CoCalc -- ax25_std

GitHub Repository: awilliam/linux-vfio
Path: blob/master/net/ax25/ax25_std_in.c
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/*
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * Copyright (C) Alan Cox GW4PTS ([email protected])
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 * Copyright (C) Jonathan Naylor G4KLX ([email protected])
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 * Copyright (C) Joerg Reuter DL1BKE ([email protected])
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 * Copyright (C) Hans-Joachim Hetscher DD8NE ([email protected])
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 *
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 * Most of this code is based on the SDL diagrams published in the 7th ARRL
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 * Computer Networking Conference papers. The diagrams have mistakes in them,
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 * but are mostly correct. Before you modify the code could you read the SDL
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 * diagrams as the code is not obvious and probably very easy to break.
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 */
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#include <linux/errno.h>
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#include <linux/types.h>
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#include <linux/socket.h>
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#include <linux/in.h>
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#include <linux/kernel.h>
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#include <linux/timer.h>
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#include <linux/string.h>
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#include <linux/sockios.h>
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#include <linux/net.h>
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#include <net/ax25.h>
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#include <linux/inet.h>
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#include <linux/netdevice.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <net/tcp_states.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <linux/fcntl.h>
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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/*
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 *	State machine for state 1, Awaiting Connection State.
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 *	The handling of the timer(s) is in file ax25_std_timer.c.
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 *	Handling of state 0 and connection release is in ax25.c.
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 */
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static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
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{
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	switch (frametype) {
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	case AX25_SABM:
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		ax25->modulus = AX25_MODULUS;
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		ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
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		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
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		break;
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	case AX25_SABME:
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		ax25->modulus = AX25_EMODULUS;
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		ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
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		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
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		break;
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	case AX25_DISC:
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		ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
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		break;
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62
	case AX25_UA:
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		if (pf) {
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			ax25_calculate_rtt(ax25);
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			ax25_stop_t1timer(ax25);
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			ax25_start_t3timer(ax25);
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			ax25_start_idletimer(ax25);
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			ax25->vs      = 0;
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			ax25->va      = 0;
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			ax25->vr      = 0;
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			ax25->state   = AX25_STATE_3;
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			ax25->n2count = 0;
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			if (ax25->sk != NULL) {
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				bh_lock_sock(ax25->sk);
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				ax25->sk->sk_state = TCP_ESTABLISHED;
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				/* For WAIT_SABM connections we will produce an accept ready socket here */
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				if (!sock_flag(ax25->sk, SOCK_DEAD))
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					ax25->sk->sk_state_change(ax25->sk);
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				bh_unlock_sock(ax25->sk);
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			}
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		}
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		break;
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	case AX25_DM:
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		if (pf) {
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			if (ax25->modulus == AX25_MODULUS) {
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				ax25_disconnect(ax25, ECONNREFUSED);
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			} else {
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				ax25->modulus = AX25_MODULUS;
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				ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
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			}
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		}
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		break;
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	default:
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		break;
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	}
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	return 0;
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}
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/*
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 *	State machine for state 2, Awaiting Release State.
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 *	The handling of the timer(s) is in file ax25_std_timer.c
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 *	Handling of state 0 and connection release is in ax25.c.
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 */
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static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
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{
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	switch (frametype) {
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	case AX25_SABM:
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	case AX25_SABME:
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		ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
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		break;
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	case AX25_DISC:
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		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
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		ax25_disconnect(ax25, 0);
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		break;
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	case AX25_DM:
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	case AX25_UA:
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		if (pf)
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			ax25_disconnect(ax25, 0);
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		break;
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	case AX25_I:
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	case AX25_REJ:
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	case AX25_RNR:
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	case AX25_RR:
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		if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
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		break;
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133
	default:
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		break;
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	}
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	return 0;
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}
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/*
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 *	State machine for state 3, Connected State.
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 *	The handling of the timer(s) is in file ax25_std_timer.c
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 *	Handling of state 0 and connection release is in ax25.c.
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 */
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static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
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{
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	int queued = 0;
148

149
	switch (frametype) {
150
	case AX25_SABM:
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	case AX25_SABME:
152
		if (frametype == AX25_SABM) {
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			ax25->modulus = AX25_MODULUS;
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			ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
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		} else {
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			ax25->modulus = AX25_EMODULUS;
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			ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
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		}
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		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
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		ax25_stop_t1timer(ax25);
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		ax25_stop_t2timer(ax25);
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		ax25_start_t3timer(ax25);
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		ax25_start_idletimer(ax25);
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		ax25->condition = 0x00;
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		ax25->vs        = 0;
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		ax25->va        = 0;
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		ax25->vr        = 0;
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		ax25_requeue_frames(ax25);
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		break;
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171
	case AX25_DISC:
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		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
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		ax25_disconnect(ax25, 0);
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		break;
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176
	case AX25_DM:
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		ax25_disconnect(ax25, ECONNRESET);
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		break;
179

