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 <net/ax25.h>
  22 #include <linux/inet.h>
  23 #include <linux/netdevice.h>
  24 #include <linux/skbuff.h>
  25 #include <net/sock.h>
  26 #include <net/tcp_states.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/system.h>
  29 #include <linux/fcntl.h>
  30 #include <linux/mm.h>
  31 #include <linux/interrupt.h>
  32
  33 /*
  34  *      This routine purges all the queues of frames.
  35  */
  36 void ax25_clear_queues(ax25_cb *ax25)
  37 {
  38         skb_queue_purge(&ax25->write_queue);
  39         skb_queue_purge(&ax25->ack_queue);
  40         skb_queue_purge(&ax25->reseq_queue);
  41         skb_queue_purge(&ax25->frag_queue);
  42 }
  43
  44 /*
  45  * This routine purges the input queue of those frames that have been
  46  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  47  * SDL diagram.
  48  */
  49 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
  50 {
  51         struct sk_buff *skb;
  52
  53         /*
  54          * Remove all the ack-ed frames from the ack queue.
  55          */
  56         if (ax25->va != nr) {
  57                 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
  58                         skb = skb_dequeue(&ax25->ack_queue);
  59                         kfree_skb(skb);
  60                         ax25->va = (ax25->va + 1) % ax25->modulus;
  61                 }
  62         }
  63 }
  64
  65 void ax25_requeue_frames(ax25_cb *ax25)
  66 {
  67         struct sk_buff *skb, *skb_prev = NULL;
  68
  69         /*
  70          * Requeue all the un-ack-ed frames on the output queue to be picked
  71          * up by ax25_kick called from the timer. This arrangement handles the
  72          * possibility of an empty output queue.
  73          */
  74         while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) {
  75                 if (skb_prev == NULL)
  76                         skb_queue_head(&ax25->write_queue, skb);
  77                 else
  78                         skb_append(skb_prev, skb, &ax25->write_queue);
  79                 skb_prev = skb;
  80         }
  81 }
  82
  83 /*
  84  *      Validate that the value of nr is between va and vs. Return true or
  85  *      false for testing.
  86  */
  87 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  88 {
  89         unsigned short vc = ax25->va;
  90
  91         while (vc != ax25->vs) {
  92                 if (nr == vc) return 1;
  93                 vc = (vc + 1) % ax25->modulus;
  94         }
  95
  96         if (nr == ax25->vs) return 1;
  97
  98         return 0;
  99 }
 100
 101 /*
 102  *      This routine is the centralised routine for parsing the control
 103  *      information for the different frame formats.
 104  */
 105 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
 106 {
 107         unsigned char *frame;
 108         int frametype = AX25_ILLEGAL;
 109
 110         frame = skb->data;
 111         *ns = *nr = *pf = 0;
 112
 113         if (ax25->modulus == AX25_MODULUS) {
 114                 if ((frame[0] & AX25_S) == 0) {
 115                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 116                         *ns = (frame[0] >> 1) & 0x07;
 117                         *nr = (frame[0] >> 5) & 0x07;
 118                         *pf = frame[0] & AX25_PF;
 119                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 120                         frametype = frame[0] & 0x0F;
 121                         *nr = (frame[0] >> 5) & 0x07;
 122                         *pf = frame[0] & AX25_PF;
 123                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 124                         frametype = frame[0] & ~AX25_PF;
 125                         *pf = frame[0] & AX25_PF;
 126                 }
 127                 skb_pull(skb, 1);
 128         } else {
 129                 if ((frame[0] & AX25_S) == 0) {
 130                         frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 131                         *ns = (frame[0] >> 1) & 0x7F;
 132                         *nr = (frame[1] >> 1) & 0x7F;
 133                         *pf = frame[1] & AX25_EPF;
 134                         skb_pull(skb, 2);
 135                 } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 136                         frametype = frame[0] & 0x0F;
 137                         *nr = (frame[1] >> 1) & 0x7F;
 138                         *pf = frame[1] & AX25_EPF;
 139                         skb_pull(skb, 2);
 140                 } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 141                         frametype = frame[0] & ~AX25_PF;
 142                         *pf = frame[0] & AX25_PF;
 143                         skb_pull(skb, 1);
 144                 }
 145         }
 146
 147         return frametype;
 148 }
 149
 150 /*
 151  *      This routine is called when the HDLC layer internally  generates a
 152  *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 153  *      Only supervisory or unnumbered frames are processed.
