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/sched.h>
  23 #include <linux/timer.h>
  24 #include <linux/string.h>
  25 #include <linux/sockios.h>
  26 #include <linux/net.h>
  27 #include <net/ax25.h>
  28 #include <linux/inet.h>
  29 #include <linux/netdevice.h>
  30 #include <linux/skbuff.h>
  31 #include <net/sock.h>
  32 #include <net/ip.h>                     /* For ip_rcv */
  33 #include <net/tcp.h>
  34 #include <asm/uaccess.h>
  35 #include <asm/system.h>
  36 #include <linux/fcntl.h>
  37 #include <linux/mm.h>
  38 #include <linux/interrupt.h>
  39
  40 /*
  41  *      State machine for state 1, Awaiting Connection State.
  42  *      The handling of the timer(s) is in file ax25_std_timer.c.
  43  *      Handling of state 0 and connection release is in ax25.c.
  44  */
  45 static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
  46 {
  47         switch (frametype) {
  48         case AX25_SABM:
  49                 ax25->modulus = AX25_MODULUS;
  50                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  51                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  52                 break;
  53
  54         case AX25_SABME:
  55                 ax25->modulus = AX25_EMODULUS;
  56                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
  57                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  58                 break;
  59
  60         case AX25_DISC:
  61                 ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
  62                 break;
  63
  64         case AX25_UA:
  65                 if (pf) {
  66                         ax25_calculate_rtt(ax25);
  67                         ax25_stop_t1timer(ax25);
  68                         ax25_start_t3timer(ax25);
  69                         ax25_start_idletimer(ax25);
  70                         ax25->vs      = 0;
  71                         ax25->va      = 0;
  72                         ax25->vr      = 0;
  73                         ax25->state   = AX25_STATE_3;
  74                         ax25->n2count = 0;
  75                         if (ax25->sk != NULL) {
  76                                 bh_lock_sock(ax25->sk);
  77                                 ax25->sk->sk_state = TCP_ESTABLISHED;
  78                                 /* For WAIT_SABM connections we will produce an accept ready socket here */
  79                                 if (!sock_flag(ax25->sk, SOCK_DEAD))
  80                                         ax25->sk->sk_state_change(ax25->sk);
  81                                 bh_unlock_sock(ax25->sk);
  82                         }
  83                 }
  84                 break;
  85
  86         case AX25_DM:
  87                 if (pf) {
  88                         if (ax25->modulus == AX25_MODULUS) {
  89                                 ax25_disconnect(ax25, ECONNREFUSED);
  90                         } else {
  91                                 ax25->modulus = AX25_MODULUS;
  92                                 ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  93                         }
  94                 }
  95                 break;
  96
  97         default:
  98                 break;
  99         }
 100
 101         return 0;
 102 }
 103
 104 /*
 105  *      State machine for state 2, Awaiting Release State.
 106  *      The handling of the timer(s) is in file ax25_std_timer.c
 107  *      Handling of state 0 and connection release is in ax25.c.
 108  */
 109 static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
 110 {
 111         switch (frametype) {
 112         case AX25_SABM:
 113         case AX25_SABME:
 114                 ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
 115                 break;
 116
 117         case AX25_DISC:
 118                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 119                 ax25_disconnect(ax25, 0);
 120                 break;
 121
 122         case AX25_DM:
 123         case AX25_UA:
 124                 if (pf)
 125                         ax25_disconnect(ax25, 0);
 126                 break;
 127
 128         case AX25_I:
 129         case AX25_REJ:
 130         case AX25_RNR:
 131         case AX25_RR:
 132                 if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
 133                 break;
 134
 135         default:
 136                 break;
 137         }
 138
 139         return 0;
 140 }
 141
 142 /*
 143  *      State machine for state 3, Connected State.
 144  *      The handling of the timer(s) is in file ax25_std_timer.c
 145  *      Handling of state 0 and connection release is in ax25.c.
