user runs "slattach -p strip ..."
 *  1. The TTY module calls strip_open
 *  2. strip_open calls strip_alloc
 *  3.                  strip_alloc calls register_netdev
 *  4.                  register_netdev calls strip_dev_init
 *  5. then strip_open finishes setting up the strip_info
 *
 * When the user runs "ifconfig st<x> up address netmask ..."
 *  6. strip_open_low gets called
 *
 * When the user runs "ifconfig st<x> down"
 *  7. strip_close_low gets called
 *
 * When the user kills the slattach process
 *  8. strip_close gets called
 *  9. strip_close calls dev_close
 * 10. if the device is still up, then dev_close calls strip_close_low
 * 11. strip_close calls strip_free
 */

/* Open the low-level part of the STRIP channel. Easy! */

static int strip_open_low(struct device *dev)
{
    struct strip *strip_info = (struct strip *)(dev->priv);
    struct in_device *in_dev = dev->ip_ptr;

    if (strip_info->tty == NULL)
        return(-ENODEV);

    if (!allocate_buffers(strip_info))
        return(-ENOMEM);

    strip_info->sx_count = 0;
    strip_info->tx_left  = 0;

    strip_info->discard  = 0;
    strip_info->working  = FALSE;
    strip_info->firmware_level = NoStructure;
    strip_info->next_command   = CompatibilityCommand;
    strip_info->user_baud      = get_baud(strip_info->tty);

    /*
     * Needed because address '0' is special
     */

    if (in_dev->ifa_list->ifa_address == 0)
        in_dev->ifa_list->ifa_address = ntohl(0xC0A80001);
    dev->tbusy  = 0;
    dev->start  = 1;

    printk(KERN_INFO "%s: Initializing Radio.\n", strip_info->dev.name);
    ResetRadio(strip_info);
    strip_info->idle_timer.expires = jiffies + 1*HZ;
    add_timer(&strip_info->idle_timer);
    return(0);
}


/*
 * Close the low-level part of the STRIP channel. Easy!
 */

static int strip_close_low(struct device *dev)
{
    struct strip *strip_info = (struct strip *)(dev->priv);

    if (strip_info->tty == NULL)
        return -EBUSY;
    strip_info->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
    dev->tbusy = 1;
    dev->start = 0;

    /*
     * Free all STRIP frame buffers.
     */
    if (strip_info->rx_buff)
    {
        kfree(strip_info->rx_buff);
        strip_info->rx_buff = NULL;
    }
    if (strip_info->sx_buff)
    {
        kfree(strip_info->sx_buff);
        strip_info->sx_buff = NULL;
    }
    if (strip_info->tx_buff)
    {
        kfree(strip_info->tx_buff);
        strip_info->tx_buff = NULL;
    }
    del_timer(&strip_info->idle_timer);
    return 0;
}

/*
 * This routine is called by DDI when the
 * (dynamically assigned) device is registered
 */

static int strip_dev_init(struct device *dev)
{
    /*
     * Finish setting up the DEVICE info.
     */

    dev->trans_start        = 0;
    dev->last_rx            = 0;
    dev->tx_queue_len       = 30;         /* Drop after 30 frames queued */

    dev->flags              = 0;
    dev->mtu                = DEFAULT_STRIP_MTU;
    dev->type               = ARPHRD_METRICOM;        /* dtang */
    dev->hard_header_len    = sizeof(STRIP_Header);
    /*
     *  dev->priv             Already holds a pointer to our struct strip
     */

    *(MetricomAddress*)&dev->broadcast = broadcast_address;
    dev->dev_addr[0]        = 0;
    dev->addr_len           = sizeof(MetricomAddress);

    /*
     * Pointers to interface service routines.
     */

    dev->open               = strip_open_low;
    dev->stop               = strip_close_low;
    dev->hard_start_xmit    = strip_xmit;
    dev->hard_header        = strip_header;
    dev->rebuild_header     = strip_rebuild_header;
    /*  dev->type_trans            unused */
    /*  dev->set_multicast_list   unused */
    dev->set_mac_address    = dev_set_mac_address;
    /*  dev->do_ioctl             unused */
    /*  dev->set_config           unused */
    dev->get_stats          = strip_get_stats;
    return 0;
}

