net/ax25/ax25

/* */
This source file includes following definitions.
ax25_output
ax25_send_iframe
ax25_kick
ax25_transmit_buffer
ax25_nr_error_recovery
ax25_establish_data_link
ax25_transmit_enquiry
ax25_enquiry_response
ax25_timeout_response
ax25_check_iframes_acked
ax25_check_need_response
dama_enquiry_response
dama_check_need_response
dama_establish_data_link
   1 /*
   2  *      AX.25 release 031
   3  *
   4  *      This is ALPHA test software. This code may break your machine, randomly fail to work with new 
   5  *      releases, misbehave and/or generally screw up. It might even work. 
   6  *
   7  *      This code REQUIRES 1.2.1 or higher/ NET3.029
   8  *
   9  *      This module:
  10  *              This module is free software; you can redistribute it and/or
  11  *              modify it under the terms of the GNU General Public License
  12  *              as published by the Free Software Foundation; either version
  13  *              2 of the License, or (at your option) any later version.
  14  *
  15  *      Most of this code is based on the SDL diagrams published in the 7th
  16  *      ARRL Computer Networking Conference papers. The diagrams have mistakes
  17  *      in them, but are mostly correct. Before you modify the code could you
  18  *      read the SDL diagrams as the code is not obvious and probably very
  19  *      easy to break;
  20  *
  21  *      History
  22  *      AX.25 028a      Jonathan(G4KLX) New state machine based on SDL diagrams.
  23  *      AX.25 029       Alan(GW4PTS)    Switched to KA9Q constant names.
  24  *                      Jonathan(G4KLX) Only poll when window is full.
  25  *      AX.25 030       Jonathan(G4KLX) Added fragmentation to ax25_output.
  26  *                                      Added support for extended AX.25.
  27  *      AX.25 031       Joerg(DL1BKE)   Added DAMA support
  28  */
  29 
  30 #include <linux/config.h>
  31 #ifdef CONFIG_AX25
  32 #include <linux/errno.h>
  33 #include <linux/types.h>
  34 #include <linux/socket.h>
  35 #include <linux/in.h>
  36 #include <linux/kernel.h>
  37 #include <linux/sched.h>
  38 #include <linux/timer.h>
  39 #include <linux/string.h>
  40 #include <linux/sockios.h>
  41 #include <linux/net.h>
  42 #include <net/ax25.h>
  43 #include <linux/inet.h>
  44 #include <linux/netdevice.h>
  45 #include <linux/skbuff.h>
  46 #include <net/sock.h>
  47 #include <asm/segment.h>
  48 #include <asm/system.h>
  49 #include <linux/fcntl.h>
  50 #include <linux/mm.h>
  51 #include <linux/interrupt.h>
  52 
  53 /*
  54  * All outgoing AX.25 I frames pass via this routine. Therefore this is
  55  * where the fragmentation of frames takes place.
