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