net/ax25/ax25_std_in.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify
   3  * it under the terms of the GNU General Public License as published by
   4  * the Free Software Foundation; either version 2 of the License, or
   5  * (at your option) any later version.
   6  *
   7  * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   8  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   9  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
  10  * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
  11  *
  12  * Most of this code is based on the SDL diagrams published in the 7th ARRL
  13  * Computer Networking Conference papers. The diagrams have mistakes in them,
  14  * but are mostly correct. Before you modify the code could you read the SDL
  15  * diagrams as the code is not obvious and probably very easy to break.
  16  */
  17 #include <linux/errno.h>
  18 #include <linux/types.h>
  19 #include <linux/socket.h>
  20 #include <linux/in.h>
  21 #include <linux/kernel.h>
  22 #include <linux/timer.h>
  23 #include <linux/string.h>
  24 #include <linux/sockios.h>
  25 #include <linux/net.h>
  26 #include <net/ax25.h>
  27 #include <linux/inet.h>
  28 #include <linux/netdevice.h>
  29 #include <linux/skbuff.h>
  30 #include <net/sock.h>
  31 #include <net/tcp_states.h>
  32 #include <linux/uaccess.h>
  33 #include <linux/fcntl.h>
  34 #include <linux/mm.h>
  35 #include <linux/interrupt.h>
  36
  37 /*
  38  *      State machine for state 1, Awaiting Connection State.
  39  *      The handling of the timer(s) is in file ax25_std_timer.c.
  40  *      Handling of state 0 and connection release is in ax25.c.
  41  */
  42 static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
  43 {
  44         switch (frametype) {
  45         case AX25_SABM:
  46                 ax25->modulus = AX25_MODULUS;
  47                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  48                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  49                 break;
  50
  51         case AX25_SABME:
  52                 ax25->modulus = AX25_EMODULUS;
  53                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
  54                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  55                 break;
  56
  57         case AX25_DISC:
  58                 ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
  59                 break;
  60
  61         case AX25_UA:
  62                 if (pf) {
  63                         ax25_calculate_rtt(ax25);
  64                         ax25_stop_t1timer(ax25);
  65                         ax25_start_t3timer(ax25);
  66                         ax25_start_idletimer(ax25);
  67                         ax25->vs      = 0;
  68                         ax25->va      = 0;
  69                         ax25->vr      = 0;
  70                         ax25->state   = AX25_STATE_3;
  71                         ax25->n2count = 0;
  72                         if (ax25->sk != NULL) {
  73                                 bh_lock_sock(ax25->sk);
  74                                 ax25->sk->sk_state = TCP_ESTABLISHED;
  75                                 /* For WAIT_SABM connections we will produce an accept ready socket here */
  76                                 if (!sock_flag(ax25->sk, SOCK_DEAD))
  77                                         ax25->sk->sk_state_change(ax25->sk);
  78                                 bh_unlock_sock(ax25->sk);
  79                         }
  80                 }
  81                 break;
  82
  83         case AX25_DM:
  84                 if (pf) {
  85                         if (ax25->modulus == AX25_MODULUS) {
  86                                 ax25_disconnect(ax25, ECONNREFUSED);
  87                         } else {
  88                                 ax25->modulus = AX25_MODULUS;
  89                                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  90                         }
  91                 }
  92                 break;
  93
  94         default:
  95                 break;
  96         }
  97
  98         return 0;
  99 }
 100
 101 /*
 102  *      State machine for state 2, Awaiting Release State.
 103  *      The handling of the timer(s) is in file ax25_std_timer.c
 104  *      Handling of state 0 and connection release is in ax25.c.
 105  */
 106 static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
 107 {
 108         switch (frametype) {
 109         case AX25_SABM:
 110         case AX25_SABME:
 111                 ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
 112                 break;
 113
 114         case AX25_DISC:
 115                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 116                 ax25_disconnect(ax25, 0);
 117                 break;
 118
 119         case AX25_DM:
 120         case AX25_UA:
 121                 if (pf)
 122                         ax25_disconnect(ax25, 0);
 123                 break;
 124
 125         case AX25_I:
 126         case AX25_REJ:
 127         case AX25_RNR:
 128         case AX25_RR:
 129                 if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
 130                 break;
 131
 132         default:
 133                 break;
 134         }
 135
 136         return 0;
 137 }
 138
 139 /*
 140  *      State machine for state 3, Connected State.
 141  *      The handling of the timer(s) is in file ax25_std_timer.c
 142  *      Handling of state 0 and connection release is in ax25.c.
