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