net/x25/x25_facilities.c

   1 /*
   2  *      X.25 Packet Layer release 002
   3  *
   4  *      This is ALPHA test software. This code may break your machine,
   5  *      randomly fail to work with new releases, misbehave and/or generally
   6  *      screw up. It might even work.
   7  *
   8  *      This code REQUIRES 2.1.15 or higher
   9  *
  10  *      This module:
  11  *              This module is free software; you can redistribute it and/or
  12  *              modify it under the terms of the GNU General Public License
  13  *              as published by the Free Software Foundation; either version
  14  *              2 of the License, or (at your option) any later version.
  15  *
  16  *      History
  17  *      X.25 001        Split from x25_subr.c
  18  *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
  19  *                                        negotiation.
  20  *      apr/14/05       Shaun Pereira - Allow fast select with no restriction
  21  *                                      on response.
  22  */
  23
  24 #define pr_fmt(fmt) "X25: " fmt
  25
  26 #include <linux/kernel.h>
  27 #include <linux/string.h>
  28 #include <linux/skbuff.h>
  29 #include <net/sock.h>
  30 #include <net/x25.h>
  31
  32 /**
  33  * x25_parse_facilities - Parse facilities from skb into the facilities structs
  34  *
  35  * @skb: sk_buff to parse
  36  * @facilities: Regular facilities, updated as facilities are found
  37  * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
  38  * @vc_fac_mask: mask is updated with all facilities found
  39  *
  40  * Return codes:
  41  *  -1 - Parsing error, caller should drop call and clean up
  42  *   0 - Parse OK, this skb has no facilities
  43  *  >0 - Parse OK, returns the length of the facilities header
  44  *
  45  */
  46 int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
  47                 struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
  48 {
  49         unsigned char *p;
  50         unsigned int len;
  51
  52         *vc_fac_mask = 0;
  53
  54         /*
  55          * The kernel knows which facilities were set on an incoming call but
  56          * currently this information is not available to userspace.  Here we
  57          * give userspace who read incoming call facilities 0 length to indicate
  58          * it wasn't set.
  59          */
  60         dte_facs->calling_len = 0;
  61         dte_facs->called_len = 0;
  62         memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
  63         memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
  64
  65         if (!pskb_may_pull(skb, 1))
  66                 return 0;
  67
  68         len = skb->data[0];
  69
  70         if (!pskb_may_pull(skb, 1 + len))
  71                 return -1;
  72
  73         p = skb->data + 1;
  74
  75         while (len > 0) {
  76                 switch (*p & X25_FAC_CLASS_MASK) {
  77                 case X25_FAC_CLASS_A:
  78                         if (len < 2)
  79                                 return -1;
  80                         switch (*p) {
  81                         case X25_FAC_REVERSE:
  82                                 if((p[1] & 0x81) == 0x81) {
  83                                         facilities->reverse = p[1] & 0x81;
  84                                         *vc_fac_mask |= X25_MASK_REVERSE;
  85                                         break;
  86                                 }
  87
  88                                 if((p[1] & 0x01) == 0x01) {
  89                                         facilities->reverse = p[1] & 0x01;
  90                                         *vc_fac_mask |= X25_MASK_REVERSE;
  91                                         break;
  92                                 }
  93
  94                                 if((p[1] & 0x80) == 0x80) {
  95                                         facilities->reverse = p[1] & 0x80;
  96                                         *vc_fac_mask |= X25_MASK_REVERSE;
  97                                         break;
  98                                 }
  99
 100                                 if(p[1] == 0x00) {
 101                                         facilities->reverse
 102                                                 = X25_DEFAULT_REVERSE;
 103                                         *vc_fac_mask |= X25_MASK_REVERSE;
 104                                         break;
 105                                 }
 106                                 /*fall through */
 107                         case X25_FAC_THROUGHPUT:
 108                                 facilities->throughput = p[1];
 109                                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
 110                                 break;
 111                         case X25_MARKER:
 112                                 break;
 113                         default:
 114                                 pr_debug("unknown facility "
 115                                        "%02X, value %02X\n",
 116                                        p[0], p[1]);
 117                                 break;
 118                         }
 119                         p   += 2;
 120                         len -= 2;
 121                         break;
 122                 case X25_FAC_CLASS_B:
 123                         if (len < 3)
 124                                 return -1;
 125                         switch (*p) {
 126                         case X25_FAC_PACKET_SIZE:
 127                                 facilities->pacsize_in  = p[1];
 128                                 facilities->pacsize_out = p[2];
