// SPDX-License-Identifier: GPL-2.0-or-later
/*
*
* Copyright (C) Alan Cox GW4PTS ([email protected])
* Copyright (C) Jonathan Naylor G4KLX ([email protected])
* Copyright (C) Joerg Reuter DL1BKE ([email protected])
* Copyright (C) Hans-Joachim Hetscher DD8NE ([email protected])
*
* 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.
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.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 <net/tcp_states.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
/*
* State machine for state 1, Awaiting Connection State.
* The handling of the timer(s) is in file ax25_std_timer.c.
* Handling of state 0 and connection release is in ax25.c.
*/
static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
{
switch (frametype) {
case AX25_SABM:
ax25->modulus = AX25_MODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
break;
case AX25_SABME:
ax25->modulus = AX25_EMODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
break;
case AX25_DISC:
ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
break;
case AX25_UA:
if (pf) {
ax25_calculate_rtt(ax25);
ax25_stop_t1timer(ax25);
ax25_start_t3timer(ax25);
ax25_start_idletimer(ax25);
ax25->vs = 0;
ax25->va = 0;
ax25->vr = 0;
ax25->state = AX25_STATE_3;
ax25->n2count = 0;
if (ax25->sk != NULL) {
bh_lock_sock(ax25->sk);
ax25->sk->sk_state = TCP_ESTABLISHED;
/* For WAIT_SABM connections we will produce an accept ready socket here */
if (!sock_flag(ax25->sk, SOCK_DEAD))
ax25->sk->sk_state_change(ax25->sk);
bh_unlock_sock(ax25->sk);
}
}
break;
case AX25_DM:
if (pf) {
if (ax25->modulus == AX25_MODULUS) {
ax25_disconnect(ax25, ECONNREFUSED);
} else {
ax25->modulus = AX25_MODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
}
}
break;
default:
break;
}
return 0;
}
/*
* State machine for state 2, Awaiting Release State.
* The handling of the timer(s) is in file ax25_std_timer.c
* Handling of state 0 and connection release is in ax25.c.
*/
static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
{
switch (frametype) {
case AX25_SABM:
case AX25_SABME:
ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
break;
case AX25_DISC:
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
ax25_disconnect(ax25, 0);
break;
case AX25_DM:
case AX25_UA:
if (pf)
ax25_disconnect(ax25, 0);
break;
case AX25_I:
case AX25_REJ:
case AX25_RNR:
case AX25_RR:
if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
break;
default:
break;
}
return 0;
}
/*
* State machine for state 3, Connected State.
* The handling of the timer(s) is in file ax25_std_timer.c
* Handling of state 0 and connection release is in ax25.c.
*/
static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
{
int queued = 0;
switch (frametype) {
case AX25_SABM:
case AX25_SABME:
if (frametype == AX25_SABM) {
ax25->modulus = AX25_MODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
} else {
ax25->modulus = AX25_EMODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
}
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
ax25_stop_t1timer(ax25);
ax25_stop_t2timer(ax25);
ax25_start_t3timer(ax25);
ax25_start_idletimer(ax25);
ax25->condition = 0x00;
ax25->vs = 0;
ax25->va = 0;
ax25->vr = 0;
ax25_requeue_frames(ax25);
break;
case AX25_DISC:
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
ax25_disconnect(ax25, 0);
break;
case AX25_DM:
ax25_disconnect(ax25, ECONNRESET);
break;
case AX25_RR:
case AX25_RNR:
if (frametype == AX25_RR)
ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
else
ax25->condition |= AX25_COND_PEER_RX_BUSY;
if (type == AX25_COMMAND && pf)
ax25_std_enquiry_response(ax25);
if (ax25_validate_nr(ax25, nr)) {
ax25_check_iframes_acked(ax25, nr);
} else {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
}
break;
case AX25_REJ:
ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
if (type == AX25_COMMAND && pf)
ax25_std_enquiry_response(ax25);
if (ax25_validate_nr(ax25, nr)) {
ax25_frames_acked(ax25, nr);
ax25_calculate_rtt(ax25);
ax25_stop_t1timer(ax25);
ax25_start_t3timer(ax25);
ax25_requeue_frames(ax25);
} else {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
}
break;
case AX25_I:
if (!ax25_validate_nr(ax25, nr)) {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
break;
}
if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
ax25_frames_acked(ax25, nr);
} else {
ax25_check_iframes_acked(ax25, nr);
}
if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
if (pf) ax25_std_enquiry_response(ax25);
break;
}
if (ns == ax25->vr) {
ax25->vr = (ax25->vr + 1) % ax25->modulus;
queued = ax25_rx_iframe(ax25, skb);
if (ax25->condition & AX25_COND_OWN_RX_BUSY)
ax25->vr = ns; /* ax25->vr - 1 */
ax25->condition &= ~AX25_COND_REJECT;
if (pf) {
ax25_std_enquiry_response(ax25);
} else {
if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
ax25->condition |= AX25_COND_ACK_PENDING;
ax25_start_t2timer(ax25);
}
}
} else {
if (ax25->condition & AX25_COND_REJECT) {
if (pf) ax25_std_enquiry_response(ax25);
} else {
ax25->condition |= AX25_COND_REJECT;
ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
ax25->condition &= ~AX25_COND_ACK_PENDING;
}
}
break;
case AX25_FRMR:
case AX25_ILLEGAL:
ax25_std_establish_data_link(ax25);
ax25->state = AX25_STATE_1;
break;
default:
break;
}
return queued;
}
/*
* State machine for state 4, Timer Recovery State.
