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