 129                                 *vc_fac_mask |= X25_MASK_PACKET_SIZE;
 130                                 break;
 131                         case X25_FAC_WINDOW_SIZE:
 132                                 facilities->winsize_in  = p[1];
 133                                 facilities->winsize_out = p[2];
 134                                 *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
 135                                 break;
 136                         default:
 137                                 pr_debug("unknown facility "
 138                                        "%02X, values %02X, %02X\n",
 139                                        p[0], p[1], p[2]);
 140                                 break;
 141                         }
 142                         p   += 3;
 143                         len -= 3;
 144                         break;
 145                 case X25_FAC_CLASS_C:
 146                         if (len < 4)
 147                                 return -1;
 148                         pr_debug("unknown facility %02X, "
 149                                "values %02X, %02X, %02X\n",
 150                                p[0], p[1], p[2], p[3]);
 151                         p   += 4;
 152                         len -= 4;
 153                         break;
 154                 case X25_FAC_CLASS_D:
 155                         if (len < p[1] + 2)
 156                                 return -1;
 157                         switch (*p) {
 158                         case X25_FAC_CALLING_AE:
 159                                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
 160                                         return -1;
 161                                 if (p[2] > X25_MAX_AE_LEN)
 162                                         return -1;
 163                                 dte_facs->calling_len = p[2];
 164                                 memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
 165                                 *vc_fac_mask |= X25_MASK_CALLING_AE;
 166                                 break;
 167                         case X25_FAC_CALLED_AE:
 168                                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
 169                                         return -1;
 170                                 if (p[2] > X25_MAX_AE_LEN)
 171                                         return -1;
 172                                 dte_facs->called_len = p[2];
 173                                 memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
 174                                 *vc_fac_mask |= X25_MASK_CALLED_AE;
 175                                 break;
 176                         default:
 177                                 pr_debug("unknown facility %02X,"
 178                                         "length %d\n", p[0], p[1]);
 179                                 break;
 180                         }
 181                         len -= p[1] + 2;
 182                         p += p[1] + 2;
 183                         break;
 184                 }
 185         }
 186
 187         return p - skb->data;
 188 }
 189
 190 /*
 191  *      Create a set of facilities.
 192  */
 193 int x25_create_facilities(unsigned char *buffer,
 194                 struct x25_facilities *facilities,
 195                 struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
 196 {
 197         unsigned char *p = buffer + 1;
 198         int len;
 199
 200         if (!facil_mask) {
 201                 /*
 202                  * Length of the facilities field in call_req or
 203                  * call_accept packets
 204                  */
 205                 buffer[0] = 0;
 206                 len = 1; /* 1 byte for the length field */
 207                 return len;
 208         }
 209
 210         if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
 211                 *p++ = X25_FAC_REVERSE;
 212                 *p++ = facilities->reverse;
 213         }
 214
 215         if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
 216                 *p++ = X25_FAC_THROUGHPUT;
 217                 *p++ = facilities->throughput;
 218         }
 219
 220         if ((facilities->pacsize_in || facilities->pacsize_out) &&
 221             (facil_mask & X25_MASK_PACKET_SIZE)) {
 222                 *p++ = X25_FAC_PACKET_SIZE;
 223                 *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
 224                 *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
 225         }
 226
 227         if ((facilities->winsize_in || facilities->winsize_out) &&
 228             (facil_mask & X25_MASK_WINDOW_SIZE)) {
 229                 *p++ = X25_FAC_WINDOW_SIZE;
 230                 *p++ = facilities->winsize_in ? : facilities->winsize_out;
 231                 *p++ = facilities->winsize_out ? : facilities->winsize_in;
 232         }
 233
 234         if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
 235                 *p++ = X25_MARKER;
 236                 *p++ = X25_DTE_SERVICES;
 237         }
 238
 239         if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
 240                 unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
 241                 *p++ = X25_FAC_CALLING_AE;
 242                 *p++ = 1 + bytecount;
 243                 *p++ = dte_facs->calling_len;
 244                 memcpy(p, dte_facs->calling_ae, bytecount);
 245                 p += bytecount;
 246         }
 247
 248         if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
 249                 unsigned int bytecount = (dte_facs->called_len % 2) ?
