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 <asm/uaccess.h>
  33 #include <asm/system.h>
  34 #include <linux/fcntl.h>
  35 #include <linux/mm.h>
  36 #include <linux/interrupt.h>
  37
  38 /*
  39  *      State machine for state 1, Awaiting Connection State.
  40  *      The handling of the timer(s) is in file ax25_std_timer.c.
  41  *      Handling of state 0 and connection release is in ax25.c.
  42  */
  43 static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
  44 {
  45         switch (frametype) {
  46         case AX25_SABM:
  47                 ax25->modulus = AX25_MODULUS;
  48                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  49                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  50                 break;
  51
  52         case AX25_SABME:
  53                 ax25->modulus = AX25_EMODULUS;
  54                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
  55                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  56                 break;
  57
  58         case AX25_DISC:
  59                 ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
  60                 break;
  61
  62         case AX25_UA:
  63                 if (pf) {
  64                         ax25_calculate_rtt(ax25);
  65                         ax25_stop_t1timer(ax25);
  66                         ax25_start_t3timer(ax25);
  67                         ax25_start_idletimer(ax25);
  68                         ax25->vs      = 0;
  69                         ax25->va      = 0;
  70                         ax25->vr      = 0;
  71                         ax25->state   = AX25_STATE_3;
  72                         ax25->n2count = 0;
  73                         if (ax25->sk != NULL) {
  74                                 bh_lock_sock(ax25->sk);
  75                                 ax25->sk->sk_state = TCP_ESTABLISHED;
  76                                 /* For WAIT_SABM connections we will produce an accept ready socket here */
  77                                 if (!sock_flag(ax25->sk, SOCK_DEAD))
  78                                         ax25->sk->sk_state_change(ax25->sk);
  79                                 bh_unlock_sock(ax25->sk);
  80                         }
  81                 }
  82                 break;
  83
  84         case AX25_DM:
  85                 if (pf) {
  86                         if (ax25->modulus == AX25_MODULUS) {
  87                                 ax25_disconnect(ax25, ECONNREFUSED);
  88                         } else {
  89                                 ax25->modulus = AX25_MODULUS;
  90                                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  91                         }
  92                 }
  93                 break;
  94
  95         default:
  96                 break;
  97         }
  98
  99         return 0;
 100 }
 101
 102 /*
 103  *      State machine for state 2, Awaiting Release State.
 104  *      The handling of the timer(s) is in file ax25_std_timer.c
 105  *      Handling of state 0 and connection release is in ax25.c.
 106  */
 107 static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
 108 {
 109         switch (frametype) {
 110         case AX25_SABM:
 111         case AX25_SABME:
 112                 ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
 113                 break;
 114
 115         case AX25_DISC:
 116                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 117                 ax25_disconnect(ax25, 0);
 118                 break;
 119
 120         case AX25_DM:
 121         case AX25_UA:
 122                 if (pf)
 123                         ax25_disconnect(ax25, 0);
 124                 break;
 125
 126         case AX25_I:
 127         case AX25_REJ:
 128         case AX25_RNR:
 129         case AX25_RR:
 130                 if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
 131                 break;
 132
 133         default:
 134                 break;
 135         }
 136
 137         return 0;
 138 }
 139
 140 /*
 141  *      State machine for state 3, Connected State.
 142  *      The handling of the timer(s) is in file ax25_std_timer.c
 143  *      Handling of state 0 and connection release is in ax25.c.
