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 facilities, 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;
  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 (!pskb_may_pull(skb, 1))
  64                 return 0;
  65
  66         len = skb->data[0];
  67
  68         if (!pskb_may_pull(skb, 1 + len))
  69                 return -1;
  70
  71         p = skb->data + 1;
  72
  73         while (len > 0) {
  74                 switch (*p & X25_FAC_CLASS_MASK) {
  75                 case X25_FAC_CLASS_A:
  76                         if (len < 2)
  77                                 return -1;
  78                         switch (*p) {
  79                         case X25_FAC_REVERSE:
  80                                 if((p[1] & 0x81) == 0x81) {
  81                                         facilities->reverse = p[1] & 0x81;
  82                                         *vc_fac_mask |= X25_MASK_REVERSE;
  83                                         break;
  84                                 }
  85
  86                                 if((p[1] & 0x01) == 0x01) {
  87                                         facilities->reverse = p[1] & 0x01;
  88                                         *vc_fac_mask |= X25_MASK_REVERSE;
  89                                         break;
  90                                 }
  91
  92                                 if((p[1] & 0x80) == 0x80) {
  93                                         facilities->reverse = p[1] & 0x80;
  94                                         *vc_fac_mask |= X25_MASK_REVERSE;
  95                                         break;
  96                                 }
  97
  98                                 if(p[1] == 0x00) {
  99                                         facilities->reverse
 100                                                 = X25_DEFAULT_REVERSE;
 101                                         *vc_fac_mask |= X25_MASK_REVERSE;
 102                                         break;
 103                                 }
 104
 105                         case X25_FAC_THROUGHPUT:
 106                                 facilities->throughput = p[1];
 107                                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
 108                                 break;
 109                         case X25_MARKER:
 110                                 break;
 111                         default:
 112                                 printk(KERN_DEBUG "X.25: unknown facility "
 113                                        "%02X, value %02X\n",
 114                                        p[0], p[1]);
 115                                 break;
 116                         }
 117                         p   += 2;
 118                         len -= 2;
 119                         break;
 120                 case X25_FAC_CLASS_B:
 121                         if (len < 3)
 122                                 return -1;
 123                         switch (*p) {
 124                         case X25_FAC_PACKET_SIZE:
 125                                 facilities->pacsize_in  = p[1];
 126                                 facilities->pacsize_out = p[2];
 127                                 *vc_fac_mask |= X25_MASK_PACKET_SIZE;
 128                                 break;
 129                         case X25_FAC_WINDOW_SIZE:
 130                                 facilities->winsize_in  = p[1];
 131                                 facilities->winsize_out = p[2];
 132                                 *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
 133                                 break;
 134                         default:
 135                                 printk(KERN_DEBUG "X.25: unknown facility "
 136                                        "%02X, values %02X, %02X\n",
 137                                        p[0], p[1], p[2]);
 138                                 break;
 139                         }
 140                         p   += 3;
 141                         len -= 3;
 142                         break;
 143                 case X25_FAC_CLASS_C:
 144                         if (len < 4)
 145                                 return -1;
 146                         printk(KERN_DEBUG "X.25: unknown facility %02X, "
 147                                "values %02X, %02X, %02X\n",
 148                                p[0], p[1], p[2], p[3]);
 149                         p   += 4;
 150                         len -= 4;
 151                         break;
 152                 case X25_FAC_CLASS_D:
 153                         if (len < p[1] + 2)
 154                                 return -1;
 155                         switch (*p) {
 156                         case X25_FAC_CALLING_AE:
 157                                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
 158                                         return -1;
 159                                 dte_facs->calling_len = p[2];
 160                                 memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
 161                                 *vc_fac_mask |= X25_MASK_CALLING_AE;
 162                                 break;
 163                         case X25_FAC_CALLED_AE:
 164                                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
 165                                         return -1;
 166                                 dte_facs->called_len = p[2];
 167                                 memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
 168                                 *vc_fac_mask |= X25_MASK_CALLED_AE;
 169                                 break;
 170                         default:
 171                                 printk(KERN_DEBUG "X.25: unknown facility %02X,"
 172                                         "length %d\n", p[0], p[1]);
 173                                 break;
 174                         }
 175                         len -= p[1] + 2;
 176                         p += p[1] + 2;
 177                         break;
 178                 }
 179         }
 180
 181         return p - skb->data;
 182 }
 183
 184 /*
 185  *      Create a set of facilities.