 250                 dte_facs->called_len / 2 + 1 :
 251                 dte_facs->called_len / 2;
 252                 *p++ = X25_FAC_CALLED_AE;
 253                 *p++ = 1 + bytecount;
 254                 *p++ = dte_facs->called_len;
 255                 memcpy(p, dte_facs->called_ae, bytecount);
 256                 p+=bytecount;
 257         }
 258
 259         len       = p - buffer;
 260         buffer[0] = len - 1;
 261
 262         return len;
 263 }
 264
 265 /*
 266  *      Try to reach a compromise on a set of facilities.
 267  *
 268  *      The only real problem is with reverse charging.
 269  */
 270 int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
 271                 struct x25_facilities *new, struct x25_dte_facilities *dte)
 272 {
 273         struct x25_sock *x25 = x25_sk(sk);
 274         struct x25_facilities *ours = &x25->facilities;
 275         struct x25_facilities theirs;
 276         int len;
 277
 278         memset(&theirs, 0, sizeof(theirs));
 279         memcpy(new, ours, sizeof(*new));
 280         memset(dte, 0, sizeof(*dte));
 281
 282         len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
 283         if (len < 0)
 284                 return len;
 285
 286         /*
 287          *      They want reverse charging, we won't accept it.
 288          */
 289         if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
 290                 SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
 291                 return -1;
 292         }
 293
 294         new->reverse = theirs.reverse;
 295
 296         if (theirs.throughput) {
 297                 int theirs_in =  theirs.throughput & 0x0f;
 298                 int theirs_out = theirs.throughput & 0xf0;
 299                 int ours_in  = ours->throughput & 0x0f;
 300                 int ours_out = ours->throughput & 0xf0;
 301                 if (!ours_in || theirs_in < ours_in) {
 302                         SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
 303                         new->throughput = (new->throughput & 0xf0) | theirs_in;
 304                 }
 305                 if (!ours_out || theirs_out < ours_out) {
 306                         SOCK_DEBUG(sk,
 307                                 "X.25: outbound throughput negotiated\n");
 308                         new->throughput = (new->throughput & 0x0f) | theirs_out;
 309                 }
 310         }
 311
 312         if (theirs.pacsize_in && theirs.pacsize_out) {
 313                 if (theirs.pacsize_in < ours->pacsize_in) {
 314                         SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
 315                         new->pacsize_in = theirs.pacsize_in;
 316                 }
 317                 if (theirs.pacsize_out < ours->pacsize_out) {
 318                         SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
 319                         new->pacsize_out = theirs.pacsize_out;
 320                 }
 321         }
 322
 323         if (theirs.winsize_in && theirs.winsize_out) {
 324                 if (theirs.winsize_in < ours->winsize_in) {
 325                         SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
 326                         new->winsize_in = theirs.winsize_in;
 327                 }
 328                 if (theirs.winsize_out < ours->winsize_out) {
 329                         SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
 330                         new->winsize_out = theirs.winsize_out;
 331                 }
 332         }
 333
 334         return len;
 335 }
 336
 337 /*
 338  *      Limit values of certain facilities according to the capability of the
 339  *      currently attached x25 link.
 340  */
 341 void x25_limit_facilities(struct x25_facilities *facilities,
 342                           struct x25_neigh *nb)
 343 {
 344
 345         if (!nb->extended) {
 346                 if (facilities->winsize_in  > 7) {
 347                         pr_debug("incoming winsize limited to 7\n");
 348                         facilities->winsize_in = 7;
 349                 }
 350                 if (facilities->winsize_out > 7) {
 351                         facilities->winsize_out = 7;
 352                         pr_debug("outgoing winsize limited to 7\n");
 353                 }
 354         }
 355 }