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/*
* AX.25 release 037
*
* This code REQUIRES 2.1.15 or higher/ NET3.038
*
* This module:
* This module is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Most of this code is based on the SDL diagrams published in the 7th
* ARRL Computer Networking Conference papers. The diagrams have mistakes
* in them, but are mostly correct. Before you modify the code could you
* read the SDL diagrams as the code is not obvious and probably very
* easy to break;
*
* History
* AX.25 029 Alan(GW4PTS) Switched to KA9Q constant names. Removed
* old BSD code.
* AX.25 030 Jonathan(G4KLX) Added support for extended AX.25.
* Added fragmentation support.
* Darryl(G7LED) Added function ax25_requeue_frames() to split
* it up from ax25_frames_acked().
* AX.25 031 Joerg(DL1BKE) DAMA needs KISS Fullduplex ON/OFF.
* Thus we have ax25_kiss_cmd() now... ;-)
* Dave Brown(N2RJT)
* Killed a silly bug in the DAMA code.
* Joerg(DL1BKE) Found the real bug in ax25.h, sri.
* AX.25 032 Joerg(DL1BKE) Added ax25_queue_length to count the number of
* enqueued buffers of a socket..
* AX.25 035 Frederic(F1OAT) Support for pseudo-digipeating.
* AX.25 037 Jonathan(G4KLX) New timer architecture.
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
/*
* This routine purges all the queues of frames.
*/
void ax25_clear_queues(ax25_cb *ax25)
{
skb_queue_purge(&ax25->write_queue);
skb_queue_purge(&ax25->ack_queue);
skb_queue_purge(&ax25->reseq_queue);
skb_queue_purge(&ax25->frag_queue);
}
/*
* This routine purges the input queue of those frames that have been
* acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
* SDL diagram.
*/
void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
{
struct sk_buff *skb;
/*
* Remove all the ack-ed frames from the ack queue.
*/
if (ax25->va != nr) {
while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
skb = skb_dequeue(&ax25->ack_queue);
kfree_skb(skb);
ax25->va = (ax25->va + 1) % ax25->modulus;
}
}
}
void ax25_requeue_frames(ax25_cb *ax25)
{
struct sk_buff *skb, *skb_prev = NULL;
/*
* Requeue all the un-ack-ed frames on the output queue to be picked
* up by ax25_kick called from the timer. This arrangement handles the
* possibility of an empty output queue.
*/
while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) {
if (skb_prev == NULL)
skb_queue_head(&ax25->write_queue, skb);
else
skb_append(skb_prev, skb);
skb_prev = skb;
}
}
/*
* Validate that the value of nr is between va and vs. Return true or
* false for testing.
*/
int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
{
unsigned short vc = ax25->va;
while (vc != ax25->vs) {
if (nr == vc) return 1;
vc = (vc + 1) % ax25->modulus;
}
if (nr == ax25->vs) return 1;
return 0;
}
/*
* This routine is the centralised routine for parsing the control
* information for the different frame formats.
*/
int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
{
unsigned char *frame;
int frametype = AX25_ILLEGAL;
frame = skb->data;
*ns = *nr = *pf = 0;
if (ax25->modulus == AX25_MODULUS) {
if ((frame[0] & AX25_S) == 0) {
frametype = AX25_I; /* I frame - carries NR/NS/PF */
*ns = (frame[0] >> 1) & 0x07;
*nr = (frame[0] >> 5) & 0x07;
*pf = frame[0] & AX25_PF;
} else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
frametype = frame[0] & 0x0F;
*nr = (frame[0] >> 5) & 0x07;
*pf = frame[0] & AX25_PF;
} else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
frametype = frame[0] & ~AX25_PF;
*pf = frame[0] & AX25_PF;
}
skb_pull(skb, 1);
} else {
if ((frame[0] & AX25_S) == 0) {
frametype = AX25_I; /* I frame - carries NR/NS/PF */
*ns = (frame[0] >> 1) & 0x7F;
*nr = (frame[1] >> 1) & 0x7F;
*pf = frame[1] & AX25_EPF;
skb_pull(skb, 2);
} else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
frametype = frame[0] & 0x0F;
*nr = (frame[1] >> 1) & 0x7F;
*pf = frame[1] & AX25_EPF;
skb_pull(skb, 2);
} else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
frametype = frame[0] & ~AX25_PF;
*pf = frame[0] & AX25_PF;
skb_pull(skb, 1);
}
}
return frametype;
}
/*
* This routine is called when the HDLC layer internally generates a
* command or response for the remote machine ( eg. RR, UA etc. ).