 143  */
 144 static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 145 {
 146         int queued = 0;
 147
 148         switch (frametype) {
 149         case AX25_SABM:
 150         case AX25_SABME:
 151                 if (frametype == AX25_SABM) {
 152                         ax25->modulus = AX25_MODULUS;
 153                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 154                 } else {
 155                         ax25->modulus = AX25_EMODULUS;
 156                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 157                 }
 158                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 159                 ax25_stop_t1timer(ax25);
 160                 ax25_stop_t2timer(ax25);
 161                 ax25_start_t3timer(ax25);
 162                 ax25_start_idletimer(ax25);
 163                 ax25->condition = 0x00;
 164                 ax25->vs        = 0;
 165                 ax25->va        = 0;
 166                 ax25->vr        = 0;
 167                 ax25_requeue_frames(ax25);
 168                 break;
 169
 170         case AX25_DISC:
 171                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 172                 ax25_disconnect(ax25, 0);
 173                 break;
 174
 175         case AX25_DM:
 176                 ax25_disconnect(ax25, ECONNRESET);
 177                 break;
 178
 179         case AX25_RR:
 180         case AX25_RNR:
 181                 if (frametype == AX25_RR)
 182                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 183                 else
 184                         ax25->condition |= AX25_COND_PEER_RX_BUSY;
 185                 if (type == AX25_COMMAND && pf)
 186                         ax25_std_enquiry_response(ax25);
 187                 if (ax25_validate_nr(ax25, nr)) {
 188                         ax25_check_iframes_acked(ax25, nr);
 189                 } else {
 190                         ax25_std_nr_error_recovery(ax25);
 191                         ax25->state = AX25_STATE_1;
 192                 }
 193                 break;
 194
 195         case AX25_REJ:
 196                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 197                 if (type == AX25_COMMAND && pf)
 198                         ax25_std_enquiry_response(ax25);
 199                 if (ax25_validate_nr(ax25, nr)) {
 200                         ax25_frames_acked(ax25, nr);
 201                         ax25_calculate_rtt(ax25);
 202                         ax25_stop_t1timer(ax25);
 203                         ax25_start_t3timer(ax25);
 204                         ax25_requeue_frames(ax25);
 205                 } else {
 206                         ax25_std_nr_error_recovery(ax25);
 207                         ax25->state = AX25_STATE_1;
 208                 }
 209                 break;
 210
 211         case AX25_I:
 212                 if (!ax25_validate_nr(ax25, nr)) {
 213                         ax25_std_nr_error_recovery(ax25);
 214                         ax25->state = AX25_STATE_1;
 215                         break;
 216                 }
 217                 if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
 218                         ax25_frames_acked(ax25, nr);
 219                 } else {
 220                         ax25_check_iframes_acked(ax25, nr);
 221                 }
 222                 if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 223                         if (pf) ax25_std_enquiry_response(ax25);
 224                         break;
 225                 }
 226                 if (ns == ax25->vr) {
 227                         ax25->vr = (ax25->vr + 1) % ax25->modulus;
 228                         queued = ax25_rx_iframe(ax25, skb);
 229                         if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 230                                 ax25->vr = ns;  /* ax25->vr - 1 */
 231                         ax25->condition &= ~AX25_COND_REJECT;
 232                         if (pf) {
 233                                 ax25_std_enquiry_response(ax25);
 234                         } else {
 235                                 if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 236                                         ax25->condition |= AX25_COND_ACK_PENDING;
 237                                         ax25_start_t2timer(ax25);
 238                                 }
 239                         }
 240                 } else {
 241                         if (ax25->condition & AX25_COND_REJECT) {
 242                                 if (pf) ax25_std_enquiry_response(ax25);
 243                         } else {
 244                                 ax25->condition |= AX25_COND_REJECT;
 245                                 ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
 246                                 ax25->condition &= ~AX25_COND_ACK_PENDING;
 247                         }
 248                 }
 249                 break;
 250
 251         case AX25_FRMR:
 252         case AX25_ILLEGAL:
 253                 ax25_std_establish_data_link(ax25);
 254                 ax25->state = AX25_STATE_1;
 255                 break;
 256
 257         default:
 258                 break;
 259         }
 260
 261         return queued;
 262 }
 263
 264 /*
 265  *      State machine for state 4, Timer Recovery State.
 266  *      The handling of the timer(s) is in file ax25_std_timer.c
 267  *      Handling of state 0 and connection release is in ax25.c.