 144  */
 145 static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 146 {
 147         int queued = 0;
 148
 149         switch (frametype) {
 150         case AX25_SABM:
 151         case AX25_SABME:
 152                 if (frametype == AX25_SABM) {
 153                         ax25->modulus = AX25_MODULUS;
 154                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 155                 } else {
 156                         ax25->modulus = AX25_EMODULUS;
 157                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 158                 }
 159                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 160                 ax25_stop_t1timer(ax25);
 161                 ax25_stop_t2timer(ax25);
 162                 ax25_start_t3timer(ax25);
 163                 ax25_start_idletimer(ax25);
 164                 ax25->condition = 0x00;
 165                 ax25->vs        = 0;
 166                 ax25->va        = 0;
 167                 ax25->vr        = 0;
 168                 ax25_requeue_frames(ax25);
 169                 break;
 170
 171         case AX25_DISC:
 172                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 173                 ax25_disconnect(ax25, 0);
 174                 break;
 175
 176         case AX25_DM:
 177                 ax25_disconnect(ax25, ECONNRESET);
 178                 break;
 179
 180         case AX25_RR:
 181         case AX25_RNR:
 182                 if (frametype == AX25_RR)
 183                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 184                 else
 185                         ax25->condition |= AX25_COND_PEER_RX_BUSY;
 186                 if (type == AX25_COMMAND && pf)
 187                         ax25_std_enquiry_response(ax25);
 188                 if (ax25_validate_nr(ax25, nr)) {
 189                         ax25_check_iframes_acked(ax25, nr);
 190                 } else {
 191                         ax25_std_nr_error_recovery(ax25);
 192                         ax25->state = AX25_STATE_1;
 193                 }
 194                 break;
 195
 196         case AX25_REJ:
 197                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 198                 if (type == AX25_COMMAND && pf)
 199                         ax25_std_enquiry_response(ax25);
 200                 if (ax25_validate_nr(ax25, nr)) {
 201                         ax25_frames_acked(ax25, nr);
 202                         ax25_calculate_rtt(ax25);
 203                         ax25_stop_t1timer(ax25);
 204                         ax25_start_t3timer(ax25);
 205                         ax25_requeue_frames(ax25);
 206                 } else {
 207                         ax25_std_nr_error_recovery(ax25);
 208                         ax25->state = AX25_STATE_1;
 209                 }
 210                 break;
 211
 212         case AX25_I:
 213                 if (!ax25_validate_nr(ax25, nr)) {
 214                         ax25_std_nr_error_recovery(ax25);
 215                         ax25->state = AX25_STATE_1;
 216                         break;
 217                 }
 218                 if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
 219                         ax25_frames_acked(ax25, nr);
 220                 } else {
 221                         ax25_check_iframes_acked(ax25, nr);
 222                 }
 223                 if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 224                         if (pf) ax25_std_enquiry_response(ax25);
 225                         break;
 226                 }
 227                 if (ns == ax25->vr) {
 228                         ax25->vr = (ax25->vr + 1) % ax25->modulus;
 229                         queued = ax25_rx_iframe(ax25, skb);
 230                         if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 231                                 ax25->vr = ns;  /* ax25->vr - 1 */
 232                         ax25->condition &= ~AX25_COND_REJECT;
 233                         if (pf) {
 234                                 ax25_std_enquiry_response(ax25);
 235                         } else {
 236                                 if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 237                                         ax25->condition |= AX25_COND_ACK_PENDING;
 238                                         ax25_start_t2timer(ax25);
 239                                 }
 240                         }
 241                 } else {
 242                         if (ax25->condition & AX25_COND_REJECT) {
 243                                 if (pf) ax25_std_enquiry_response(ax25);
 244                         } else {
 245                                 ax25->condition |= AX25_COND_REJECT;
 246                                 ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
 247                                 ax25->condition &= ~AX25_COND_ACK_PENDING;
 248                         }
 249                 }
 250                 break;
 251
 252         case AX25_FRMR:
 253         case AX25_ILLEGAL:
 254                 ax25_std_establish_data_link(ax25);
 255                 ax25->state = AX25_STATE_1;
 256                 break;
 257
 258         default:
 259                 break;
 260         }
 261
 262         return queued;
 263 }
 264
 265 /*
 266  *      State machine for state 4, Timer Recovery State.
 267  *      The handling of the timer(s) is in file ax25_std_timer.c
 268  *      Handling of state 0 and connection release is in ax25.c.
 269  */
 270 static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 271 {
 272         int queued = 0;
 273
 274         switch (frametype) {
 275         case AX25_SABM:
 276         case AX25_SABME:
 277                 if (frametype == AX25_SABM) {
 278                         ax25->modulus = AX25_MODULUS;
 279                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 280                 } else {
 281                         ax25->modulus = AX25_EMODULUS;
 282                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 283                 }
 284                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 285                 ax25_stop_t1timer(ax25);
 286                 ax25_stop_t2timer(ax25);
 287                 ax25_start_t3timer(ax25);
 288                 ax25_start_idletimer(ax25);
 289                 ax25->condition = 0x00;
 290                 ax25->vs        = 0;
 291                 ax25->va        = 0;
 292                 ax25->vr        = 0;
 293                 ax25->state     = AX25_STATE_3;
 294                 ax25->n2count   = 0;
 295                 ax25_requeue_frames(ax25);
 296                 break;
