net/ax25/ax25_subr.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *
0004  * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
0005  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
0006  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
0007  * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
0008  */
0009 #include <linux/errno.h>
0010 #include <linux/types.h>
0011 #include <linux/socket.h>
0012 #include <linux/in.h>
0013 #include <linux/kernel.h>
0014 #include <linux/timer.h>
0015 #include <linux/string.h>
0016 #include <linux/sockios.h>
0017 #include <linux/net.h>
0018 #include <linux/slab.h>
0019 #include <net/ax25.h>
0020 #include <linux/inet.h>
0021 #include <linux/netdevice.h>
0022 #include <linux/skbuff.h>
0023 #include <net/sock.h>
0024 #include <net/tcp_states.h>
0025 #include <linux/uaccess.h>
0026 #include <linux/fcntl.h>
0027 #include <linux/mm.h>
0028 #include <linux/interrupt.h>
0029
0030 /*
0031  *  This routine purges all the queues of frames.
0032  */
0033 void ax25_clear_queues(ax25_cb *ax25)
0034 {
0035     skb_queue_purge(&ax25->write_queue);
0036     skb_queue_purge(&ax25->ack_queue);
0037     skb_queue_purge(&ax25->reseq_queue);
0038     skb_queue_purge(&ax25->frag_queue);
0039 }
0040
0041 /*
0042  * This routine purges the input queue of those frames that have been
0043  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
0044  * SDL diagram.
0045  */
0046 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
0047 {
0048     struct sk_buff *skb;
0049
0050     /*
0051      * Remove all the ack-ed frames from the ack queue.
0052      */
0053     if (ax25->va != nr) {
0054         while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
0055             skb = skb_dequeue(&ax25->ack_queue);
0056             kfree_skb(skb);
0057             ax25->va = (ax25->va + 1) % ax25->modulus;
0058         }
0059     }
0060 }
0061
0062 void ax25_requeue_frames(ax25_cb *ax25)
0063 {
0064     struct sk_buff *skb;
0065
0066     /*
0067      * Requeue all the un-ack-ed frames on the output queue to be picked
0068      * up by ax25_kick called from the timer. This arrangement handles the
0069      * possibility of an empty output queue.
0070      */
0071     while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
0072         skb_queue_head(&ax25->write_queue, skb);
0073 }
0074
0075 /*
0076  *  Validate that the value of nr is between va and vs. Return true or
0077  *  false for testing.
0078  */
0079 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
0080 {
0081     unsigned short vc = ax25->va;
0082
0083     while (vc != ax25->vs) {
0084         if (nr == vc) return 1;
0085         vc = (vc + 1) % ax25->modulus;
0086     }
0087
0088     if (nr == ax25->vs) return 1;
0089
0090     return 0;
0091 }
0092
0093 /*
0094  *  This routine is the centralised routine for parsing the control
0095  *  information for the different frame formats.
0096  */
0097 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
0098 {
0099     unsigned char *frame;
0100     int frametype = AX25_ILLEGAL;
0101
0102     frame = skb->data;
0103     *ns = *nr = *pf = 0;
0104
0105     if (ax25->modulus == AX25_MODULUS) {
0106         if ((frame[0] & AX25_S) == 0) {
0107             frametype = AX25_I;         /* I frame - carries NR/NS/PF */
0108             *ns = (frame[0] >> 1) & 0x07;
0109             *nr = (frame[0] >> 5) & 0x07;
0110             *pf = frame[0] & AX25_PF;
0111         } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
0112             frametype = frame[0] & 0x0F;
0113             *nr = (frame[0] >> 5) & 0x07;
0114             *pf = frame[0] & AX25_PF;
0115         } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
0116             frametype = frame[0] & ~AX25_PF;
0117             *pf = frame[0] & AX25_PF;
0118         }
0119         skb_pull(skb, 1);
0120     } else {
0121         if ((frame[0] & AX25_S) == 0) {
0122             frametype = AX25_I;         /* I frame - carries NR/NS/PF */
0123             *ns = (frame[0] >> 1) & 0x7F;
0124             *nr = (frame[1] >> 1) & 0x7F;
0125             *pf = frame[1] & AX25_EPF;
0126             skb_pull(skb, 2);
0127         } else if ((frame[0] & AX25_U) == 1) {  /* S frame - take out PF/NR */
0128             frametype = frame[0] & 0x0F;
0129             *nr = (frame[1] >> 1) & 0x7F;
0130             *pf = frame[1] & AX25_EPF;
0131             skb_pull(skb, 2);
0132         } else if ((frame[0] & AX25_U) == 3) {  /* U frame - take out PF */
0133             frametype = frame[0] & ~AX25_PF;
0134             *pf = frame[0] & AX25_PF;
0135             skb_pull(skb, 1);
0136         }
0137     }
0138
0139     return frametype;
0140 }
0141
0142 /*
0143  *  This routine is called when the HDLC layer internally  generates a
0144  *  command or  response  for  the remote machine ( eg. RR, UA etc. ).
