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/sched.h>
  18 #include <linux/timer.h>
  19 #include <linux/string.h>
  20 #include <linux/sockios.h>
  21 #include <linux/net.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                                         skbn->h.raw = skbn->data;
  66                                         skbn->nh.raw = skbn->data;
  67
  68                                         /* Copy data from the fragments */
  69                                         while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
  70                                                 memcpy(skb_put(skbn, skbo->len), skbo->data, skbo->len);
  71                                                 kfree_skb(skbo);
  72                                         }
  73
  74                                         ax25->fraglen = 0;
  75
  76                                         if (ax25_rx_iframe(ax25, skbn) == 0)
  77                                                 kfree_skb(skbn);
  78                                 }
  79
  80                                 return 1;
  81                         }
  82                 }
  83         } else {
  84                 /* First fragment received */
  85                 if (*skb->data & AX25_SEG_FIRST) {
  86                         skb_queue_purge(&ax25->frag_queue);
  87                         ax25->fragno = *skb->data & AX25_SEG_REM;
  88                         skb_pull(skb, 1);               /* skip fragno */
  89                         ax25->fraglen = skb->len;
  90                         skb_queue_tail(&ax25->frag_queue, skb);
  91                         return 1;
  92                 }
  93         }
  94
  95         return 0;
  96 }
  97
  98 /*
  99  *      This is where all valid I frames are sent to, to be dispatched to
 100  *      whichever protocol requires them.
 101  */
 102 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
 103 {
 104         int (*func)(struct sk_buff *, ax25_cb *);
 105         unsigned char pid;
 106         int queued = 0;
 107
 108         if (skb == NULL) return 0;
 109
 110         ax25_start_idletimer(ax25);
 111
 112         pid = *skb->data;
 113
 114         if (pid == AX25_P_IP) {
 115                 /* working around a TCP bug to keep additional listeners
 116                  * happy. TCP re-uses the buffer and destroys the original
 117                  * content.
 118                  */
 119                 struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
 120                 if (skbn != NULL) {
 121                         kfree_skb(skb);
 122                         skb = skbn;
 123                 }
 124
 125                 skb_pull(skb, 1);       /* Remove PID */
 126                 skb->mac.raw  = skb->nh.raw;
 127                 skb->nh.raw   = skb->data;
 128                 skb->dev      = ax25->ax25_dev->dev;
 129                 skb->pkt_type = PACKET_HOST;
 130                 skb->protocol = htons(ETH_P_IP);
 131                 netif_rx(skb);
 132                 return 1;
 133         }
 134         if (pid == AX25_P_SEGMENT) {
 135                 skb_pull(skb, 1);       /* Remove PID */
 136                 return ax25_rx_fragment(ax25, skb);
 137         }
 138
 139         if ((func = ax25_protocol_function(pid)) != NULL) {
 140                 skb_pull(skb, 1);       /* Remove PID */
 141                 return (*func)(skb, ax25);
 142         }
 143
 144         if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
 145                 if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
 146                     ax25->pidincl) {
 147                         if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
 148                                 queued = 1;
 149                         else
 150                                 ax25->condition |= AX25_COND_OWN_RX_BUSY;
 151                 }
 152         }
 153
 154         return queued;
 155 }
 156
 157 /*
 158  *      Higher level upcall for a LAPB frame
 159  */
 160 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
 161 {
 162         int queued = 0;
 163
 164         if (ax25->state == AX25_STATE_0)
 165                 return 0;
 166
 167         switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 168         case AX25_PROTO_STD_SIMPLEX:
 169         case AX25_PROTO_STD_DUPLEX:
 170                 queued = ax25_std_frame_in(ax25, skb, type);
 171                 break;
 172
 173 #ifdef CONFIG_AX25_DAMA_SLAVE
 174         case AX25_PROTO_DAMA_SLAVE:
 175                 if (dama || ax25->ax25_dev->dama.slave)
 176                         queued = ax25_ds_frame_in(ax25, skb, type);
 177                 else
 178                         queued = ax25_std_frame_in(ax25, skb, type);
 179                 break;
 180 #endif
 181         }
 182
 183         return queued;
 184 }
 185
 186 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
 187         ax25_address *dev_addr, struct packet_type *ptype)
 188 {
 189         ax25_address src, dest, *next_digi = NULL;
 190         int type = 0, mine = 0, dama;
 191         struct sock *make, *sk;
 192         ax25_digi dp, reverse_dp;
 193         ax25_cb *ax25;
 194         ax25_dev *ax25_dev;
 195
 196         /*
 197          *      Process the AX.25/LAPB frame.
