net/ax25/ax25_in.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *
   4  * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   5  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   6  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   7  * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
   8  */
   9 #include <linux/errno.h>
  10 #include <linux/types.h>
  11 #include <linux/socket.h>
  12 #include <linux/in.h>
  13 #include <linux/kernel.h>
  14 #include <linux/timer.h>
  15 #include <linux/string.h>
  16 #include <linux/sockios.h>
  17 #include <linux/net.h>
  18 #include <linux/slab.h>
  19 #include <net/ax25.h>
  20 #include <linux/inet.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/skbuff.h>
  23 #include <net/sock.h>
  24 #include <net/tcp_states.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/fcntl.h>
  27 #include <linux/mm.h>
  28 #include <linux/interrupt.h>
  29
  30 /*
  31  *      Given a fragment, queue it on the fragment queue and if the fragment
  32  *      is complete, send it back to ax25_rx_iframe.
  33  */
  34 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
  35 {
  36         struct sk_buff *skbn, *skbo;
  37
  38         if (ax25->fragno != 0) {
  39                 if (!(*skb->data & AX25_SEG_FIRST)) {
  40                         if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
  41                                 /* Enqueue fragment */
  42                                 ax25->fragno = *skb->data & AX25_SEG_REM;
  43                                 skb_pull(skb, 1);       /* skip fragno */
  44                                 ax25->fraglen += skb->len;
  45                                 skb_queue_tail(&ax25->frag_queue, skb);
  46
  47                                 /* Last fragment received ? */
  48                                 if (ax25->fragno == 0) {
  49                                         skbn = alloc_skb(AX25_MAX_HEADER_LEN +
  50                                                          ax25->fraglen,
  51                                                          GFP_ATOMIC);
  52                                         if (!skbn) {
  53                                                 skb_queue_purge(&ax25->frag_queue);
  54                                                 return 1;
  55                                         }
  56
  57                                         skb_reserve(skbn, AX25_MAX_HEADER_LEN);
  58
  59                                         skbn->dev   = ax25->ax25_dev->dev;
  60                                         skb_reset_network_header(skbn);
  61                                         skb_reset_transport_header(skbn);
  62
  63                                         /* Copy data from the fragments */
  64                                         while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
  65                                                 skb_copy_from_linear_data(skbo,
  66                                                           skb_put(skbn, skbo->len),
  67                                                                           skbo->len);
  68                                                 kfree_skb(skbo);
  69                                         }
  70
  71                                         ax25->fraglen = 0;
  72
  73                                         if (ax25_rx_iframe(ax25, skbn) == 0)
  74                                                 kfree_skb(skbn);
  75                                 }
  76
  77                                 return 1;
  78                         }
  79                 }
  80         } else {
  81                 /* First fragment received */
  82                 if (*skb->data & AX25_SEG_FIRST) {
  83                         skb_queue_purge(&ax25->frag_queue);
  84                         ax25->fragno = *skb->data & AX25_SEG_REM;
  85                         skb_pull(skb, 1);               /* skip fragno */
  86                         ax25->fraglen = skb->len;
  87                         skb_queue_tail(&ax25->frag_queue, skb);
  88                         return 1;
  89                 }
  90         }
  91
  92         return 0;
  93 }
  94
  95 /*
  96  *      This is where all valid I frames are sent to, to be dispatched to
  97  *      whichever protocol requires them.
  98  */
  99 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
 100 {
 101         int (*func)(struct sk_buff *, ax25_cb *);
 102         unsigned char pid;
 103         int queued = 0;
 104
 105         if (skb == NULL) return 0;
 106
 107         ax25_start_idletimer(ax25);
 108
 109         pid = *skb->data;
 110
 111         if (pid == AX25_P_IP) {
 112                 /* working around a TCP bug to keep additional listeners
 113                  * happy. TCP re-uses the buffer and destroys the original
 114                  * content.
