linux/net/x25/x25_facilities.c
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   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 */
  41int 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 */
 188int 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 */
 265int 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 */
 336void 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}
 351