linux/net/rose/rose_in.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *
   4 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   5 *
   6 * Most of this code is based on the SDL diagrams published in the 7th ARRL
   7 * Computer Networking Conference papers. The diagrams have mistakes in them,
   8 * but are mostly correct. Before you modify the code could you read the SDL
   9 * diagrams as the code is not obvious and probably very easy to break.
  10 */
  11#include <linux/errno.h>
  12#include <linux/types.h>
  13#include <linux/socket.h>
  14#include <linux/in.h>
  15#include <linux/kernel.h>
  16#include <linux/timer.h>
  17#include <linux/string.h>
  18#include <linux/sockios.h>
  19#include <linux/net.h>
  20#include <net/ax25.h>
  21#include <linux/inet.h>
  22#include <linux/netdevice.h>
  23#include <linux/skbuff.h>
  24#include <net/sock.h>
  25#include <net/tcp_states.h>
  26#include <linux/fcntl.h>
  27#include <linux/mm.h>
  28#include <linux/interrupt.h>
  29#include <net/rose.h>
  30
  31/*
  32 * State machine for state 1, Awaiting Call Accepted State.
  33 * The handling of the timer(s) is in file rose_timer.c.
  34 * Handling of state 0 and connection release is in af_rose.c.
  35 */
  36static int rose_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
  37{
  38        struct rose_sock *rose = rose_sk(sk);
  39
  40        switch (frametype) {
  41        case ROSE_CALL_ACCEPTED:
  42                rose_stop_timer(sk);
  43                rose_start_idletimer(sk);
  44                rose->condition = 0x00;
  45                rose->vs        = 0;
  46                rose->va        = 0;
  47                rose->vr        = 0;
  48                rose->vl        = 0;
  49                rose->state     = ROSE_STATE_3;
  50                sk->sk_state    = TCP_ESTABLISHED;
  51                if (!sock_flag(sk, SOCK_DEAD))
  52                        sk->sk_state_change(sk);
  53                break;
  54
  55        case ROSE_CLEAR_REQUEST:
  56                rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
  57                rose_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
  58                rose->neighbour->use--;
  59                break;
  60
  61        default:
  62                break;
  63        }
  64
  65        return 0;
  66}
  67
  68/*
  69 * State machine for state 2, Awaiting Clear Confirmation State.
  70 * The handling of the timer(s) is in file rose_timer.c
  71 * Handling of state 0 and connection release is in af_rose.c.
  72 */
  73static int rose_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
  74{
  75        struct rose_sock *rose = rose_sk(sk);
  76
  77        switch (frametype) {
  78        case ROSE_CLEAR_REQUEST:
  79                rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
  80                rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
  81                rose->neighbour->use--;
  82                break;
  83
  84        case ROSE_CLEAR_CONFIRMATION:
  85                rose_disconnect(sk, 0, -1, -1);
  86                rose->neighbour->use--;
  87                break;
  88
  89        default:
  90                break;
  91        }
  92
  93        return 0;
  94}
  95
  96/*
  97 * State machine for state 3, Connected State.
  98 * The handling of the timer(s) is in file rose_timer.c
  99 * Handling of state 0 and connection release is in af_rose.c.
 100 */
 101static int rose_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
 102{
 103        struct rose_sock *rose = rose_sk(sk);
 104        int queued = 0;
 105
 106        switch (frametype) {
 107        case ROSE_RESET_REQUEST:
 108                rose_stop_timer(sk);
 109                rose_start_idletimer(sk);
 110                rose_write_internal(sk, ROSE_RESET_CONFIRMATION);
 111                rose->condition = 0x00;
 112                rose->vs        = 0;
 113                rose->vr        = 0;
 114                rose->va        = 0;
 115                rose->vl        = 0;
 116                rose_requeue_frames(sk);
 117                break;
 118
 119        case ROSE_CLEAR_REQUEST:
 120                rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
 121                rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
 122                rose->neighbour->use--;
 123                break;
 124
 125        case ROSE_RR:
 126        case ROSE_RNR:
 127                if (!rose_validate_nr(sk, nr)) {
 128                        rose_write_internal(sk, ROSE_RESET_REQUEST);
 129                        rose->condition = 0x00;
 130                        rose->vs        = 0;
 131                        rose->vr        = 0;
 132                        rose->va        = 0;
 133                        rose->vl        = 0;
 134                        rose->state     = ROSE_STATE_4;
 135                        rose_start_t2timer(sk);
 136                        rose_stop_idletimer(sk);
 137                } else {
 138                        rose_frames_acked(sk, nr);
 139                        if (frametype == ROSE_RNR) {
 140                                rose->condition |= ROSE_COND_PEER_RX_BUSY;
 141                        } else {
 142                                rose->condition &= ~ROSE_COND_PEER_RX_BUSY;
 143                        }
 144                }
 145                break;
 146
 147        case ROSE_DATA: /* XXX */
 148                rose->condition &= ~ROSE_COND_PEER_RX_BUSY;
 149                if (!rose_validate_nr(sk, nr)) {
 150                        rose_write_internal(sk, ROSE_RESET_REQUEST);
 151                        rose->condition = 0x00;
 152                        rose->vs        = 0;
