net/ax25/ax25_out.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  */
   8 #include <linux/errno.h>
   9 #include <linux/types.h>
  10 #include <linux/socket.h>
  11 #include <linux/in.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/timer.h>
  15 #include <linux/string.h>
  16 #include <linux/sockios.h>
  17 #include <linux/spinlock.h>
  18 #include <linux/net.h>
  19 #include <linux/slab.h>
  20 #include <net/ax25.h>
  21 #include <linux/inet.h>
  22 #include <linux/netdevice.h>
  23 #include <linux/skbuff.h>
  24 #include <net/sock.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/fcntl.h>
  27 #include <linux/mm.h>
  28 #include <linux/interrupt.h>
  29
  30 static DEFINE_SPINLOCK(ax25_frag_lock);
  31
  32 ax25_cb *ax25_send_frame(struct sk_buff *skb, int paclen, const ax25_address *src, ax25_address *dest, ax25_digi *digi, struct net_device *dev)
  33 {
  34         ax25_dev *ax25_dev;
  35         ax25_cb *ax25;
  36
  37         /*
  38          * Take the default packet length for the device if zero is
  39          * specified.
  40          */
  41         if (paclen == 0) {
  42                 rcu_read_lock();
  43                 ax25_dev = ax25_dev_ax25dev(dev);
  44                 if (!ax25_dev) {
  45                         rcu_read_unlock();
  46                         return NULL;
  47                 }
  48                 paclen = ax25_dev->values[AX25_VALUES_PACLEN];
  49                 rcu_read_unlock();
  50         }
  51
  52         /*
  53          * Look for an existing connection.
  54          */
  55         if ((ax25 = ax25_find_cb(src, dest, digi, dev)) != NULL) {
  56                 ax25_output(ax25, paclen, skb);
  57                 return ax25;            /* It already existed */
  58         }
  59
  60         rcu_read_lock();
  61         ax25_dev = ax25_dev_ax25dev(dev);
  62         if (!ax25_dev) {
  63                 rcu_read_unlock();
  64                 return NULL;
  65         }
  66
  67         if ((ax25 = ax25_create_cb()) == NULL) {
  68                 rcu_read_unlock();
  69                 return NULL;
  70         }
  71         ax25_fillin_cb(ax25, ax25_dev);
  72         rcu_read_unlock();
  73
  74         ax25->source_addr = *src;
  75         ax25->dest_addr   = *dest;
  76
  77         if (digi != NULL) {
  78                 ax25->digipeat = kmemdup(digi, sizeof(*digi), GFP_ATOMIC);
  79                 if (ax25->digipeat == NULL) {
  80                         ax25_cb_put(ax25);
  81                         return NULL;
  82                 }
  83         }
  84
  85         switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
  86         case AX25_PROTO_STD_SIMPLEX:
  87         case AX25_PROTO_STD_DUPLEX:
  88                 ax25_std_establish_data_link(ax25);
  89                 break;
  90
  91 #ifdef CONFIG_AX25_DAMA_SLAVE
  92         case AX25_PROTO_DAMA_SLAVE:
  93                 if (ax25_dev->dama.slave)
  94                         ax25_ds_establish_data_link(ax25);
  95                 else
  96                         ax25_std_establish_data_link(ax25);
  97                 break;
  98 #endif
  99         }
 100
 101         /*
 102          * There is one ref for the state machine; a caller needs
 103          * one more to put it back, just like with the existing one.
 104          */
 105         ax25_cb_hold(ax25);
 106
 107         ax25_cb_add(ax25);
 108
 109         ax25->state = AX25_STATE_1;
 110
 111         ax25_start_heartbeat(ax25);
 112
 113         ax25_output(ax25, paclen, skb);
 114
 115         return ax25;                    /* We had to create it */
 116 }
 117
 118 EXPORT_SYMBOL(ax25_send_frame);
 119
 120 /*
 121  *      All outgoing AX.25 I frames pass via this routine. Therefore this is
 122  *      where the fragmentation of frames takes place. If fragment is set to
 123  *      zero then we are not allowed to do fragmentation, even if the frame
 124  *      is too large.
