net/ax25/ax25_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 #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 <asm/system.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/mm.h>
  33 #include <linux/interrupt.h>
  34
  35 /*
  36  *      Given a fragment, queue it on the fragment queue and if the fragment
  37  *      is complete, send it back to ax25_rx_iframe.
  38  */
  39 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
  40 {
  41         struct sk_buff *skbn, *skbo;
  42
  43         if (ax25->fragno != 0) {
  44                 if (!(*skb->data & AX25_SEG_FIRST)) {
  45                         if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
  46                                 /* Enqueue fragment */
  47                                 ax25->fragno = *skb->data & AX25_SEG_REM;
  48                                 skb_pull(skb, 1);       /* skip fragno */
  49                                 ax25->fraglen += skb->len;
  50                                 skb_queue_tail(&ax25->frag_queue, skb);
  51
  52                                 /* Last fragment received ? */
  53                                 if (ax25->fragno == 0) {
  54                                         skbn = alloc_skb(AX25_MAX_HEADER_LEN +
  55                                                          ax25->fraglen,
  56                                                          GFP_ATOMIC);
  57                                         if (!skbn) {
  58                                                 skb_queue_purge(&ax25->frag_queue);
  59                                                 return 1;
  60                                         }
  61
  62                                         skb_reserve(skbn, AX25_MAX_HEADER_LEN);
  63
  64                                         skbn->dev   = ax25->ax25_dev->dev;
  65                                         skb_reset_network_header(skbn);
  66                                         skb_reset_transport_header(skbn);
  67
  68                                         /* Copy data from the fragments */
  69                                         while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
  70                                                 skb_copy_from_linear_data(skbo,
  71                                                           skb_put(skbn, skbo->len),
  72                                                                           skbo->len);
  73                                                 kfree_skb(skbo);
  74                                         }
  75
  76                                         ax25->fraglen = 0;
  77
  78                                         if (ax25_rx_iframe(ax25, skbn) == 0)
  79                                                 kfree_skb(skbn);
  80                                 }
  81
  82                                 return 1;
  83                         }
  84                 }
  85         } else {
  86                 /* First fragment received */
  87                 if (*skb->data & AX25_SEG_FIRST) {
  88                         skb_queue_purge(&ax25->frag_queue);
  89                         ax25->fragno = *skb->data & AX25_SEG_REM;
  90                         skb_pull(skb, 1);               /* skip fragno */
  91                         ax25->fraglen = skb->len;
  92                         skb_queue_tail(&ax25->frag_queue, skb);
  93                         return 1;
  94                 }
  95         }
  96
  97         return 0;
  98 }
  99
 100 /*
 101  *      This is where all valid I frames are sent to, to be dispatched to
 102  *      whichever protocol requires them.
 103  */
 104 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
 105 {
 106         int (*func)(struct sk_buff *, ax25_cb *);
 107         unsigned char pid;
 108         int queued = 0;
 109
 110         if (skb == NULL) return 0;
 111
 112         ax25_start_idletimer(ax25);
 113
 114         pid = *skb->data;
 115
 116         if (pid == AX25_P_IP) {
 117                 /* working around a TCP bug to keep additional listeners
 118                  * happy. TCP re-uses the buffer and destroys the original
 119                  * content.