 146  */
 147 static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 148 {
 149         int queued = 0;
 150
 151         switch (frametype) {
 152         case AX25_SABM:
 153         case AX25_SABME:
 154                 if (frametype == AX25_SABM) {
 155                         ax25->modulus = AX25_MODULUS;
 156                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 157                 } else {
 158                         ax25->modulus = AX25_EMODULUS;
 159                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 160                 }
 161                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 162                 ax25_stop_t1timer(ax25);
 163                 ax25_stop_t2timer(ax25);
 164                 ax25_start_t3timer(ax25);
 165                 ax25_start_idletimer(ax25);
 166                 ax25->condition = 0x00;
 167                 ax25->vs        = 0;
 168                 ax25->va        = 0;
 169                 ax25->vr        = 0;
 170                 ax25_requeue_frames(ax25);
 171                 break;
 172
 173         case AX25_DISC:
 174                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 175                 ax25_disconnect(ax25, 0);
 176                 break;
 177
 178         case AX25_DM:
 179                 ax25_disconnect(ax25, ECONNRESET);
 180                 break;
 181
 182         case AX25_RR:
 183         case AX25_RNR:
 184                 if (frametype == AX25_RR)
 185                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 186                 else
 187                         ax25->condition |= AX25_COND_PEER_RX_BUSY;
 188                 if (type == AX25_COMMAND && pf)
 189                         ax25_std_enquiry_response(ax25);
 190                 if (ax25_validate_nr(ax25, nr)) {
 191                         ax25_check_iframes_acked(ax25, nr);
 192                 } else {
 193                         ax25_std_nr_error_recovery(ax25);
 194                         ax25->state = AX25_STATE_1;
 195                 }
 196                 break;
 197
 198         case AX25_REJ:
 199                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 200                 if (type == AX25_COMMAND && pf)
 201                         ax25_std_enquiry_response(ax25);
 202                 if (ax25_validate_nr(ax25, nr)) {
 203                         ax25_frames_acked(ax25, nr);
 204                         ax25_calculate_rtt(ax25);
 205                         ax25_stop_t1timer(ax25);
 206                         ax25_start_t3timer(ax25);
 207                         ax25_requeue_frames(ax25);
 208                 } else {
 209                         ax25_std_nr_error_recovery(ax25);
 210                         ax25->state = AX25_STATE_1;
 211                 }
 212                 break;
 213
 214         case AX25_I:
 215                 if (!ax25_validate_nr(ax25, nr)) {
 216                         ax25_std_nr_error_recovery(ax25);
 217                         ax25->state = AX25_STATE_1;
 218                         break;
 219                 }
 220                 if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
 221                         ax25_frames_acked(ax25, nr);
 222                 } else {
 223                         ax25_check_iframes_acked(ax25, nr);
 224                 }
 225                 if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 226                         if (pf) ax25_std_enquiry_response(ax25);
 227                         break;
 228                 }
 229                 if (ns == ax25->vr) {
 230                         ax25->vr = (ax25->vr + 1) % ax25->modulus;
 231                         queued = ax25_rx_iframe(ax25, skb);
 232                         if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 233                                 ax25->vr = ns;  /* ax25->vr - 1 */
 234                         ax25->condition &= ~AX25_COND_REJECT;
 235                         if (pf) {
 236                                 ax25_std_enquiry_response(ax25);
 237                         } else {
 238                                 if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 239                                         ax25->condition |= AX25_COND_ACK_PENDING;
 240                                         ax25_start_t2timer(ax25);
 241                                 }
 242                         }
 243                 } else {
 244                         if (ax25->condition & AX25_COND_REJECT) {
 245                                 if (pf) ax25_std_enquiry_response(ax25);
 246                         } else {
 247                                 ax25->condition |= AX25_COND_REJECT;
 248                                 ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
 249                                 ax25->condition &= ~AX25_COND_ACK_PENDING;
 250                         }
 251                 }
 252                 break;
 253
 254         case AX25_FRMR:
 255         case AX25_ILLEGAL:
 256                 ax25_std_establish_data_link(ax25);
 257                 ax25->state = AX25_STATE_1;
 258                 break;
 259
 260         default:
 261                 break;
 262         }
 263
 264         return queued;
 265 }
 266
 267 /*
 268  *      State machine for state 4, Timer Recovery State.
 269  *      The handling of the timer(s) is in file ax25_std_timer.c
 270  *      Handling of state 0 and connection release is in ax25.c.
