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                                         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  */
 103 int 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  */
 161 static 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
 187 static 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                 kfree_skb(skb);
 205                 return 0;
 206         }
 207
 208         /*
 209          *      Parse the address header.
 210          */
 211
 212         if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL) {
 213                 kfree_skb(skb);
 214                 return 0;
 215         }
 216
 217         /*
 218          *      Ours perhaps ?
 219          */
 220         if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
 221                 next_digi = &dp.calls[dp.lastrepeat + 1];
 222
 223         /*
 224          *      Pull of the AX.25 headers leaving the CTRL/PID bytes
 225          */
 226         skb_pull(skb, ax25_addr_size(&dp));
 227
 228         /* For our port addresses ? */
 229         if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 230                 mine = 1;
 231
 232         /* Also match on any registered callsign from L3/4 */
 233         if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 234                 mine = 1;
 235
 236         /* UI frame - bypass LAPB processing */
 237         if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 238                 skb_set_transport_header(skb, 2); /* skip control and pid */
 239
 240                 ax25_send_to_raw(&dest, skb, skb->data[1]);
 241
 242                 if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0) {
 243                         kfree_skb(skb);
 244                         return 0;
 245                 }
 246
 247                 /* Now we are pointing at the pid byte */
 248                 switch (skb->data[1]) {
 249                 case AX25_P_IP:
 250                         skb_pull(skb,2);                /* drop PID/CTRL */
 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_IP);
 256                         netif_rx(skb);
 257                         break;
 258
 259                 case AX25_P_ARP:
 260                         skb_pull(skb,2);
 261                         skb_reset_transport_header(skb);
 262                         skb_reset_network_header(skb);
 263                         skb->dev      = dev;
 264                         skb->pkt_type = PACKET_HOST;
 265                         skb->protocol = htons(ETH_P_ARP);
 266                         netif_rx(skb);
 267                         break;
 268                 case AX25_P_TEXT:
 269                         /* Now find a suitable dgram socket */
 270                         sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 271                         if (sk != NULL) {
 272                                 bh_lock_sock(sk);
 273                                 if (atomic_read(&sk->sk_rmem_alloc) >=
 274                                     sk->sk_rcvbuf) {
 275                                         kfree_skb(skb);
 276                                 } else {
 277                                         /*
 278                                          *      Remove the control and PID.
 279                                          */
 280                                         skb_pull(skb, 2);
 281                                         if (sock_queue_rcv_skb(sk, skb) != 0)
 282                                                 kfree_skb(skb);
 283                                 }
 284                                 bh_unlock_sock(sk);
 285                                 sock_put(sk);
 286                         } else {
 287                                 kfree_skb(skb);
 288                         }
 289                         break;
 290
 291                 default:
 292                         kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
 293                         break;
 294                 }
 295
 296                 return 0;
 297         }
 298
 299         /*
 300          *      Is connected mode supported on this device ?
 301          *      If not, should we DM the incoming frame (except DMs) or
 302          *      silently ignore them. For now we stay quiet.
 303          */
 304         if (ax25_dev->values[AX25_VALUES_CONMODE] == 0) {
 305                 kfree_skb(skb);
 306                 return 0;
 307         }
 308
 309         /* LAPB */
 310
 311         /* AX.25 state 1-4 */
 312
 313         ax25_digi_invert(&dp, &reverse_dp);
 314
 315         if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 316                 /*
 317                  *      Process the frame. If it is queued up internally it
 318                  *      returns one otherwise we free it immediately. This
 319                  *      routine itself wakes the user context layers so we do
 320                  *      no further work
 321                  */
 322                 if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 323                         kfree_skb(skb);
 324
 325                 ax25_cb_put(ax25);
 326                 return 0;
 327         }
 328
 329         /* AX.25 state 0 (disconnected) */
 330
 331         /* a) received not a SABM(E) */
 332
 333         if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 334             (*skb->data & ~AX25_PF) != AX25_SABME) {
 335                 /*
 336                  *      Never reply to a DM. Also ignore any connects for
 337                  *      addresses that are not our interfaces and not a socket.
