linux/net/ax25/ax25_in.c
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   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#include <linux/errno.h>
  13#include <linux/types.h>
  14#include <linux/socket.h>
  15#include <linux/in.h>
  16#include <linux/kernel.h>
  17#include <linux/timer.h>
  18#include <linux/string.h>
  19#include <linux/sockios.h>
  20#include <linux/net.h>
  21#include <linux/slab.h>
  22#include <net/ax25.h>
  23#include <linux/inet.h>
  24#include <linux/netdevice.h>
  25#include <linux/skbuff.h>
  26#include <linux/netfilter.h>
  27#include <net/sock.h>
  28#include <net/tcp_states.h>
  29#include <asm/uaccess.h>
  30#include <linux/fcntl.h>
  31#include <linux/mm.h>
  32#include <linux/interrupt.h>
  33
  34/*
  35 *      Given a fragment, queue it on the fragment queue and if the fragment
  36 *      is complete, send it back to ax25_rx_iframe.
  37 */
  38static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
  39{
  40        struct sk_buff *skbn, *skbo;
  41
  42        if (ax25->fragno != 0) {
  43                if (!(*skb->data & AX25_SEG_FIRST)) {
  44                        if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
  45                                /* Enqueue fragment */
  46                                ax25->fragno = *skb->data & AX25_SEG_REM;
  47                                skb_pull(skb, 1);       /* skip fragno */
  48                                ax25->fraglen += skb->len;
  49                                skb_queue_tail(&ax25->frag_queue, skb);
  50
  51                                /* Last fragment received ? */
  52                                if (ax25->fragno == 0) {
  53                                        skbn = alloc_skb(AX25_MAX_HEADER_LEN +
  54                                                         ax25->fraglen,
  55                                                         GFP_ATOMIC);
  56                                        if (!skbn) {
  57                                                skb_queue_purge(&ax25->frag_queue);
  58                                                return 1;
  59                                        }
  60
  61                                        skb_reserve(skbn, AX25_MAX_HEADER_LEN);
  62
  63                                        skbn->dev   = ax25->ax25_dev->dev;
  64                                        skb_reset_network_header(skbn);
  65                                        skb_reset_transport_header(skbn);
  66
  67                                        /* Copy data from the fragments */
  68                                        while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
  69                                                skb_copy_from_linear_data(skbo,
  70                                                          skb_put(skbn, skbo->len),
  71                                                                          skbo->len);
  72                                                kfree_skb(skbo);
  73                                        }
  74
  75                                        ax25->fraglen = 0;
  76
  77                                        if (ax25_rx_iframe(ax25, skbn) == 0)
  78                                                kfree_skb(skbn);
  79                                }
  80
  81                                return 1;
  82                        }
  83                }
  84        } else {
  85                /* First fragment received */
  86                if (*skb->data & AX25_SEG_FIRST) {
  87                        skb_queue_purge(&ax25->frag_queue);
  88                        ax25->fragno = *skb->data & AX25_SEG_REM;
  89                        skb_pull(skb, 1);               /* skip fragno */
  90                        ax25->fraglen = skb->len;
  91                        skb_queue_tail(&ax25->frag_queue, skb);
  92                        return 1;
  93                }
  94        }
  95
  96        return 0;
  97}
  98
  99/*
 100 *      This is where all valid I frames are sent to, to be dispatched to
 101 *      whichever protocol requires them.
 102 */
 103int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
 104{
 105        int (*func)(struct sk_buff *, ax25_cb *);
 106        unsigned char pid;
 107        int queued = 0;
 108
 109        if (skb == NULL) return 0;
 110
 111        ax25_start_idletimer(ax25);
 112
 113        pid = *skb->data;
 114
 115        if (pid == AX25_P_IP) {
 116                /* working around a TCP bug to keep additional listeners
 117                 * happy. TCP re-uses the buffer and destroys the original
 118                 * content.