 120                  */
 121                 struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
 122                 if (skbn != NULL) {
 123                         kfree_skb(skb);
 124                         skb = skbn;
 125                 }
 126
 127                 skb_pull(skb, 1);       /* Remove PID */
 128                 skb->mac_header = skb->network_header;
 129                 skb_reset_network_header(skb);
 130                 skb->dev      = ax25->ax25_dev->dev;
 131                 skb->pkt_type = PACKET_HOST;
 132                 skb->protocol = htons(ETH_P_IP);
 133                 netif_rx(skb);
 134                 return 1;
 135         }
 136         if (pid == AX25_P_SEGMENT) {
 137                 skb_pull(skb, 1);       /* Remove PID */
 138                 return ax25_rx_fragment(ax25, skb);
 139         }
 140
 141         if ((func = ax25_protocol_function(pid)) != NULL) {
 142                 skb_pull(skb, 1);       /* Remove PID */
 143                 return (*func)(skb, ax25);
 144         }
 145
 146         if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
 147                 if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
 148                     ax25->pidincl) {
 149                         if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
 150                                 queued = 1;
 151                         else
 152                                 ax25->condition |= AX25_COND_OWN_RX_BUSY;
 153                 }
 154         }
 155
 156         return queued;
 157 }
 158
 159 /*
 160  *      Higher level upcall for a LAPB frame
 161  */
 162 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
 163 {
 164         int queued = 0;
 165
 166         if (ax25->state == AX25_STATE_0)
 167                 return 0;
 168
 169         switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 170         case AX25_PROTO_STD_SIMPLEX:
 171         case AX25_PROTO_STD_DUPLEX:
 172                 queued = ax25_std_frame_in(ax25, skb, type);
 173                 break;
 174
 175 #ifdef CONFIG_AX25_DAMA_SLAVE
 176         case AX25_PROTO_DAMA_SLAVE:
 177                 if (dama || ax25->ax25_dev->dama.slave)
 178                         queued = ax25_ds_frame_in(ax25, skb, type);
 179                 else
 180                         queued = ax25_std_frame_in(ax25, skb, type);
 181                 break;
 182 #endif
 183         }
 184
 185         return queued;
 186 }
 187
 188 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
 189         ax25_address *dev_addr, struct packet_type *ptype)
 190 {
 191         ax25_address src, dest, *next_digi = NULL;
 192         int type = 0, mine = 0, dama;
 193         struct sock *make, *sk;
 194         ax25_digi dp, reverse_dp;
 195         ax25_cb *ax25;
 196         ax25_dev *ax25_dev;
 197
 198         /*
 199          *      Process the AX.25/LAPB frame.
 200          */
 201
 202         skb_reset_transport_header(skb);
 203
 204         if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
 205                 goto free;
 206
 207         /*
 208          *      Parse the address header.
 209          */
 210
 211         if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
 212                 goto free;
 213
 214         /*
 215          *      Ours perhaps ?
 216          */
 217         if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
 218                 next_digi = &dp.calls[dp.lastrepeat + 1];
 219
 220         /*
 221          *      Pull of the AX.25 headers leaving the CTRL/PID bytes
 222          */
 223         skb_pull(skb, ax25_addr_size(&dp));
 224
 225         /* For our port addresses ? */
 226         if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 227                 mine = 1;
 228
 229         /* Also match on any registered callsign from L3/4 */
 230         if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 231                 mine = 1;
 232
 233         /* UI frame - bypass LAPB processing */
 234         if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 235                 skb_set_transport_header(skb, 2); /* skip control and pid */
 236
 237                 ax25_send_to_raw(&dest, skb, skb->data[1]);
 238
 239                 if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
 240                         goto free;
 241
 242                 /* Now we are pointing at the pid byte */
 243                 switch (skb->data[1]) {
 244                 case AX25_P_IP:
 245                         skb_pull(skb,2);                /* drop PID/CTRL */
 246                         skb_reset_transport_header(skb);
 247                         skb_reset_network_header(skb);
 248                         skb->dev      = dev;
 249                         skb->pkt_type = PACKET_HOST;
 250                         skb->protocol = htons(ETH_P_IP);
 251                         netif_rx(skb);
 252                         break;
 253
 254                 case AX25_P_ARP:
 255                         skb_pull(skb,2);
 256                         skb_reset_transport_header(skb);
 257                         skb_reset_network_header(skb);
 258                         skb->dev      = dev;
 259                         skb->pkt_type = PACKET_HOST;
 260                         skb->protocol = htons(ETH_P_ARP);
 261                         netif_rx(skb);
 262                         break;
 263                 case AX25_P_TEXT:
 264                         /* Now find a suitable dgram socket */
 265                         sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 266                         if (sk != NULL) {
 267                                 bh_lock_sock(sk);
 268                                 if (atomic_read(&sk->sk_rmem_alloc) >=
 269                                     sk->sk_rcvbuf) {
 270                                         kfree_skb(skb);
 271                                 } else {
 272                                         /*
 273                                          *      Remove the control and PID.
 274                                          */
 275                                         skb_pull(skb, 2);
 276                                         if (sock_queue_rcv_skb(sk, skb) != 0)
 277                                                 kfree_skb(skb);
 278                                 }
 279                                 bh_unlock_sock(sk);
 280                                 sock_put(sk);
 281                         } else {
 282                                 kfree_skb(skb);
 283                         }
 284                         break;
 285
 286                 default:
 287                         kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
 288                         break;
 289                 }
 290
 291                 return 0;
 292         }
 293
 294         /*
 295          *      Is connected mode supported on this device ?
 296          *      If not, should we DM the incoming frame (except DMs) or
 297          *      silently ignore them. For now we stay quiet.