* Only supervisory or unnumbered frames are processed.
*/
void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
{
struct sk_buff *skb;
unsigned char *dptr;
if ((skb = alloc_skb(AX25_BPQ_HEADER_LEN + ax25_addr_size(ax25->digipeat) + 2, GFP_ATOMIC)) == NULL)
return;
skb_reserve(skb, AX25_BPQ_HEADER_LEN + ax25_addr_size(ax25->digipeat));
skb->nh.raw = skb->data;
/* Assume a response - address structure for DTE */
if (ax25->modulus == AX25_MODULUS) {
dptr = skb_put(skb, 1);
*dptr = frametype;
*dptr |= (poll_bit) ? AX25_PF : 0;
if ((frametype & AX25_U) == AX25_S) /* S frames carry NR */
*dptr |= (ax25->vr << 5);
} else {
if ((frametype & AX25_U) == AX25_U) {
dptr = skb_put(skb, 1);
*dptr = frametype;
*dptr |= (poll_bit) ? AX25_PF : 0;
} else {
dptr = skb_put(skb, 2);
dptr[0] = frametype;
dptr[1] = (ax25->vr << 1);
dptr[1] |= (poll_bit) ? AX25_EPF : 0;
}
}
ax25_transmit_buffer(ax25, skb, type);
}
/*
* Send a 'DM' to an unknown connection attempt, or an invalid caller.
*
* Note: src here is the sender, thus it's the target of the DM
*/
void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
{
struct sk_buff *skb;
char *dptr;
ax25_digi retdigi;
if (dev == NULL)
return;
if ((skb = alloc_skb(AX25_BPQ_HEADER_LEN + ax25_addr_size(digi) + 1, GFP_ATOMIC)) == NULL)
return; /* Next SABM will get DM'd */
skb_reserve(skb, AX25_BPQ_HEADER_LEN + ax25_addr_size(digi));
skb->nh.raw = skb->data;
ax25_digi_invert(digi, &retdigi);
dptr = skb_put(skb, 1);
*dptr = AX25_DM | AX25_PF;
/*
* Do the address ourselves
*/
dptr = skb_push(skb, ax25_addr_size(digi));
dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
skb->dev = dev;
ax25_queue_xmit(skb);
}
/*
* Exponential backoff for AX.25
*/
void ax25_calculate_t1(ax25_cb *ax25)
{
int n, t = 2;
switch (ax25->backoff) {
case 0:
break;
case 1:
t += 2 * ax25->n2count;
break;
case 2:
for (n = 0; n < ax25->n2count; n++)
t *= 2;
if (t > 8) t = 8;
break;
}
ax25->t1 = t * ax25->rtt;
}
/*
* Calculate the Round Trip Time
*/
void ax25_calculate_rtt(ax25_cb *ax25)
{
if (ax25->backoff == 0)
return;
if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
if (ax25->rtt < AX25_T1CLAMPLO)
ax25->rtt = AX25_T1CLAMPLO;
if (ax25->rtt > AX25_T1CLAMPHI)
ax25->rtt = AX25_T1CLAMPHI;
}
void ax25_disconnect(ax25_cb *ax25, int reason)
{
ax25_clear_queues(ax25);
ax25_stop_t1timer(ax25);
ax25_stop_t2timer(ax25);
ax25_stop_t3timer(ax25);
ax25_stop_idletimer(ax25);
ax25->state = AX25_STATE_0;
ax25_link_failed(ax25, reason);
if (ax25->sk != NULL) {
ax25->sk->state = TCP_CLOSE;
ax25->sk->err = reason;
ax25->sk->shutdown |= SEND_SHUTDOWN;
if (!ax25->sk->dead)
ax25->sk->state_change(ax25->sk);
ax25->sk->dead = 1;
}
}
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