 115                  */
 116                 struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
 117                 if (skbn != NULL) {
 118                         kfree_skb(skb);
 119                         skb = skbn;
 120                 }
 121
 122                 skb_pull(skb, 1);       /* Remove PID */
 123                 skb->mac_header = skb->network_header;
 124                 skb_reset_network_header(skb);
 125                 skb->dev      = ax25->ax25_dev->dev;
 126                 skb->pkt_type = PACKET_HOST;
 127                 skb->protocol = htons(ETH_P_IP);
 128                 netif_rx(skb);
 129                 return 1;
 130         }
 131         if (pid == AX25_P_SEGMENT) {
 132                 skb_pull(skb, 1);       /* Remove PID */
 133                 return ax25_rx_fragment(ax25, skb);
 134         }
 135
 136         if ((func = ax25_protocol_function(pid)) != NULL) {
 137                 skb_pull(skb, 1);       /* Remove PID */
 138                 return (*func)(skb, ax25);
 139         }
 140
 141         if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
 142                 if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
 143                     ax25->pidincl) {
 144                         if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
 145                                 queued = 1;
 146                         else
 147                                 ax25->condition |= AX25_COND_OWN_RX_BUSY;
 148                 }
 149         }
 150
 151         return queued;
 152 }
 153
 154 /*
 155  *      Higher level upcall for a LAPB frame
 156  */
 157 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
 158 {
 159         int queued = 0;
 160
 161         if (ax25->state == AX25_STATE_0)
 162                 return 0;
 163
 164         switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 165         case AX25_PROTO_STD_SIMPLEX:
 166         case AX25_PROTO_STD_DUPLEX:
 167                 queued = ax25_std_frame_in(ax25, skb, type);
 168                 break;
 169
 170 #ifdef CONFIG_AX25_DAMA_SLAVE
 171         case AX25_PROTO_DAMA_SLAVE:
 172                 if (dama || ax25->ax25_dev->dama.slave)
 173                         queued = ax25_ds_frame_in(ax25, skb, type);
 174                 else
 175                         queued = ax25_std_frame_in(ax25, skb, type);
 176                 break;
 177 #endif
 178         }
 179
 180         return queued;
 181 }
 182
 183 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
 184         ax25_address *dev_addr, struct packet_type *ptype)
 185 {
 186         ax25_address src, dest, *next_digi = NULL;
 187         int type = 0, mine = 0, dama;
 188         struct sock *make, *sk;
 189         ax25_digi dp, reverse_dp;
 190         ax25_cb *ax25;
 191         ax25_dev *ax25_dev;
 192
 193         /*
 194          *      Process the AX.25/LAPB frame.
 195          */
 196
 197         skb_reset_transport_header(skb);
 198
 199         if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
 200                 goto free;
 201
 202         /*
 203          *      Parse the address header.
 204          */
 205
 206         if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
 207                 goto free;
 208
 209         /*
 210          *      Ours perhaps ?
 211          */
 212         if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
 213                 next_digi = &dp.calls[dp.lastrepeat + 1];
 214
 215         /*
 216          *      Pull of the AX.25 headers leaving the CTRL/PID bytes
 217          */
 218         skb_pull(skb, ax25_addr_size(&dp));
 219
 220         /* For our port addresses ? */
 221         if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
 222                 mine = 1;
 223
 224         /* Also match on any registered callsign from L3/4 */
 225         if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
 226                 mine = 1;
 227
 228         /* UI frame - bypass LAPB processing */
 229         if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
 230                 skb_set_transport_header(skb, 2); /* skip control and pid */
 231
 232                 ax25_send_to_raw(&dest, skb, skb->data[1]);
 233
 234                 if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
 235                         goto free;
 236
 237                 /* Now we are pointing at the pid byte */
 238                 switch (skb->data[1]) {
 239                 case AX25_P_IP:
 240                         skb_pull(skb,2);                /* drop PID/CTRL */
 241                         skb_reset_transport_header(skb);
 242                         skb_reset_network_header(skb);
 243                         skb->dev      = dev;
 244                         skb->pkt_type = PACKET_HOST;
 245                         skb->protocol = htons(ETH_P_IP);
 246                         netif_rx(skb);
 247                         break;
 248
 249                 case AX25_P_ARP:
 250                         skb_pull(skb,2);
 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_ARP);
 256                         netif_rx(skb);
 257                         break;
 258                 case AX25_P_TEXT:
 259                         /* Now find a suitable dgram socket */
 260                         sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
 261                         if (sk != NULL) {
 262                                 bh_lock_sock(sk);
 263                                 if (atomic_read(&sk->sk_rmem_alloc) >=
 264                                     sk->sk_rcvbuf) {
 265                                         kfree_skb(skb);
 266                                 } else {
 267                                         /*
 268                                          *      Remove the control and PID.
 269                                          */
 270                                         skb_pull(skb, 2);
 271                                         if (sock_queue_rcv_skb(sk, skb) != 0)
 272                                                 kfree_skb(skb);
 273                                 }
 274                                 bh_unlock_sock(sk);
 275                                 sock_put(sk);
 276                         } else {
 277                                 kfree_skb(skb);
 278                         }
 279                         break;
 280
 281                 default:
 282                         kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
 283                         break;
 284                 }
 285
 286                 return 0;
 287         }
 288
 289         /*
 290          *      Is connected mode supported on this device ?
 291          *      If not, should we DM the incoming frame (except DMs) or
 292          *      silently ignore them. For now we stay quiet.
