net/ax25/ax25_ds_in.c

   1 /*
   2  *      AX.25 release 037
   3  *
   4  *      This code REQUIRES 2.1.15 or higher/ NET3.038
   5  *
   6  *      This module:
   7  *              This module is free software; you can redistribute it and/or
   8  *              modify it under the terms of the GNU General Public License
   9  *              as published by the Free Software Foundation; either version
  10  *              2 of the License, or (at your option) any later version.
  11  *
  12  *      Most of this code is based on the SDL diagrams published in the 7th
  13  *      ARRL Computer Networking Conference papers. The diagrams have mistakes
  14  *      in them, but are mostly correct. Before you modify the code could you
  15  *      read the SDL diagrams as the code is not obvious and probably very
  16  *      easy to break;
  17  *
  18  *      History
  19  *      AX.25 036       Jonathan(G4KLX) Cloned from ax25_in.c
  20  *                      Joerg(DL1BKE)   Fixed it.
  21  *      AX.25 037       Jonathan(G4KLX) New timer architecture.
  22  *                      Joerg(DL1BKE)   ax25->n2count never got reset
  23  */
  24
  25 #include <linux/errno.h>
  26 #include <linux/types.h>
  27 #include <linux/socket.h>
  28 #include <linux/in.h>
  29 #include <linux/kernel.h>
  30 #include <linux/sched.h>
  31 #include <linux/timer.h>
  32 #include <linux/string.h>
  33 #include <linux/sockios.h>
  34 #include <linux/net.h>
  35 #include <net/ax25.h>
  36 #include <linux/inet.h>
  37 #include <linux/netdevice.h>
  38 #include <linux/skbuff.h>
  39 #include <net/sock.h>
  40 #include <net/ip.h>                     /* For ip_rcv */
  41 #include <asm/uaccess.h>
  42 #include <asm/system.h>
  43 #include <linux/fcntl.h>
  44 #include <linux/mm.h>
  45 #include <linux/interrupt.h>
  46
  47 /*
  48  *      State machine for state 1, Awaiting Connection State.
  49  *      The handling of the timer(s) is in file ax25_ds_timer.c.
  50  *      Handling of state 0 and connection release is in ax25.c.
  51  */
  52 static int ax25_ds_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
  53 {
  54         switch (frametype) {
  55                 case AX25_SABM:
  56                         ax25->modulus = AX25_MODULUS;
  57                         ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
  58                         ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  59                         break;
  60
  61                 case AX25_SABME:
  62                         ax25->modulus = AX25_EMODULUS;
  63                         ax25->window  =  ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
  64                         ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
  65                         break;
  66
  67                 case AX25_DISC:
  68                         ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
  69                         break;
  70
  71                 case AX25_UA:
  72                         ax25_calculate_rtt(ax25);
  73                         ax25_stop_t1timer(ax25);
  74                         ax25_start_t3timer(ax25);
  75                         ax25_start_idletimer(ax25);
  76                         ax25->vs      = 0;
  77                         ax25->va      = 0;
  78                         ax25->vr      = 0;
  79                         ax25->state   = AX25_STATE_3;
  80                         ax25->n2count = 0;
  81                         if (ax25->sk != NULL) {
  82                                 ax25->sk->state = TCP_ESTABLISHED;
  83                                 /* For WAIT_SABM connections we will produce an accept ready socket here */
  84                                 if (!ax25->sk->dead)
  85                                         ax25->sk->state_change(ax25->sk);
  86                         }
  87                         ax25_dama_on(ax25);
  88
  89                         /* according to DK4EG´s spec we are required to
  90                          * send a RR RESPONSE FINAL NR=0.
  91                          */
  92
  93                         ax25_std_enquiry_response(ax25);
  94                         break;
  95
  96                 case AX25_DM:
  97                         if (pf) ax25_disconnect(ax25, ECONNREFUSED);
  98                         break;
  99
 100                 default:
 101                         if (pf) ax25_send_control(ax25, AX25_SABM, AX25_POLLON, AX25_COMMAND);
 102                         break;
 103         }
 104
 105         return 0;
 106 }
 107
 108 /*
 109  *      State machine for state 2, Awaiting Release State.
 110  *      The handling of the timer(s) is in file ax25_ds_timer.c
 111  *      Handling of state 0 and connection release is in ax25.c.
 112  */
 113 static int ax25_ds_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
 114 {
 115         switch (frametype) {
 116                 case AX25_SABM:
 117                 case AX25_SABME:
 118                         ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
 119                         ax25_dama_off(ax25);
 120                         break;
 121
 122                 case AX25_DISC:
 123                         ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 124                         ax25_dama_off(ax25);
 125                         ax25_disconnect(ax25, 0);
 126                         break;
 127
 128                 case AX25_DM:
 129                 case AX25_UA:
 130                         if (pf) {
 131                                 ax25_dama_off(ax25);
 132                                 ax25_disconnect(ax25, 0);
 133                         }
 134                         break;
 135
 136                 case AX25_I:
 137                 case AX25_REJ:
 138                 case AX25_RNR:
 139                 case AX25_RR:
 140                         if (pf) {
 141                                 ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
 142                                 ax25_dama_off(ax25);
 143                         }
 144                         break;
 145
 146                 default:
 147                         break;
 148         }
 149
 150         return 0;
 151 }
 152
 153 /*
 154  *      State machine for state 3, Connected State.
 155  *      The handling of the timer(s) is in file ax25_timer.c
 156  *      Handling of state 0 and connection release is in ax25.c.
