/*
* AX.25 release 032
*
* This is ALPHA test software. This code may break your machine, randomly fail to work with new
* releases, misbehave and/or generally screw up. It might even work.
*
* This code REQUIRES 1.2.1 or higher/ NET3.029
*
* 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 028a Jonathan(G4KLX) New state machine based on SDL diagrams.
* AX.25 029 Alan(GW4PTS) Switched to KA9Q constant names.
* Jonathan(G4KLX) Only poll when window is full.
* AX.25 030 Jonathan(G4KLX) Added fragmentation to ax25_output.
* Added support for extended AX.25.
* AX.25 031 Joerg(DL1BKE) Added DAMA support
* Joerg(DL1BKE) Modified fragmenter to fragment vanilla
* AX.25 I-Frames. Added PACLEN parameter.
* Joerg(DL1BKE) Fixed a problem with buffer allocation
* for fragments.
*/
#include <linux/config.h>
#ifdef CONFIG_AX25
#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/segment.h>
#include <asm/system.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
/*
* All outgoing AX.25 I frames pass via this routine. Therefore this is
* where the fragmentation of frames takes place.
*/
void ax25_output(ax25_cb *ax25, struct sk_buff *skb)
{
struct sk_buff *skbn;
unsigned char *p;
int frontlen, mtu, len, fragno, ka9qfrag, first = 1;
long flags;
/*
* dl1bke 960301: We use the new PACLEN parameter as MTU of the AX.25 layer.
* This will (hopefully) allow user programs to write() data
* w/o having to think of the maximal amount of data we can
* send with one call. It's called PACLEN to (1) avoid confusion
* with (IP) MTU and (2) TAPR calls this PACLEN, too ;-)
*/
mtu = ax25->paclen;
if ((skb->len - 1) > mtu) {
if (*skb->data == AX25_P_TEXT) {
skb_pull(skb, 1); /* skip PID */
ka9qfrag = 0;
} else {
mtu -= 2; /* Allow for fragment control info */
ka9qfrag = 1;
}
fragno = skb->len / mtu;
if (skb->len % mtu == 0) fragno--;
frontlen = skb_headroom(skb); /* Address space + CTRL */
while (skb->len > 0) {
save_flags(flags);
cli();
/*
* do _not_ use sock_alloc_send_skb, our socket may have
* sk->shutdown set...
*/
if ((skbn = alloc_skb(mtu + 2 + frontlen, GFP_ATOMIC)) == NULL) {
restore_flags(flags);
printk(KERN_DEBUG "ax25_output: alloc_skb returned NULL\n");
if (skb_device_locked(skb))
skb_device_unlock(skb);
return;
}
skbn->sk = skb->sk;
if (skbn->sk)
atomic_add(skbn->truesize, &skbn->sk->wmem_alloc);
restore_flags(flags);
skbn->free = 1;
skbn->arp = 1;
len = (mtu > skb->len) ? skb->len : mtu;
if (ka9qfrag == 1) {
skb_reserve(skbn, frontlen + 2);
memcpy(skb_put(skbn, len), skb->data, len);
p = skb_push(skbn, 2);
*p++ = AX25_P_SEGMENT;
*p = fragno--;
if (first) {
*p |= SEG_FIRST;
first = 0;
}
} else {
skb_reserve(skbn, frontlen + 1);
memcpy(skb_put(skbn, len), skb->data, len);
p = skb_push(skbn, 1);
*p = AX25_P_TEXT;
}
skb_pull(skb, len);
skb_queue_tail(&ax25->write_queue, skbn); /* Throw it on the queue */
}
skb->free = 1;
kfree_skb(skb, FREE_WRITE);
} else {
skb_queue_tail(&ax25->write_queue, skb); /* Throw it on the queue */
}
if (ax25->state == AX25_STATE_3 || ax25->state == AX25_STATE_4) {
if (!ax25->dama_slave) /* bke 960114: we aren't allowed to transmit */
ax25_kick(ax25); /* in DAMA mode unless we received a Poll */
}
}
/*
* This procedure is passed a buffer descriptor for an iframe. It builds
* the rest of the control part of the frame and then writes it out.