 293          */
 294         if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
 295                 goto free;
 296
 297         /* LAPB */
 298
 299         /* AX.25 state 1-4 */
 300
 301         ax25_digi_invert(&dp, &reverse_dp);
 302
 303         if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
 304                 /*
 305                  *      Process the frame. If it is queued up internally it
 306                  *      returns one otherwise we free it immediately. This
 307                  *      routine itself wakes the user context layers so we do
 308                  *      no further work
 309                  */
 310                 if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
 311                         kfree_skb(skb);
 312
 313                 ax25_cb_put(ax25);
 314                 return 0;
 315         }
 316
 317         /* AX.25 state 0 (disconnected) */
 318
 319         /* a) received not a SABM(E) */
 320
 321         if ((*skb->data & ~AX25_PF) != AX25_SABM &&
 322             (*skb->data & ~AX25_PF) != AX25_SABME) {
 323                 /*
 324                  *      Never reply to a DM. Also ignore any connects for
 325                  *      addresses that are not our interfaces and not a socket.
 326                  */
 327                 if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
 328                         ax25_return_dm(dev, &src, &dest, &dp);
 329
 330                 goto free;
 331         }
 332
 333         /* b) received SABM(E) */
 334
 335         if (dp.lastrepeat + 1 == dp.ndigi)
 336                 sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
 337         else
 338                 sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
 339
 340         if (sk != NULL) {
 341                 bh_lock_sock(sk);
 342                 if (sk_acceptq_is_full(sk) ||
 343                     (make = ax25_make_new(sk, ax25_dev)) == NULL) {
 344                         if (mine)
 345                                 ax25_return_dm(dev, &src, &dest, &dp);
 346                         kfree_skb(skb);
 347                         bh_unlock_sock(sk);
 348                         sock_put(sk);
 349
 350                         return 0;
 351                 }
 352
 353                 ax25 = sk_to_ax25(make);
 354                 skb_set_owner_r(skb, make);
 355                 skb_queue_head(&sk->sk_receive_queue, skb);
 356
 357                 make->sk_state = TCP_ESTABLISHED;
 358
 359                 sk_acceptq_added(sk);
 360                 bh_unlock_sock(sk);
 361         } else {
 362                 if (!mine)
 363                         goto free;
 364
 365                 if ((ax25 = ax25_create_cb()) == NULL) {
 366                         ax25_return_dm(dev, &src, &dest, &dp);
 367                         goto free;
 368                 }
 369
 370                 ax25_fillin_cb(ax25, ax25_dev);
 371         }
 372
 373         ax25->source_addr = dest;
 374         ax25->dest_addr   = src;
 375
 376         /*
 377          *      Sort out any digipeated paths.
 378          */
 379         if (dp.ndigi && !ax25->digipeat &&
 380             (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
 381                 kfree_skb(skb);
 382                 ax25_destroy_socket(ax25);
 383                 if (sk)
 384                         sock_put(sk);
 385                 return 0;
 386         }
 387
 388         if (dp.ndigi == 0) {
 389                 kfree(ax25->digipeat);
 390                 ax25->digipeat = NULL;
 391         } else {
 392                 /* Reverse the source SABM's path */
 393                 memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
 394         }
 395
 396         if ((*skb->data & ~AX25_PF) == AX25_SABME) {
 397                 ax25->modulus = AX25_EMODULUS;
 398                 ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
 399         } else {
 400                 ax25->modulus = AX25_MODULUS;
 401                 ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
 402         }
 403
 404         ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
 405
 406 #ifdef CONFIG_AX25_DAMA_SLAVE
 407         if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
 408                 ax25_dama_on(ax25);
 409 #endif
 410
 411         ax25->state = AX25_STATE_3;
 412
 413         ax25_cb_add(ax25);
 414
 415         ax25_start_heartbeat(ax25);
 416         ax25_start_t3timer(ax25);
 417         ax25_start_idletimer(ax25);
 418
 419         if (sk) {
 420                 if (!sock_flag(sk, SOCK_DEAD))
 421                         sk->sk_data_ready(sk);
 422                 sock_put(sk);
 423         } else {
 424 free:
 425                 kfree_skb(skb);
 426         }
 427         return 0;
 428 }
 429
 430 /*
 431  *      Receive an AX.25 frame via a SLIP interface.
 432  */
 433 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
 434                   struct packet_type *ptype, struct net_device *orig_dev)
 435 {
 436         skb_orphan(skb);
 437
 438         if (!net_eq(dev_net(dev), &init_net)) {
 439                 kfree_skb(skb);
 440                 return 0;
 441         }
 442
 443         if ((*skb->data & 0x0F) != 0) {
 444                 kfree_skb(skb); /* Not a KISS data frame */
 445                 return 0;
 446         }
 447
 448         skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
 449
 450         return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
 451 }