 297
 298         case AX25_DISC:
 299                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 300                 ax25_disconnect(ax25, 0);
 301                 break;
 302
 303         case AX25_DM:
 304                 ax25_disconnect(ax25, ECONNRESET);
 305                 break;
 306
 307         case AX25_RR:
 308         case AX25_RNR:
 309                 if (frametype == AX25_RR)
 310                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 311                 else
 312                         ax25->condition |= AX25_COND_PEER_RX_BUSY;
 313                 if (type == AX25_RESPONSE && pf) {
 314                         ax25_stop_t1timer(ax25);
 315                         ax25->n2count = 0;
 316                         if (ax25_validate_nr(ax25, nr)) {
 317                                 ax25_frames_acked(ax25, nr);
 318                                 if (ax25->vs == ax25->va) {
 319                                         ax25_start_t3timer(ax25);
 320                                         ax25->state   = AX25_STATE_3;
 321                                 } else {
 322                                         ax25_requeue_frames(ax25);
 323                                 }
 324                         } else {
 325                                 ax25_std_nr_error_recovery(ax25);
 326                                 ax25->state = AX25_STATE_1;
 327                         }
 328                         break;
 329                 }
 330                 if (type == AX25_COMMAND && pf)
 331                         ax25_std_enquiry_response(ax25);
 332                 if (ax25_validate_nr(ax25, nr)) {
 333                         ax25_frames_acked(ax25, nr);
 334                 } else {
 335                         ax25_std_nr_error_recovery(ax25);
 336                         ax25->state = AX25_STATE_1;
 337                 }
 338                 break;
 339
 340         case AX25_REJ:
 341                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 342                 if (pf && type == AX25_RESPONSE) {
 343                         ax25_stop_t1timer(ax25);
 344                         ax25->n2count = 0;
 345                         if (ax25_validate_nr(ax25, nr)) {
 346                                 ax25_frames_acked(ax25, nr);
 347                                 if (ax25->vs == ax25->va) {
 348                                         ax25_start_t3timer(ax25);
 349                                         ax25->state   = AX25_STATE_3;
 350                                 } else {
 351                                         ax25_requeue_frames(ax25);
 352                                 }
 353                         } else {
 354                                 ax25_std_nr_error_recovery(ax25);
 355                                 ax25->state = AX25_STATE_1;
 356                         }
 357                         break;
 358                 }
 359                 if (type == AX25_COMMAND && pf)
 360                         ax25_std_enquiry_response(ax25);
 361                 if (ax25_validate_nr(ax25, nr)) {
 362                         ax25_frames_acked(ax25, nr);
 363                         ax25_requeue_frames(ax25);
 364                 } else {
 365                         ax25_std_nr_error_recovery(ax25);
 366                         ax25->state = AX25_STATE_1;
 367                 }
 368                 break;
 369
 370         case AX25_I:
 371                 if (!ax25_validate_nr(ax25, nr)) {
 372                         ax25_std_nr_error_recovery(ax25);
 373                         ax25->state = AX25_STATE_1;
 374                         break;
 375                 }
 376                 ax25_frames_acked(ax25, nr);
 377                 if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 378                         if (pf)
 379                                 ax25_std_enquiry_response(ax25);
 380                         break;
 381                 }
 382                 if (ns == ax25->vr) {
 383                         ax25->vr = (ax25->vr + 1) % ax25->modulus;
 384                         queued = ax25_rx_iframe(ax25, skb);
 385                         if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 386                                 ax25->vr = ns;  /* ax25->vr - 1 */
 387                         ax25->condition &= ~AX25_COND_REJECT;
 388                         if (pf) {
 389                                 ax25_std_enquiry_response(ax25);
 390                         } else {
 391                                 if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 392                                         ax25->condition |= AX25_COND_ACK_PENDING;
 393                                         ax25_start_t2timer(ax25);
 394                                 }
 395                         }
 396                 } else {
 397                         if (ax25->condition & AX25_COND_REJECT) {
 398                                 if (pf) ax25_std_enquiry_response(ax25);
 399                         } else {
 400                                 ax25->condition |= AX25_COND_REJECT;
 401                                 ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
 402                                 ax25->condition &= ~AX25_COND_ACK_PENDING;
 403                         }
 404                 }
 405                 break;
 406
 407         case AX25_FRMR:
 408         case AX25_ILLEGAL:
 409                 ax25_std_establish_data_link(ax25);
 410                 ax25->state = AX25_STATE_1;
 411                 break;
 412
 413         default:
 414                 break;
 415         }
 416
 417         return queued;
 418 }
 419
 420 /*
 421  *      Higher level upcall for a LAPB frame
 422  */
 423 int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
 424 {
 425         int queued = 0, frametype, ns, nr, pf;
 426
 427         frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
 428
 429         switch (ax25->state) {
 430         case AX25_STATE_1:
 431                 queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type);
 432                 break;
 433         case AX25_STATE_2:
 434                 queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type);
 435                 break;
 436         case AX25_STATE_3:
 437                 queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
 438                 break;
 439         case AX25_STATE_4:
 440                 queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type);
 441                 break;
 442         }
 443
 444         ax25_kick(ax25);
 445
 446         return queued;
 447 }