 157  */
 158 static int ax25_ds_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
 159 {
 160         int queued = 0;
 161
 162         switch (frametype) {
 163                 case AX25_SABM:
 164                 case AX25_SABME:
 165                         if (frametype == AX25_SABM) {
 166                                 ax25->modulus   = AX25_MODULUS;
 167                                 ax25->window    = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
 168                         } else {
 169                                 ax25->modulus   = AX25_EMODULUS;
 170                                 ax25->window    = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
 171                         }
 172                         ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 173                         ax25_stop_t1timer(ax25);
 174                         ax25_start_t3timer(ax25);
 175                         ax25_start_idletimer(ax25);
 176                         ax25->condition = 0x00;
 177                         ax25->vs        = 0;
 178                         ax25->va        = 0;
 179                         ax25->vr        = 0;
 180                         ax25_requeue_frames(ax25);
 181                         ax25_dama_on(ax25);
 182                         break;
 183
 184                 case AX25_DISC:
 185                         ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
 186                         ax25_dama_off(ax25);
 187                         ax25_disconnect(ax25, 0);
 188                         break;
 189
 190                 case AX25_DM:
 191                         ax25_dama_off(ax25);
 192                         ax25_disconnect(ax25, ECONNRESET);
 193                         break;
 194
 195                 case AX25_RR:
 196                 case AX25_RNR:
 197                         if (frametype == AX25_RR)
 198                                 ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 199                         else
 200                                 ax25->condition |= AX25_COND_PEER_RX_BUSY;
 201
 202                         if (ax25_validate_nr(ax25, nr)) {
 203                                 if (ax25_check_iframes_acked(ax25, nr))
 204                                         ax25->n2count=0;
 205                                 if (type == AX25_COMMAND && pf)
 206                                         ax25_ds_enquiry_response(ax25);
 207                         } else {
 208                                 ax25_ds_nr_error_recovery(ax25);
 209                                 ax25->state = AX25_STATE_1;
 210                         }
 211                         break;
 212
 213                 case AX25_REJ:
 214                         ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
 215
 216                         if (ax25_validate_nr(ax25, nr)) {
 217                                 if (ax25->va != nr)
 218                                         ax25->n2count=0;
 219
 220                                 ax25_frames_acked(ax25, nr);
 221                                 ax25_calculate_rtt(ax25);
 222                                 ax25_stop_t1timer(ax25);
 223                                 ax25_start_t3timer(ax25);
 224                                 ax25_requeue_frames(ax25);
 225
 226                                 if (type == AX25_COMMAND && pf)
 227                                         ax25_ds_enquiry_response(ax25);
 228                         } else {
 229                                 ax25_ds_nr_error_recovery(ax25);
 230                                 ax25->state = AX25_STATE_1;
 231                         }
 232                         break;
 233
 234                 case AX25_I:
 235                         if (!ax25_validate_nr(ax25, nr)) {
 236                                 ax25_ds_nr_error_recovery(ax25);
 237                                 ax25->state = AX25_STATE_1;
 238                                 break;
 239                         }
 240                         if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
 241                                 ax25_frames_acked(ax25, nr);
 242                                 ax25->n2count = 0;
 243                         } else {
 244                                 if (ax25_check_iframes_acked(ax25, nr))
 245                                         ax25->n2count = 0;
 246                         }
 247                         if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
 248                                 if (pf) ax25_ds_enquiry_response(ax25);
 249                                 break;
 250                         }
 251                         if (ns == ax25->vr) {
 252                                 ax25->vr = (ax25->vr + 1) % ax25->modulus;
 253                                 queued = ax25_rx_iframe(ax25, skb);
 254                                 if (ax25->condition & AX25_COND_OWN_RX_BUSY)
 255                                         ax25->vr = ns;  /* ax25->vr - 1 */
 256                                 ax25->condition &= ~AX25_COND_REJECT;
 257                                 if (pf) {
 258                                         ax25_ds_enquiry_response(ax25);
 259                                 } else {
 260                                         if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
 261                                                 ax25->condition |= AX25_COND_ACK_PENDING;
 262                                                 ax25_start_t2timer(ax25);
 263                                         }
 264                                 }
 265                         } else {
 266                                 if (ax25->condition & AX25_COND_REJECT) {
 267                                         if (pf) ax25_ds_enquiry_response(ax25);
 268                                 } else {
 269                                         ax25->condition |= AX25_COND_REJECT;
 270                                         ax25_ds_enquiry_response(ax25);
 271                                         ax25->condition &= ~AX25_COND_ACK_PENDING;
 272                                 }
 273                         }
 274                         break;
 275
 276                 case AX25_FRMR:
 277                 case AX25_ILLEGAL:
 278                         ax25_ds_establish_data_link(ax25);
 279                         ax25->state = AX25_STATE_1;
 280                         break;
 281
 282                 default:
 283                         break;
 284         }
 285
 286         return queued;
 287 }
 288
 289 /*
 290  *      Higher level upcall for a LAPB frame
 291  */
 292 int ax25_ds_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
 293 {
 294         int queued = 0, frametype, ns, nr, pf;
 295
 296         frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
 297
 298         switch (ax25->state) {
 299                 case AX25_STATE_1:
 300                         queued = ax25_ds_state1_machine(ax25, skb, frametype, pf, type);
 301                         break;
 302                 case AX25_STATE_2:
 303                         queued = ax25_ds_state2_machine(ax25, skb, frametype, pf, type);
 304                         break;
 305                 case AX25_STATE_3:
 306                         queued = ax25_ds_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
 307                         break;
 308         }
 309
 310         return queued;
 311 }
 312