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	case AX25_RR:
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	case AX25_RNR:
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		if (frametype == AX25_RR)
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			ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
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		else
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			ax25->condition |= AX25_COND_PEER_RX_BUSY;
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		if (type == AX25_COMMAND && pf)
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			ax25_std_enquiry_response(ax25);
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		if (ax25_validate_nr(ax25, nr)) {
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			ax25_check_iframes_acked(ax25, nr);
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		} else {
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			ax25_std_nr_error_recovery(ax25);
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			ax25->state = AX25_STATE_1;
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		}
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		break;
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	case AX25_REJ:
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		ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
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		if (type == AX25_COMMAND && pf)
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			ax25_std_enquiry_response(ax25);
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		if (ax25_validate_nr(ax25, nr)) {
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			ax25_frames_acked(ax25, nr);
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			ax25_calculate_rtt(ax25);
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			ax25_stop_t1timer(ax25);
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			ax25_start_t3timer(ax25);
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			ax25_requeue_frames(ax25);
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		} else {
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			ax25_std_nr_error_recovery(ax25);
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			ax25->state = AX25_STATE_1;
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		}
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		break;
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	case AX25_I:
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		if (!ax25_validate_nr(ax25, nr)) {
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			ax25_std_nr_error_recovery(ax25);
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			ax25->state = AX25_STATE_1;
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			break;
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		}
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		if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
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			ax25_frames_acked(ax25, nr);
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		} else {
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			ax25_check_iframes_acked(ax25, nr);
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		}
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		if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
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			if (pf) ax25_std_enquiry_response(ax25);
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			break;
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		}
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		if (ns == ax25->vr) {
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			ax25->vr = (ax25->vr + 1) % ax25->modulus;
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			queued = ax25_rx_iframe(ax25, skb);
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			if (ax25->condition & AX25_COND_OWN_RX_BUSY)
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				ax25->vr = ns;	/* ax25->vr - 1 */
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			ax25->condition &= ~AX25_COND_REJECT;
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			if (pf) {
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				ax25_std_enquiry_response(ax25);
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			} else {
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				if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
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					ax25->condition |= AX25_COND_ACK_PENDING;
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					ax25_start_t2timer(ax25);
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				}
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			}
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		} else {
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			if (ax25->condition & AX25_COND_REJECT) {
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				if (pf) ax25_std_enquiry_response(ax25);
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			} else {
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				ax25->condition |= AX25_COND_REJECT;
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				ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
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				ax25->condition &= ~AX25_COND_ACK_PENDING;
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			}
249
		}
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		break;
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252
	case AX25_FRMR:
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	case AX25_ILLEGAL:
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		ax25_std_establish_data_link(ax25);
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		ax25->state = AX25_STATE_1;
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		break;
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258
	default:
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		break;
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	}
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	return queued;
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}
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/*
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 *	State machine for state 4, Timer Recovery State.
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 *	The handling of the timer(s) is in file ax25_std_timer.c
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 *	Handling of state 0 and connection release is in ax25.c.
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 */
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static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
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{
272
	int queued = 0;
273

274
	switch (frametype) {
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	case AX25_SABM:
276
	case AX25_SABME:
277
		if (frametype == AX25_SABM) {
278
			ax25->modulus = AX25_MODULUS;
279
			ax25->window  = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
280
		} else {
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			ax25->modulus = AX25_EMODULUS;
282
			ax25->window  = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
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		}
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		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
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		ax25_stop_t1timer(ax25);
286
		ax25_stop_t2timer(ax25);
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		ax25_start_t3timer(ax25);
288
		ax25_start_idletimer(ax25);
289
		ax25->condition = 0x00;
290
		ax25->vs        = 0;
291
		ax25->va        = 0;
292
		ax25->vr        = 0;
293
		ax25->state     = AX25_STATE_3;
294
		ax25->n2count   = 0;
295
		ax25_requeue_frames(ax25);
296
		break;
297

298
	case AX25_DISC:
299
		ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
300
		ax25_disconnect(ax25, 0);
301
		break;
302

