q921.c

Q.931/Q.921 source code compiles

/*
 * libpri: An implementation of Primary Rate ISDN
 *
 * Written by Mark Spencer <[e-mail]>
 *
 * Copyright (C) 2001-2005, Digium, Inc.
 * All Rights Reserved.
 */

/*
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2 as published by the
 * Free Software Foundation. See the LICENSE file included with
 * this program for more details.
 *
 * In addition, when this program is distributed with Asterisk in
 * any form that would qualify as a 'combined work' or as a
 * 'derivative work' (but not mere aggregation), you can redistribute
 * and/or modify the combination under the terms of the license
 * provided with that copy of Asterisk, instead of the license
 * terms granted here.
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include "compat.h"
#include "libpri.h"
#include "pri_internal.h"
#include "pri_q921.h" 
#include "pri_q931.h"

/*
 * Define RANDOM_DROPS To randomly drop packets in order to simulate loss for testing
 * retransmission functionality
 */

/*
#define RANDOM_DROPS
*/

#define Q921_INIT(pri, hf) do { \
	memset(&(hf),0,sizeof(hf)); \
	(hf).h.sapi = (pri)->sapi; \
	(hf).h.ea1 = 0; \
	(hf).h.ea2 = 1; \
	(hf).h.tei = (pri)->tei; \
} while(0)

static void reschedule_t203(struct pri *pri);
static void reschedule_t200(struct pri *pri);
static void q921_restart(struct pri *pri, int now);
static void q921_tei_release_and_reacquire(struct pri *master);

static void q921_discard_retransmissions(struct pri *pri)
{
	struct q921_frame *f, *p;
	f = pri->txqueue;
	while(f) {
		p = f;
		f = f->next;
		/* Free frame */
		free(p);
	}
	pri->txqueue = NULL;
}

static int q921_transmit(struct pri *pri, q921_h *h, int len) 
{
	int res;

	if (pri->master)
		pri = pri->master;

#ifdef RANDOM_DROPS
   if (!(random() % 3)) {
         pri_message(pri, " === Dropping Packet ===\n");
         return 0;
   }
#endif   
#ifdef LIBPRI_COUNTERS
	pri->q921_txcount++;      
#endif
	/* Just send it raw */
	if (pri->debug & (PRI_DEBUG_Q921_DUMP | PRI_DEBUG_Q921_RAW))
		q921_dump(pri, h, len, pri->debug & PRI_DEBUG_Q921_RAW, 1);
	/* Write an extra two bytes for the FCS */
	res = pri->write_func ? pri->write_func(pri, h, len + 2) : 0;
	if (res != (len + 2)) {
		pri_error(pri, "Short write: %d/%d (%s)\n", res, len + 2, strerror(errno));
		return -1;
	}
	return 0;
}

static void q921_send_tei(struct pri *pri, int message, int ri, int ai, int iscommand)
{
	q921_u *f;

	if (!(f = calloc(1, sizeof(*f) + 5)))
		return;

	Q921_INIT(pri, *f);
	f->h.c_r = (pri->localtype == PRI_NETWORK) ? iscommand : !iscommand;
	f->ft = Q921_FRAMETYPE_U;
	f->data[0] = 0x0f;	/* Management entity */
	f->data[1] = (ri >> 8) & 0xff;
	f->data[2] = ri & 0xff;
	f->data[3] = message;
	f->data[4] = (ai << 1) | 1;
	if (pri->debug & PRI_DEBUG_Q921_STATE)
		pri_message(pri, "Sending TEI management message %d, TEI=%d\n", message, ai);
	q921_transmit(pri, (q921_h *)f, 8);
	free(f);
}

static void q921_tei_request(void *vpri)
{
	struct pri *pri = (struct pri *)vpri;

	if (pri->subchannel) {
		pri_error(pri, "Cannot request TEI while its already assigned\n");
		return;
	}
	pri->n202_counter++;
#if 0
	if (pri->n202_counter > pri->timers[PRI_TIMER_N202]) {
		pri_error(pri, "Unable to assign TEI from network\n");
		return;
	}
#endif
	pri->ri = random() % 65535;
	q921_send_tei(pri, Q921_TEI_IDENTITY_REQUEST, pri->ri, Q921_TEI_GROUP, 1);
	if (pri->t202_timer)
		pri_schedule_del(pri, pri->t202_timer);
	pri->t202_timer = pri_schedule_event(pri, pri->timers[PRI_TIMER_T202], q921_tei_request, pri);
}

