net/ax25/ax25_addr.c

   1 /*
   2  *      AX.25 release 037
   3  *
   4  *      This code REQUIRES 2.1.15 or higher/ NET3.038
   5  *
   6  *      This module:
   7  *              This module is free software; you can redistribute it and/or
   8  *              modify it under the terms of the GNU General Public License
   9  *              as published by the Free Software Foundation; either version
  10  *              2 of the License, or (at your option) any later version.
  11  *
  12  *      Most of this code is based on the SDL diagrams published in the 7th
  13  *      ARRL Computer Networking Conference papers. The diagrams have mistakes
  14  *      in them, but are mostly correct. Before you modify the code could you
  15  *      read the SDL diagrams as the code is not obvious and probably very
  16  *      easy to break;
  17  *
  18  *      History
  19  *      AX.25 036       Jonathan(G4KLX) Split from ax25_subr.c.
  20  */
  21
  22 #include <linux/config.h>
  23 #if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
  24 #include <linux/errno.h>
  25 #include <linux/types.h>
  26 #include <linux/socket.h>
  27 #include <linux/in.h>
  28 #include <linux/kernel.h>
  29 #include <linux/sched.h>
  30 #include <linux/timer.h>
  31 #include <linux/string.h>
  32 #include <linux/sockios.h>
  33 #include <linux/net.h>
  34 #include <net/ax25.h>
  35 #include <linux/inet.h>
  36 #include <linux/netdevice.h>
  37 #include <linux/skbuff.h>
  38 #include <net/sock.h>
  39 #include <asm/uaccess.h>
  40 #include <asm/system.h>
  41 #include <linux/fcntl.h>
  42 #include <linux/mm.h>
  43 #include <linux/interrupt.h>
  44
  45 /*
  46  *      The null address is defined as a callsign of all spaces with an
  47  *      SSID of zero.
  48  */
  49 ax25_address null_ax25_address = {{0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x00}};
  50
  51 /*
  52  *      ax25 -> ascii conversion
  53  */
  54 char *ax2asc(ax25_address *a)
  55 {
  56         static char buf[11];
  57         char c, *s;
  58         int n;
  59
  60         for (n = 0, s = buf; n < 6; n++) {
  61                 c = (a->ax25_call[n] >> 1) & 0x7F;
  62
  63                 if (c != ' ') *s++ = c;
  64         }
  65
  66         *s++ = '-';
  67
  68         if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
  69                 *s++ = '1';
  70                 n -= 10;
  71         }
  72
  73         *s++ = n + '0';
  74         *s++ = '\0';
  75
  76         if (*buf == '\0' || *buf == '-')
  77            return "*";
  78
  79         return buf;
  80
  81 }
  82
  83 /*
  84  *      ascii -> ax25 conversion
  85  */
  86 ax25_address *asc2ax(char *callsign)
  87 {
  88         static ax25_address addr;
  89         char *s;
  90         int n;
  91
  92         for (s = callsign, n = 0; n < 6; n++) {
  93                 if (*s != '\0' && *s != '-')
  94                         addr.ax25_call[n] = *s++;
  95                 else
  96                         addr.ax25_call[n] = ' ';
  97                 addr.ax25_call[n] <<= 1;
  98                 addr.ax25_call[n] &= 0xFE;
  99         }
 100
 101         if (*s++ == '\0') {
 102                 addr.ax25_call[6] = 0x00;
 103                 return &addr;
 104         }
 105
 106         addr.ax25_call[6] = *s++ - '0';
 107
 108         if (*s != '\0') {
 109                 addr.ax25_call[6] *= 10;
 110                 addr.ax25_call[6] += *s++ - '0';
 111         }
 112
 113         addr.ax25_call[6] <<= 1;
 114         addr.ax25_call[6] &= 0x1E;
 115
 116         return &addr;
 117 }
 118
 119 /*
 120  *      Compare two ax.25 addresses
 121  */
 122 int ax25cmp(ax25_address *a, ax25_address *b)
 123 {
 124         int ct = 0;
 125
 126         while (ct < 6) {
 127                 if ((a->ax25_call[ct] & 0xFE) != (b->ax25_call[ct] & 0xFE))     /* Clean off repeater bits */
 128                         return 1;
 129                 ct++;
 130         }
 131
 132         if ((a->ax25_call[ct] & 0x1E) == (b->ax25_call[ct] & 0x1E))     /* SSID without control bit */
 133                 return 0;
 134
 135         return 2;                       /* Partial match */
 136 }
 137
 138 /*
 139  *      Compare two AX.25 digipeater paths.
