net/x25/x25_facilities.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      X.25 Packet Layer release 002
   4  *
   5  *      This is ALPHA test software. This code may break your machine,
   6  *      randomly fail to work with new releases, misbehave and/or generally
   7  *      screw up. It might even work.
   8  *
   9  *      This code REQUIRES 2.1.15 or higher
  10  *
  11  *      History
  12  *      X.25 001        Split from x25_subr.c
  13  *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
  14  *                                        negotiation.
  15  *      apr/14/05       Shaun Pereira - Allow fast select with no restriction
  16  *                                      on response.
  17  */
  18
  19 #define pr_fmt(fmt) "X25: " fmt
  20
  21 #include <linux/kernel.h>
  22 #include <linux/string.h>
  23 #include <linux/skbuff.h>
  24 #include <net/sock.h>
  25 #include <net/x25.h>
  26
  27 /**
  28  * x25_parse_facilities - Parse facilities from skb into the facilities structs
  29  *
  30  * @skb: sk_buff to parse
  31  * @facilities: Regular facilities, updated as facilities are found
  32  * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
  33  * @vc_fac_mask: mask is updated with all facilities found
  34  *
  35  * Return codes:
  36  *  -1 - Parsing error, caller should drop call and clean up
  37  *   0 - Parse OK, this skb has no facilities
  38  *  >0 - Parse OK, returns the length of the facilities header
  39  *
  40  */
  41 int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
  42                 struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
  43 {
  44         unsigned char *p;
  45         unsigned int len;
  46
  47         *vc_fac_mask = 0;
  48
  49         /*
  50          * The kernel knows which facilities were set on an incoming call but
  51          * currently this information is not available to userspace.  Here we
  52          * give userspace who read incoming call facilities 0 length to indicate
  53          * it wasn't set.
  54          */
  55         dte_facs->calling_len = 0;
  56         dte_facs->called_len = 0;
  57         memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
  58         memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
  59
  60         if (!pskb_may_pull(skb, 1))
  61                 return 0;
  62
  63         len = skb->data[0];
  64
  65         if (!pskb_may_pull(skb, 1 + len))
  66                 return -1;
  67
  68         p = skb->data + 1;
  69
  70         while (len > 0) {
  71                 switch (*p & X25_FAC_CLASS_MASK) {
  72                 case X25_FAC_CLASS_A:
  73                         if (len < 2)
  74                                 return -1;
  75                         switch (*p) {
  76                         case X25_FAC_REVERSE:
  77                                 if((p[1] & 0x81) == 0x81) {
  78                                         facilities->reverse = p[1] & 0x81;
  79                                         *vc_fac_mask |= X25_MASK_REVERSE;
  80                                         break;
  81                                 }
  82
  83                                 if((p[1] & 0x01) == 0x01) {
  84                                         facilities->reverse = p[1] & 0x01;
  85                                         *vc_fac_mask |= X25_MASK_REVERSE;
  86                                         break;
  87                                 }
  88
  89                                 if((p[1] & 0x80) == 0x80) {
  90                                         facilities->reverse = p[1] & 0x80;
  91                                         *vc_fac_mask |= X25_MASK_REVERSE;
  92                                         break;
  93                                 }
  94
  95                                 if(p[1] == 0x00) {
  96                                         facilities->reverse
  97                                                 = X25_DEFAULT_REVERSE;
  98                                         *vc_fac_mask |= X25_MASK_REVERSE;
  99                                         break;
 100                                 }
 101                                 fallthrough;
 102                         case X25_FAC_THROUGHPUT:
 103                                 facilities->throughput = p[1];
 104                                 *vc_fac_mask |= X25_MASK_THROUGHPUT;
 105                                 break;
 106                         case X25_MARKER:
 107                                 break;
 108                         default:
 109                                 pr_debug("unknown facility "
 110                                        "%02X, value %02X\n",
 111                                        p[0], p[1]);
 112                                 break;
 113                         }
 114                         p   += 2;
 115                         len -= 2;
 116                         break;
 117                 case X25_FAC_CLASS_B:
 118                         if (len < 3)
 119                                 return -1;
 120                         switch (*p) {
 121                         case X25_FAC_PACKET_SIZE:
 122                                 facilities->pacsize_in  = p[1];
 123                                 facilities->pacsize_out = p[2];
 124                                 *vc_fac_mask |= X25_MASK_PACKET_SIZE;
 125                                 break;
 126                         case X25_FAC_WINDOW_SIZE:
 127                                 facilities->winsize_in  = p[1];
 128                                 facilities->winsize_out = p[2];
 129                                 *vc_fac_mask |= X25_MASK_WINDOW_SIZE;
 130                                 break;
 131                         default:
 132                                 pr_debug("unknown facility "
 133                                        "%02X, values %02X, %02X\n",
 134                                        p[0], p[1], p[2]);
 135                                 break;
 136                         }
 137                         p   += 3;
 138                         len -= 3;
 139                         break;
 140                 case X25_FAC_CLASS_C:
 141                         if (len < 4)
 142                                 return -1;
 143                         pr_debug("unknown facility %02X, "
 144                                "values %02X, %02X, %02X\n",
 145                                p[0], p[1], p[2], p[3]);
 146                         p   += 4;
 147                         len -= 4;
 148                         break;
 149                 case X25_FAC_CLASS_D:
 150                         if (len < p[1] + 2)
 151                                 return -1;
 152                         switch (*p) {
 153                         case X25_FAC_CALLING_AE:
 154                                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
 155                                         return -1;
 156                                 if (p[2] > X25_MAX_AE_LEN)
 157                                         return -1;
 158                                 dte_facs->calling_len = p[2];
 159                                 memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
 160                                 *vc_fac_mask |= X25_MASK_CALLING_AE;
 161                                 break;
 162                         case X25_FAC_CALLED_AE:
 163                                 if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
 164                                         return -1;
 165                                 if (p[2] > X25_MAX_AE_LEN)
 166                                         return -1;
 167                                 dte_facs->called_len = p[2];
 168                                 memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
 169                                 *vc_fac_mask |= X25_MASK_CALLED_AE;
 170                                 break;
 171                         default:
 172                                 pr_debug("unknown facility %02X,"
 173                                         "length %d\n", p[0], p[1]);
 174                                 break;
 175                         }
 176                         len -= p[1] + 2;
 177                         p += p[1] + 2;
 178                         break;
 179                 }
 180         }
 181
 182         return p - skb->data;
 183 }
 184
 185 /*
 186  *      Create a set of facilities.
 187  */
 188 int x25_create_facilities(unsigned char *buffer,
 189                 struct x25_facilities *facilities,
 190                 struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
 191 {
 192         unsigned char *p = buffer + 1;
 193         int len;
 194
 195         if (!facil_mask) {
 196                 /*
 197                  * Length of the facilities field in call_req or
 198                  * call_accept packets
 199                  */
 200                 buffer[0] = 0;
 201                 len = 1; /* 1 byte for the length field */
 202                 return len;
 203         }
 204
 205         if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
 206                 *p++ = X25_FAC_REVERSE;
 207                 *p++ = facilities->reverse;
 208         }
 209
 210         if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
 211                 *p++ = X25_FAC_THROUGHPUT;
 212                 *p++ = facilities->throughput;
 213         }
 214
 215         if ((facilities->pacsize_in || facilities->pacsize_out) &&
 216             (facil_mask & X25_MASK_PACKET_SIZE)) {
 217                 *p++ = X25_FAC_PACKET_SIZE;
 218                 *p++ = facilities->pacsize_in ? : facilities->pacsize_out;
 219                 *p++ = facilities->pacsize_out ? : facilities->pacsize_in;
 220         }
 221
 222         if ((facilities->winsize_in || facilities->winsize_out) &&
 223             (facil_mask & X25_MASK_WINDOW_SIZE)) {
 224                 *p++ = X25_FAC_WINDOW_SIZE;
 225                 *p++ = facilities->winsize_in ? : facilities->winsize_out;
 226                 *p++ = facilities->winsize_out ? : facilities->winsize_in;
 227         }
 228
 229         if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
 230                 *p++ = X25_MARKER;
 231                 *p++ = X25_DTE_SERVICES;
 232         }
 233
 234         if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
 235                 unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
 236                 *p++ = X25_FAC_CALLING_AE;
 237                 *p++ = 1 + bytecount;
 238                 *p++ = dte_facs->calling_len;
 239                 memcpy(p, dte_facs->calling_ae, bytecount);
 240                 p += bytecount;
 241         }
 242
 243         if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
 244                 unsigned int bytecount = (dte_facs->called_len % 2) ?