 186  */
 187 int x25_create_facilities(unsigned char *buffer,
 188                 struct x25_facilities *facilities,
 189                 struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
 190 {
 191         unsigned char *p = buffer + 1;
 192         int len;
 193
 194         if (!facil_mask) {
 195                 /*
 196                  * Length of the facilities field in call_req or
 197                  * call_accept packets
 198                  */
 199                 buffer[0] = 0;
 200                 len = 1; /* 1 byte for the length field */
 201                 return len;
 202         }
 203
 204         if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
 205                 *p++ = X25_FAC_REVERSE;
 206                 *p++ = facilities->reverse;
 207         }
 208
 209         if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
 210                 *p++ = X25_FAC_THROUGHPUT;
 211                 *p++ = facilities->throughput;
 212         }
 213
 214         if ((facilities->pacsize_in || facilities->pacsize_out) &&
 215             (facil_mask & X25_MASK_PACKET_SIZE)) {
 216                 *p++ = X25_FAC_PACKET_SIZE;
 217                 *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
 218                 *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
 219         }
 220
 221         if ((facilities->winsize_in || facilities->winsize_out) &&
 222             (facil_mask & X25_MASK_WINDOW_SIZE)) {
 223                 *p++ = X25_FAC_WINDOW_SIZE;
 224                 *p++ = facilities->winsize_in ? : facilities->winsize_out;
 225                 *p++ = facilities->winsize_out ? : facilities->winsize_in;
 226         }
 227
 228         if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
 229                 *p++ = X25_MARKER;
 230                 *p++ = X25_DTE_SERVICES;
 231         }
 232
 233         if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
 234                 unsigned bytecount = (dte_facs->calling_len + 1) >> 1;
 235                 *p++ = X25_FAC_CALLING_AE;
 236                 *p++ = 1 + bytecount;
 237                 *p++ = dte_facs->calling_len;
 238                 memcpy(p, dte_facs->calling_ae, bytecount);
 239                 p += bytecount;
 240         }
 241
 242         if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
 243                 unsigned bytecount = (dte_facs->called_len % 2) ?
 244                 dte_facs->called_len / 2 + 1 :
 245                 dte_facs->called_len / 2;
 246                 *p++ = X25_FAC_CALLED_AE;
 247                 *p++ = 1 + bytecount;
 248                 *p++ = dte_facs->called_len;
 249                 memcpy(p, dte_facs->called_ae, bytecount);
 250                 p+=bytecount;
 251         }
 252
 253         len       = p - buffer;
 254         buffer[0] = len - 1;
 255
 256         return len;
 257 }
 258
 259 /*
 260  *      Try to reach a compromise on a set of facilities.
 261  *
 262  *      The only real problem is with reverse charging.
 263  */
 264 int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
 265                 struct x25_facilities *new, struct x25_dte_facilities *dte)
 266 {
 267         struct x25_sock *x25 = x25_sk(sk);
 268         struct x25_facilities *ours = &x25->facilities;
 269         struct x25_facilities theirs;
 270         int len;
 271
 272         memset(&theirs, 0, sizeof(theirs));
 273         memcpy(new, ours, sizeof(*new));
 274
 275         len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
 276         if (len < 0)
 277                 return len;
 278
 279         /*
 280          *      They want reverse charging, we won't accept it.
 281          */
 282         if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
 283                 SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
 284                 return -1;
 285         }
 286
 287         new->reverse = theirs.reverse;
 288
 289         if (theirs.throughput) {
 290                 int theirs_in =  theirs.throughput & 0x0f;
 291                 int theirs_out = theirs.throughput & 0xf0;
 292                 int ours_in  = ours->throughput & 0x0f;
 293                 int ours_out = ours->throughput & 0xf0;
 294                 if (!ours_in || theirs_in < ours_in) {
 295                         SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
 296                         new->throughput = (new->throughput & 0xf0) | theirs_in;
 297                 }
 298                 if (!ours_out || theirs_out < ours_out) {
 299                         SOCK_DEBUG(sk,
 300                                 "X.25: outbound throughput negotiated\n");
 301                         new->throughput = (new->throughput & 0x0f) | theirs_out;
 302                 }
 303         }
 304
 305         if (theirs.pacsize_in && theirs.pacsize_out) {
 306                 if (theirs.pacsize_in < ours->pacsize_in) {
 307                         SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
 308                         new->pacsize_in = theirs.pacsize_in;
 309                 }
 310                 if (theirs.pacsize_out < ours->pacsize_out) {
 311                         SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
 312                         new->pacsize_out = theirs.pacsize_out;
 313                 }
 314         }
 315
 316         if (theirs.winsize_in && theirs.winsize_out) {
 317                 if (theirs.winsize_in < ours->winsize_in) {
 318                         SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
 319                         new->winsize_in = theirs.winsize_in;
 320                 }
 321                 if (theirs.winsize_out < ours->winsize_out) {
 322                         SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
 323                         new->winsize_out = theirs.winsize_out;
 324                 }
 325         }
 326
 327         return len;
 328 }
 329
 330 /*
 331  *      Limit values of certain facilities according to the capability of the
 332  *      currently attached x25 link.
 333  */
 334 void x25_limit_facilities(struct x25_facilities *facilities,
 335                           struct x25_neigh *nb)
 336 {
 337
 338         if (!nb->extended) {
 339                 if (facilities->winsize_in  > 7) {
 340                         printk(KERN_DEBUG "X.25: incoming winsize limited to 7\n");
 341                         facilities->winsize_in = 7;
 342                 }
 343                 if (facilities->winsize_out > 7) {
 344                         facilities->winsize_out = 7;
 345                         printk( KERN_DEBUG "X.25: outgoing winsize limited to 7\n");
 346                 }
 347         }
 348 }