 268  */
 269 static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 270 {
 271         int queued = 0;
 272
 273         switch (frametype) {
 274         case AX25_SABM:
 275         case AX25_SABME:
 276                 if (frametype == AX25_SABM) {
 277                         ax25->modulus = AX25_MODULUS;
 278                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 279                 } else {
 280                         ax25->modulus = AX25_EMODULUS;
 281                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 282                 }
 283                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 284                 ax25_stop_t1timer(ax25);
 285                 ax25_stop_t2timer(ax25);
 286                 ax25_start_t3timer(ax25);
 287                 ax25_start_idletimer(ax25);
 288                 ax25->condition = 0x00;
 289                 ax25->vs        = 0;
 290                 ax25->va        = 0;
 291                 ax25->vr        = 0;
 292                 ax25->state     = AX25_STATE_3;
 293                 ax25->n2count   = 0;
 294                 ax25_requeue_frames(ax25);
 295                 break;
 296
 297         case AX25_DISC:
 298                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 299                 ax25_disconnect(ax25, 0);
 300                 break;
 301
 302         case AX25_DM:
 303                 ax25_disconnect(ax25, ECONNRESET);
 304                 break;
 305
 306         case AX25_RR:
 307         case AX25_RNR:
 308                 if (frametype == AX25_RR)
 309                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 310                 else
 311                         ax25->condition |= AX25_COND_PEER_RX_BUSY;
 312                 if (type == AX25_RESPONSE && pf) {
 313                         ax25_stop_t1timer(ax25);
 314                         ax25->n2count = 0;
 315                         if (ax25_validate_nr(ax25, nr)) {
 316                                 ax25_frames_acked(ax25, nr);
 317                                 if (ax25->vs == ax25->va) {
 318                                         ax25_start_t3timer(ax25);
 319                                         ax25->state   = AX25_STATE_3;
 320                                 } else {
 321                                         ax25_requeue_frames(ax25);
 322                                 }
 323                         } else {
 324                                 ax25_std_nr_error_recovery(ax25);
 325                                 ax25->state = AX25_STATE_1;
 326                         }
 327                         break;
 328                 }
 329                 if (type == AX25_COMMAND && pf)
 330                         ax25_std_enquiry_response(ax25);
 331                 if (ax25_validate_nr(ax25, nr)) {
 332                         ax25_frames_acked(ax25, nr);
 333                 } else {
 334                         ax25_std_nr_error_recovery(ax25);
 335                         ax25->state = AX25_STATE_1;
 336                 }
 337                 break;
 338
 339         case AX25_REJ:
 340                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 341                 if (pf && type == AX25_RESPONSE) {
 342                         ax25_stop_t1timer(ax25);
 343                         ax25->n2count = 0;
 344                         if (ax25_validate_nr(ax25, nr)) {
 345                                 ax25_frames_acked(ax25, nr);
 346                                 if (ax25->vs == ax25->va) {
 347                                         ax25_start_t3timer(ax25);
 348                                         ax25->state   = AX25_STATE_3;
 349                                 } else {
 350                                         ax25_requeue_frames(ax25);
 351                                 }
 352                         } else {
 353                                 ax25_std_nr_error_recovery(ax25);
 354                                 ax25->state = AX25_STATE_1;
 355                         }
 356                         break;
 357                 }
 358                 if (type == AX25_COMMAND && pf)
 359                         ax25_std_enquiry_response(ax25);
 360                 if (ax25_validate_nr(ax25, nr)) {
 361                         ax25_frames_acked(ax25, nr);
 362                         ax25_requeue_frames(ax25);
 363                 } else {
 364                         ax25_std_nr_error_recovery(ax25);
 365                         ax25->state = AX25_STATE_1;
 366                 }
 367                 break;
 368
 369         case AX25_I:
 370                 if (!ax25_validate_nr(ax25, nr)) {
 371                         ax25_std_nr_error_recovery(ax25);
 372                         ax25->state = AX25_STATE_1;
 373                         break;
 374                 }
 375                 ax25_frames_acked(ax25, nr);
 376                 if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 377                         if (pf)
 378                                 ax25_std_enquiry_response(ax25);
 379                         break;
 380                 }
 381                 if (ns == ax25->vr) {
 382                         ax25->vr = (ax25->vr + 1) % ax25->modulus;
 383                         queued = ax25_rx_iframe(ax25, skb);
 384                         if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 385                                 ax25->vr = ns;  /* ax25->vr - 1 */
 386                         ax25->condition &= ~AX25_COND_REJECT;
 387                         if (pf) {
 388                                 ax25_std_enquiry_response(ax25);
 389                         } else {
 390                                 if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 391                                         ax25->condition |= AX25_COND_ACK_PENDING;
 392                                         ax25_start_t2timer(ax25);
 393                                 }
 394                         }
 395                 } else {
 396                         if (ax25->condition & AX25_COND_REJECT) {
 397                                 if (pf) ax25_std_enquiry_response(ax25);
 398                         } else {
 399                                 ax25->condition |= AX25_COND_REJECT;
 400                                 ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
 401                                 ax25->condition &= ~AX25_COND_ACK_PENDING;
 402                         }
 403                 }
 404                 break;
 405
 406         case AX25_FRMR:
 407         case AX25_ILLEGAL:
 408                 ax25_std_establish_data_link(ax25);
 409                 ax25->state = AX25_STATE_1;
 410                 break;
 411
 412         default:
 413                 break;
 414         }
 415
 416         return queued;
 417 }
 418
 419 /*
 420  *      Higher level upcall for a LAPB frame
 421  */
 422 int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
 423 {
 424         int queued = 0, frametype, ns, nr, pf;
 425
 426         frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
 427
 428         switch (ax25->state) {
 429         case AX25_STATE_1:
 430                 queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type);
 431                 break;
 432         case AX25_STATE_2:
 433                 queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type);
 434                 break;
 435         case AX25_STATE_3:
 436                 queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
 437                 break;
 438         case AX25_STATE_4:
 439                 queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type);
 440                 break;
 441         }
 442
 443         ax25_kick(ax25);
 444
 445         return queued;
 446 }