net/ax25/ax25_addr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *
   4  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   5  */
   6 #include <linux/errno.h>
   7 #include <linux/types.h>
   8 #include <linux/socket.h>
   9 #include <linux/in.h>
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/timer.h>
  13 #include <linux/string.h>
  14 #include <linux/sockios.h>
  15 #include <linux/net.h>
  16 #include <net/ax25.h>
  17 #include <linux/inet.h>
  18 #include <linux/netdevice.h>
  19 #include <linux/skbuff.h>
  20 #include <net/sock.h>
  21 #include <linux/uaccess.h>
  22 #include <linux/fcntl.h>
  23 #include <linux/mm.h>
  24 #include <linux/interrupt.h>
  25
  26 /*
  27  * The default broadcast address of an interface is QST-0; the default address
  28  * is LINUX-1.  The null address is defined as a callsign of all spaces with
  29  * an SSID of zero.
  30  */
  31
  32 const ax25_address ax25_bcast =
  33         {{'Q' << 1, 'S' << 1, 'T' << 1, ' ' << 1, ' ' << 1, ' ' << 1, 0 << 1}};
  34 const ax25_address ax25_defaddr =
  35         {{'L' << 1, 'I' << 1, 'N' << 1, 'U' << 1, 'X' << 1, ' ' << 1, 1 << 1}};
  36 const ax25_address null_ax25_address =
  37         {{' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, ' ' << 1, 0 << 1}};
  38
  39 EXPORT_SYMBOL_GPL(ax25_bcast);
  40 EXPORT_SYMBOL_GPL(ax25_defaddr);
  41 EXPORT_SYMBOL(null_ax25_address);
  42
  43 /*
  44  *      ax25 -> ascii conversion
  45  */
  46 char *ax2asc(char *buf, const ax25_address *a)
  47 {
  48         char c, *s;
  49         int n;
  50
  51         for (n = 0, s = buf; n < 6; n++) {
  52                 c = (a->ax25_call[n] >> 1) & 0x7F;
  53
  54                 if (c != ' ') *s++ = c;
  55         }
  56
  57         *s++ = '-';
  58
  59         if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
  60                 *s++ = '1';
  61                 n -= 10;
  62         }
  63
  64         *s++ = n + '0';
  65         *s++ = '\0';
  66
  67         if (*buf == '\0' || *buf == '-')
  68            return "*";
  69
  70         return buf;
  71
  72 }
  73
  74 EXPORT_SYMBOL(ax2asc);
  75
  76 /*
  77  *      ascii -> ax25 conversion
  78  */
  79 void asc2ax(ax25_address *addr, const char *callsign)
  80 {
  81         const char *s;
  82         int n;
  83
  84         for (s = callsign, n = 0; n < 6; n++) {
  85                 if (*s != '\0' && *s != '-')
  86                         addr->ax25_call[n] = *s++;
  87                 else
  88                         addr->ax25_call[n] = ' ';
  89                 addr->ax25_call[n] <<= 1;
  90                 addr->ax25_call[n] &= 0xFE;
  91         }
  92
  93         if (*s++ == '\0') {
  94                 addr->ax25_call[6] = 0x00;
  95                 return;
  96         }
  97
  98         addr->ax25_call[6] = *s++ - '0';
  99
 100         if (*s != '\0') {
 101                 addr->ax25_call[6] *= 10;
 102                 addr->ax25_call[6] += *s++ - '0';
 103         }
 104
 105         addr->ax25_call[6] <<= 1;
 106         addr->ax25_call[6] &= 0x1E;
 107 }
 108
 109 EXPORT_SYMBOL(asc2ax);
 110
 111 /*
 112  *      Compare two ax.25 addresses
 113  */
 114 int ax25cmp(const ax25_address *a, const ax25_address *b)
 115 {
 116         int ct = 0;
 117
 118         while (ct < 6) {
 119                 if ((a->ax25_call[ct] & 0xFE) != (b->ax25_call[ct] & 0xFE))     /* Clean off repeater bits */
 120                         return 1;
 121                 ct++;
 122         }
 123
 124         if ((a->ax25_call[ct] & 0x1E) == (b->ax25_call[ct] & 0x1E))     /* SSID without control bit */
 125                 return 0;
 126
 127         return 2;                       /* Partial match */
 128 }
 129
 130 EXPORT_SYMBOL(ax25cmp);
 131
 132 /*
 133  *      Compare two AX.25 digipeater paths.
