strip.c

讲述linux的初始化过程

    *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;
    u32 addr, brd;

    /*
     * 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; }

    if (1) {
	    struct in_device *in_dev = in_dev_get(&strip_info->dev);
	    brd = addr = 0;
	    if (in_dev) {
		    read_lock(&in_dev->lock);
		    if (in_dev->ifa_list) {
			    brd = in_dev->ifa_list->ifa_broadcast;
			    addr = in_dev->ifa_list->ifa_local;
		    }
		    read_unlock(&in_dev->lock);
		    in_dev_put(in_dev);
	    }
    }
    

    /*
     * 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, brd, &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 (addr)
	    arp_send(
		ARPOP_REPLY, ETH_P_ARP,
		addr, /* Target address of ARP packet is our address */
		&strip_info->dev,	       /* Device to send packet on */
		addr, /* 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 net_device *dev)
{
    struct strip *strip_info = (struct strip *)(dev->priv);

    if (!netif_running(dev))
    {
        printk(KERN_ERR "%s: xmit call when iface is down\n", dev->name);
        return(1);
    }

    netif_stop_queue(dev);
    
    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 net_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 net_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 (