* The handling of the timer(s) is in file ax25_std_timer.c
* Handling of state 0 and connection release is in ax25.c.
*/
static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
{
int queued = 0;
switch (frametype) {
case AX25_SABM:
case AX25_SABME:
if (frametype == AX25_SABM) {
ax25->modulus = AX25_MODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
} else {
ax25->modulus = AX25_EMODULUS;
ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
}
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
ax25_stop_t1timer(ax25);
ax25_stop_t2timer(ax25);
ax25_start_t3timer(ax25);
ax25_start_idletimer(ax25);
ax25->condition = 0x00;
ax25->vs = 0;
ax25->va = 0;
ax25->vr = 0;
ax25->state = AX25_STATE_3;
ax25->n2count = 0;
ax25_requeue_frames(ax25);
break;
case AX25_DISC:
ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
ax25_disconnect(ax25, 0);
break;
case AX25_DM:
ax25_disconnect(ax25, ECONNRESET);
break;
case AX25_RR:
case AX25_RNR:
if (frametype == AX25_RR)
ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
else
ax25->condition |= AX25_COND_PEER_RX_BUSY;
if (type == AX25_RESPONSE && pf) {
ax25_stop_t1timer(ax25);
ax25->n2count = 0;
if (ax25_validate_nr(ax25, nr)) {
ax25_frames_acked(ax25, nr);
if (ax25->vs == ax25->va) {
ax25_start_t3timer(ax25);
ax25->state = AX25_STATE_3;
} else {
ax25_requeue_frames(ax25);
}
} else {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
}
break;
}
if (type == AX25_COMMAND && pf)
ax25_std_enquiry_response(ax25);
if (ax25_validate_nr(ax25, nr)) {
ax25_frames_acked(ax25, nr);
} else {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
}
break;
case AX25_REJ:
ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
if (pf && type == AX25_RESPONSE) {
ax25_stop_t1timer(ax25);
ax25->n2count = 0;
if (ax25_validate_nr(ax25, nr)) {
ax25_frames_acked(ax25, nr);
if (ax25->vs == ax25->va) {
ax25_start_t3timer(ax25);
ax25->state = AX25_STATE_3;
} else {
ax25_requeue_frames(ax25);
}
} else {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
}
break;
}
if (type == AX25_COMMAND && pf)
ax25_std_enquiry_response(ax25);
if (ax25_validate_nr(ax25, nr)) {
ax25_frames_acked(ax25, nr);
ax25_requeue_frames(ax25);
} else {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
}
break;
case AX25_I:
if (!ax25_validate_nr(ax25, nr)) {
ax25_std_nr_error_recovery(ax25);
ax25->state = AX25_STATE_1;
break;
}
ax25_frames_acked(ax25, nr);
if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
if (pf)
ax25_std_enquiry_response(ax25);
break;
}
if (ns == ax25->vr) {
ax25->vr = (ax25->vr + 1) % ax25->modulus;
queued = ax25_rx_iframe(ax25, skb);
if (ax25->condition & AX25_COND_OWN_RX_BUSY)
ax25->vr = ns; /* ax25->vr - 1 */
ax25->condition &= ~AX25_COND_REJECT;
if (pf) {
ax25_std_enquiry_response(ax25);
} else {
if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
ax25->condition |= AX25_COND_ACK_PENDING;
ax25_start_t2timer(ax25);
}
}
} else {
if (ax25->condition & AX25_COND_REJECT) {
if (pf) ax25_std_enquiry_response(ax25);
} else {
ax25->condition |= AX25_COND_REJECT;
ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
ax25->condition &= ~AX25_COND_ACK_PENDING;
}
}
break;
case AX25_FRMR:
case AX25_ILLEGAL:
ax25_std_establish_data_link(ax25);
ax25->state = AX25_STATE_1;
break;
default:
break;
}
return queued;
}
/*
* Higher level upcall for a LAPB frame
*/
int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
{
int queued = 0, frametype, ns, nr, pf;
frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
switch (ax25->state) {
case AX25_STATE_1:
queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type);
break;
case AX25_STATE_2:
queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type);
break;
case AX25_STATE_3:
queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
break;
case AX25_STATE_4:
queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type);
break;
}
ax25_kick(ax25);
return queued;
}
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