*/
static void ax25_send_iframe(ax25_cb *ax25, struct sk_buff *skb, int poll_bit)
{
unsigned char *frame;
if (skb == NULL)
return;
if (ax25->modulus == MODULUS) {
frame = skb_push(skb, 1);
*frame = I;
*frame |= (poll_bit) ? PF : 0;
*frame |= (ax25->vr << 5);
*frame |= (ax25->vs << 1);
} else {
frame = skb_push(skb, 2);
frame[0] = I;
frame[0] |= (ax25->vs << 1);
frame[1] = (poll_bit) ? EPF : 0;
frame[1] |= (ax25->vr << 1);
}
ax25_transmit_buffer(ax25, skb, C_COMMAND);
}
void ax25_kick(ax25_cb *ax25)
{
struct sk_buff *skb, *skbn;
int last = 1;
unsigned short start, end, next;
del_timer(&ax25->timer);
start = (skb_peek(&ax25->ack_queue) == NULL) ? ax25->va : ax25->vs;
end = (ax25->va + ax25->window) % ax25->modulus;
if (!(ax25->condition & PEER_RX_BUSY_CONDITION) &&
start != end &&
skb_peek(&ax25->write_queue) != NULL) {
ax25->vs = start;
/*
* Transmit data until either we're out of data to send or
* the window is full. Send a poll on the final I frame if
* the window is filled.
*/
/*
* Dequeue the frame and copy it.
*/
skb = skb_dequeue(&ax25->write_queue);
do {
if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
skb_queue_head(&ax25->write_queue, skb);
break;
}
next = (ax25->vs + 1) % ax25->modulus;
#ifdef notdef
last = (next == end) || skb_peek(&ax25->write_queue) == NULL;
#else
last = (next == end);
#endif
/*
* Transmit the frame copy.
* bke 960114: do not set the Poll bit on the last frame
* in DAMA mode.
*/
ax25_send_iframe(ax25, skbn, (last && !ax25->dama_slave) ? POLLON : POLLOFF);
ax25->vs = next;
/*
* Requeue the original data frame.
*/
skb_queue_tail(&ax25->ack_queue, skb);
#ifdef notdef
} while (!last);
#else
} while (!last && (skb = skb_dequeue(&ax25->write_queue)) != NULL);
#endif
ax25->condition &= ~ACK_PENDING_CONDITION;
if (ax25->t1timer == 0) {
ax25->t3timer = 0;
ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
}
}
ax25_set_timer(ax25);
}
void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
{
unsigned char *ptr;
if (ax25->device == NULL) {
if (ax25->sk != NULL) {
ax25->sk->state = TCP_CLOSE;
ax25->sk->err = ENETUNREACH;
if (!ax25->sk->dead)
ax25->sk->state_change(ax25->sk);
ax25->sk->dead = 1;
}
return;
}
if (skb_headroom(skb) < size_ax25_addr(ax25->digipeat)) {
printk(KERN_CRIT "ax25_transmit_buffer: not enough room for digi-peaters\n");
skb->free = 1;
kfree_skb(skb, FREE_WRITE);
return;
}
ptr = skb_push(skb, size_ax25_addr(ax25->digipeat));
build_ax25_addr(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);
skb->arp = 1;
ax25_queue_xmit(skb, ax25->device, SOPRI_NORMAL);
}
/*
* The following routines are taken from page 170 of the 7th ARRL Computer
* Networking Conference paper, as is the whole state machine.
