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