 153                        rose->vr        = 0;
 154                        rose->va        = 0;
 155                        rose->vl        = 0;
 156                        rose->state     = ROSE_STATE_4;
 157                        rose_start_t2timer(sk);
 158                        rose_stop_idletimer(sk);
 159                        break;
 160                }
 161                rose_frames_acked(sk, nr);
 162                if (ns == rose->vr) {
 163                        rose_start_idletimer(sk);
 164                        if (sk_filter_trim_cap(sk, skb, ROSE_MIN_LEN) == 0 &&
 165                            __sock_queue_rcv_skb(sk, skb) == 0) {
 166                                rose->vr = (rose->vr + 1) % ROSE_MODULUS;
 167                                queued = 1;
 168                        } else {
 169                                /* Should never happen ! */
 170                                rose_write_internal(sk, ROSE_RESET_REQUEST);
 171                                rose->condition = 0x00;
 172                                rose->vs        = 0;
 173                                rose->vr        = 0;
 174                                rose->va        = 0;
 175                                rose->vl        = 0;
 176                                rose->state     = ROSE_STATE_4;
 177                                rose_start_t2timer(sk);
 178                                rose_stop_idletimer(sk);
 179                                break;
 180                        }
 181                        if (atomic_read(&sk->sk_rmem_alloc) >
 182                            (sk->sk_rcvbuf >> 1))
 183                                rose->condition |= ROSE_COND_OWN_RX_BUSY;
 184                }
 185                /*
 186                 * If the window is full, ack the frame, else start the
 187                 * acknowledge hold back timer.
 188                 */
 189                if (((rose->vl + sysctl_rose_window_size) % ROSE_MODULUS) == rose->vr) {
 190                        rose->condition &= ~ROSE_COND_ACK_PENDING;
 191                        rose_stop_timer(sk);
 192                        rose_enquiry_response(sk);
 193                } else {
 194                        rose->condition |= ROSE_COND_ACK_PENDING;
 195                        rose_start_hbtimer(sk);
 196                }
 197                break;
 198
 199        default:
 200                printk(KERN_WARNING "ROSE: unknown %02X in state 3\n", frametype);
 201                break;
 202        }
 203
 204        return queued;
 205}
 206
 207/*
 208 * State machine for state 4, Awaiting Reset Confirmation State.
 209 * The handling of the timer(s) is in file rose_timer.c
 210 * Handling of state 0 and connection release is in af_rose.c.
 211 */
 212static int rose_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
 213{
 214        struct rose_sock *rose = rose_sk(sk);
 215
 216        switch (frametype) {
 217        case ROSE_RESET_REQUEST:
 218                rose_write_internal(sk, ROSE_RESET_CONFIRMATION);
 219                fallthrough;
 220        case ROSE_RESET_CONFIRMATION:
 221                rose_stop_timer(sk);
 222                rose_start_idletimer(sk);
 223                rose->condition = 0x00;
 224                rose->va        = 0;
 225                rose->vr        = 0;
 226                rose->vs        = 0;
 227                rose->vl        = 0;
 228                rose->state     = ROSE_STATE_3;
 229                rose_requeue_frames(sk);
 230                break;
 231
 232        case ROSE_CLEAR_REQUEST:
 233                rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
 234                rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
 235                rose->neighbour->use--;
 236                break;
 237
 238        default:
 239                break;
 240        }
 241
 242        return 0;
 243}
 244
 245/*
 246 * State machine for state 5, Awaiting Call Acceptance State.
 247 * The handling of the timer(s) is in file rose_timer.c
 248 * Handling of state 0 and connection release is in af_rose.c.
 249 */
 250static int rose_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype)
 251{
 252        if (frametype == ROSE_CLEAR_REQUEST) {
 253                rose_write_internal(sk, ROSE_CLEAR_CONFIRMATION);
 254                rose_disconnect(sk, 0, skb->data[3], skb->data[4]);
 255                rose_sk(sk)->neighbour->use--;
 256        }
 257
 258        return 0;
 259}
 260
 261/* Higher level upcall for a LAPB frame */
 262int rose_process_rx_frame(struct sock *sk, struct sk_buff *skb)
 263{
 264        struct rose_sock *rose = rose_sk(sk);
 265        int queued = 0, frametype, ns, nr, q, d, m;
 266
 267        if (rose->state == ROSE_STATE_0)
 268                return 0;
 269
 270        frametype = rose_decode(skb, &ns, &nr, &q, &d, &m);
 271
 272        switch (rose->state) {
 273        case ROSE_STATE_1:
 274                queued = rose_state1_machine(sk, skb, frametype);
 275                break;
 276        case ROSE_STATE_2:
 277                queued = rose_state2_machine(sk, skb, frametype);
 278                break;
 279        case ROSE_STATE_3:
 280                queued = rose_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
 281                break;
 282        case ROSE_STATE_4:
 283                queued = rose_state4_machine(sk, skb, frametype);
 284                break;
 285        case ROSE_STATE_5:
 286                queued = rose_state5_machine(sk, skb, frametype);
 287                break;
 288        }
 289
 290        rose_kick(sk);
 291
 292        return queued;
 293}
 294
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