 245                 dte_facs->called_len / 2 + 1 :
 246                 dte_facs->called_len / 2;
 247                 *p++ = X25_FAC_CALLED_AE;
 248                 *p++ = 1 + bytecount;
 249                 *p++ = dte_facs->called_len;
 250                 memcpy(p, dte_facs->called_ae, bytecount);
 251                 p+=bytecount;
 252         }
 253
 254         len       = p - buffer;
 255         buffer[0] = len - 1;
 256
 257         return len;
 258 }
 259
 260 /*
 261  *      Try to reach a compromise on a set of facilities.
 262  *
 263  *      The only real problem is with reverse charging.
 264  */
 265 int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
 266                 struct x25_facilities *new, struct x25_dte_facilities *dte)
 267 {
 268         struct x25_sock *x25 = x25_sk(sk);
 269         struct x25_facilities *ours = &x25->facilities;
 270         struct x25_facilities theirs;
 271         int len;
 272
 273         memset(&theirs, 0, sizeof(theirs));
 274         memcpy(new, ours, sizeof(*new));
 275         memset(dte, 0, sizeof(*dte));
 276
 277         len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
 278         if (len < 0)
 279                 return len;
 280
 281         /*
 282          *      They want reverse charging, we won't accept it.
 283          */
 284         if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
 285                 SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
 286                 return -1;
 287         }
 288
 289         new->reverse = theirs.reverse;
 290
 291         if (theirs.throughput) {
 292                 int theirs_in =  theirs.throughput & 0x0f;
 293                 int theirs_out = theirs.throughput & 0xf0;
 294                 int ours_in  = ours->throughput & 0x0f;
 295                 int ours_out = ours->throughput & 0xf0;
 296                 if (!ours_in || theirs_in < ours_in) {
 297                         SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
 298                         new->throughput = (new->throughput & 0xf0) | theirs_in;
 299                 }
 300                 if (!ours_out || theirs_out < ours_out) {
 301                         SOCK_DEBUG(sk,
 302                                 "X.25: outbound throughput negotiated\n");
 303                         new->throughput = (new->throughput & 0x0f) | theirs_out;
 304                 }
 305         }
 306
 307         if (theirs.pacsize_in && theirs.pacsize_out) {
 308                 if (theirs.pacsize_in < ours->pacsize_in) {
 309                         SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
 310                         new->pacsize_in = theirs.pacsize_in;
 311                 }
 312                 if (theirs.pacsize_out < ours->pacsize_out) {
 313                         SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
 314                         new->pacsize_out = theirs.pacsize_out;
 315                 }
 316         }
 317
 318         if (theirs.winsize_in && theirs.winsize_out) {
 319                 if (theirs.winsize_in < ours->winsize_in) {
 320                         SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
 321                         new->winsize_in = theirs.winsize_in;
 322                 }
 323                 if (theirs.winsize_out < ours->winsize_out) {
 324                         SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
 325                         new->winsize_out = theirs.winsize_out;
 326                 }
 327         }
 328
 329         return len;
 330 }
 331
 332 /*
 333  *      Limit values of certain facilities according to the capability of the
 334  *      currently attached x25 link.
 335  */
 336 void x25_limit_facilities(struct x25_facilities *facilities,
 337                           struct x25_neigh *nb)
 338 {
 339
 340         if (!nb->extended) {
 341                 if (facilities->winsize_in  > 7) {
 342                         pr_debug("incoming winsize limited to 7\n");
 343                         facilities->winsize_in = 7;
 344                 }
 345                 if (facilities->winsize_out > 7) {
 346                         facilities->winsize_out = 7;
 347                         pr_debug("outgoing winsize limited to 7\n");
 348                 }
 349         }
 350 }