LXR linux/net/ax25/ax25

   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 */
  37void 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 */
  50void 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
  66void 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 */
  83int 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 */
 101int 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 */
 151void 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 */
 191void 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 */
 224void 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 */
 249void 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
 264void 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}
 291