ax25_addr.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Copyright (C) Jonathan Naylor G4KLX ([email protected])
 */
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>

/*
 * The default broadcast address of an interface is QST-0; the default address
 * is LINUX-1.  The null address is defined as a callsign of all spaces with
 * an SSID of zero.
 */

const ax25_address ax25_bcast =
    {{'Q' << 1, 'S' << 1, 'T' << 1, ' ' << 1, ' ' << 1, ' ' << 1, 0 << 1}};
const ax25_address ax25_defaddr =
    {{'L' << 1, 'I' << 1, 'N' << 1, 'U' << 1, 'X' << 1, ' ' << 1, 1 << 1}};
const ax25_address null_ax25_address =
    {{' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, 0 << 1}};

EXPORT_SYMBOL_GPL(ax25_bcast);
EXPORT_SYMBOL_GPL(ax25_defaddr);
EXPORT_SYMBOL(null_ax25_address);

/*
 *  ax25 -> ascii conversion
 */
char *ax2asc(char *buf, const ax25_address *a)
{
    char c, *s;
    int n;

    for (n = 0, s = buf; n < 6; n++) {
        c = (a->ax25_call[n] >> 1) & 0x7F;

        if (c != ' ') *s++ = c;
    }

    *s++ = '-';

    if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
        *s++ = '1';
        n -= 10;
    }

    *s++ = n + '0';
    *s++ = '\0';

    if (*buf == '\0' || *buf == '-')
       return "*";

    return buf;

}

EXPORT_SYMBOL(ax2asc);

/*
 *  ascii -> ax25 conversion
 */
void asc2ax(ax25_address *addr, const char *callsign)
{
    const char *s;
    int n;

    for (s = callsign, n = 0; n < 6; n++) {
        if (*s != '\0' && *s != '-')
            addr->ax25_call[n] = *s++;
        else
            addr->ax25_call[n] = ' ';
        addr->ax25_call[n] <<= 1;
        addr->ax25_call[n] &= 0xFE;
    }

    if (*s++ == '\0') {
        addr->ax25_call[6] = 0x00;
        return;
    }

    addr->ax25_call[6] = *s++ - '0';

    if (*s != '\0') {
        addr->ax25_call[6] *= 10;
        addr->ax25_call[6] += *s++ - '0';
    }

    addr->ax25_call[6] <<= 1;
    addr->ax25_call[6] &= 0x1E;
}

EXPORT_SYMBOL(asc2ax);

/*
 *  Compare two ax.25 addresses
 */
int ax25cmp(const ax25_address *a, const ax25_address *b)
{
    int ct = 0;

    while (ct < 6) {
        if ((a->ax25_call[ct] & 0xFE) != (b->ax25_call[ct] & 0xFE)) /* Clean off repeater bits */
            return 1;
        ct++;
    }

    if ((a->ax25_call[ct] & 0x1E) == (b->ax25_call[ct] & 0x1E)) /* SSID without control bit */
        return 0;

    return 2;           /* Partial match */
}

EXPORT_SYMBOL(ax25cmp);

/*
 *  Compare two AX.25 digipeater paths.
 */
int ax25digicmp(const ax25_digi *digi1, const ax25_digi *digi2)
{
    int i;

    if (digi1->ndigi != digi2->ndigi)
        return 1;

    if (digi1->lastrepeat != digi2->lastrepeat)
        return 1;

    for (i = 0; i < digi1->ndigi; i++)
        if (ax25cmp(&digi1->calls[i], &digi2->calls[i]) != 0)
            return 1;

    return 0;
}

/*
 *  Given an AX.25 address pull of to, from, digi list, command/response and the start of data
 *
 */
const unsigned char *ax25_addr_parse(const unsigned char *buf, int len,
    ax25_address *src, ax25_address *dest, ax25_digi *digi, int *flags,
    int *dama)
{
    int d = 0;

    if (len < 14) return NULL;

    if (flags != NULL) {
        *flags = 0;

        if (buf[6] & AX25_CBIT)
            *flags = AX25_COMMAND;
        if (buf[13] & AX25_CBIT)
            *flags = AX25_RESPONSE;
    }

    if (dama != NULL)
        *dama = ~buf[13] & AX25_DAMA_FLAG;