 119                 */
 120                struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
 121                if (skbn != NULL) {
 122                        kfree_skb(skb);
 123                        skb = skbn;
 124                }
 125
 126                skb_pull(skb, 1);       /* Remove PID */
 127                skb->mac_header = skb->network_header;
 128                skb_reset_network_header(skb);
 129                skb->dev      = ax25->ax25_dev->dev;
 130                skb->pkt_type = PACKET_HOST;
 131                skb->protocol = htons(ETH_P_IP);
 132                netif_rx(skb);
 133                return 1;
 134        }
 135        if (pid == AX25_P_SEGMENT) {
 136                skb_pull(skb, 1);       /* Remove PID */
 137                return ax25_rx_fragment(ax25, skb);
 138        }
 139
 140        if ((func = ax25_protocol_function(pid)) != NULL) {
 141                skb_pull(skb, 1);       /* Remove PID */
 142                return (*func)(skb, ax25);
 143        }
 144
 145        if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
 146                if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
 147                    ax25->pidincl) {
 148                        if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
 149                                queued = 1;
 150                        else
 151                                ax25->condition |= AX25_COND_OWN_RX_BUSY;
 152                }
 153        }
 154
 155        return queued;
 156}
 157
 158/*
 159 *      Higher level upcall for a LAPB frame
 160 */
 161static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
 162{
 163        int queued = 0;
 164
 165        if (ax25->state == AX25_STATE_0)
 166                return 0;
 167
 168        switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 169        case AX25_PROTO_STD_SIMPLEX:
 170        case AX25_PROTO_STD_DUPLEX:
 171                queued = ax25_std_frame_in(ax25, skb, type);
 172                break;
 173
 174#ifdef CONFIG_AX25_DAMA_SLAVE
 175        case AX25_PROTO_DAMA_SLAVE:
 176                if (dama || ax25->ax25_dev->dama.slave)
 177                        queued = ax25_ds_frame_in(ax25, skb, type);
 178                else
 179                        queued = ax25_std_frame_in(ax25, skb, type);
 180                break;
 181#endif
 182        }
 183
 184        return queued;
 185}
 186
 187static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
 188        ax25_address *dev_addr, struct packet_type *ptype)
 189{
 190        ax25_address src, dest, *next_digi = NULL;
 191        int type = 0, mine = 0, dama;
 192        struct sock *make, *sk;
 193        ax25_digi dp, reverse_dp;
 194        ax25_cb *ax25;
 195        ax25_dev *ax25_dev;
 196
 197        /*
 198         *      Process the AX.25/LAPB frame.
 199         */
 200
 201        skb_reset_transport_header(skb);
 202
 203        if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
 204                goto free;
 205
 206        /*
 207         *      Parse the address header.
 208         */
 209
 210        if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
 211                goto free;
 212
 213        /*
 214         *      Ours perhaps ?
 215         */
 216        if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
 217                next_digi = &dp.calls[dp.lastrepeat + 1];
 218
 219        /*
 220         *      Pull of the AX.25 headers leaving the CTRL/PID bytes
 221         */
 222        skb_pull(skb, ax25_addr_size(&dp));
 223
 224        /* For our port addresses ? */
 225        if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 226                mine = 1;
 227
 228        /* Also match on any registered callsign from L3/4 */
 229        if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 230                mine = 1;
 231
 232        /* UI frame - bypass LAPB processing */
 233        if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 234                skb_set_transport_header(skb, 2); /* skip control and pid */
 235
 236                ax25_send_to_raw(&dest, skb, skb->data[1]);
 237
 238                if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
 239                        goto free;
 240
 241                /* Now we are pointing at the pid byte */
 242                switch (skb->data[1]) {
 243                case AX25_P_IP:
 244                        skb_pull(skb,2);                /* drop PID/CTRL */
 245                        skb_reset_transport_header(skb);
 246                        skb_reset_network_header(skb);
 247                        skb->dev      = dev;
 248                        skb->pkt_type = PACKET_HOST;
 249                        skb->protocol = htons(ETH_P_IP);
 250                        netif_rx(skb);
 251                        break;
 252
 253                case AX25_P_ARP:
 254                        skb_pull(skb,2);
 255                        skb_reset_transport_header(skb);
 256                        skb_reset_network_header(skb);
 257                        skb->dev      = dev;
 258                        skb->pkt_type = PACKET_HOST;
 259                        skb->protocol = htons(ETH_P_ARP);
 260                        netif_rx(skb);
 261                        break;
 262                case AX25_P_TEXT:
 263                        /* Now find a suitable dgram socket */
 264                        sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 265                        if (sk != NULL) {
 266                                bh_lock_sock(sk);
 267                                if (atomic_read(&sk->sk_rmem_alloc) >=
 268                                    sk->sk_rcvbuf) {
 269                                        kfree_skb(skb);
 270                                } else {
 271                                        /*
 272                                         *      Remove the control and PID.
 273                                         */
 274                                        skb_pull(skb, 2);
 275                                        if (sock_queue_rcv_skb(sk, skb) != 0)
 276                                                kfree_skb(skb);
 277                                }
 278                                bh_unlock_sock(sk);
 279                                sock_put(sk);
 280                        } else {
 281                                kfree_skb(skb);
 282                        }
 283                        break;
 284
 285                default:
 286                        kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
 287                        break;
 288                }
 289
 290                return 0;
 291        }
 292
 293        /*
 294         *      Is connected mode supported on this device ?