*/
void ax25_nr_error_recovery(ax25_cb *ax25)
{
ax25_establish_data_link(ax25);
}
void ax25_establish_data_link(ax25_cb *ax25)
{
ax25->condition = 0x00;
ax25->n2count = 0;
if (ax25->modulus == MODULUS) {
ax25_send_control(ax25, SABM, POLLON, C_COMMAND);
} else {
ax25_send_control(ax25, SABME, POLLON, C_COMMAND);
}
ax25->t3timer = 0;
ax25->t2timer = 0;
ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
}
void ax25_transmit_enquiry(ax25_cb *ax25)
{
if (ax25->condition & OWN_RX_BUSY_CONDITION)
ax25_send_control(ax25, RNR, POLLON, C_COMMAND);
else
ax25_send_control(ax25, RR, POLLON, C_COMMAND);
ax25->condition &= ~ACK_PENDING_CONDITION;
ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
}
void ax25_enquiry_response(ax25_cb *ax25)
{
if (ax25->condition & OWN_RX_BUSY_CONDITION)
ax25_send_control(ax25, RNR, POLLON, C_RESPONSE);
else
ax25_send_control(ax25, RR, POLLON, C_RESPONSE);
ax25->condition &= ~ACK_PENDING_CONDITION;
}
void ax25_timeout_response(ax25_cb *ax25)
{
if (ax25->condition & OWN_RX_BUSY_CONDITION)
ax25_send_control(ax25, RNR, POLLOFF, C_RESPONSE);
else
ax25_send_control(ax25, RR, POLLOFF, C_RESPONSE);
ax25->condition &= ~ACK_PENDING_CONDITION;
}
void ax25_check_iframes_acked(ax25_cb *ax25, unsigned short nr)
{
if (ax25->vs == nr) {
ax25_frames_acked(ax25, nr);
ax25_calculate_rtt(ax25);
ax25->t1timer = 0;
ax25->t3timer = ax25->t3;
} else {
if (ax25->va != nr) {
ax25_frames_acked(ax25, nr);
ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
}
}
}
/*
* dl1bke 960114: shouldn't ax25/dama_check_need_response reside as
* static inline void ...() in ax25.h, should it? ;-)
*/
void ax25_check_need_response(ax25_cb *ax25, int type, int pf)
{
if (!ax25->dama_slave && type == C_COMMAND && pf)
ax25_enquiry_response(ax25);
}
/*
* dl1bke 960114: transmit I frames on DAMA poll
*/
void dama_enquiry_response(ax25_cb *ax25)
{
ax25_cb *ax25o;
if (!(ax25->condition & PEER_RX_BUSY_CONDITION)) {
ax25_requeue_frames(ax25);
ax25_kick(ax25);
}
if (ax25->state == AX25_STATE_1 || ax25->state == AX25_STATE_2 ||
skb_peek(&ax25->ack_queue) != NULL) {
ax25_t1_timeout(ax25);
} else {
ax25->n2count = 0;
}
ax25->t3timer = ax25->t3;
/* The FLEXNET DAMA master implementation refuses to send us ANY */
/* I frame for this connection if we send a REJ here, probably */
/* due to its frame collector scheme? A simple RR or RNR will */
/* invoke the retransmission, and in fact REJs are superfluous */
/* in DAMA mode anyway... */
#if 0
if (ax25->condition & REJECT_CONDITION)
ax25_send_control(ax25, REJ, POLLOFF, C_RESPONSE);
else
#endif
ax25_enquiry_response(ax25);
/* Note that above response to the poll could be sent behind the */
/* transmissions of the other channels as well... This version */
/* gives better performance on FLEXNET nodes. (Why, Gunter?) */
for (ax25o = ax25_list; ax25o != NULL; ax25o = ax25o->next) {
if (ax25o == ax25)
continue;
if (ax25o->device != ax25->device)
continue;
if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2) {
ax25_t1_timeout(ax25o);
continue;
}
if (!ax25o->dama_slave)
continue;
if ( !(ax25o->condition & PEER_RX_BUSY_CONDITION) &&
(ax25o->state == AX25_STATE_3 ||
(ax25o->state == AX25_STATE_4 && ax25o->t1timer == 0))) {
ax25_requeue_frames(ax25o);
ax25_kick(ax25o);
}
if (ax25o->state == AX25_STATE_1 || ax25o->state == AX25_STATE_2 ||
skb_peek(&ax25o->ack_queue) != NULL) {
ax25_t1_timeout(ax25o);
}
ax25o->t3timer = ax25o->t3;
}
}
void dama_check_need_response(ax25_cb *ax25, int type, int pf)
{
if (ax25->dama_slave && type == C_COMMAND && pf)
dama_enquiry_response(ax25);
}
void dama_establish_data_link(ax25_cb *ax25)
{
ax25->condition = 0x00;
ax25->n2count = 0;
ax25->t3timer = ax25->t3;
ax25->t2timer = 0;
ax25->t1timer = ax25->t1 = ax25_calculate_t1(ax25);
}
#endif