/*
 * Free a STRIP channel.
 */

static void strip_free(struct strip *strip_info)
{
    *(strip_info->referrer) = strip_info->next;
    if (strip_info->next)
        strip_info->next->referrer = strip_info->referrer;
    strip_info->magic = 0;
    kfree(strip_info);
}

/*
 * Allocate a new free STRIP channel
 */

static struct strip *strip_alloc(void)
{
    int channel_id = 0;
    struct strip **s = &struct_strip_list;
    struct strip *strip_info = (struct strip *)
        kmalloc(sizeof(struct strip), GFP_KERNEL);

    if (!strip_info)
        return(NULL);        /* If no more memory, return */

    /*
     * Clear the allocated memory
     */

    memset(strip_info, 0, sizeof(struct strip));

    /*
     * Search the list to find where to put our new entry
     * (and in the process decide what channel number it is
     * going to be)
     */

    while (*s && (*s)->dev.base_addr == channel_id)
    {
        channel_id++;
        s = &(*s)->next;
    }

    /*
     * Fill in the link pointers
     */

    strip_info->next = *s;
    if (*s)
        (*s)->referrer = &strip_info->next;
    strip_info->referrer = s;
    *s = strip_info;

    strip_info->magic = STRIP_MAGIC;
    strip_info->tty   = NULL;

    strip_info->gratuitous_arp   = jiffies + LongTime;
    strip_info->arp_interval     = 0;
    init_timer(&strip_info->idle_timer);
    strip_info->idle_timer.data     = (long)&strip_info->dev;
    strip_info->idle_timer.function = strip_IdleTask;

    /* Note: strip_info->if_name is currently 8 characters long */
    sprintf(strip_info->if_name.c, "st%d", channel_id);
    strip_info->dev.name         = strip_info->if_name.c;
    strip_info->dev.base_addr    = channel_id;
    strip_info->dev.priv         = (void*)strip_info;
    strip_info->dev.next         = NULL;
    strip_info->dev.init         = strip_dev_init;

    return(strip_info);
}

/*
 * Open the high-level part of the STRIP channel.
 * This function is called by the TTY module when the
 * STRIP line discipline is called for.  Because we are
 * sure the tty line exists, we only have to link it to
 * a free STRIP channel...
 */

static int strip_open(struct tty_struct *tty)
{
    struct strip *strip_info = (struct strip *) tty->disc_data;

    /*
     * First make sure we're not already connected.
     */

    if (strip_info && strip_info->magic == STRIP_MAGIC)
        return -EEXIST;

    /*
     * OK.  Find a free STRIP channel to use.
     */
    if ((strip_info = strip_alloc()) == NULL)
        return -ENFILE;

    /*
     * Register our newly created device so it can be ifconfig'd
     * strip_dev_init() will be called as a side-effect
     */

    if (register_netdev(&strip_info->dev) != 0)
    {
        printk(KERN_ERR "strip: register_netdev() failed.\n");
        strip_free(strip_info);
        return -ENFILE;
    }

    strip_info->tty = tty;
    tty->disc_data = strip_info;
    if (tty->driver.flush_buffer)
        tty->driver.flush_buffer(tty);
    if (tty->ldisc.flush_buffer)
        tty->ldisc.flush_buffer(tty);

    /*
     * Restore default settings
     */

    strip_info->dev.type = ARPHRD_METRICOM;    /* dtang */

    /*
     * Set tty options
     */

    tty->termios->c_iflag |= IGNBRK |IGNPAR;/* Ignore breaks and parity errors. */
    tty->termios->c_cflag |= CLOCAL;    /* Ignore modem control signals. */
    tty->termios->c_cflag &= ~HUPCL;    /* Don't close on hup */

#ifdef MODULE
    MOD_INC_USE_COUNT;
#endif

    printk(KERN_INFO "STRIP: device \"%s\" activated\n", strip_info->if_name.c);

    /*
     * Done.  We have linked the TTY line to a channel.
     */
    return(strip_info->dev.base_addr);
}

/*
 * Close down a STRIP channel.
 * This means flushing out any pending queues, and then restoring the
 * TTY line discipline to what it was before it got hooked to STRIP
 * (which usually is TTY again).
 */

static void strip_close(struct tty_struct *tty)
{
    struct strip *strip_info = (struct strip *) tty->disc_data;