 338                  */
 339                 if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 340                         ax25_return_dm(dev, &src, &dest, &dp);
 341
 342                 kfree_skb(skb);
 343                 return 0;
 344         }
 345
 346         /* b) received SABM(E) */
 347
 348         if (dp.lastrepeat + 1 == dp.ndigi)
 349                 sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 350         else
 351                 sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
 352
 353         if (sk != NULL) {
 354                 bh_lock_sock(sk);
 355                 if (sk_acceptq_is_full(sk) ||
 356                     (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 357                         if (mine)
 358                                 ax25_return_dm(dev, &src, &dest, &dp);
 359                         kfree_skb(skb);
 360                         bh_unlock_sock(sk);
 361                         sock_put(sk);
 362
 363                         return 0;
 364                 }
 365
 366                 ax25 = ax25_sk(make);
 367                 skb_set_owner_r(skb, make);
 368                 skb_queue_head(&sk->sk_receive_queue, skb);
 369
 370                 make->sk_state = TCP_ESTABLISHED;
 371
 372                 sk->sk_ack_backlog++;
 373                 bh_unlock_sock(sk);
 374         } else {
 375                 if (!mine) {
 376                         kfree_skb(skb);
 377                         return 0;
 378                 }
 379
 380                 if ((ax25 = ax25_create_cb()) == NULL) {
 381                         ax25_return_dm(dev, &src, &dest, &dp);
 382                         kfree_skb(skb);
 383                         return 0;
 384                 }
 385
 386                 ax25_fillin_cb(ax25, ax25_dev);
 387         }
 388
 389         ax25->source_addr = dest;
 390         ax25->dest_addr   = src;
 391
 392         /*
 393          *      Sort out any digipeated paths.
 394          */
 395         if (dp.ndigi && !ax25->digipeat &&
 396             (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 397                 kfree_skb(skb);
 398                 ax25_destroy_socket(ax25);
 399                 if (sk)
 400                         sock_put(sk);
 401                 return 0;
 402         }
 403
 404         if (dp.ndigi == 0) {
 405                 kfree(ax25->digipeat);
 406                 ax25->digipeat = NULL;
 407         } else {
 408                 /* Reverse the source SABM's path */
 409                 memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 410         }
 411
 412         if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 413                 ax25->modulus = AX25_EMODULUS;
 414                 ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 415         } else {
 416                 ax25->modulus = AX25_MODULUS;
 417                 ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 418         }
 419
 420         ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
 421
 422 #ifdef CONFIG_AX25_DAMA_SLAVE
 423         if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 424                 ax25_dama_on(ax25);
 425 #endif
 426
 427         ax25->state = AX25_STATE_3;
 428
 429         ax25_cb_add(ax25);
 430
 431         ax25_start_heartbeat(ax25);
 432         ax25_start_t3timer(ax25);
 433         ax25_start_idletimer(ax25);
 434
 435         if (sk) {
 436                 if (!sock_flag(sk, SOCK_DEAD))
 437                         sk->sk_data_ready(sk, skb->len);
 438                 sock_put(sk);
 439         } else
 440                 kfree_skb(skb);
 441
 442         return 0;
 443 }
 444
 445 /*
 446  *      Receive an AX.25 frame via a SLIP interface.
 447  */
 448 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 449                   struct packet_type *ptype, struct net_device *orig_dev)
 450 {
 451         skb->sk = NULL;         /* Initially we don't know who it's for */
 452         skb->destructor = NULL; /* Who initializes this, dammit?! */
 453
 454         if (dev->nd_net != &init_net) {
 455                 kfree_skb(skb);
 456                 return 0;
 457         }
 458
 459         if ((*skb->data & 0x0F) != 0) {
 460                 kfree_skb(skb); /* Not a KISS data frame */
 461                 return 0;
 462         }
 463
 464         skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
 465
 466         return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 467 }