  56  */
  57 void ax25_output(ax25_cb *ax25, struct sk_buff *skb)
     /*  */
  58 {
  59         struct sk_buff *skbn;
  60         unsigned char *p;
  61         int err, frontlen, mtu, len, fragno, first = 1;
  62         
  63         mtu = ax25->device->mtu;
  64         
  65         if ((skb->len - 1) > mtu) {
  66                 mtu -= 2;               /* Allow for fragment control info */
  67                 
  68                 fragno = skb->len / mtu;
  69                 if (skb->len % mtu == 0) fragno--;
  70 
  71                 frontlen = skb_headroom(skb);   /* Address space + CTRL */
  72 
  73                 while (skb->len > 0) {
  74                         if (skb->sk != NULL) {
  75                                 if ((skbn = sock_alloc_send_skb(skb->sk, mtu + 2 + frontlen, 0, 0, &err)) == NULL)
  76                                         return;
  77                         } else {
  78                                 if ((skbn = alloc_skb(mtu + 2 + frontlen, GFP_ATOMIC)) == NULL)
  79                                         return;
  80                         }
  81 
  82                         skbn->sk   = skb->sk;
  83                         skbn->free = 1;
  84                         skbn->arp  = 1;
  85 
  86                         skb_reserve(skbn, frontlen + 2);
  87 
  88                         len = (mtu > skb->len) ? skb->len : mtu;
  89                         
  90                         memcpy(skb_put(skbn, len), skb->data, len);
  91                         skb_pull(skb, len);
  92 
  93                         p = skb_push(skbn, 2);
  94 
  95                         *p++ = AX25_P_SEGMENT;
  96 
  97                         *p = fragno--;
  98                         if (first) {
  99                                 *p |= SEG_FIRST;
 100                                 first = 0;
 101                         }
 102 
 103                         skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
 104                 }
 105                 
 106                 skb->free = 1;
 107                 kfree_skb(skb, FREE_WRITE);
 108         } else {
 109                 skb_queue_tail(&ax25->write_queue, skb);          /* Throw it on the queue */
 110         }
 111 
 112         if (ax25->state == AX25_STATE_3 || ax25->state == AX25_STATE_4) {
 113                 if (!ax25->dama_slave)          /* bke 960114: we aren't allowed to transmit */
 114                         ax25_kick(ax25);        /* in DAMA mode unless we received a Poll */
 115         }
 116 }
 117 
 118 /* 
 119  *  This procedure is passed a buffer descriptor for an iframe. It builds
 120  *  the rest of the control part of the frame and then writes it out.
 121  */
 122 static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
     /*  */
 123 {
 124         unsigned char *frame;
 125 
 126         if (skb == NULL)
 127                 return;
 128 
 129         if (ax25->modulus == MODULUS) {
 130                 frame = skb_push(skb, 1);
 131 
 132                 *frame = I;
 133                 *frame |= (poll_bit) ? PF : 0;
 134                 *frame |= (ax25->vr << 5);
 135                 *frame |= (ax25->vs << 1);
 136         } else {
 137                 frame = skb_push(skb, 2);
 138 
 139                 frame[0] = I;
 140                 frame[0] |= (ax25->vs << 1);
 141                 frame[1] = (poll_bit) ? EPF : 0;
 142                 frame[1] |= (ax25->vr << 1);
 143         }
 144 
 145         ax25_transmit_buffer(ax25, skb, C_COMMAND);     
 146 }
 147 
 148 void ax25_kick(ax25_cb *ax25)
     /*  */
 149 {
 150         struct sk_buff *skb, *skbn;
 151         int last = 1;
 152         unsigned short start, end, next;
 153 
 154         del_timer(&ax25->timer);
 155 
 156         start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
 157         end   = (ax25->va + ax25->window) % ax25->modulus;
 158 
 159         if (!(ax25->condition & PEER_RX_BUSY_CONDITION) &&
 160             start != end                                   &&
 161             skb_peek(&ax25->write_queue) != NULL) {
 162 
 163                 ax25->vs = start;
 164 
 165                 /*
 166                  * Transmit data until either we're out of data to send or
 167                  * the window is full. Send a poll on the final I frame if
 168                  * the window is filled.
 169                  */
 170 
 171                 /*
 172                  * Dequeue the frame and copy it.
 173                  */
 174                 skb  = skb_dequeue(&ax25->write_queue);
 175 
 176                 do {
 177                         if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
 178                                 skb_queue_head(&ax25->write_queue, skb);
 179                                 return;
 180                         }
 181 
 182                         next = (ax25->vs + 1) % ax25->modulus;
 183 #ifdef notdef
 184                         last = (next == end) || skb_peek(&ax25->write_queue) == NULL;
 185 #else
 186                         last = (next == end);
 187 #endif
 188                         /*
 189                          * Transmit the frame copy.
 190                          * bke 960114: do not set the Poll bit on the last frame
 191                          * in DAMA mode.
 192                          */
 193                         ax25_send_iframe(ax25, skbn, (last && !ax25->dama_slave) ? POLLON : POLLOFF);
 194 
 195                         ax25->vs = next;
 196 
 197                         /*
 198                          * Requeue the original data frame.
