LXR linux/net/ax25/ax25

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *
   4 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   5 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   6 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   7 * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
   8 */
   9#include <linux/errno.h>
  10#include <linux/types.h>
  11#include <linux/socket.h>
  12#include <linux/in.h>
  13#include <linux/kernel.h>
  14#include <linux/timer.h>
  15#include <linux/string.h>
  16#include <linux/sockios.h>
  17#include <linux/net.h>
  18#include <linux/slab.h>
  19#include <net/ax25.h>
  20#include <linux/inet.h>
  21#include <linux/netdevice.h>
  22#include <linux/skbuff.h>
  23#include <net/sock.h>
  24#include <net/tcp_states.h>
  25#include <linux/uaccess.h>
  26#include <linux/fcntl.h>
  27#include <linux/mm.h>
  28#include <linux/interrupt.h>
  29
  30/*
  31 *      Given a fragment, queue it on the fragment queue and if the fragment
  32 *      is complete, send it back to ax25_rx_iframe.
  33 */
  34static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
  35{
  36        struct sk_buff *skbn, *skbo;
  37
  38        if (ax25->fragno != 0) {
  39                if (!(*skb->data & AX25_SEG_FIRST)) {
  40                        if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
  41                                /* Enqueue fragment */
  42                                ax25->fragno = *skb->data & AX25_SEG_REM;
  43                                skb_pull(skb, 1);       /* skip fragno */
  44                                ax25->fraglen += skb->len;
  45                                skb_queue_tail(&ax25->frag_queue, skb);
  46
  47                                /* Last fragment received ? */
  48                                if (ax25->fragno == 0) {
  49                                        skbn = alloc_skb(AX25_MAX_HEADER_LEN +
  50                                                         ax25->fraglen,
  51                                                         GFP_ATOMIC);
  52                                        if (!skbn) {
  53                                                skb_queue_purge(&ax25->frag_queue);
  54                                                return 1;
  55                                        }
  56
  57                                        skb_reserve(skbn, AX25_MAX_HEADER_LEN);
  58
  59                                        skbn->dev   = ax25->ax25_dev->dev;
  60                                        skb_reset_network_header(skbn);
  61                                        skb_reset_transport_header(skbn);
  62
  63                                        /* Copy data from the fragments */
  64                                        while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
  65                                                skb_copy_from_linear_data(skbo,
  66                                                          skb_put(skbn, skbo->len),
  67                                                                          skbo->len);
  68                                                kfree_skb(skbo);
  69                                        }
  70
  71                                        ax25->fraglen = 0;
  72
  73                                        if (ax25_rx_iframe(ax25, skbn) == 0)
  74                                                kfree_skb(skbn);
  75                                }
  76
  77                                return 1;
  78                        }
  79                }
  80        } else {
  81                /* First fragment received */
  82                if (*skb->data & AX25_SEG_FIRST) {
  83                        skb_queue_purge(&ax25->frag_queue);
  84                        ax25->fragno = *skb->data & AX25_SEG_REM;
  85                        skb_pull(skb, 1);               /* skip fragno */
  86                        ax25->fraglen = skb->len;
  87                        skb_queue_tail(&ax25->frag_queue, skb);
  88                        return 1;
  89                }
  90        }
  91
  92        return 0;
  93}
  94
  95/*
  96 *      This is where all valid I frames are sent to, to be dispatched to
  97 *      whichever protocol requires them.
  98 */
  99int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
 100{
 101        int (*func)(struct sk_buff *, ax25_cb *);
 102        unsigned char pid;
 103        int queued = 0;
 104
 105        if (skb == NULL) return 0;
 106
 107        ax25_start_idletimer(ax25);
 108
 109        pid = *skb->data;
 110
 111        if (pid == AX25_P_IP) {
 112                /* working around a TCP bug to keep additional listeners
 113                 * happy. TCP re-uses the buffer and destroys the original
 114                 * content.