 271  */
 272 static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 273 {
 274         int queued = 0;
 275
 276         switch (frametype) {
 277         case AX25_SABM:
 278         case AX25_SABME:
 279                 if (frametype == AX25_SABM) {
 280                         ax25->modulus = AX25_MODULUS;
 281                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 282                 } else {
 283                         ax25->modulus = AX25_EMODULUS;
 284                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 285                 }
 286                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 287                 ax25_stop_t1timer(ax25);
 288                 ax25_stop_t2timer(ax25);
 289                 ax25_start_t3timer(ax25);
 290                 ax25_start_idletimer(ax25);
 291                 ax25->condition = 0x00;
 292                 ax25->vs        = 0;
 293                 ax25->va        = 0;
 294                 ax25->vr        = 0;
 295                 ax25->state     = AX25_STATE_3;
 296                 ax25->n2count   = 0;
 297                 ax25_requeue_frames(ax25);
 298                 break;
 299
 300         case AX25_DISC:
 301                 ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 302                 ax25_disconnect(ax25, 0);
 303                 break;
 304
 305         case AX25_DM:
 306                 ax25_disconnect(ax25, ECONNRESET);
 307                 break;
 308
 309         case AX25_RR:
 310         case AX25_RNR:
 311                 if (frametype == AX25_RR)
 312                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 313                 else
 314                         ax25->condition |= AX25_COND_PEER_RX_BUSY;
 315                 if (type == AX25_RESPONSE && pf) {
 316                         ax25_stop_t1timer(ax25);
 317                         ax25->n2count = 0;
 318                         if (ax25_validate_nr(ax25, nr)) {
 319                                 ax25_frames_acked(ax25, nr);
 320                                 if (ax25->vs == ax25->va) {
 321                                         ax25_start_t3timer(ax25);
 322                                         ax25->state   = AX25_STATE_3;
 323                                 } else {
 324                                         ax25_requeue_frames(ax25);
 325                                 }
 326                         } else {
 327                                 ax25_std_nr_error_recovery(ax25);
 328                                 ax25->state = AX25_STATE_1;
 329                         }
 330                         break;
 331                 }
 332                 if (type == AX25_COMMAND && pf)
 333                         ax25_std_enquiry_response(ax25);
 334                 if (ax25_validate_nr(ax25, nr)) {
 335                         ax25_frames_acked(ax25, nr);
 336                 } else {
 337                         ax25_std_nr_error_recovery(ax25);
 338                         ax25->state = AX25_STATE_1;
 339                 }
 340                 break;
 341
 342         case AX25_REJ:
 343                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 344                 if (pf && type == AX25_RESPONSE) {
 345                         ax25_stop_t1timer(ax25);
 346                         ax25->n2count = 0;
 347                         if (ax25_validate_nr(ax25, nr)) {
 348                                 ax25_frames_acked(ax25, nr);
 349                                 if (ax25->vs == ax25->va) {
 350                                         ax25_start_t3timer(ax25);
 351                                         ax25->state   = AX25_STATE_3;
 352                                 } else {
 353                                         ax25_requeue_frames(ax25);
 354                                 }
 355                         } else {
 356                                 ax25_std_nr_error_recovery(ax25);
 357                                 ax25->state = AX25_STATE_1;
 358                         }
 359                         break;
 360                 }
 361                 if (type == AX25_COMMAND && pf)
 362                         ax25_std_enquiry_response(ax25);
 363                 if (ax25_validate_nr(ax25, nr)) {
 364                         ax25_frames_acked(ax25, nr);
 365                         ax25_requeue_frames(ax25);
 366                 } else {
 367                         ax25_std_nr_error_recovery(ax25);
 368                         ax25->state = AX25_STATE_1;
 369                 }
 370                 break;
 371
 372         case AX25_I:
 373                 if (!ax25_validate_nr(ax25, nr)) {
 374                         ax25_std_nr_error_recovery(ax25);
 375                         ax25->state = AX25_STATE_1;
 376                         break;
 377                 }
 378                 ax25_frames_acked(ax25, nr);
 379                 if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 380                         if (pf)
 381                                 ax25_std_enquiry_response(ax25);
 382                         break;
 383                 }
 384                 if (ns == ax25->vr) {
 385                         ax25->vr = (ax25->vr + 1) % ax25->modulus;
 386                         queued = ax25_rx_iframe(ax25, skb);
 387                         if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 388                                 ax25->vr = ns;  /* ax25->vr - 1 */
 389                         ax25->condition &= ~AX25_COND_REJECT;
 390                         if (pf) {
 391                                 ax25_std_enquiry_response(ax25);
 392                         } else {
 393                                 if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 394                                         ax25->condition |= AX25_COND_ACK_PENDING;
 395                                         ax25_start_t2timer(ax25);
 396                                 }
 397                         }
 398                 } else {
 399                         if (ax25->condition & AX25_COND_REJECT) {
 400                                 if (pf) ax25_std_enquiry_response(ax25);
 401                         } else {
 402                                 ax25->condition |= AX25_COND_REJECT;
 403                                 ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
 404                                 ax25->condition &= ~AX25_COND_ACK_PENDING;
 405                         }
 406                 }
 407                 break;
 408
 409         case AX25_FRMR:
 410         case AX25_ILLEGAL:
 411                 ax25_std_establish_data_link(ax25);
 412                 ax25->state = AX25_STATE_1;
 413                 break;
 414
 415         default:
 416                 break;
 417         }
 418
 419         return queued;
 420 }
 421
 422 /*
 423  *      Higher level upcall for a LAPB frame
 424  */
 425 int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
 426 {
 427         int queued = 0, frametype, ns, nr, pf;
 428
 429         frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
 430
 431         switch (ax25->state) {
 432         case AX25_STATE_1:
 433                 queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type);
 434                 break;
 435         case AX25_STATE_2:
 436                 queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type);
 437                 break;
 438         case AX25_STATE_3:
 439                 queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
 440                 break;
 441         case AX25_STATE_4:
 442                 queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type);
 443                 break;
 444         }
 445
 446         ax25_kick(ax25);
 447
 448         return queued;
 449 }