    /*
     * First make sure we're connected.
     */

    if (!strip_info || strip_info->magic != STRIP_MAGIC)
        return;

    dev_close(&strip_info->dev);
    unregister_netdev(&strip_info->dev);

    tty->disc_data = 0;
    strip_info->tty = NULL;
    printk(KERN_INFO "STRIP: device \"%s\" closed down\n", strip_info->if_name.c);
    strip_free(strip_info);
    tty->disc_data = NULL;
#ifdef MODULE
    MOD_DEC_USE_COUNT;
#endif
}


/************************************************************************/
/* Perform I/O control calls on an active STRIP channel.                */

static int strip_ioctl(struct tty_struct *tty, struct file *file,
    unsigned int cmd, unsigned long arg)
{
    struct strip *strip_info = (struct strip *) tty->disc_data;

    /*
     * First make sure we're connected.
     */

    if (!strip_info || strip_info->magic != STRIP_MAGIC)
        return -EINVAL;

    switch(cmd)
    {
        case SIOCGIFNAME:
            return copy_to_user((void*)arg, strip_info->dev.name,
                                strlen(strip_info->dev.name) + 1) ? 
                -EFAULT : 0;
            break;
        case SIOCSIFHWADDR:
            {
            MetricomAddress addr;
            printk(KERN_INFO "%s: SIOCSIFHWADDR\n", strip_info->dev.name);
            return copy_from_user(&addr, (void*)arg, sizeof(MetricomAddress)) ?
                -EFAULT : set_mac_address(strip_info, &addr);
            break;
            }
        /*
         * Allow stty to read, but not set, the serial port
         */

        case TCGETS:
        case TCGETA:
            return n_tty_ioctl(tty, (struct file *) file, cmd,
                (unsigned long) arg);
            break;
        default:
            return -ENOIOCTLCMD;
            break;
    }
}


/************************************************************************/
/* Initialization                                                       */

/*
 * Initialize the STRIP driver.
 * This routine is called at boot time, to bootstrap the multi-channel
 * STRIP driver
 */

#ifdef MODULE
static
#endif
int strip_init_ctrl_dev(struct device *dummy)
{
    static struct tty_ldisc strip_ldisc;
    int status;

    printk(KERN_INFO "STRIP: Version %s (unlimited channels)\n", StripVersion);

    /*
     * Fill in our line protocol discipline, and register it
     */

    memset(&strip_ldisc, 0, sizeof(strip_ldisc));
    strip_ldisc.magic        = TTY_LDISC_MAGIC;
    strip_ldisc.flags        = 0;
    strip_ldisc.open         = strip_open;
    strip_ldisc.close        = strip_close;
    strip_ldisc.read         = NULL;
    strip_ldisc.write        = NULL;
    strip_ldisc.ioctl        = strip_ioctl;
    strip_ldisc.poll         = NULL;
    strip_ldisc.receive_buf  = strip_receive_buf;
    strip_ldisc.receive_room = strip_receive_room;
    strip_ldisc.write_wakeup = strip_write_some_more;
    status = tty_register_ldisc(N_STRIP, &strip_ldisc);
    if (status != 0)
    {
        printk(KERN_ERR "STRIP: can't register line discipline (err = %d)\n", status);
    }

    /*
     * Register the status file with /proc
     */
#ifdef CONFIG_PROC_FS 
    if (proc_net_register(&proc_strip_get_status_info) != 0)
    {
        printk(KERN_ERR "strip: status proc_net_register() failed.\n");
    }
#endif

#ifdef MODULE
     return status;
#else

    /* Return "not found", so that dev_init() will unlink
     * the placeholder device entry for us.
     */
    return ENODEV;
#endif
}


/************************************************************************/
/* From here down is only used when compiled as an external module      */

#ifdef MODULE

int init_module(void)
{
    return strip_init_ctrl_dev(0);
}

void cleanup_module(void)
{
    int i;
    while (struct_strip_list)
        strip_free(struct_strip_list);

    /* Unregister with the /proc/net file here. */
#ifdef CONFIG_PROC_FS
    proc_net_unregister(PROC_NET_STRIP_STATUS);
#endif

    if ((i = tty_register_ldisc(N_STRIP, NULL)))
        printk(KERN_ERR "STRIP: can't unregister line discipline (err = %d)\n", i);

    printk(KERN_INFO "STRIP: Module Unloaded\n");
}
#endif /* MODULE */