 199                          */
 200                         skb_queue_tail(&ax25->ack_queue, skb);
 201 #ifdef notdef
 202                 } while (!last);
 203 #else
 204                 } while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
 205 #endif
 206                 ax25->condition &= ~ACK_PENDING_CONDITION;
 207 
 208                 if (ax25->t1timer == 0) {
 209                         ax25->t3timer = 0;
 210                         ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
 211                 }
 212         }
 213 
 214         ax25_set_timer(ax25);
 215 }
 216 
 217 void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
     /*  */
 218 {
 219         unsigned char *ptr;
 220 
 221         if (ax25->device == NULL) {
 222                 if (ax25->sk != NULL) {
 223                         ax25->sk->state = TCP_CLOSE;
 224                         ax25->sk->err   = ENETUNREACH;
 225                         if (!ax25->sk->dead)
 226                                 ax25->sk->state_change(ax25->sk);
 227                         ax25->sk->dead  = 1;
 228                 }
 229                 return;
 230         }
 231 
 232         if (skb_headroom(skb) < size_ax25_addr(ax25->digipeat)) {
 233                 printk("ax25_transmit_buffer: not enough room for digi-peaters\n");
 234                 skb->free = 1;
 235                 kfree_skb(skb, FREE_WRITE);
 236                 return;
 237         }
 238 
 239         ptr = skb_push(skb, size_ax25_addr(ax25->digipeat));
 240         build_ax25_addr(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
 241 
 242         skb->arp = 1;
 243 
 244         ax25_queue_xmit(skb, ax25->device, SOPRI_NORMAL);
 245 }
 246 
 247 /*
 248  * The following routines are taken from page 170 of the 7th ARRL Computer
 249  * Networking Conference paper, as is the whole state machine.
 250  */
 251 
 252 void ax25_nr_error_recovery(ax25_cb *ax25)
     /*  */
 253 {
 254         ax25_establish_data_link(ax25);
 255 }
 256 
 257 void ax25_establish_data_link(ax25_cb *ax25)
     /*  */
 258 {
 259         ax25->condition = 0x00;
 260         ax25->n2count   = 0;
 261 
 262         if (ax25->modulus == MODULUS) {
 263                 ax25_send_control(ax25, SABM, POLLON, C_COMMAND);
 264         } else {
 265                 ax25_send_control(ax25, SABME, POLLON, C_COMMAND);
 266         }
 267         
 268         ax25->t3timer = 0;
 269         ax25->t2timer = 0;
 270         ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
 271 }
 272 
 273 void ax25_transmit_enquiry(ax25_cb *ax25)
     /*  */
 274 {
 275         if (ax25->condition & OWN_RX_BUSY_CONDITION)
 276                 ax25_send_control(ax25, RNR, POLLON, C_COMMAND);
 277         else
 278                 ax25_send_control(ax25, RR, POLLON, C_COMMAND);
 279 
 280         ax25->condition &= ~ACK_PENDING_CONDITION;
 281 
 282         ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
 283 }
 284         
 285 void ax25_enquiry_response(ax25_cb *ax25)
     /*  */
 286 {
 287         if (ax25->condition & OWN_RX_BUSY_CONDITION)
 288                 ax25_send_control(ax25, RNR, POLLON, C_RESPONSE);
 289         else
 290                 ax25_send_control(ax25, RR, POLLON, C_RESPONSE);
 291 
 292         ax25->condition &= ~ACK_PENDING_CONDITION;
 293 }
 294 
 295 void ax25_timeout_response(ax25_cb *ax25)
     /*  */
 296 {
 297         if (ax25->condition & OWN_RX_BUSY_CONDITION)
 298                 ax25_send_control(ax25, RNR, POLLOFF, C_RESPONSE);
 299         else
 300                 ax25_send_control(ax25, RR, POLLOFF, C_RESPONSE);
 301 
 302         ax25->condition &= ~ACK_PENDING_CONDITION;
 303 }
 304 
 305 void ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
     /*  */
 306 {
 307         if (ax25->vs == nr) {
 308                 ax25_frames_acked(ax25, nr);
 309                 ax25_calculate_rtt(ax25);
 310                 ax25->t1timer = 0;