    /* Copy to, from */
    if (dest != NULL)
        memcpy(dest, buf + 0, AX25_ADDR_LEN);
    if (src != NULL)
        memcpy(src,  buf + 7, AX25_ADDR_LEN);

    buf += 2 * AX25_ADDR_LEN;
    len -= 2 * AX25_ADDR_LEN;

    digi->lastrepeat = -1;
    digi->ndigi      = 0;

    while (!(buf[-1] & AX25_EBIT)) {
        if (d >= AX25_MAX_DIGIS)
            return NULL;
        if (len < AX25_ADDR_LEN)
            return NULL;

        memcpy(&digi->calls[d], buf, AX25_ADDR_LEN);
        digi->ndigi = d + 1;

        if (buf[6] & AX25_HBIT) {
            digi->repeated[d] = 1;
            digi->lastrepeat  = d;
        } else {
            digi->repeated[d] = 0;
        }

        buf += AX25_ADDR_LEN;
        len -= AX25_ADDR_LEN;
        d++;
    }

    return buf;
}

/*
 *  Assemble an AX.25 header from the bits
 */
int ax25_addr_build(unsigned char *buf, const ax25_address *src,
    const ax25_address *dest, const ax25_digi *d, int flag, int modulus)
{
    int len = 0;
    int ct  = 0;

    memcpy(buf, dest, AX25_ADDR_LEN);
    buf[6] &= ~(AX25_EBIT | AX25_CBIT);
    buf[6] |= AX25_SSSID_SPARE;

    if (flag == AX25_COMMAND) buf[6] |= AX25_CBIT;

    buf += AX25_ADDR_LEN;
    len += AX25_ADDR_LEN;

    memcpy(buf, src, AX25_ADDR_LEN);
    buf[6] &= ~(AX25_EBIT | AX25_CBIT);
    buf[6] &= ~AX25_SSSID_SPARE;

    if (modulus == AX25_MODULUS)
        buf[6] |= AX25_SSSID_SPARE;
    else
        buf[6] |= AX25_ESSID_SPARE;

    if (flag == AX25_RESPONSE) buf[6] |= AX25_CBIT;

    /*
     *  Fast path the normal digiless path
     */
    if (d == NULL || d->ndigi == 0) {
        buf[6] |= AX25_EBIT;
        return 2 * AX25_ADDR_LEN;
    }

    buf += AX25_ADDR_LEN;
    len += AX25_ADDR_LEN;

    while (ct < d->ndigi) {
        memcpy(buf, &d->calls[ct], AX25_ADDR_LEN);

        if (d->repeated[ct])
            buf[6] |= AX25_HBIT;
        else
            buf[6] &= ~AX25_HBIT;

        buf[6] &= ~AX25_EBIT;
        buf[6] |= AX25_SSSID_SPARE;

        buf += AX25_ADDR_LEN;
        len += AX25_ADDR_LEN;
        ct++;
    }

    buf[-1] |= AX25_EBIT;

    return len;
}

int ax25_addr_size(const ax25_digi *dp)
{
    if (dp == NULL)
        return 2 * AX25_ADDR_LEN;

    return AX25_ADDR_LEN * (2 + dp->ndigi);
}

/*
 *  Reverse Digipeat List. May not pass both parameters as same struct
 */
void ax25_digi_invert(const ax25_digi *in, ax25_digi *out)
{
    int ct;

    out->ndigi      = in->ndigi;
    out->lastrepeat = in->ndigi - in->lastrepeat - 2;

    /* Invert the digipeaters */
    for (ct = 0; ct < in->ndigi; ct++) {
        out->calls[ct] = in->calls[in->ndigi - ct - 1];

        if (ct <= out->lastrepeat) {
            out->calls[ct].ax25_call[6] |= AX25_HBIT;
            out->repeated[ct]            = 1;
        } else {
            out->calls[ct].ax25_call[6] &= ~AX25_HBIT;
            out->repeated[ct]            = 0;
        }
    }
}