 295         *      If not, should we DM the incoming frame (except DMs) or
 296         *      silently ignore them. For now we stay quiet.
 297         */
 298        if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
 299                goto free;
 300
 301        /* LAPB */
 302
 303        /* AX.25 state 1-4 */
 304
 305        ax25_digi_invert(&dp, &reverse_dp);
 306
 307        if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 308                /*
 309                 *      Process the frame. If it is queued up internally it
 310                 *      returns one otherwise we free it immediately. This
 311                 *      routine itself wakes the user context layers so we do
 312                 *      no further work
 313                 */
 314                if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 315                        kfree_skb(skb);
 316
 317                ax25_cb_put(ax25);
 318                return 0;
 319        }
 320
 321        /* AX.25 state 0 (disconnected) */
 322
 323        /* a) received not a SABM(E) */
 324
 325        if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 326            (*skb->data & ~AX25_PF) != AX25_SABME) {
 327                /*
 328                 *      Never reply to a DM. Also ignore any connects for
 329                 *      addresses that are not our interfaces and not a socket.
 330                 */
 331                if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 332                        ax25_return_dm(dev, &src, &dest, &dp);
 333
 334                goto free;
 335        }
 336
 337        /* b) received SABM(E) */
 338
 339        if (dp.lastrepeat + 1 == dp.ndigi)
 340                sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 341        else
 342                sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
 343
 344        if (sk != NULL) {
 345                bh_lock_sock(sk);
 346                if (sk_acceptq_is_full(sk) ||
 347                    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 348                        if (mine)
 349                                ax25_return_dm(dev, &src, &dest, &dp);
 350                        kfree_skb(skb);
 351                        bh_unlock_sock(sk);
 352                        sock_put(sk);
 353
 354                        return 0;
 355                }
 356
 357                ax25 = ax25_sk(make);
 358                skb_set_owner_r(skb, make);
 359                skb_queue_head(&sk->sk_receive_queue, skb);
 360
 361                make->sk_state = TCP_ESTABLISHED;
 362
 363                sk->sk_ack_backlog++;
 364                bh_unlock_sock(sk);
 365        } else {
 366                if (!mine)
 367                        goto free;
 368
 369                if ((ax25 = ax25_create_cb()) == NULL) {
 370                        ax25_return_dm(dev, &src, &dest, &dp);
 371                        goto free;
 372                }
 373
 374                ax25_fillin_cb(ax25, ax25_dev);
 375        }
 376
 377        ax25->source_addr = dest;
 378        ax25->dest_addr   = src;
 379
 380        /*
 381         *      Sort out any digipeated paths.
 382         */
 383        if (dp.ndigi && !ax25->digipeat &&
 384            (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 385                kfree_skb(skb);
 386                ax25_destroy_socket(ax25);
 387                if (sk)
 388                        sock_put(sk);
 389                return 0;
 390        }
 391
 392        if (dp.ndigi == 0) {
 393                kfree(ax25->digipeat);
 394                ax25->digipeat = NULL;
 395        } else {
 396                /* Reverse the source SABM's path */
 397                memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 398        }
 399
 400        if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 401                ax25->modulus = AX25_EMODULUS;
 402                ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 403        } else {
 404                ax25->modulus = AX25_MODULUS;
 405                ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 406        }
 407
 408        ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
 409
 410#ifdef CONFIG_AX25_DAMA_SLAVE
 411        if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 412                ax25_dama_on(ax25);
 413#endif
 414
 415        ax25->state = AX25_STATE_3;
 416
 417        ax25_cb_add(ax25);
 418
 419        ax25_start_heartbeat(ax25);
 420        ax25_start_t3timer(ax25);
 421        ax25_start_idletimer(ax25);
 422
 423        if (sk) {
 424                if (!sock_flag(sk, SOCK_DEAD))
 425                        sk->sk_data_ready(sk, skb->len);
 426                sock_put(sk);
 427        } else {
 428free:
 429                kfree_skb(skb);
 430        }
 431        return 0;
 432}
 433
 434/*
 435 *      Receive an AX.25 frame via a SLIP interface.
 436 */
 437int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 438                  struct packet_type *ptype, struct net_device *orig_dev)
 439{
 440        skb_orphan(skb);
 441
 442        if (!net_eq(dev_net(dev), &init_net)) {
 443                kfree_skb(skb);
 444                return 0;
 445        }
 446
 447        if ((*skb->data & 0x0F) != 0) {
 448                kfree_skb(skb); /* Not a KISS data frame */
 449                return 0;
 450        }
 451
 452        skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
 453
 454        return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 455}
 456
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