 198          */
 199
 200         skb->h.raw = skb->data;
 201
 202         if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
 203                 kfree_skb(skb);
 204                 return 0;
 205         }
 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                 kfree_skb(skb);
 213                 return 0;
 214         }
 215
 216         /*
 217          *      Ours perhaps ?
 218          */
 219         if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
 220                 next_digi = &dp.calls[dp.lastrepeat + 1];
 221
 222         /*
 223          *      Pull of the AX.25 headers leaving the CTRL/PID bytes
 224          */
 225         skb_pull(skb, ax25_addr_size(&dp));
 226
 227         /* For our port addresses ? */
 228         if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 229                 mine = 1;
 230
 231         /* Also match on any registered callsign from L3/4 */
 232         if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 233                 mine = 1;
 234
 235         /* UI frame - bypass LAPB processing */
 236         if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 237                 skb->h.raw = skb->data + 2;             /* skip control and pid */
 238
 239                 ax25_send_to_raw(&dest, skb, skb->data[1]);
 240
 241                 if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0) {
 242                         kfree_skb(skb);
 243                         return 0;
 244                 }
 245
 246                 /* Now we are pointing at the pid byte */
 247                 switch (skb->data[1]) {
 248                 case AX25_P_IP:
 249                         skb_pull(skb,2);                /* drop PID/CTRL */
 250                         skb->h.raw    = skb->data;
 251                         skb->nh.raw   = skb->data;
 252                         skb->dev      = dev;
 253                         skb->pkt_type = PACKET_HOST;
 254                         skb->protocol = htons(ETH_P_IP);
 255                         netif_rx(skb);
 256                         break;
 257
 258                 case AX25_P_ARP:
 259                         skb_pull(skb,2);
 260                         skb->h.raw    = skb->data;
 261                         skb->nh.raw   = skb->data;
 262                         skb->dev      = dev;
 263                         skb->pkt_type = PACKET_HOST;
 264                         skb->protocol = htons(ETH_P_ARP);
 265                         netif_rx(skb);
 266                         break;
 267                 case AX25_P_TEXT:
 268                         /* Now find a suitable dgram socket */
 269                         sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 270                         if (sk != NULL) {
 271                                 bh_lock_sock(sk);
 272                                 if (atomic_read(&sk->sk_rmem_alloc) >=
 273                                     sk->sk_rcvbuf) {
 274                                         kfree_skb(skb);
 275                                 } else {
 276                                         /*
 277                                          *      Remove the control and PID.
 278                                          */
 279                                         skb_pull(skb, 2);
 280                                         if (sock_queue_rcv_skb(sk, skb) != 0)
 281                                                 kfree_skb(skb);
 282                                 }
 283                                 bh_unlock_sock(sk);
 284                                 sock_put(sk);
 285                         } else {
 286                                 kfree_skb(skb);
 287                         }
 288                         break;
 289
 290                 default:
 291                         kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
 292                         break;
 293                 }
 294
 295                 return 0;
 296         }
 297
 298         /*
 299          *      Is connected mode supported on this device ?
 300          *      If not, should we DM the incoming frame (except DMs) or
 301          *      silently ignore them. For now we stay quiet.
 302          */
 303         if (ax25_dev->values[AX25_VALUES_CONMODE] == 0) {
 304                 kfree_skb(skb);
 305                 return 0;
 306         }
 307
 308         /* LAPB */
 309
 310         /* AX.25 state 1-4 */
 311
 312         ax25_digi_invert(&dp, &reverse_dp);
 313
 314         if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 315                 /*
 316                  *      Process the frame. If it is queued up internally it
 317                  *      returns one otherwise we free it immediately. This
 318                  *      routine itself wakes the user context layers so we do
 319                  *      no further work
 320                  */
 321                 if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 322                         kfree_skb(skb);
 323
 324                 ax25_cb_put(ax25);
 325                 return 0;
 326         }
 327
 328         /* AX.25 state 0 (disconnected) */
 329
 330         /* a) received not a SABM(E) */
 331
 332         if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 333             (*skb->data & ~AX25_PF) != AX25_SABME) {
 334                 /*
 335                  *      Never reply to a DM. Also ignore any connects for
 336                  *      addresses that are not our interfaces and not a socket.