 115                 */
 116                struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
 117                if (skbn != NULL) {
 118                        kfree_skb(skb);
 119                        skb = skbn;
 120                }
 121
 122                skb_pull(skb, 1);       /* Remove PID */
 123                skb->mac_header = skb->network_header;
 124                skb_reset_network_header(skb);
 125                skb->dev      = ax25->ax25_dev->dev;
 126                skb->pkt_type = PACKET_HOST;
 127                skb->protocol = htons(ETH_P_IP);
 128                netif_rx(skb);
 129                return 1;
 130        }
 131        if (pid == AX25_P_SEGMENT) {
 132                skb_pull(skb, 1);       /* Remove PID */
 133                return ax25_rx_fragment(ax25, skb);
 134        }
 135
 136        if ((func = ax25_protocol_function(pid)) != NULL) {
 137                skb_pull(skb, 1);       /* Remove PID */
 138                return (*func)(skb, ax25);
 139        }
 140
 141        if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
 142                if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
 143                    ax25->pidincl) {
 144                        if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
 145                                queued = 1;
 146                        else
 147                                ax25->condition |= AX25_COND_OWN_RX_BUSY;
 148                }
 149        }
 150
 151        return queued;
 152}
 153
 154/*
 155 *      Higher level upcall for a LAPB frame
 156 */
 157static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
 158{
 159        int queued = 0;
 160
 161        if (ax25->state == AX25_STATE_0)
 162                return 0;
 163
 164        switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 165        case AX25_PROTO_STD_SIMPLEX:
 166        case AX25_PROTO_STD_DUPLEX:
 167                queued = ax25_std_frame_in(ax25, skb, type);
 168                break;
 169
 170#ifdef CONFIG_AX25_DAMA_SLAVE
 171        case AX25_PROTO_DAMA_SLAVE:
 172                if (dama || ax25->ax25_dev->dama.slave)
 173                        queued = ax25_ds_frame_in(ax25, skb, type);
 174                else
 175                        queued = ax25_std_frame_in(ax25, skb, type);
 176                break;
 177#endif
 178        }
 179
 180        return queued;
 181}
 182
 183static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
 184        ax25_address *dev_addr, struct packet_type *ptype)
 185{
 186        ax25_address src, dest, *next_digi = NULL;
 187        int type = 0, mine = 0, dama;
 188        struct sock *make, *sk;
 189        ax25_digi dp, reverse_dp;
 190        ax25_cb *ax25;
 191        ax25_dev *ax25_dev;
 192
 193        /*
 194         *      Process the AX.25/LAPB frame.
 195         */
 196
 197        skb_reset_transport_header(skb);
 198
 199        if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
 200                goto free;
 201
 202        /*
 203         *      Parse the address header.
 204         */
 205
 206        if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
 207                goto free;
 208
 209        /*
 210         *      Ours perhaps ?
 211         */
 212        if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
 213                next_digi = &dp.calls[dp.lastrepeat + 1];
 214
 215        /*
 216         *      Pull of the AX.25 headers leaving the CTRL/PID bytes
 217         */
 218        skb_pull(skb, ax25_addr_size(&dp));
 219
 220        /* For our port addresses ? */
 221        if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 222                mine = 1;
 223
 224        /* Also match on any registered callsign from L3/4 */
 225        if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 226                mine = 1;
 227
 228        /* UI frame - bypass LAPB processing */
 229        if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 230                skb_set_transport_header(skb, 2); /* skip control and pid */
 231
 232                ax25_send_to_raw(&dest, skb, skb->data[1]);
 233
 234                if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
 235                        goto free;
 236
 237                /* Now we are pointing at the pid byte */
 238                switch (skb->data[1]) {
 239                case AX25_P_IP:
 240                        skb_pull(skb,2);                /* drop PID/CTRL */
 241                        skb_reset_transport_header(skb);
 242                        skb_reset_network_header(skb);
 243                        skb->dev      = dev;
 244                        skb->pkt_type = PACKET_HOST;
 245                        skb->protocol = htons(ETH_P_IP);
 246                        netif_rx(skb);
 247                        break;
 248
 249                case AX25_P_ARP:
 250                        skb_pull(skb,2);
 251                        skb_reset_transport_header(skb);
 252                        skb_reset_network_header(skb);
 253                        skb->dev      = dev;
 254                        skb->pkt_type = PACKET_HOST;
 255                        skb->protocol = htons(ETH_P_ARP);
 256                        netif_rx(skb);
 257                        break;
 258                case AX25_P_TEXT:
 259                        /* Now find a suitable dgram socket */
 260                        sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 261                        if (sk != NULL) {
 262                                bh_lock_sock(sk);
 263                                if (atomic_read(&sk->sk_rmem_alloc) >=
 264                                    sk->sk_rcvbuf) {
 265                                        kfree_skb(skb);
 266                                } else {
 267                                        /*
 268                                         *      Remove the control and PID.
 269                                         */
 270                                        skb_pull(skb, 2);
 271                                        if (sock_queue_rcv_skb(sk, skb) != 0)
 272                                                kfree_skb(skb);
 273                                }
 274                                bh_unlock_sock(sk);
 275                                sock_put(sk);
 276                        } else {
 277                                kfree_skb(skb);
 278                        }
 279                        break;
 280
 281                default:
 282                        kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
 283                        break;
 284                }
 285
 286                return 0;
 287        }
 288
 289        /*
 290         *      Is connected mode supported on this device ?
