LXR linux/net/x25/x25

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