net/ax25/ax25_subr.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) Frederic Rible F1OAT (frible@teaser.fr)
  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/sched.h>
  18 #include <linux/timer.h>
  19 #include <linux/string.h>
  20 #include <linux/sockios.h>
  21 #include <linux/net.h>
  22 #include <net/ax25.h>
  23 #include <linux/inet.h>
  24 #include <linux/netdevice.h>
  25 #include <linux/skbuff.h>
  26 #include <net/sock.h>
  27 #include <net/tcp.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  *      This routine purges all the queues of frames.
  36  */
  37 void ax25_clear_queues(ax25_cb *ax25)
  38 {
  39         skb_queue_purge(&ax25->write_queue);
  40         skb_queue_purge(&ax25->ack_queue);
  41         skb_queue_purge(&ax25->reseq_queue);
  42         skb_queue_purge(&ax25->frag_queue);
  43 }
  44
  45 /*
  46  * This routine purges the input queue of those frames that have been
  47  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  48  * SDL diagram.
  49  */
  50 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
  51 {
  52         struct sk_buff *skb;
  53
  54         /*
  55          * Remove all the ack-ed frames from the ack queue.
  56          */
  57         if (ax25->va != nr) {
  58                 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
  59                         skb = skb_dequeue(&ax25->ack_queue);
  60                         kfree_skb(skb);
  61                         ax25->va = (ax25->va + 1) % ax25->modulus;
  62                 }
  63         }
  64 }
  65
  66 void ax25_requeue_frames(ax25_cb *ax25)
  67 {
  68         struct sk_buff *skb, *skb_prev = NULL;
  69
  70         /*
  71          * Requeue all the un-ack-ed frames on the output queue to be picked
  72          * up by ax25_kick called from the timer. This arrangement handles the
  73          * possibility of an empty output queue.
  74          */
  75         while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) {
  76                 if (skb_prev == NULL)
  77                         skb_queue_head(&ax25->write_queue, skb);
  78                 else
  79                         skb_append(skb_prev, skb);
  80                 skb_prev = skb;
  81         }
  82 }
  83
  84 /*
  85  *      Validate that the value of nr is between va and vs. Return true or
  86  *      false for testing.
  87  */
  88 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  89 {
  90         unsigned short vc = ax25->va;
  91
  92         while (vc != ax25->vs) {
  93                 if (nr == vc) return 1;
  94                 vc = (vc + 1) % ax25->modulus;
  95         }
  96
  97         if (nr == ax25->vs) return 1;
  98
  99         return 0;
 100 }
 101
 102 /*
 103  *      This routine is the centralised routine for parsing the control
 104  *      information for the different frame formats.
 105  */
 106 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
 107 {
 108         unsigned char *frame;
 109         int frametype = AX25_ILLEGAL;
 110
 111         frame = skb->data;
 112         *ns = *nr = *pf = 0;
 113
 114         if (ax25->modulus == AX25_MODULUS) {
 115                 if ((frame[0] & AX25_S) == 0) {
 116                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 117                         *ns = (frame[0] >> 1) & 0x07;
 118                         *nr = (frame[0] >> 5) & 0x07;
 119                         *pf = frame[0] & AX25_PF;
 120                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 121                         frametype = frame[0] & 0x0F;
 122                         *nr = (frame[0] >> 5) & 0x07;
 123                         *pf = frame[0] & AX25_PF;
 124                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 125                         frametype = frame[0] & ~AX25_PF;
 126                         *pf = frame[0] & AX25_PF;
 127                 }
 128                 skb_pull(skb, 1);
 129         } else {
 130                 if ((frame[0] & AX25_S) == 0) {
 131                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 132                         *ns = (frame[0] >> 1) & 0x7F;
 133                         *nr = (frame[1] >> 1) & 0x7F;
 134                         *pf = frame[1] & AX25_EPF;
 135                         skb_pull(skb, 2);
 136                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 137                         frametype = frame[0] & 0x0F;
 138                         *nr = (frame[1] >> 1) & 0x7F;
 139                         *pf = frame[1] & AX25_EPF;
 140                         skb_pull(skb, 2);
 141                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 142                         frametype = frame[0] & ~AX25_PF;
 143                         *pf = frame[0] & AX25_PF;
 144                         skb_pull(skb, 1);
 145                 }
 146         }
 147
 148         return frametype;
 149 }
 150
 151 /*
 152  *      This routine is called when the HDLC layer internally  generates a
 153  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 154  *      Only supervisory or unnumbered frames are processed.