 298          */
 299         if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
 300                 goto free;
 301
 302         /* LAPB */
 303
 304         /* AX.25 state 1-4 */
 305
 306         ax25_digi_invert(&dp, &reverse_dp);
 307
 308         if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 309                 /*
 310                  *      Process the frame. If it is queued up internally it
 311                  *      returns one otherwise we free it immediately. This
 312                  *      routine itself wakes the user context layers so we do
 313                  *      no further work
 314                  */
 315                 if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 316                         kfree_skb(skb);
 317
 318                 ax25_cb_put(ax25);
 319                 return 0;
 320         }
 321
 322         /* AX.25 state 0 (disconnected) */
 323
 324         /* a) received not a SABM(E) */
 325
 326         if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 327             (*skb->data & ~AX25_PF) != AX25_SABME) {
 328                 /*
 329                  *      Never reply to a DM. Also ignore any connects for
 330                  *      addresses that are not our interfaces and not a socket.
 331                  */
 332                 if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 333                         ax25_return_dm(dev, &src, &dest, &dp);
 334
 335                 goto free;
 336         }
 337
 338         /* b) received SABM(E) */
 339
 340         if (dp.lastrepeat + 1 == dp.ndigi)
 341                 sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 342         else
 343                 sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
 344
 345         if (sk != NULL) {
 346                 bh_lock_sock(sk);
 347                 if (sk_acceptq_is_full(sk) ||
 348                     (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 349                         if (mine)
 350                                 ax25_return_dm(dev, &src, &dest, &dp);
 351                         kfree_skb(skb);
 352                         bh_unlock_sock(sk);
 353                         sock_put(sk);
 354
 355                         return 0;
 356                 }
 357
 358                 ax25 = ax25_sk(make);
 359                 skb_set_owner_r(skb, make);
 360                 skb_queue_head(&sk->sk_receive_queue, skb);
 361
 362                 make->sk_state = TCP_ESTABLISHED;
 363
 364                 sk->sk_ack_backlog++;
 365                 bh_unlock_sock(sk);
 366         } else {
 367                 if (!mine)
 368                         goto free;
 369
 370                 if ((ax25 = ax25_create_cb()) == NULL) {
 371                         ax25_return_dm(dev, &src, &dest, &dp);
 372                         goto free;
 373                 }
 374
 375                 ax25_fillin_cb(ax25, ax25_dev);
 376         }
 377
 378         ax25->source_addr = dest;
 379         ax25->dest_addr   = src;
 380
 381         /*
 382          *      Sort out any digipeated paths.
 383          */
 384         if (dp.ndigi && !ax25->digipeat &&
 385             (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 386                 kfree_skb(skb);
 387                 ax25_destroy_socket(ax25);
 388                 if (sk)
 389                         sock_put(sk);
 390                 return 0;
 391         }
 392
 393         if (dp.ndigi == 0) {
 394                 kfree(ax25->digipeat);
 395                 ax25->digipeat = NULL;
 396         } else {
 397                 /* Reverse the source SABM's path */
 398                 memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 399         }
 400
 401         if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 402                 ax25->modulus = AX25_EMODULUS;
 403                 ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 404         } else {
 405                 ax25->modulus = AX25_MODULUS;
 406                 ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 407         }
 408
 409         ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
 410
 411 #ifdef CONFIG_AX25_DAMA_SLAVE
 412         if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 413                 ax25_dama_on(ax25);
 414 #endif
 415
 416         ax25->state = AX25_STATE_3;
 417
 418         ax25_cb_add(ax25);
 419
 420         ax25_start_heartbeat(ax25);
 421         ax25_start_t3timer(ax25);
 422         ax25_start_idletimer(ax25);
 423
 424         if (sk) {
 425                 if (!sock_flag(sk, SOCK_DEAD))
 426                         sk->sk_data_ready(sk, skb->len);
 427                 sock_put(sk);
 428         } else {
 429 free:
 430                 kfree_skb(skb);
 431         }
 432         return 0;
 433 }
 434
 435 /*
 436  *      Receive an AX.25 frame via a SLIP interface.
 437  */
 438 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 439                   struct packet_type *ptype, struct net_device *orig_dev)
 440 {
 441         skb_orphan(skb);
 442
 443         if (!net_eq(dev_net(dev), &init_net)) {
 444                 kfree_skb(skb);
 445                 return 0;
 446         }
 447
 448         if ((*skb->data & 0x0F) != 0) {
 449                 kfree_skb(skb); /* Not a KISS data frame */
 450                 return 0;
 451         }
 452
 453         skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
 454
 455         return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 456 }