303
	case AX25_DM:
304
		ax25_disconnect(ax25, ECONNRESET);
305
		break;
306

307
	case AX25_RR:
308
	case AX25_RNR:
309
		if (frametype == AX25_RR)
310
			ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
311
		else
312
			ax25->condition |= AX25_COND_PEER_RX_BUSY;
313
		if (type == AX25_RESPONSE && pf) {
314
			ax25_stop_t1timer(ax25);
315
			ax25->n2count = 0;
316
			if (ax25_validate_nr(ax25, nr)) {
317
				ax25_frames_acked(ax25, nr);
318
				if (ax25->vs == ax25->va) {
319
					ax25_start_t3timer(ax25);
320
					ax25->state   = AX25_STATE_3;
321
				} else {
322
					ax25_requeue_frames(ax25);
323
				}
324
			} else {
325
				ax25_std_nr_error_recovery(ax25);
326
				ax25->state = AX25_STATE_1;
327
			}
328
			break;
329
		}
330
		if (type == AX25_COMMAND && pf)
331
			ax25_std_enquiry_response(ax25);
332
		if (ax25_validate_nr(ax25, nr)) {
333
			ax25_frames_acked(ax25, nr);
334
		} else {
335
			ax25_std_nr_error_recovery(ax25);
336
			ax25->state = AX25_STATE_1;
337
		}
338
		break;
339

340
	case AX25_REJ:
341
		ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
342
		if (pf && type == AX25_RESPONSE) {
343
			ax25_stop_t1timer(ax25);
344
			ax25->n2count = 0;
345
			if (ax25_validate_nr(ax25, nr)) {
346
				ax25_frames_acked(ax25, nr);
347
				if (ax25->vs == ax25->va) {
348
					ax25_start_t3timer(ax25);
349
					ax25->state   = AX25_STATE_3;
350
				} else {
351
					ax25_requeue_frames(ax25);
352
				}
353
			} else {
354
				ax25_std_nr_error_recovery(ax25);
355
				ax25->state = AX25_STATE_1;
356
			}
357
			break;
358
		}
359
		if (type == AX25_COMMAND && pf)
360
			ax25_std_enquiry_response(ax25);
361
		if (ax25_validate_nr(ax25, nr)) {
362
			ax25_frames_acked(ax25, nr);
363
			ax25_requeue_frames(ax25);
364
		} else {
365
			ax25_std_nr_error_recovery(ax25);
366
			ax25->state = AX25_STATE_1;
367
		}
368
		break;
369

370
	case AX25_I:
371
		if (!ax25_validate_nr(ax25, nr)) {
372
			ax25_std_nr_error_recovery(ax25);
373
			ax25->state = AX25_STATE_1;
374
			break;
375
		}
376
		ax25_frames_acked(ax25, nr);
377
		if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
378
			if (pf)
379
				ax25_std_enquiry_response(ax25);
380
			break;
381
		}
382
		if (ns == ax25->vr) {
383
			ax25->vr = (ax25->vr + 1) % ax25->modulus;
384
			queued = ax25_rx_iframe(ax25, skb);
385
			if (ax25->condition & AX25_COND_OWN_RX_BUSY)
386
				ax25->vr = ns;	/* ax25->vr - 1 */
387
			ax25->condition &= ~AX25_COND_REJECT;
388
			if (pf) {
389
				ax25_std_enquiry_response(ax25);
390
			} else {
391
				if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
392
					ax25->condition |= AX25_COND_ACK_PENDING;
393
					ax25_start_t2timer(ax25);
394
				}
395
			}
396
		} else {
397
			if (ax25->condition & AX25_COND_REJECT) {
398
				if (pf) ax25_std_enquiry_response(ax25);
399
			} else {
400
				ax25->condition |= AX25_COND_REJECT;
401
				ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
402
				ax25->condition &= ~AX25_COND_ACK_PENDING;
403
			}
404
		}
405
		break;
406

407
	case AX25_FRMR:
408
	case AX25_ILLEGAL:
409
		ax25_std_establish_data_link(ax25);
410
		ax25->state = AX25_STATE_1;
411
		break;
412

413
	default:
414
		break;
415
	}
416

417
	return queued;
418
}
419

420
/*
421
 *	Higher level upcall for a LAPB frame
422
 */
423
int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
424
{
425
	int queued = 0, frametype, ns, nr, pf;
426

427
	frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
428

429
	switch (ax25->state) {
430
	case AX25_STATE_1:
431
		queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type);
432
		break;
433
	case AX25_STATE_2:
434
		queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type);
435
		break;
436
	case AX25_STATE_3:
437
		queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
438
		break;
439
	case AX25_STATE_4:
440
		queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type);
441
		break;
442
	}
443

444
	ax25_kick(ax25);
445

446
	return queued;
447
}
448

449
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