 155  */
 156 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
 157 {
 158         struct sk_buff *skb;
 159         unsigned char  *dptr;
 160
 161         if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
 162                 return;
 163
 164         skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
 165
 166         skb->nh.raw = skb->data;
 167
 168         /* Assume a response - address structure for DTE */
 169         if (ax25->modulus == AX25_MODULUS) {
 170                 dptr = skb_put(skb, 1);
 171                 *dptr = frametype;
 172                 *dptr |= (poll_bit) ? AX25_PF : 0;
 173                 if ((frametype & AX25_U) == AX25_S)             /* S frames carry NR */
 174                         *dptr |= (ax25->vr << 5);
 175         } else {
 176                 if ((frametype & AX25_U) == AX25_U) {
 177                         dptr = skb_put(skb, 1);
 178                         *dptr = frametype;
 179                         *dptr |= (poll_bit) ? AX25_PF : 0;
 180                 } else {
 181                         dptr = skb_put(skb, 2);
 182                         dptr[0] = frametype;
 183                         dptr[1] = (ax25->vr << 1);
 184                         dptr[1] |= (poll_bit) ? AX25_EPF : 0;
 185                 }
 186         }
 187
 188         ax25_transmit_buffer(ax25, skb, type);
 189 }
 190
 191 /*
 192  *      Send a 'DM' to an unknown connection attempt, or an invalid caller.
 193  *
 194  *      Note: src here is the sender, thus it's the target of the DM
 195  */
 196 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
 197 {
 198         struct sk_buff *skb;
 199         char *dptr;
 200         ax25_digi retdigi;
 201
 202         if (dev == NULL)
 203                 return;
 204
 205         if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
 206                 return; /* Next SABM will get DM'd */
 207
 208         skb_reserve(skb, dev->hard_header_len);
 209         skb->nh.raw = skb->data;
 210
 211         ax25_digi_invert(digi, &retdigi);
 212
 213         dptr = skb_put(skb, 1);
 214
 215         *dptr = AX25_DM | AX25_PF;
 216
 217         /*
 218          *      Do the address ourselves
 219          */
 220         dptr  = skb_push(skb, ax25_addr_size(digi));
 221         dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
 222
 223         ax25_queue_xmit(skb, dev);
 224 }
 225
 226 /*
 227  *      Exponential backoff for AX.25
 228  */
 229 void ax25_calculate_t1(ax25_cb *ax25)
 230 {
 231         int n, t = 2;
 232
 233         switch (ax25->backoff) {
 234         case 0:
 235                 break;
 236
 237         case 1:
 238                 t += 2 * ax25->n2count;
 239                 break;
 240
 241         case 2:
 242                 for (n = 0; n < ax25->n2count; n++)
 243                         t *= 2;
 244                 if (t > 8) t = 8;
 245                 break;
 246         }
 247
 248         ax25->t1 = t * ax25->rtt;
 249 }
 250
 251 /*
 252  *      Calculate the Round Trip Time
 253  */
 254 void ax25_calculate_rtt(ax25_cb *ax25)
 255 {
 256         if (ax25->backoff == 0)
 257                 return;
 258
 259         if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
 260                 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
 261
 262         if (ax25->rtt < AX25_T1CLAMPLO)
 263                 ax25->rtt = AX25_T1CLAMPLO;
 264
 265         if (ax25->rtt > AX25_T1CLAMPHI)
 266                 ax25->rtt = AX25_T1CLAMPHI;
 267 }
 268
 269 void ax25_disconnect(ax25_cb *ax25, int reason)
 270 {
 271         ax25_clear_queues(ax25);
 272
 273         ax25_stop_t1timer(ax25);
 274         ax25_stop_t2timer(ax25);
 275         ax25_stop_t3timer(ax25);
 276         ax25_stop_idletimer(ax25);
 277
 278         ax25->state = AX25_STATE_0;
 279
 280         ax25_link_failed(ax25, reason);
 281
 282         if (ax25->sk != NULL) {
 283                 bh_lock_sock(ax25->sk);
 284                 ax25->sk->sk_state     = TCP_CLOSE;
 285                 ax25->sk->sk_err       = reason;
 286                 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 287                 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 288                         ax25->sk->sk_state_change(ax25->sk);
 289                         sock_set_flag(ax25->sk, SOCK_DEAD);
 290                 }
 291                 bh_unlock_sock(ax25->sk);
 292         }
 293 }