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/timer.h>
  18 #include <linux/string.h>
  19 #include <linux/sockios.h>
  20 #include <linux/net.h>
  21 #include <linux/slab.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_states.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;
  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_tail(&ax25->ack_queue)) != NULL)
  76                 skb_queue_head(&ax25->write_queue, skb);
  77 }
  78
  79 /*
  80  *      Validate that the value of nr is between va and vs. Return true or
  81  *      false for testing.
  82  */
  83 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  84 {
  85         unsigned short vc = ax25->va;
  86
  87         while (vc != ax25->vs) {
  88                 if (nr == vc) return 1;
  89                 vc = (vc + 1) % ax25->modulus;
  90         }
  91
  92         if (nr == ax25->vs) return 1;
  93
  94         return 0;
  95 }
  96
  97 /*
  98  *      This routine is the centralised routine for parsing the control
  99  *      information for the different frame formats.
 100  */
 101 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
 102 {
 103         unsigned char *frame;
 104         int frametype = AX25_ILLEGAL;
 105
 106         frame = skb->data;
 107         *ns = *nr = *pf = 0;
 108
 109         if (ax25->modulus == AX25_MODULUS) {
 110                 if ((frame[0] & AX25_S) == 0) {
 111                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 112                         *ns = (frame[0] >> 1) & 0x07;
 113                         *nr = (frame[0] >> 5) & 0x07;
 114                         *pf = frame[0] & AX25_PF;
 115                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 116                         frametype = frame[0] & 0x0F;
 117                         *nr = (frame[0] >> 5) & 0x07;
 118                         *pf = frame[0] & AX25_PF;
 119                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 120                         frametype = frame[0] & ~AX25_PF;
 121                         *pf = frame[0] & AX25_PF;
 122                 }
 123                 skb_pull(skb, 1);
 124         } else {
 125                 if ((frame[0] & AX25_S) == 0) {
 126                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 127                         *ns = (frame[0] >> 1) & 0x7F;
 128                         *nr = (frame[1] >> 1) & 0x7F;
 129                         *pf = frame[1] & AX25_EPF;
 130                         skb_pull(skb, 2);
 131                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 132                         frametype = frame[0] & 0x0F;
 133                         *nr = (frame[1] >> 1) & 0x7F;
 134                         *pf = frame[1] & AX25_EPF;
 135                         skb_pull(skb, 2);
 136                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 137                         frametype = frame[0] & ~AX25_PF;
 138                         *pf = frame[0] & AX25_PF;
 139                         skb_pull(skb, 1);
 140                 }
 141         }
 142
 143         return frametype;
 144 }
 145
 146 /*
 147  *      This routine is called when the HDLC layer internally  generates a
 148  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 149  *      Only supervisory or unnumbered frames are processed.
 150  */
 151 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
 152 {
 153         struct sk_buff *skb;
 154         unsigned char  *dptr;
 155
 156         if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
 157                 return;
 158
 159         skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
 160
 161         skb_reset_network_header(skb);
 162
 163         /* Assume a response - address structure for DTE */
 164         if (ax25->modulus == AX25_MODULUS) {
 165                 dptr = skb_put(skb, 1);
 166                 *dptr = frametype;
 167                 *dptr |= (poll_bit) ? AX25_PF : 0;
 168                 if ((frametype & AX25_U) == AX25_S)             /* S frames carry NR */
 169                         *dptr |= (ax25->vr << 5);
 170         } else {
 171                 if ((frametype & AX25_U) == AX25_U) {
 172                         dptr = skb_put(skb, 1);
 173                         *dptr = frametype;
 174                         *dptr |= (poll_bit) ? AX25_PF : 0;
 175                 } else {
 176                         dptr = skb_put(skb, 2);
 177                         dptr[0] = frametype;
 178                         dptr[1] = (ax25->vr << 1);
 179                         dptr[1] |= (poll_bit) ? AX25_EPF : 0;
 180                 }
 181         }
 182
 183         ax25_transmit_buffer(ax25, skb, type);
 184 }
 185
 186 /*
 187  *      Send a 'DM' to an unknown connection attempt, or an invalid caller.
 188  *
 189  *      Note: src here is the sender, thus it's the target of the DM
 190  */
 191 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
 192 {
 193         struct sk_buff *skb;
 194         char *dptr;
 195         ax25_digi retdigi;
 196
 197         if (dev == NULL)
 198                 return;
 199
 200         if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
 201                 return; /* Next SABM will get DM'd */
 202
 203         skb_reserve(skb, dev->hard_header_len);
 204         skb_reset_network_header(skb);
 205
 206         ax25_digi_invert(digi, &retdigi);
 207
 208         dptr = skb_put(skb, 1);
 209
 210         *dptr = AX25_DM | AX25_PF;
 211
 212         /*
 213          *      Do the address ourselves
 214          */
 215         dptr  = skb_push(skb, ax25_addr_size(digi));
 216         dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
 217
 218         ax25_queue_xmit(skb, dev);
 219 }
 220
 221 /*
 222  *      Exponential backoff for AX.25
 223  */
 224 void ax25_calculate_t1(ax25_cb *ax25)
 225 {
 226         int n, t = 2;
 227
 228         switch (ax25->backoff) {
 229         case 0:
 230                 break;
 231
 232         case 1:
 233                 t += 2 * ax25->n2count;
 234                 break;
 235
 236         case 2:
 237                 for (n = 0; n < ax25->n2count; n++)
 238                         t *= 2;
 239                 if (t > 8) t = 8;
 240                 break;
 241         }
 242
 243         ax25->t1 = t * ax25->rtt;
 244 }
 245
 246 /*
 247  *      Calculate the Round Trip Time
 248  */
 249 void ax25_calculate_rtt(ax25_cb *ax25)
 250 {
 251         if (ax25->backoff == 0)
 252                 return;
 253
 254         if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
 255                 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
 256
 257         if (ax25->rtt < AX25_T1CLAMPLO)
 258                 ax25->rtt = AX25_T1CLAMPLO;
 259
 260         if (ax25->rtt > AX25_T1CLAMPHI)
 261                 ax25->rtt = AX25_T1CLAMPHI;
 262 }
 263
 264 void ax25_disconnect(ax25_cb *ax25, int reason)
 265 {
 266         ax25_clear_queues(ax25);
 267
 268         ax25_stop_t1timer(ax25);
 269         ax25_stop_t2timer(ax25);
 270         ax25_stop_t3timer(ax25);
 271         ax25_stop_idletimer(ax25);
 272
 273         ax25->state = AX25_STATE_0;
 274
 275         ax25_link_failed(ax25, reason);
 276
 277         if (ax25->sk != NULL) {
 278                 local_bh_disable();
 279                 bh_lock_sock(ax25->sk);
 280                 ax25->sk->sk_state     = TCP_CLOSE;
 281                 ax25->sk->sk_err       = reason;
 282                 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 283                 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 284                         ax25->sk->sk_state_change(ax25->sk);
 285                         sock_set_flag(ax25->sk, SOCK_DEAD);
 286                 }
 287                 bh_unlock_sock(ax25->sk);
 288                 local_bh_enable();
 289         }
 290 }