text: /*
   *	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 028a	Jonathan(G4KLX)	New state machine based on SDL diagrams.
   *	AX.25 028b	Jonathan(G4KLX) Extracted AX25 control block from
   *					the sock structure.
   *	AX.25 029	Alan(GW4PTS)	Switched to KA9Q constant names.
   *			Jonathan(G4KLX)	Added IP mode registration.
   *	AX.25 030	Jonathan(G4KLX)	Added AX.25 fragment reception.
   *					Upgraded state machine for SABME.
   *					Added arbitrary protocol id support.
   *	AX.25 031	Joerg(DL1BKE)	Added DAMA support
   *			HaJo(DD8NE)	Added Idle Disc Timer T5
   *			Joerg(DL1BKE)   Renamed it to "IDLE" with a slightly
   *					different behaviour. Fixed defrag
   *					routine (I hope)
   *	AX.25 032	Darryl(G7LED)	AX.25 segmentation fixed.
   *	AX.25 033	Jonathan(G4KLX)	Remove auto-router.
   *					Modularisation changes.
   *	AX.25 035	Hans(PE1AYX)	Fixed interface to IP layer.
   *	AX.25 036	Jonathan(G4KLX)	Cloned from ax25_in.c.
   *	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 <net/ip.h>			/* For ip_rcv */
  #include <asm/uaccess.h>
  #include <asm/system.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) {
  					ax25->sk->state = TCP_ESTABLISHED;
  					/* For WAIT_SABM connections we will produce an accept ready socket here */
  					if (!ax25->sk->dead)
  						ax25->sk->state_change(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;
  }
  