net/ax25/ax25_subr.c

   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  */
  33 void 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  */
  46 void 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
  62 void 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  */
  79 int 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  */
  97 int 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  */
 147 void 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  */
 187 void 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  */
 220 void 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  */
 245 void 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
 260 void ax25_disconnect(ax25_cb *ax25, int reason)
 261 {
 262         ax25_clear_queues(ax25);
 263
 264         if (reason == ENETUNREACH) {
 265                 del_timer_sync(&ax25->timer);
 266                 del_timer_sync(&ax25->t1timer);
 267                 del_timer_sync(&ax25->t2timer);
 268                 del_timer_sync(&ax25->t3timer);
 269                 del_timer_sync(&ax25->idletimer);
 270         } else {
 271                 if (ax25->sk && !sock_flag(ax25->sk, SOCK_DESTROY))
 272                         ax25_stop_heartbeat(ax25);
 273                 ax25_stop_t1timer(ax25);
 274                 ax25_stop_t2timer(ax25);
 275                 ax25_stop_t3timer(ax25);
 276                 ax25_stop_idletimer(ax25);
 277         }
 278
 279         ax25->state = AX25_STATE_0;
 280
 281         ax25_link_failed(ax25, reason);
 282
 283         if (ax25->sk != NULL) {
 284                 local_bh_disable();
 285                 bh_lock_sock(ax25->sk);
 286                 ax25->sk->sk_state     = TCP_CLOSE;
 287                 ax25->sk->sk_err       = reason;
 288                 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
 289                 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
 290                         ax25->sk->sk_state_change(ax25->sk);
 291                         sock_set_flag(ax25->sk, SOCK_DEAD);
 292                 }
 293                 bh_unlock_sock(ax25->sk);
 294                 local_bh_enable();
 295         }
 296 }