 125  */
 126 void ax25_output(ax25_cb *ax25, int paclen, struct sk_buff *skb)
 127 {
 128         struct sk_buff *skbn;
 129         unsigned char *p;
 130         int frontlen, len, fragno, ka9qfrag, first = 1;
 131
 132         if (paclen < 16) {
 133                 WARN_ON_ONCE(1);
 134                 kfree_skb(skb);
 135                 return;
 136         }
 137
 138         if ((skb->len - 1) > paclen) {
 139                 if (*skb->data == AX25_P_TEXT) {
 140                         skb_pull(skb, 1); /* skip PID */
 141                         ka9qfrag = 0;
 142                 } else {
 143                         paclen -= 2;    /* Allow for fragment control info */
 144                         ka9qfrag = 1;
 145                 }
 146
 147                 fragno = skb->len / paclen;
 148                 if (skb->len % paclen == 0) fragno--;
 149
 150                 frontlen = skb_headroom(skb);   /* Address space + CTRL */
 151
 152                 while (skb->len > 0) {
 153                         spin_lock_bh(&ax25_frag_lock);
 154                         if ((skbn = alloc_skb(paclen + 2 + frontlen, GFP_ATOMIC)) == NULL) {
 155                                 spin_unlock_bh(&ax25_frag_lock);
 156                                 printk(KERN_CRIT "AX.25: ax25_output - out of memory\n");
 157                                 return;
 158                         }
 159
 160                         if (skb->sk != NULL)
 161                                 skb_set_owner_w(skbn, skb->sk);
 162
 163                         spin_unlock_bh(&ax25_frag_lock);
 164
 165                         len = (paclen > skb->len) ? skb->len : paclen;
 166
 167                         if (ka9qfrag == 1) {
 168                                 skb_reserve(skbn, frontlen + 2);
 169                                 skb_set_network_header(skbn,
 170                                                       skb_network_offset(skb));
 171                                 skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
 172                                 p = skb_push(skbn, 2);
 173
 174                                 *p++ = AX25_P_SEGMENT;
 175
 176                                 *p = fragno--;
 177                                 if (first) {
 178                                         *p |= AX25_SEG_FIRST;
 179                                         first = 0;
 180                                 }
 181                         } else {
 182                                 skb_reserve(skbn, frontlen + 1);
 183                                 skb_set_network_header(skbn,
 184                                                       skb_network_offset(skb));
 185                                 skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
 186                                 p = skb_push(skbn, 1);
 187                                 *p = AX25_P_TEXT;
 188                         }
 189
 190                         skb_pull(skb, len);
 191                         skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
 192                 }
 193
 194                 kfree_skb(skb);
 195         } else {
 196                 skb_queue_tail(&ax25->write_queue, skb);          /* Throw it on the queue */
 197         }
 198
 199         switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 200         case AX25_PROTO_STD_SIMPLEX:
 201         case AX25_PROTO_STD_DUPLEX:
 202                 ax25_kick(ax25);
 203                 break;
 204
 205 #ifdef CONFIG_AX25_DAMA_SLAVE
 206         /*
 207          * A DAMA slave is _required_ to work as normal AX.25L2V2
 208          * if no DAMA master is available.
 209          */
 210         case AX25_PROTO_DAMA_SLAVE:
 211                 if (!ax25->ax25_dev->dama.slave) ax25_kick(ax25);
 212                 break;
 213 #endif
 214         }
 215 }
 216
 217 /*
 218  *  This procedure is passed a buffer descriptor for an iframe. It builds
 219  *  the rest of the control part of the frame and then writes it out.
 220  */
 221 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
 222 {
 223         unsigned char *frame;
 224
 225         if (skb == NULL)
 226                 return;
 227
 228         skb_reset_network_header(skb);
 229
 230         if (ax25->modulus == AX25_MODULUS) {
 231                 frame = skb_push(skb, 1);
 232
 233                 *frame = AX25_I;
 234                 *frame |= (poll_bit) ? AX25_PF : 0;
 235                 *frame |= (ax25->vr << 5);
 236                 *frame |= (ax25->vs << 1);
 237         } else {
 238                 frame = skb_push(skb, 2);
 239
 240                 frame[0] = AX25_I;
 241                 frame[0] |= (ax25->vs << 1);
 242                 frame[1] = (poll_bit) ? AX25_EPF : 0;
 243                 frame[1] |= (ax25->vr << 1);
 244         }
 245
 246         ax25_start_idletimer(ax25);
 247
 248         ax25_transmit_buffer(ax25, skb, AX25_COMMAND);
 249 }
 250
 251 void ax25_kick(ax25_cb *ax25)
 252 {
 253         struct sk_buff *skb, *skbn;
 254         int last = 1;
 255         unsigned short start, end, next;
 256
 257         if (ax25->state != AX25_STATE_3 && ax25->state != AX25_STATE_4)
 258                 return;
 259
 260         if (ax25->condition & AX25_COND_PEER_RX_BUSY)
 261                 return;
 262
 263         if (skb_peek(&ax25->write_queue) == NULL)
 264                 return;
 265
 266         start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
 267         end   = (ax25->va + ax25->window) % ax25->modulus;
 268
 269         if (start == end)
 270                 return;
 271
 272         /*
 273          * Transmit data until either we're out of data to send or
 274          * the window is full. Send a poll on the final I frame if
 275          * the window is filled.