 154  */
 155 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
 156 {
 157         struct sk_buff *skb;
 158         unsigned char  *dptr;
 159
 160         if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
 161                 return;
 162
 163         skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
 164
 165         skb_reset_network_header(skb);
 166
 167         /* Assume a response - address structure for DTE */
 168         if (ax25->modulus == AX25_MODULUS) {
 169                 dptr = skb_put(skb, 1);
 170                 *dptr = frametype;
 171                 *dptr |= (poll_bit) ? AX25_PF : 0;
 172                 if ((frametype & AX25_U) == AX25_S)             /* S frames carry NR */
 173                         *dptr |= (ax25->vr << 5);
 174         } else {
 175                 if ((frametype & AX25_U) == AX25_U) {
 176                         dptr = skb_put(skb, 1);
 177                         *dptr = frametype;
 178                         *dptr |= (poll_bit) ? AX25_PF : 0;
 179                 } else {
 180                         dptr = skb_put(skb, 2);
 181                         dptr[0] = frametype;
 182                         dptr[1] = (ax25->vr << 1);
 183                         dptr[1] |= (poll_bit) ? AX25_EPF : 0;
 184                 }
 185         }
 186
 187         ax25_transmit_buffer(ax25, skb, type);
 188 }
 189
 190 /*
 191  *      Send a 'DM' to an unknown connection attempt, or an invalid caller.
 192  *
 193  *      Note: src here is the sender, thus it's the target of the DM
 194  */
 195 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
 196 {
 197         struct sk_buff *skb;
 198         char *dptr;
 199         ax25_digi retdigi;
 200
 201         if (dev == NULL)
 202                 return;
 203
 204         if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
 205                 return; /* Next SABM will get DM'd */
 206
 207         skb_reserve(skb, dev->hard_header_len);
 208         skb_reset_network_header(skb);
 209
 210         ax25_digi_invert(digi, &retdigi);
 211
 212         dptr = skb_put(skb, 1);
 213
 214         *dptr = AX25_DM | AX25_PF;
 215
 216         /*
 217          *      Do the address ourselves
 218          */
 219         dptr  = skb_push(skb, ax25_addr_size(digi));
 220         dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
 221
 222         ax25_queue_xmit(skb, dev);
 223 }
 224
 225 /*
 226  *      Exponential backoff for AX.25
 227  */
 228 void ax25_calculate_t1(ax25_cb *ax25)
 229 {
 230         int n, t = 2;
 231
 232         switch (ax25->backoff) {
 233         case 0:
 234                 break;
 235
 236         case 1:
 237                 t += 2 * ax25->n2count;
 238                 break;
 239
 240         case 2:
 241                 for (n = 0; n < ax25->n2count; n++)
 242                         t *= 2;
 243                 if (t > 8) t = 8;
 244                 break;
 245         }
 246
 247         ax25->t1 = t * ax25->rtt;
 248 }
 249
 250 /*
 251  *      Calculate the Round Trip Time
 252  */
 253 void ax25_calculate_rtt(ax25_cb *ax25)
 254 {
 255         if (ax25->backoff == 0)
 256                 return;
 257
 258         if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
 259                 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
 260
 261         if (ax25->rtt < AX25_T1CLAMPLO)
 262                 ax25->rtt = AX25_T1CLAMPLO;
 263
 264         if (ax25->rtt > AX25_T1CLAMPHI)
 265                 ax25->rtt = AX25_T1CLAMPHI;
 266 }
 267
 268 void ax25_disconnect(ax25_cb *ax25, int reason)
 269 {
 270         ax25_clear_queues(ax25);
 271
 272         ax25_stop_t1timer(ax25);
 273         ax25_stop_t2timer(ax25);
 274         ax25_stop_t3timer(ax25);
 275         ax25_stop_idletimer(ax25);
 276
 277         ax25->state = AX25_STATE_0;
 278
 279         ax25_link_failed(ax25, reason);
 280
 281         if (ax25->sk != NULL) {
 282                 bh_lock_sock(ax25->sk);
 283                 ax25->sk->sk_state     = TCP_CLOSE;
 284                 ax25->sk->sk_err       = reason;
 285                 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 286                 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 287                         ax25->sk->sk_state_change(ax25->sk);
 288                         sock_set_flag(ax25->sk, SOCK_DEAD);
 289                 }
 290                 bh_unlock_sock(ax25->sk);
 291         }
 292 }