 311                 ax25->t3timer = ax25->t3;
 312         } else {
 313                 if (ax25->va != nr) {
 314                         ax25_frames_acked(ax25, nr);
 315                         ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
 316                 }
 317         }
 318 }
 319 
 320 /*
 321  *      dl1bke 960114: shouldn't ax25/dama_check_need_response reside as
 322  *                static inline void ...() in ax25.h, should it? ;-)
 323  */
 324 void ax25_check_need_response(ax25_cb *ax25, int type, int pf)
     /*  */
 325 {
 326         if (!ax25->dama_slave && type == C_COMMAND && pf)
 327                 ax25_enquiry_response(ax25);
 328 }
 329 
 330 /*
 331  *      dl1bke 960114: transmit I frames on DAMA poll
 332  */
 333 void dama_enquiry_response(ax25_cb *ax25)
     /*  */
 334 {
 335         ax25_cb *ax25o;
 336         
 337         if (!(ax25->condition & PEER_RX_BUSY_CONDITION)) {
 338                 ax25_requeue_frames(ax25);
 339                 ax25_kick(ax25);
 340         }
 341 
 342         if (ax25->state == AX25_STATE_1 || ax25->state == AX25_STATE_2 ||
 343             skb_peek(&ax25->ack_queue) != NULL) {
 344                 ax25_t1_timeout(ax25);
 345         } else {
 346                 ax25->n2count = 0;
 347         }
 348         
 349         ax25->t3timer = ax25->t3;
 350         
 351 
 352         /* The FLEXNET DAMA master implementation refuses to send us ANY */
 353         /* I frame for this connection if we send a REJ here, probably   */
 354         /* due to it's frame collector scheme? A simple RR or  RNR will  */
 355         /* invoke the retransmission, and in fact REJs are superflous    */
 356         /* in DAMA mode anyway...                                        */
 357         
 358 #if 0
 359         if (ax25->condition & REJECT_CONDITION)
 360                 ax25_send_control(ax25, REJ, POLLOFF, C_RESPONSE);
 361         else
 362 #endif  
 363                 ax25_enquiry_response(ax25);
 364                 
 365         /* Note that above response to the poll could be sent behind the  */
 366         /* transmissions of the other channels as well... This version    */    
 367         /* gives better performance on FLEXNET nodes. (Why, Gunter?)      */
 368 
 369         for (ax25o = ax25_list; ax25o != NULL; ax25o = ax25o->next) {
 370                 if (ax25o->device != ax25->device)
 371                         continue;
 372 
 373                 if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2) {
 374                         ax25_t1_timeout(ax25o);
 375                         continue;
 376                 }
 377 
 378                 if (!ax25o->dama_slave)
 379                         continue;
 380                         
 381                 if ( !(ax25o->condition & PEER_RX_BUSY_CONDITION) && 
 382                      (ax25o->state == AX25_STATE_3 || 
 383                      (ax25o->state == AX25_STATE_4 && ax25o->t1timer == 0))) {
 384                         ax25_requeue_frames(ax25o);
 385                         ax25_kick(ax25o);
 386                 }
 387                 
 388                 if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2 ||
 389                     skb_peek(&ax25o->ack_queue) != NULL) {
 390                         ax25_t1_timeout(ax25o);
 391                 }
 392 
 393                 ax25o->t3timer = ax25o->t3;
 394         }
 395 }
 396 
 397 void dama_check_need_response(ax25_cb *ax25, int type, int pf)
     /*  */
 398 {
 399         if (ax25->dama_slave && type == C_COMMAND && pf)
 400                 dama_enquiry_response(ax25);
 401 }
 402 
 403 void dama_establish_data_link(ax25_cb *ax25)
     /*  */
 404 {
 405         ax25->condition = 0x00;
 406         ax25->n2count   = 0;
 407 
 408         ax25->t3timer = 0;
 409         ax25->t2timer = 0;
 410         ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
 411 }
 412 
 413 #endif
/* */
root/net/ax25/ax25_out.c

DEFINITIONS