0145  *  Only supervisory or unnumbered frames are processed.
0146  */
0147 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
0148 {
0149     struct sk_buff *skb;
0150     unsigned char  *dptr;
0151
0152     if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
0153         return;
0154
0155     skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
0156
0157     skb_reset_network_header(skb);
0158
0159     /* Assume a response - address structure for DTE */
0160     if (ax25->modulus == AX25_MODULUS) {
0161         dptr = skb_put(skb, 1);
0162         *dptr = frametype;
0163         *dptr |= (poll_bit) ? AX25_PF : 0;
0164         if ((frametype & AX25_U) == AX25_S)     /* S frames carry NR */
0165             *dptr |= (ax25->vr << 5);
0166     } else {
0167         if ((frametype & AX25_U) == AX25_U) {
0168             dptr = skb_put(skb, 1);
0169             *dptr = frametype;
0170             *dptr |= (poll_bit) ? AX25_PF : 0;
0171         } else {
0172             dptr = skb_put(skb, 2);
0173             dptr[0] = frametype;
0174             dptr[1] = (ax25->vr << 1);
0175             dptr[1] |= (poll_bit) ? AX25_EPF : 0;
0176         }
0177     }
0178
0179     ax25_transmit_buffer(ax25, skb, type);
0180 }
0181
0182 /*
0183  *  Send a 'DM' to an unknown connection attempt, or an invalid caller.
0184  *
0185  *  Note: src here is the sender, thus it's the target of the DM
0186  */
0187 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
0188 {
0189     struct sk_buff *skb;
0190     char *dptr;
0191     ax25_digi retdigi;
0192
0193     if (dev == NULL)
0194         return;
0195
0196     if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
0197         return; /* Next SABM will get DM'd */
0198
0199     skb_reserve(skb, dev->hard_header_len);
0200     skb_reset_network_header(skb);
0201
0202     ax25_digi_invert(digi, &retdigi);
0203
0204     dptr = skb_put(skb, 1);
0205
0206     *dptr = AX25_DM | AX25_PF;
0207
0208     /*
0209      *  Do the address ourselves
0210      */
0211     dptr  = skb_push(skb, ax25_addr_size(digi));
0212     dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
0213
0214     ax25_queue_xmit(skb, dev);
0215 }
0216
0217 /*
0218  *  Exponential backoff for AX.25
0219  */
0220 void ax25_calculate_t1(ax25_cb *ax25)
0221 {
0222     int n, t = 2;
0223
0224     switch (ax25->backoff) {
0225     case 0:
0226         break;
0227
0228     case 1:
0229         t += 2 * ax25->n2count;
0230         break;
0231
0232     case 2:
0233         for (n = 0; n < ax25->n2count; n++)
0234             t *= 2;
0235         if (t > 8) t = 8;
0236         break;
0237     }
0238
0239     ax25->t1 = t * ax25->rtt;
0240 }
0241
0242 /*
0243  *  Calculate the Round Trip Time
0244  */
0245 void ax25_calculate_rtt(ax25_cb *ax25)
0246 {
0247     if (ax25->backoff == 0)
0248         return;
0249
0250     if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
0251         ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
0252
0253     if (ax25->rtt < AX25_T1CLAMPLO)
0254         ax25->rtt = AX25_T1CLAMPLO;
0255
0256     if (ax25->rtt > AX25_T1CLAMPHI)
0257         ax25->rtt = AX25_T1CLAMPHI;
0258 }
0259
0260 void ax25_disconnect(ax25_cb *ax25, int reason)
0261 {
0262     ax25_clear_queues(ax25);
0263
0264     if (reason == ENETUNREACH) {
0265         del_timer_sync(&ax25->timer);
0266         del_timer_sync(&ax25->t1timer);
0267         del_timer_sync(&ax25->t2timer);
0268         del_timer_sync(&ax25->t3timer);
0269         del_timer_sync(&ax25->idletimer);
0270     } else {
0271         if (ax25->sk && !sock_flag(ax25->sk, SOCK_DESTROY))
0272             ax25_stop_heartbeat(ax25);
0273         ax25_stop_t1timer(ax25);
0274         ax25_stop_t2timer(ax25);
0275         ax25_stop_t3timer(ax25);
0276         ax25_stop_idletimer(ax25);
0277     }
0278
0279     ax25->state = AX25_STATE_0;
0280
0281     ax25_link_failed(ax25, reason);
0282
0283     if (ax25->sk != NULL) {
0284         local_bh_disable();
0285         bh_lock_sock(ax25->sk);
0286         ax25->sk->sk_state     = TCP_CLOSE;
0287         ax25->sk->sk_err       = reason;
0288         ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
0289         if (!sock_flag(ax25->sk, SOCK_DEAD)) {
0290             ax25->sk->sk_state_change(ax25->sk);
0291             sock_set_flag(ax25->sk, SOCK_DEAD);
0292         }
0293         bh_unlock_sock(ax25->sk);
0294         local_bh_enable();
0295     }
0296 }