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