static void q921_send_ua(struct pri *pri, int pfbit)
{
	q921_h h;
	Q921_INIT(pri, h);
	h.u.m3 = 3;		/* M3 = 3 */
	h.u.m2 = 0;		/* M2 = 0 */
	h.u.p_f = pfbit;	/* Final bit on */
	h.u.ft = Q921_FRAMETYPE_U;
	switch(pri->localtype) {
	case PRI_NETWORK:
		h.h.c_r = 0;
		break;
	case PRI_CPE:
		h.h.c_r = 1;
		break;
	default:
		pri_error(pri, "Don't know how to U/A on a type %d node\n", pri->localtype);
		return;
	}
	if (pri->debug & (PRI_DEBUG_Q921_STATE | PRI_DEBUG_Q921_DUMP))
		pri_message(pri, "Sending Unnumbered Acknowledgement\n");
	q921_transmit(pri, &h, 3);
}

static void q921_send_sabme_now(void *vpri);

static void q921_send_sabme(void *vpri, int now)
{
	struct pri *pri = vpri;
	q921_h h;
	pri_schedule_del(pri, pri->sabme_timer);
	pri->sabme_timer = 0;
	pri->sabme_timer = pri_schedule_event(pri, pri->timers[PRI_TIMER_T200], q921_send_sabme_now, pri);
	if (!now)
		return;
	Q921_INIT(pri, h);
	h.u.m3 = 3;	/* M3 = 3 */
	h.u.m2 = 3;	/* M2 = 3 */
	h.u.p_f = 1;	/* Poll bit set */
	h.u.ft = Q921_FRAMETYPE_U;
	switch(pri->localtype) {
	case PRI_NETWORK:
		h.h.c_r = 1;
		break;
	case PRI_CPE:
		h.h.c_r = 0;
		break;
	default:
		pri_error(pri, "Don't know how to U/A on a type %d node\n", pri->localtype);
		return;
	}
	if (pri->bri && (pri->state == Q921_AWAITING_ESTABLISH)) {
		if (pri->sabme_count >= pri->timers[PRI_TIMER_N200]) {
			pri_schedule_del(pri, pri->sabme_timer);
			pri->sabme_timer = 0;
			q921_tei_release_and_reacquire(pri->master);
		} else {
			pri->sabme_count++;
		}
	}
	if (pri->debug & (PRI_DEBUG_Q921_STATE | PRI_DEBUG_Q921_DUMP))
		pri_message(pri, "Sending Set Asynchronous Balanced Mode Extended\n");
	q921_transmit(pri, &h, 3);
	if (pri->debug & PRI_DEBUG_Q921_STATE && pri->q921_state != Q921_AWAITING_ESTABLISH)
		pri_message(pri, DBGHEAD "q921_state now is Q921_AWAITING_ESTABLISH\n", DBGINFO);
	pri->q921_state = Q921_AWAITING_ESTABLISH;
}

static void q921_send_sabme_now(void *vpri)
{
	q921_send_sabme(vpri, 1);
}

static int q921_ack_packet(struct pri *pri, int num)
{
	struct q921_frame *f, *prev = NULL;
	f = pri->txqueue;
	while(f) {
		if (f->h.n_s == num) {
			/* Cancel each packet as necessary */
			/* That's our packet */
			if (prev)
				prev->next = f->next;
			else
				pri->txqueue = f->next;
			if (pri->debug & PRI_DEBUG_Q921_DUMP)
				pri_message(pri, "-- ACKing packet %d, new txqueue is %d (-1 means empty)\n", f->h.n_s, pri->txqueue ? pri->txqueue->h.n_s : -1);
			/* Update v_a */
			pri->v_a = num;
			free(f);
			/* Reset retransmission counter if we actually acked something */
			pri->retrans = 0;
			/* Decrement window size */
			pri->windowlen--;
			return 1;
		}
		prev = f;
		f = f->next;
	}
	return 0;
}

static void t203_expire(void *);
static void t200_expire(void *);
static pri_event *q921_dchannel_down(struct pri *pri);

static void reschedule_t200(struct pri *pri)
{
	if (pri->debug & PRI_DEBUG_Q921_DUMP)
		pri_message(pri, "-- Restarting T200 timer\n");
	if (pri->t200_timer)
		pri_schedule_del(pri, pri->t200_timer);
	pri->t200_timer = pri_schedule_event(pri, pri->timers[PRI_TIMER_T200], t200_expire, pri);
}

static void reschedule_t203(struct pri *pri)
{
	if (pri->debug & PRI_DEBUG_Q921_DUMP)
		pri_message(pri, "-- Restarting T203 timer\n");
	if (pri->t203_timer) 
		pri_schedule_del(pri, pri->t203_timer);
	pri->t203_timer = pri_schedule_event(pri, pri->timers[PRI_TIMER_T203], t203_expire, pri);
}