 337                  */
 338                 if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 339                         ax25_return_dm(dev, &src, &dest, &dp);
 340
 341                 kfree_skb(skb);
 342                 return 0;
 343         }
 344
 345         /* b) received SABM(E) */
 346
 347         if (dp.lastrepeat + 1 == dp.ndigi)
 348                 sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 349         else
 350                 sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
 351
 352         if (sk != NULL) {
 353                 bh_lock_sock(sk);
 354                 if (sk_acceptq_is_full(sk) ||
 355                     (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 356                         if (mine)
 357                                 ax25_return_dm(dev, &src, &dest, &dp);
 358                         kfree_skb(skb);
 359                         bh_unlock_sock(sk);
 360                         sock_put(sk);
 361
 362                         return 0;
 363                 }
 364
 365                 ax25 = ax25_sk(make);
 366                 skb_set_owner_r(skb, make);
 367                 skb_queue_head(&sk->sk_receive_queue, skb);
 368
 369                 make->sk_state = TCP_ESTABLISHED;
 370
 371                 sk->sk_ack_backlog++;
 372                 bh_unlock_sock(sk);
 373         } else {
 374                 if (!mine) {
 375                         kfree_skb(skb);
 376                         return 0;
 377                 }
 378
 379                 if ((ax25 = ax25_create_cb()) == NULL) {
 380                         ax25_return_dm(dev, &src, &dest, &dp);
 381                         kfree_skb(skb);
 382                         return 0;
 383                 }
 384
 385                 ax25_fillin_cb(ax25, ax25_dev);
 386         }
 387
 388         ax25->source_addr = dest;
 389         ax25->dest_addr   = src;
 390
 391         /*
 392          *      Sort out any digipeated paths.
 393          */
 394         if (dp.ndigi && !ax25->digipeat &&
 395             (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 396                 kfree_skb(skb);
 397                 ax25_destroy_socket(ax25);
 398                 if (sk)
 399                         sock_put(sk);
 400                 return 0;
 401         }
 402
 403         if (dp.ndigi == 0) {
 404                 kfree(ax25->digipeat);
 405                 ax25->digipeat = NULL;
 406         } else {
 407                 /* Reverse the source SABM's path */
 408                 memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 409         }
 410
 411         if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 412                 ax25->modulus = AX25_EMODULUS;
 413                 ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 414         } else {
 415                 ax25->modulus = AX25_MODULUS;
 416                 ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 417         }
 418
 419         ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
 420
 421 #ifdef CONFIG_AX25_DAMA_SLAVE
 422         if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 423                 ax25_dama_on(ax25);
 424 #endif
 425
 426         ax25->state = AX25_STATE_3;
 427
 428         ax25_cb_add(ax25);
 429
 430         ax25_start_heartbeat(ax25);
 431         ax25_start_t3timer(ax25);
 432         ax25_start_idletimer(ax25);
 433
 434         if (sk) {
 435                 if (!sock_flag(sk, SOCK_DEAD))
 436                         sk->sk_data_ready(sk, skb->len);
 437                 sock_put(sk);
 438         } else
 439                 kfree_skb(skb);
 440
 441         return 0;
 442 }
 443
 444 /*
 445  *      Receive an AX.25 frame via a SLIP interface.
 446  */
 447 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 448                   struct packet_type *ptype, struct net_device *orig_dev)
 449 {
 450         skb->sk = NULL;         /* Initially we don't know who it's for */
 451         skb->destructor = NULL; /* Who initializes this, dammit?! */
 452
 453         if ((*skb->data & 0x0F) != 0) {
 454                 kfree_skb(skb); /* Not a KISS data frame */
 455                 return 0;
 456         }
 457
 458         skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
 459
 460         return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 461 }