net/x25/x25_subr.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        Jonathan Naylor   Started coding.
  18  *      X.25 002        Jonathan Naylor   Centralised disconnection processing.
  19  *      mar/20/00       Daniela Squassoni Disabling/enabling of facilities
  20  *                                        negotiation.
  21  *      jun/24/01       Arnaldo C. Melo   use skb_queue_purge, cleanups
  22  *      apr/04/15       Shaun Pereira           Fast select with no
  23  *                                              restriction on response.
  24  */
  25
  26 #define pr_fmt(fmt) "X25: " fmt
  27
  28 #include <linux/slab.h>
  29 #include <linux/kernel.h>
  30 #include <linux/string.h>
  31 #include <linux/skbuff.h>
  32 #include <net/sock.h>
  33 #include <net/tcp_states.h>
  34 #include <net/x25.h>
  35
  36 /*
  37  *      This routine purges all of the queues of frames.
  38  */
  39 void x25_clear_queues(struct sock *sk)
  40 {
  41         struct x25_sock *x25 = x25_sk(sk);
  42
  43         skb_queue_purge(&sk->sk_write_queue);
  44         skb_queue_purge(&x25->ack_queue);
  45         skb_queue_purge(&x25->interrupt_in_queue);
  46         skb_queue_purge(&x25->interrupt_out_queue);
  47         skb_queue_purge(&x25->fragment_queue);
  48 }
  49
  50
  51 /*
  52  * This routine purges the input queue of those frames that have been
  53  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  54  * SDL diagram.
  55 */
  56 void x25_frames_acked(struct sock *sk, unsigned short nr)
  57 {
  58         struct sk_buff *skb;
  59         struct x25_sock *x25 = x25_sk(sk);
  60         int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
  61
  62         /*
  63          * Remove all the ack-ed frames from the ack queue.
  64          */
  65         if (x25->va != nr)
  66                 while (skb_peek(&x25->ack_queue) && x25->va != nr) {
  67                         skb = skb_dequeue(&x25->ack_queue);
  68                         kfree_skb(skb);
  69                         x25->va = (x25->va + 1) % modulus;
  70                 }
  71 }
  72
  73 void x25_requeue_frames(struct sock *sk)
  74 {
  75         struct sk_buff *skb, *skb_prev = NULL;
  76
  77         /*
  78          * Requeue all the un-ack-ed frames on the output queue to be picked
  79          * up by x25_kick. This arrangement handles the possibility of an empty
  80          * output queue.
  81          */
  82         while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
  83                 if (!skb_prev)
  84                         skb_queue_head(&sk->sk_write_queue, skb);
  85                 else
  86                         skb_append(skb_prev, skb, &sk->sk_write_queue);
  87                 skb_prev = skb;
  88         }
  89 }
  90
  91 /*
  92  *      Validate that the value of nr is between va and vs. Return true or
  93  *      false for testing.
  94  */
  95 int x25_validate_nr(struct sock *sk, unsigned short nr)
  96 {
  97         struct x25_sock *x25 = x25_sk(sk);
  98         unsigned short vc = x25->va;
  99         int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
 100
 101         while (vc != x25->vs) {
 102                 if (nr == vc)
 103                         return 1;
 104                 vc = (vc + 1) % modulus;
 105         }
 106
 107         return nr == x25->vs ? 1 : 0;
 108 }
 109
 110 /*
 111  *  This routine is called when the packet layer internally generates a
 112  *  control frame.
 113  */
 114 void x25_write_internal(struct sock *sk, int frametype)
 115 {
 116         struct x25_sock *x25 = x25_sk(sk);
 117         struct sk_buff *skb;
 118         unsigned char  *dptr;
 119         unsigned char  facilities[X25_MAX_FAC_LEN];
 120         unsigned char  addresses[1 + X25_ADDR_LEN];
 121         unsigned char  lci1, lci2;
 122         /*
 123          *      Default safe frame size.
 124          */
 125         int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
 126
 127         /*
 128          *      Adjust frame size.
 129          */
 130         switch (frametype) {
 131         case X25_CALL_REQUEST:
 132                 len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
 133                 break;
 134         case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
 135                 if (x25->facilities.reverse & 0x80) {
 136                         len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
 137                 } else {
 138                         len += 1 + X25_MAX_FAC_LEN;
 139                 }
 140                 break;
 141         case X25_CLEAR_REQUEST:
 142         case X25_RESET_REQUEST:
 143                 len += 2;
 144                 break;
 145         case X25_RR:
 146         case X25_RNR:
 147         case X25_REJ:
 148         case X25_CLEAR_CONFIRMATION:
 149         case X25_INTERRUPT_CONFIRMATION:
 150         case X25_RESET_CONFIRMATION:
 151                 break;
 152         default:
 153                 pr_err("invalid frame type %02X\n", frametype);
 154                 return;
 155         }
 156
 157         if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
 158                 return;
 159
 160         /*
 161          *      Space for Ethernet and 802.2 LLC headers.
