LXR linux/net/ax25/ax25

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *
   4 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
   5 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
   6 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
   7 * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
   8 */
   9#include <linux/errno.h>
  10#include <linux/types.h>
  11#include <linux/socket.h>
  12#include <linux/in.h>
  13#include <linux/kernel.h>
  14#include <linux/timer.h>
  15#include <linux/string.h>
  16#include <linux/sockios.h>
  17#include <linux/net.h>
  18#include <linux/slab.h>
  19#include <net/ax25.h>
  20#include <linux/inet.h>
  21#include <linux/netdevice.h>
  22#include <linux/skbuff.h>
  23#include <net/sock.h>
  24#include <net/tcp_states.h>
  25#include <linux/uaccess.h>
  26#include <linux/fcntl.h>
  27#include <linux/mm.h>
  28#include <linux/interrupt.h>
  29
  30/*
  31 *      This routine purges all the queues of frames.
  32 */
  33void ax25_clear_queues(ax25_cb *ax25)
  34{
  35        skb_queue_purge(&ax25->write_queue);
  36        skb_queue_purge(&ax25->ack_queue);
  37        skb_queue_purge(&ax25->reseq_queue);
  38        skb_queue_purge(&ax25->frag_queue);
  39}
  40
  41/*
  42 * This routine purges the input queue of those frames that have been
  43 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
  44 * SDL diagram.
  45 */
  46void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
  47{
  48        struct sk_buff *skb;
  49
  50        /*
  51         * Remove all the ack-ed frames from the ack queue.
  52         */
  53        if (ax25->va != nr) {
  54                while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
  55                        skb = skb_dequeue(&ax25->ack_queue);
  56                        kfree_skb(skb);
  57                        ax25->va = (ax25->va + 1) % ax25->modulus;
  58                }
  59        }
  60}
  61
  62void ax25_requeue_frames(ax25_cb *ax25)
  63{
  64        struct sk_buff *skb;
  65
  66        /*
  67         * Requeue all the un-ack-ed frames on the output queue to be picked
  68         * up by ax25_kick called from the timer. This arrangement handles the
  69         * possibility of an empty output queue.
  70         */
  71        while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
  72                skb_queue_head(&ax25->write_queue, skb);
  73}
  74
  75/*
  76 *      Validate that the value of nr is between va and vs. Return true or
  77 *      false for testing.
  78 */
  79int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
  80{
  81        unsigned short vc = ax25->va;
  82
  83        while (vc != ax25->vs) {
  84                if (nr == vc) return 1;
  85                vc = (vc + 1) % ax25->modulus;
  86        }
  87
  88        if (nr == ax25->vs) return 1;
  89
  90        return 0;
  91}
  92
  93/*
  94 *      This routine is the centralised routine for parsing the control
  95 *      information for the different frame formats.
  96 */
  97int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
  98{
  99        unsigned char *frame;
 100        int frametype = AX25_ILLEGAL;
 101
 102        frame = skb->data;
 103        *ns = *nr = *pf = 0;
 104
 105        if (ax25->modulus == AX25_MODULUS) {
 106                if ((frame[0] & AX25_S) == 0) {
 107                        frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 108                        *ns = (frame[0] >> 1) & 0x07;
 109                        *nr = (frame[0] >> 5) & 0x07;
 110                        *pf = frame[0] & AX25_PF;
 111                } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 112                        frametype = frame[0] & 0x0F;
 113                        *nr = (frame[0] >> 5) & 0x07;
 114                        *pf = frame[0] & AX25_PF;
 115                } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 116                        frametype = frame[0] & ~AX25_PF;
 117                        *pf = frame[0] & AX25_PF;
 118                }
 119                skb_pull(skb, 1);
 120        } else {
 121                if ((frame[0] & AX25_S) == 0) {
 122                        frametype = AX25_I;                     /* I frame - carries NR/NS/PF */
 123                        *ns = (frame[0] >> 1) & 0x7F;
 124                        *nr = (frame[1] >> 1) & 0x7F;
 125                        *pf = frame[1] & AX25_EPF;
 126                        skb_pull(skb, 2);
 127                } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
 128                        frametype = frame[0] & 0x0F;
 129                        *nr = (frame[1] >> 1) & 0x7F;
 130                        *pf = frame[1] & AX25_EPF;
 131                        skb_pull(skb, 2);
 132                } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
 133                        frametype = frame[0] & ~AX25_PF;
 134                        *pf = frame[0] & AX25_PF;
 135                        skb_pull(skb, 1);
 136                }
 137        }
 138
 139        return frametype;
 140}
 141
 142/*
 143 *      This routine is called when the HDLC layer internally  generates a
 144 *      command or  response  for  the remote machine ( eg. RR, UA etc. ).