 134  */
 135 int ax25digicmp(const ax25_digi *digi1, const ax25_digi *digi2)
 136 {
 137         int i;
 138
 139         if (digi1->ndigi != digi2->ndigi)
 140                 return 1;
 141
 142         if (digi1->lastrepeat != digi2->lastrepeat)
 143                 return 1;
 144
 145         for (i = 0; i < digi1->ndigi; i++)
 146                 if (ax25cmp(&digi1->calls[i], &digi2->calls[i]) != 0)
 147                         return 1;
 148
 149         return 0;
 150 }
 151
 152 /*
 153  *      Given an AX.25 address pull of to, from, digi list, command/response and the start of data
 154  *
 155  */
 156 const unsigned char *ax25_addr_parse(const unsigned char *buf, int len,
 157         ax25_address *src, ax25_address *dest, ax25_digi *digi, int *flags,
 158         int *dama)
 159 {
 160         int d = 0;
 161
 162         if (len < 14) return NULL;
 163
 164         if (flags != NULL) {
 165                 *flags = 0;
 166
 167                 if (buf[6] & AX25_CBIT)
 168                         *flags = AX25_COMMAND;
 169                 if (buf[13] & AX25_CBIT)
 170                         *flags = AX25_RESPONSE;
 171         }
 172
 173         if (dama != NULL)
 174                 *dama = ~buf[13] & AX25_DAMA_FLAG;
 175
 176         /* Copy to, from */
 177         if (dest != NULL)
 178                 memcpy(dest, buf + 0, AX25_ADDR_LEN);
 179         if (src != NULL)
 180                 memcpy(src,  buf + 7, AX25_ADDR_LEN);
 181
 182         buf += 2 * AX25_ADDR_LEN;
 183         len -= 2 * AX25_ADDR_LEN;
 184
 185         digi->lastrepeat = -1;
 186         digi->ndigi      = 0;
 187
 188         while (!(buf[-1] & AX25_EBIT)) {
 189                 if (d >= AX25_MAX_DIGIS)
 190                         return NULL;
 191                 if (len < AX25_ADDR_LEN)
 192                         return NULL;
 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, const ax25_address *src,
 216         const ax25_address *dest, const ax25_digi *d, int flag, int modulus)
 217 {
 218         int len = 0;
 219         int ct  = 0;
 220
 221         memcpy(buf, dest, AX25_ADDR_LEN);
 222         buf[6] &= ~(AX25_EBIT | AX25_CBIT);
 223         buf[6] |= AX25_SSSID_SPARE;
 224
 225         if (flag == AX25_COMMAND) buf[6] |= AX25_CBIT;
 226
 227         buf += AX25_ADDR_LEN;
 228         len += AX25_ADDR_LEN;
 229
 230         memcpy(buf, src, AX25_ADDR_LEN);
 231         buf[6] &= ~(AX25_EBIT | AX25_CBIT);
 232         buf[6] &= ~AX25_SSSID_SPARE;
 233
 234         if (modulus == AX25_MODULUS)
 235                 buf[6] |= AX25_SSSID_SPARE;
 236         else
 237                 buf[6] |= AX25_ESSID_SPARE;
 238
 239         if (flag == AX25_RESPONSE) buf[6] |= AX25_CBIT;
 240
 241         /*
 242          *      Fast path the normal digiless path
 243          */
 244         if (d == NULL || d->ndigi == 0) {
 245                 buf[6] |= AX25_EBIT;
 246                 return 2 * AX25_ADDR_LEN;
 247         }
 248
 249         buf += AX25_ADDR_LEN;
 250         len += AX25_ADDR_LEN;
 251
 252         while (ct < d->ndigi) {
 253                 memcpy(buf, &d->calls[ct], AX25_ADDR_LEN);
 254
 255                 if (d->repeated[ct])
 256                         buf[6] |= AX25_HBIT;
 257                 else
 258                         buf[6] &= ~AX25_HBIT;
 259
 260                 buf[6] &= ~AX25_EBIT;
 261                 buf[6] |= AX25_SSSID_SPARE;
 262
 263                 buf += AX25_ADDR_LEN;
 264                 len += AX25_ADDR_LEN;
 265                 ct++;
 266         }
 267
 268         buf[-1] |= AX25_EBIT;
 269
 270         return len;
 271 }
 272
 273 int ax25_addr_size(const ax25_digi *dp)
 274 {
 275         if (dp == NULL)
 276                 return 2 * AX25_ADDR_LEN;
 277
 278         return AX25_ADDR_LEN * (2 + dp->ndigi);
 279 }
 280
 281 /*
 282  *      Reverse Digipeat List. May not pass both parameters as same struct
 283  */
 284 void ax25_digi_invert(const ax25_digi *in, ax25_digi *out)
 285 {
 286         int ct;
 287
 288         out->ndigi      = in->ndigi;
 289         out->lastrepeat = in->ndigi - in->lastrepeat - 2;
 290
 291         /* Invert the digipeaters */
 292         for (ct = 0; ct < in->ndigi; ct++) {
 293                 out->calls[ct] = in->calls[in->ndigi - ct - 1];
 294
 295                 if (ct <= out->lastrepeat) {
 296                         out->calls[ct].ax25_call[6] |= AX25_HBIT;
 297                         out->repeated[ct]            = 1;
 298                 } else {
 299                         out->calls[ct].ax25_call[6] &= ~AX25_HBIT;
 300                         out->repeated[ct]            = 0;
 301                 }
 302         }
 303 }