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 <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 */
  36void 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 */
  49void 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
  65void ax25_requeue_frames(ax25_cb *ax25)
  66{
  67        struct sk_buff *skb;
  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_tail(&ax25->ack_queue)) != NULL)
  75                skb_queue_head(&ax25->write_queue, skb);
  76}
  77
  78/*
  79 *      Validate that the value of nr is between va and vs. Return true or
  80 *      false for testing.
  81 */
  82int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  83{
  84        unsigned short vc = ax25->va;
  85
  86        while (vc != ax25->vs) {
  87                if (nr == vc) return 1;
  88                vc = (vc + 1) % ax25->modulus;
  89        }
  90
  91        if (nr == ax25->vs) return 1;
  92
  93        return 0;
  94}
  95
  96/*
  97 *      This routine is the centralised routine for parsing the control
  98 *      information for the different frame formats.
  99 */
 100int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
 101{
 102        unsigned char *frame;
 103        int frametype = AX25_ILLEGAL;
 104
 105        frame = skb->data;
 106        *ns = *nr = *pf = 0;
 107
 108        if (ax25->modulus == AX25_MODULUS) {
 109                if ((frame[0] & AX25_S) == 0) {
 110                        frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 111                        *ns = (frame[0] >> 1) & 0x07;
 112                        *nr = (frame[0] >> 5) & 0x07;
 113                        *pf = frame[0] & AX25_PF;
 114                } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 115                        frametype = frame[0] & 0x0F;
 116                        *nr = (frame[0] >> 5) & 0x07;
 117                        *pf = frame[0] & AX25_PF;
 118                } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 119                        frametype = frame[0] & ~AX25_PF;
 120                        *pf = frame[0] & AX25_PF;
 121                }
 122                skb_pull(skb, 1);
 123        } else {
 124                if ((frame[0] & AX25_S) == 0) {
 125                        frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 126                        *ns = (frame[0] >> 1) & 0x7F;
 127                        *nr = (frame[1] >> 1) & 0x7F;
 128                        *pf = frame[1] & AX25_EPF;
 129                        skb_pull(skb, 2);
 130                } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 131                        frametype = frame[0] & 0x0F;
 132                        *nr = (frame[1] >> 1) & 0x7F;
 133                        *pf = frame[1] & AX25_EPF;
 134                        skb_pull(skb, 2);
 135                } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 136                        frametype = frame[0] & ~AX25_PF;
 137                        *pf = frame[0] & AX25_PF;
 138                        skb_pull(skb, 1);
 139                }
 140        }
 141
 142        return frametype;
 143}
 144
 145/*
 146 *      This routine is called when the HDLC layer internally  generates a
 147 *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 148 *      Only supervisory or unnumbered frames are processed.
 149 */
 150void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
 151{
 152        struct sk_buff *skb;
 153        unsigned char  *dptr;
 154
 155        if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
 156                return;
 157
 158        skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
 159
 160        skb_reset_network_header(skb);
 161
 162        /* Assume a response - address structure for DTE */
 163        if (ax25->modulus == AX25_MODULUS) {
 164                dptr = skb_put(skb, 1);
 165                *dptr = frametype;
 166                *dptr |= (poll_bit) ? AX25_PF : 0;
 167                if ((frametype & AX25_U) == AX25_S)             /* S frames carry NR */
 168                        *dptr |= (ax25->vr << 5);
 169        } else {
 170                if ((frametype & AX25_U) == AX25_U) {
 171                        dptr = skb_put(skb, 1);
 172                        *dptr = frametype;
 173                        *dptr |= (poll_bit) ? AX25_PF : 0;
 174                } else {
 175                        dptr = skb_put(skb, 2);
 176                        dptr[0] = frametype;
 177                        dptr[1] = (ax25->vr << 1);
 178                        dptr[1] |= (poll_bit) ? AX25_EPF : 0;
 179                }
 180        }
 181
 182        ax25_transmit_buffer(ax25, skb, type);
 183}
 184
 185/*
 186 *      Send a 'DM' to an unknown connection attempt, or an invalid caller.
 187 *
 188 *      Note: src here is the sender, thus it's the target of the DM
 189 */
 190void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
 191{
 192        struct sk_buff *skb;
 193        char *dptr;
 194        ax25_digi retdigi;
 195
 196        if (dev == NULL)
 197                return;
 198
 199        if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
 200                return; /* Next SABM will get DM'd */
 201
 202        skb_reserve(skb, dev->hard_header_len);
 203        skb_reset_network_header(skb);
 204
 205        ax25_digi_invert(digi, &retdigi);
 206
 207        dptr = skb_put(skb, 1);
 208
 209        *dptr = AX25_DM | AX25_PF;
 210
 211        /*
 212         *      Do the address ourselves
 213         */
 214        dptr  = skb_push(skb, ax25_addr_size(digi));
 215        dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
 216
 217        ax25_queue_xmit(skb, dev);
 218}
 219
 220/*
 221 *      Exponential backoff for AX.25
 222 */
 223void ax25_calculate_t1(ax25_cb *ax25)
 224{
 225        int n, t = 2;
 226
 227        switch (ax25->backoff) {
 228        case 0:
 229                break;
 230
 231        case 1:
 232                t += 2 * ax25->n2count;
 233                break;
 234
 235        case 2:
 236                for (n = 0; n < ax25->n2count; n++)
 237                        t *= 2;
 238                if (t > 8) t = 8;
 239                break;
 240        }
 241
 242        ax25->t1 = t * ax25->rtt;
 243}
 244
 245/*
 246 *      Calculate the Round Trip Time
 247 */
 248void ax25_calculate_rtt(ax25_cb *ax25)
 249{
 250        if (ax25->backoff == 0)
 251                return;
 252
 253        if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
 254                ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
 255
 256        if (ax25->rtt < AX25_T1CLAMPLO)
 257                ax25->rtt = AX25_T1CLAMPLO;
 258
 259        if (ax25->rtt > AX25_T1CLAMPHI)
 260                ax25->rtt = AX25_T1CLAMPHI;
 261}
 262
 263void ax25_disconnect(ax25_cb *ax25, int reason)
 264{
 265        ax25_clear_queues(ax25);
 266
 267        ax25_stop_t1timer(ax25);
 268        ax25_stop_t2timer(ax25);
 269        ax25_stop_t3timer(ax25);
 270        ax25_stop_idletimer(ax25);
 271
 272        ax25->state = AX25_STATE_0;
 273
 274        ax25_link_failed(ax25, reason);
 275
 276        if (ax25->sk != NULL) {
 277                local_bh_disable();
 278                bh_lock_sock(ax25->sk);
 279                ax25->sk->sk_state     = TCP_CLOSE;
 280                ax25->sk->sk_err       = reason;
 281                ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 282                if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 283                        ax25->sk->sk_state_change(ax25->sk);
 284                        sock_set_flag(ax25->sk, SOCK_DEAD);
 285                }
 286                bh_unlock_sock(ax25->sk);
 287                local_bh_enable();
 288        }
 289}
 290