 162          */
 163         skb_reserve(skb, X25_MAX_L2_LEN);
 164
 165         /*
 166          *      Make space for the GFI and LCI, and fill them in.
 167          */
 168         dptr = skb_put(skb, 2);
 169
 170         lci1 = (x25->lci >> 8) & 0x0F;
 171         lci2 = (x25->lci >> 0) & 0xFF;
 172
 173         if (x25->neighbour->extended) {
 174                 *dptr++ = lci1 | X25_GFI_EXTSEQ;
 175                 *dptr++ = lci2;
 176         } else {
 177                 *dptr++ = lci1 | X25_GFI_STDSEQ;
 178                 *dptr++ = lci2;
 179         }
 180
 181         /*
 182          *      Now fill in the frame type specific information.
 183          */
 184         switch (frametype) {
 185
 186                 case X25_CALL_REQUEST:
 187                         dptr    = skb_put(skb, 1);
 188                         *dptr++ = X25_CALL_REQUEST;
 189                         len     = x25_addr_aton(addresses, &x25->dest_addr,
 190                                                 &x25->source_addr);
 191                         skb_put_data(skb, addresses, len);
 192                         len     = x25_create_facilities(facilities,
 193                                         &x25->facilities,
 194                                         &x25->dte_facilities,
 195                                         x25->neighbour->global_facil_mask);
 196                         skb_put_data(skb, facilities, len);
 197                         skb_put_data(skb, x25->calluserdata.cuddata,
 198                                      x25->calluserdata.cudlength);
 199                         x25->calluserdata.cudlength = 0;
 200                         break;
 201
 202                 case X25_CALL_ACCEPTED:
 203                         dptr    = skb_put(skb, 2);
 204                         *dptr++ = X25_CALL_ACCEPTED;
 205                         *dptr++ = 0x00;         /* Address lengths */
 206                         len     = x25_create_facilities(facilities,
 207                                                         &x25->facilities,
 208                                                         &x25->dte_facilities,
 209                                                         x25->vc_facil_mask);
 210                         skb_put_data(skb, facilities, len);
 211
 212                         /* fast select with no restriction on response
 213                                 allows call user data. Userland must
 214                                 ensure it is ours and not theirs */
 215                         if(x25->facilities.reverse & 0x80) {
 216                                 skb_put_data(skb,
 217                                              x25->calluserdata.cuddata,
 218                                              x25->calluserdata.cudlength);
 219                         }
 220                         x25->calluserdata.cudlength = 0;
 221                         break;
 222
 223                 case X25_CLEAR_REQUEST:
 224                         dptr    = skb_put(skb, 3);
 225                         *dptr++ = frametype;
 226                         *dptr++ = x25->causediag.cause;
 227                         *dptr++ = x25->causediag.diagnostic;
 228                         break;
 229
 230                 case X25_RESET_REQUEST:
 231                         dptr    = skb_put(skb, 3);
 232                         *dptr++ = frametype;
 233                         *dptr++ = 0x00;         /* XXX */
 234                         *dptr++ = 0x00;         /* XXX */
 235                         break;
 236
 237                 case X25_RR:
 238                 case X25_RNR:
 239                 case X25_REJ:
 240                         if (x25->neighbour->extended) {
 241                                 dptr     = skb_put(skb, 2);
 242                                 *dptr++  = frametype;
 243                                 *dptr++  = (x25->vr << 1) & 0xFE;
 244                         } else {
 245                                 dptr     = skb_put(skb, 1);
 246                                 *dptr    = frametype;
 247                                 *dptr++ |= (x25->vr << 5) & 0xE0;
 248                         }
 249                         break;
 250
 251                 case X25_CLEAR_CONFIRMATION:
 252                 case X25_INTERRUPT_CONFIRMATION:
 253                 case X25_RESET_CONFIRMATION:
 254                         dptr  = skb_put(skb, 1);
 255                         *dptr = frametype;
 256                         break;
 257         }
 258
 259         x25_transmit_link(skb, x25->neighbour);
 260 }
 261
 262 /*
 263  *      Unpick the contents of the passed X.25 Packet Layer frame.