 140  */
 141 int ax25digicmp(ax25_digi *digi1, ax25_digi *digi2)
 142 {
 143         int i;
 144
 145         if (digi1->ndigi != digi2->ndigi)
 146                 return 1;
 147
 148         if (digi1->lastrepeat != digi2->lastrepeat)
 149                 return 1;
 150
 151         for (i = 0; i < digi1->ndigi; i++)
 152                 if (ax25cmp(&digi1->calls[i], &digi2->calls[i]) != 0)
 153                         return 1;
 154
 155         return 0;
 156 }
 157
 158 /*
 159  *      Given an AX.25 address pull of to, from, digi list, command/response and the start of data
 160  *
 161  */
 162 unsigned char *ax25_addr_parse(unsigned char *buf, int len, ax25_address *src, ax25_address *dest, ax25_digi *digi, int *flags, int *dama)
 163 {
 164         int d = 0;
 165
 166         if (len < 14) return NULL;
 167
 168         if (flags != NULL) {
 169                 *flags = 0;
 170
 171                 if (buf[6] & AX25_CBIT)
 172                         *flags = AX25_COMMAND;
 173                 if (buf[13] & AX25_CBIT)
 174                         *flags = AX25_RESPONSE;
 175         }
 176
 177         if (dama != NULL)
 178                 *dama = ~buf[13] & AX25_DAMA_FLAG;
 179
 180         /* Copy to, from */
 181         if (dest != NULL)
 182                 memcpy(dest, buf + 0, AX25_ADDR_LEN);
 183         if (src != NULL)
 184                 memcpy(src,  buf + 7, AX25_ADDR_LEN);
 185
 186         buf += 2 * AX25_ADDR_LEN;
 187         len -= 2 * AX25_ADDR_LEN;
 188
 189         digi->lastrepeat = -1;
 190         digi->ndigi      = 0;
 191
 192         while (!(buf[-1] & AX25_EBIT)) {
 193                 if (d >= AX25_MAX_DIGIS)  return NULL;  /* Max of 6 digis */
 194                 if (len < 7) return NULL;       /* Short packet */
 195
 196                 memcpy(&digi->calls[d], buf, AX25_ADDR_LEN);
 197                 digi->ndigi = d + 1;
 198
 199                 if (buf[6] & AX25_HBIT) {
 200                         digi->repeated[d] = 1;
 201                         digi->lastrepeat  = d;
 202                 } else {
 203                         digi->repeated[d] = 0;
 204                 }
 205
 206                 buf += AX25_ADDR_LEN;
 207                 len -= AX25_ADDR_LEN;
 208                 d++;
 209         }
 210
 211         return buf;
 212 }
 213
 214 /*
 215  *      Assemble an AX.25 header from the bits
 216  */
 217 int ax25_addr_build(unsigned char *buf, ax25_address *src, ax25_address *dest, ax25_digi *d, int flag, int modulus)
 218 {
 219         int len = 0;
 220         int ct  = 0;
 221
 222         memcpy(buf, dest, AX25_ADDR_LEN);
 223         buf[6] &= ~(AX25_EBIT | AX25_CBIT);
 224         buf[6] |= AX25_SSSID_SPARE;
 225
 226         if (flag == AX25_COMMAND) buf[6] |= AX25_CBIT;
 227
 228         buf += AX25_ADDR_LEN;
 229         len += AX25_ADDR_LEN;
 230
 231         memcpy(buf, src, AX25_ADDR_LEN);
 232         buf[6] &= ~(AX25_EBIT | AX25_CBIT);
 233         buf[6] &= ~AX25_SSSID_SPARE;
 234
 235         if (modulus == AX25_MODULUS)
 236                 buf[6] |= AX25_SSSID_SPARE;
 237         else
 238                 buf[6] |= AX25_ESSID_SPARE;
 239
 240         if (flag == AX25_RESPONSE) buf[6] |= AX25_CBIT;
 241
 242         /*
 243          *      Fast path the normal digiless path
 244          */
 245         if (d == NULL || d->ndigi == 0) {
 246                 buf[6] |= AX25_EBIT;
 247                 return 2 * AX25_ADDR_LEN;
 248         }
 249
 250         buf += AX25_ADDR_LEN;
 251         len += AX25_ADDR_LEN;
 252
 253         while (ct < d->ndigi) {
 254                 memcpy(buf, &d->calls[ct], AX25_ADDR_LEN);
 255
 256                 if (d->repeated[ct])
 257                         buf[6] |= AX25_HBIT;
 258                 else
 259                         buf[6] &= ~AX25_HBIT;
 260
 261                 buf[6] &= ~AX25_EBIT;
 262                 buf[6] |= AX25_SSSID_SPARE;
 263
 264                 buf += AX25_ADDR_LEN;
 265                 len += AX25_ADDR_LEN;
 266                 ct++;
 267         }
 268
 269         buf[-1] |= AX25_EBIT;
 270
 271         return len;
 272 }
 273
 274 int ax25_addr_size(ax25_digi *dp)
 275 {
 276         if (dp == NULL)
 277                 return 2 * AX25_ADDR_LEN;
 278
 279         return AX25_ADDR_LEN * (2 + dp->ndigi);
 280 }
 281
 282 /*
 283  *      Reverse Digipeat List. May not pass both parameters as same struct
 284  */
 285 void ax25_digi_invert(ax25_digi *in, ax25_digi *out)
 286 {
 287         int ct;
 288
 289         out->ndigi      = in->ndigi;
 290         out->lastrepeat = in->ndigi - in->lastrepeat - 2;
 291
 292         /* Invert the digipeaters */
 293         for (ct = 0; ct < in->ndigi; ct++) {
 294                 out->calls[ct] = in->calls[in->ndigi - ct - 1];
 295
 296                 if (ct <= out->lastrepeat) {
 297                         out->calls[ct].ax25_call[6] |= AX25_HBIT;
 298                         out->repeated[ct]            = 1;
 299                 } else {
 300                         out->calls[ct].ax25_call[6] &= ~AX25_HBIT;
 301                         out->repeated[ct]            = 0;
 302                 }
 303         }
 304 }
 305
 306 #endif