 291         *      If not, should we DM the incoming frame (except DMs) or
 292         *      silently ignore them. For now we stay quiet.
 293         */
 294        if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
 295                goto free;
 296
 297        /* LAPB */
 298
 299        /* AX.25 state 1-4 */
 300
 301        ax25_digi_invert(&dp, &reverse_dp);
 302
 303        if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 304                /*
 305                 *      Process the frame. If it is queued up internally it
 306                 *      returns one otherwise we free it immediately. This
 307                 *      routine itself wakes the user context layers so we do
 308                 *      no further work
 309                 */
 310                if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 311                        kfree_skb(skb);
 312
 313                ax25_cb_put(ax25);
 314                return 0;
 315        }
 316
 317        /* AX.25 state 0 (disconnected) */
 318
 319        /* a) received not a SABM(E) */
 320
 321        if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 322            (*skb->data & ~AX25_PF) != AX25_SABME) {
 323                /*
 324                 *      Never reply to a DM. Also ignore any connects for
 325                 *      addresses that are not our interfaces and not a socket.
 326                 */
 327                if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 328                        ax25_return_dm(dev, &src, &dest, &dp);
 329
 330                goto free;
 331        }
 332
 333        /* b) received SABM(E) */
 334
 335        if (dp.lastrepeat + 1 == dp.ndigi)
 336                sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 337        else
 338                sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
 339
 340        if (sk != NULL) {
 341                bh_lock_sock(sk);
 342                if (sk_acceptq_is_full(sk) ||
 343                    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 344                        if (mine)
 345                                ax25_return_dm(dev, &src, &dest, &dp);
 346                        kfree_skb(skb);
 347                        bh_unlock_sock(sk);
 348                        sock_put(sk);
 349
 350                        return 0;
 351                }
 352
 353                ax25 = sk_to_ax25(make);
 354                skb_set_owner_r(skb, make);
 355                skb_queue_head(&sk->sk_receive_queue, skb);
 356
 357                make->sk_state = TCP_ESTABLISHED;
 358
 359                sk_acceptq_added(sk);
 360                bh_unlock_sock(sk);
 361        } else {
 362                if (!mine)
 363                        goto free;
 364
 365                if ((ax25 = ax25_create_cb()) == NULL) {
 366                        ax25_return_dm(dev, &src, &dest, &dp);
 367                        goto free;
 368                }
 369
 370                ax25_fillin_cb(ax25, ax25_dev);
 371        }
 372
 373        ax25->source_addr = dest;
 374        ax25->dest_addr   = src;
 375
 376        /*
 377         *      Sort out any digipeated paths.
 378         */
 379        if (dp.ndigi && !ax25->digipeat &&
 380            (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 381                kfree_skb(skb);
 382                ax25_destroy_socket(ax25);
 383                if (sk)
 384                        sock_put(sk);
 385                return 0;
 386        }
 387
 388        if (dp.ndigi == 0) {
 389                kfree(ax25->digipeat);
 390                ax25->digipeat = NULL;
 391        } else {
 392                /* Reverse the source SABM's path */
 393                memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 394        }
 395
 396        if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 397                ax25->modulus = AX25_EMODULUS;
 398                ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 399        } else {
 400                ax25->modulus = AX25_MODULUS;
 401                ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 402        }
 403
 404        ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
 405
 406#ifdef CONFIG_AX25_DAMA_SLAVE
 407        if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 408                ax25_dama_on(ax25);
 409#endif
 410
 411        ax25->state = AX25_STATE_3;
 412
 413        ax25_cb_add(ax25);
 414
 415        ax25_start_heartbeat(ax25);
 416        ax25_start_t3timer(ax25);
 417        ax25_start_idletimer(ax25);
 418
 419        if (sk) {
 420                if (!sock_flag(sk, SOCK_DEAD))
 421                        sk->sk_data_ready(sk);
 422                sock_put(sk);
 423        } else {
 424free:
 425                kfree_skb(skb);
 426        }
 427        return 0;
 428}
 429
 430/*
 431 *      Receive an AX.25 frame via a SLIP interface.
 432 */
 433int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 434                  struct packet_type *ptype, struct net_device *orig_dev)
 435{
 436        skb_orphan(skb);
 437
 438        if (!net_eq(dev_net(dev), &init_net)) {
 439                kfree_skb(skb);
 440                return 0;
 441        }
 442
 443        if ((*skb->data & 0x0F) != 0) {
 444                kfree_skb(skb); /* Not a KISS data frame */
 445                return 0;
 446        }
 447
 448        skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
 449
 450        return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 451}
 452