 264  */
 265 int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
 266                int *d, int *m)
 267 {
 268         struct x25_sock *x25 = x25_sk(sk);
 269         unsigned char *frame;
 270
 271         if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
 272                 return X25_ILLEGAL;
 273         frame = skb->data;
 274
 275         *ns = *nr = *q = *d = *m = 0;
 276
 277         switch (frame[2]) {
 278         case X25_CALL_REQUEST:
 279         case X25_CALL_ACCEPTED:
 280         case X25_CLEAR_REQUEST:
 281         case X25_CLEAR_CONFIRMATION:
 282         case X25_INTERRUPT:
 283         case X25_INTERRUPT_CONFIRMATION:
 284         case X25_RESET_REQUEST:
 285         case X25_RESET_CONFIRMATION:
 286         case X25_RESTART_REQUEST:
 287         case X25_RESTART_CONFIRMATION:
 288         case X25_REGISTRATION_REQUEST:
 289         case X25_REGISTRATION_CONFIRMATION:
 290         case X25_DIAGNOSTIC:
 291                 return frame[2];
 292         }
 293
 294         if (x25->neighbour->extended) {
 295                 if (frame[2] == X25_RR  ||
 296                     frame[2] == X25_RNR ||
 297                     frame[2] == X25_REJ) {
 298                         if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
 299                                 return X25_ILLEGAL;
 300                         frame = skb->data;
 301
 302                         *nr = (frame[3] >> 1) & 0x7F;
 303                         return frame[2];
 304                 }
 305         } else {
 306                 if ((frame[2] & 0x1F) == X25_RR  ||
 307                     (frame[2] & 0x1F) == X25_RNR ||
 308                     (frame[2] & 0x1F) == X25_REJ) {
 309                         *nr = (frame[2] >> 5) & 0x07;
 310                         return frame[2] & 0x1F;
 311                 }
 312         }
 313
 314         if (x25->neighbour->extended) {
 315                 if ((frame[2] & 0x01) == X25_DATA) {
 316                         if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
 317                                 return X25_ILLEGAL;
 318                         frame = skb->data;
 319
 320                         *q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
 321                         *d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
 322                         *m  = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
 323                         *nr = (frame[3] >> 1) & 0x7F;
 324                         *ns = (frame[2] >> 1) & 0x7F;
 325                         return X25_DATA;
 326                 }
 327         } else {
 328                 if ((frame[2] & 0x01) == X25_DATA) {
 329                         *q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
 330                         *d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
 331                         *m  = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
 332                         *nr = (frame[2] >> 5) & 0x07;
 333                         *ns = (frame[2] >> 1) & 0x07;
 334                         return X25_DATA;
 335                 }
 336         }
 337
 338         pr_debug("invalid PLP frame %02X %02X %02X\n",
 339                frame[0], frame[1], frame[2]);
 340
 341         return X25_ILLEGAL;
 342 }
 343
 344 void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
 345                     unsigned char diagnostic)
 346 {
 347         struct x25_sock *x25 = x25_sk(sk);
 348
 349         x25_clear_queues(sk);
 350         x25_stop_timer(sk);
 351
 352         x25->lci   = 0;
 353         x25->state = X25_STATE_0;
 354
 355         x25->causediag.cause      = cause;
 356         x25->causediag.diagnostic = diagnostic;
 357
 358         sk->sk_state     = TCP_CLOSE;
 359         sk->sk_err       = reason;
 360         sk->sk_shutdown |= SEND_SHUTDOWN;
 361
 362         if (!sock_flag(sk, SOCK_DEAD)) {
 363                 sk->sk_state_change(sk);
 364                 sock_set_flag(sk, SOCK_DEAD);
 365         }
 366         if (x25->neighbour) {
 367                 read_lock_bh(&x25_list_lock);
 368                 x25_neigh_put(x25->neighbour);
 369                 x25->neighbour = NULL;
 370                 read_unlock_bh(&x25_list_lock);
 371         }
 372 }
 373
 374 /*
 375  * Clear an own-rx-busy condition and tell the peer about this, provided
 376  * that there is a significant amount of free receive buffer space available.
 377  */
 378 void x25_check_rbuf(struct sock *sk)
 379 {
 380         struct x25_sock *x25 = x25_sk(sk);
 381
 382         if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf >> 1) &&
 383             (x25->condition & X25_COND_OWN_RX_BUSY)) {
 384                 x25->condition &= ~X25_COND_OWN_RX_BUSY;
 385                 x25->condition &= ~X25_COND_ACK_PENDING;
 386                 x25->vl         = x25->vr;
 387                 x25_write_internal(sk, X25_RR);
 388                 x25_stop_timer(sk);
 389         }
 390 }
 391