 145 *      Only supervisory or unnumbered frames are processed.
 146 */
 147void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
 148{
 149        struct sk_buff *skb;
 150        unsigned char  *dptr;
 151
 152        if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
 153                return;
 154
 155        skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
 156
 157        skb_reset_network_header(skb);
 158
 159        /* Assume a response - address structure for DTE */
 160        if (ax25->modulus == AX25_MODULUS) {
 161                dptr = skb_put(skb, 1);
 162                *dptr = frametype;
 163                *dptr |= (poll_bit) ? AX25_PF : 0;
 164                if ((frametype & AX25_U) == AX25_S)             /* S frames carry NR */
 165                        *dptr |= (ax25->vr << 5);
 166        } else {
 167                if ((frametype & AX25_U) == AX25_U) {
 168                        dptr = skb_put(skb, 1);
 169                        *dptr = frametype;
 170                        *dptr |= (poll_bit) ? AX25_PF : 0;
 171                } else {
 172                        dptr = skb_put(skb, 2);
 173                        dptr[0] = frametype;
 174                        dptr[1] = (ax25->vr << 1);
 175                        dptr[1] |= (poll_bit) ? AX25_EPF : 0;
 176                }
 177        }
 178
 179        ax25_transmit_buffer(ax25, skb, type);
 180}
 181
 182/*
 183 *      Send a 'DM' to an unknown connection attempt, or an invalid caller.
 184 *
 185 *      Note: src here is the sender, thus it's the target of the DM
 186 */
 187void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
 188{
 189        struct sk_buff *skb;
 190        char *dptr;
 191        ax25_digi retdigi;
 192
 193        if (dev == NULL)
 194                return;
 195
 196        if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
 197                return; /* Next SABM will get DM'd */
 198
 199        skb_reserve(skb, dev->hard_header_len);
 200        skb_reset_network_header(skb);
 201
 202        ax25_digi_invert(digi, &retdigi);
 203
 204        dptr = skb_put(skb, 1);
 205
 206        *dptr = AX25_DM | AX25_PF;
 207
 208        /*
 209         *      Do the address ourselves
 210         */
 211        dptr  = skb_push(skb, ax25_addr_size(digi));
 212        dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
 213
 214        ax25_queue_xmit(skb, dev);
 215}
 216
 217/*
 218 *      Exponential backoff for AX.25
 219 */
 220void ax25_calculate_t1(ax25_cb *ax25)
 221{
 222        int n, t = 2;
 223
 224        switch (ax25->backoff) {
 225        case 0:
 226                break;
 227
 228        case 1:
 229                t += 2 * ax25->n2count;
 230                break;
 231
 232        case 2:
 233                for (n = 0; n < ax25->n2count; n++)
 234                        t *= 2;
 235                if (t > 8) t = 8;
 236                break;
 237        }
 238
 239        ax25->t1 = t * ax25->rtt;
 240}
 241
 242/*
 243 *      Calculate the Round Trip Time
 244 */
 245void ax25_calculate_rtt(ax25_cb *ax25)
 246{
 247        if (ax25->backoff == 0)
 248                return;
 249
 250        if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
 251                ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
 252
 253        if (ax25->rtt < AX25_T1CLAMPLO)
 254                ax25->rtt = AX25_T1CLAMPLO;
 255
 256        if (ax25->rtt > AX25_T1CLAMPHI)
 257                ax25->rtt = AX25_T1CLAMPHI;
 258}
 259
 260void ax25_disconnect(ax25_cb *ax25, int reason)
 261{
 262        ax25_clear_queues(ax25);
 263
 264        if (!ax25->sk || !sock_flag(ax25->sk, SOCK_DESTROY))
 265                ax25_stop_heartbeat(ax25);
 266        ax25_stop_t1timer(ax25);
 267        ax25_stop_t2timer(ax25);
 268        ax25_stop_t3timer(ax25);
 269        ax25_stop_idletimer(ax25);
 270
 271        ax25->state = AX25_STATE_0;
 272
 273        ax25_link_failed(ax25, reason);
 274
 275        if (ax25->sk != NULL) {
 276                local_bh_disable();
 277                bh_lock_sock(ax25->sk);
 278                ax25->sk->sk_state     = TCP_CLOSE;
 279                ax25->sk->sk_err       = reason;
 280                ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 281                if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 282                        ax25->sk->sk_state_change(ax25->sk);
 283                        sock_set_flag(ax25->sk, SOCK_DEAD);
 284                }
 285                bh_unlock_sock(ax25->sk);
 286                local_bh_enable();
 287        }
 288}
 289