 276          */
 277
 278         /*
 279          * Dequeue the frame and copy it.
 280          * Check for race with ax25_clear_queues().
 281          */
 282         skb  = skb_dequeue(&ax25->write_queue);
 283         if (!skb)
 284                 return;
 285
 286         ax25->vs = start;
 287
 288         do {
 289                 if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
 290                         skb_queue_head(&ax25->write_queue, skb);
 291                         break;
 292                 }
 293
 294                 if (skb->sk != NULL)
 295                         skb_set_owner_w(skbn, skb->sk);
 296
 297                 next = (ax25->vs + 1) % ax25->modulus;
 298                 last = (next == end);
 299
 300                 /*
 301                  * Transmit the frame copy.
 302                  * bke 960114: do not set the Poll bit on the last frame
 303                  * in DAMA mode.
 304                  */
 305                 switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
 306                 case AX25_PROTO_STD_SIMPLEX:
 307                 case AX25_PROTO_STD_DUPLEX:
 308                         ax25_send_iframe(ax25, skbn, (last) ? AX25_POLLON : AX25_POLLOFF);
 309                         break;
 310
 311 #ifdef CONFIG_AX25_DAMA_SLAVE
 312                 case AX25_PROTO_DAMA_SLAVE:
 313                         ax25_send_iframe(ax25, skbn, AX25_POLLOFF);
 314                         break;
 315 #endif
 316                 }
 317
 318                 ax25->vs = next;
 319
 320                 /*
 321                  * Requeue the original data frame.
 322                  */
 323                 skb_queue_tail(&ax25->ack_queue, skb);
 324
 325         } while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
 326
 327         ax25->condition &= ~AX25_COND_ACK_PENDING;
 328
 329         if (!ax25_t1timer_running(ax25)) {
 330                 ax25_stop_t3timer(ax25);
 331                 ax25_calculate_t1(ax25);
 332                 ax25_start_t1timer(ax25);
 333         }
 334 }
 335
 336 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
 337 {
 338         unsigned char *ptr;
 339         int headroom;
 340
 341         if (ax25->ax25_dev == NULL) {
 342                 ax25_disconnect(ax25, ENETUNREACH);
 343                 return;
 344         }
 345
 346         headroom = ax25_addr_size(ax25->digipeat);
 347
 348         if (unlikely(skb_headroom(skb) < headroom)) {
 349                 skb = skb_expand_head(skb, headroom);
 350                 if (!skb) {
 351                         printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
 352                         return;
 353                 }
 354         }
 355
 356         ptr = skb_push(skb, headroom);
 357
 358         ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
 359
 360         ax25_queue_xmit(skb, ax25->ax25_dev->dev);
 361 }
 362
 363 /*
 364  *      A small shim to dev_queue_xmit to add the KISS control byte, and do
 365  *      any packet forwarding in operation.
 366  */
 367 void ax25_queue_xmit(struct sk_buff *skb, struct net_device *dev)
 368 {
 369         unsigned char *ptr;
 370
 371         rcu_read_lock();
 372         skb->protocol = ax25_type_trans(skb, ax25_fwd_dev(dev));
 373         rcu_read_unlock();
 374
 375         ptr  = skb_push(skb, 1);
 376         *ptr = 0x00;                    /* KISS */
 377
 378         dev_queue_xmit(skb);
 379 }
 380
 381 int ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
 382 {
 383         if (ax25->vs == nr) {
 384                 ax25_frames_acked(ax25, nr);
 385                 ax25_calculate_rtt(ax25);
 386                 ax25_stop_t1timer(ax25);
 387                 ax25_start_t3timer(ax25);
 388                 return 1;
 389         } else {
 390                 if (ax25->va != nr) {
 391                         ax25_frames_acked(ax25, nr);
 392                         ax25_calculate_t1(ax25);
 393                         ax25_start_t1timer(ax25);
 394                         return 1;
 395                 }
 396         }
 397         return 0;
 398 }