static pri_event *q921_ack_rx(struct pri *pri, int ack, int send_untransmitted_frames)
{
	int x;
	int cnt=0;
	pri_event *ev;
	struct q921_frame *f;
	/* Make sure the ACK was within our window */
	for (x=pri->v_a; (x != pri->v_s) && (x != ack); Q921_INC(x));
	if (x != ack) {
		/* ACK was outside of our window --- ignore */
		pri_error(pri, "ACK received for '%d' outside of window of '%d' to '%d', restarting\n", ack, pri->v_a, pri->v_s);
		ev = q921_dchannel_down(pri);
		q921_start(pri, 1);
		pri->schedev = 1;
		return ev;
	}
	/* Cancel each packet as necessary */
	if (pri->debug & PRI_DEBUG_Q921_DUMP)
		pri_message(pri, "-- ACKing all packets from %d to (but not including) %d\n", pri->v_a, ack);
	for (x=pri->v_a; x != ack; Q921_INC(x)) 
		cnt += q921_ack_packet(pri, x);	
	if (!pri->txqueue) {
		if (pri->debug & PRI_DEBUG_Q921_DUMP)
			pri_message(pri, "-- Since there was nothing left, stopping T200 counter\n");
		/* Something was ACK'd.  Stop T200 counter */
		if (pri->t200_timer) {
			pri_schedule_del(pri, pri->t200_timer);
			pri->t200_timer = 0;
		}
	}
	if (pri->t203_timer) {
		if (pri->debug & PRI_DEBUG_Q921_DUMP)
			pri_message(pri, "-- Stopping T203 counter since we got an ACK\n");
		pri_schedule_del(pri, pri->t203_timer);
		pri->t203_timer = 0;
	}
	if (pri->txqueue) {
		/* Something left to transmit, Start the T200 counter again if we stopped it */
		if (!pri->busy && send_untransmitted_frames) {
			pri->retrans = 0;
			/* Search for something to send */
			f = pri->txqueue;
			while(f && (pri->windowlen < pri->window)) {
				if (!f->transmitted) {
					/* Send it now... */
					if (pri->debug & PRI_DEBUG_Q921_DUMP)
						pri_message(pri, "-- Finally transmitting %d, since window opened up (%d)\n", f->h.n_s, pri->windowlen);
					f->transmitted++;
					pri->windowlen++;
					f->h.n_r = pri->v_r;
					f->h.p_f = 0;
					q921_transmit(pri, (q921_h *)(&f->h), f->len);
				}
				f = f->next;
			}
		}
		if (pri->debug & PRI_DEBUG_Q921_DUMP)
			pri_message(pri, "-- Waiting for acknowledge, restarting T200 counter\n");		
		reschedule_t200(pri);
	} else {
		if (pri->debug & PRI_DEBUG_Q921_DUMP)
			pri_message(pri, "-- Nothing left, starting T203 counter\n");
		/* Nothing to transmit, start the T203 counter instead */
		pri->t203_timer = pri_schedule_event(pri, pri->timers[PRI_TIMER_T203], t203_expire, pri);
	}
	return NULL;
}

static void q921_reject(struct pri *pri, int pf)
{
	q921_h h;
	Q921_INIT(pri, h);
	h.s.x0 = 0;	/* Always 0 */
	h.s.ss = 2;	/* Reject */
	h.s.ft = 1;	/* Frametype (01) */
	h.s.n_r = pri->v_r;	/* Where to start retransmission */
	h.s.p_f = pf;	
	switch(pri->localtype) {
	case PRI_NETWORK:
		h.h.c_r = 0;
		break;
	case PRI_CPE:
		h.h.c_r = 1;
		break;
	default:
		pri_error(pri, "Don't know how to U/A on a type %d node\n", pri->localtype);
		return;
	}
	if (pri->debug & PRI_DEBUG_Q921_DUMP)
		pri_message(pri, "Sending Reject (%d)\n", pri->v_r);
	pri->sentrej = 1;
	q921_transmit(pri, &h, 4);
}

static void q921_rr(struct pri *pri, int pbit, int cmd) {
	q921_h h;
	Q921_INIT(pri, h);
	h.s.x0 = 0;	/* Always 0 */
	h.s.ss = 0; /* Receive Ready */
	h.s.ft = 1;	/* Frametype (01) */
	h.s.n_r = pri->v_r;	/* N/R */
	h.s.p_f = pbit;		/* Poll/Final set appropriately */
	switch(pri->localtype) {
	case PRI_NETWORK:
		if (cmd)
			h.h.c_r = 1;
		else
			h.h.c_r = 0;
		break;
	case PRI_CPE:
		if (cmd)
			h.h.c_r = 0;
		else
			h.h.c_r = 1;
		break;
	default:
		pri_error(pri, "Don't know how to U/A on a type %d node\n", pri->localtype);
		return;
	}
	pri->v_na = pri->v_r;	/* Make a note that we've already acked this */
	if (pri->debug & PRI_DEBUG_Q921_DUMP)
		pri_message(pri, "Sending Receiver Ready (%d)\n", pri->v_r);
	q921_transmit(pri, &h, 4);
}

static void t200_expire(void *vpri)
{
	struct pri *pri = vpri;
	q921_frame *f, *lastframe=NULL;

	if (pri->txqueue) {
		/* Retransmit first packet in the queue, setting the poll bit */
		if (pri->debug & PRI_DEBUG_Q921_DUMP)
			pri_message(pri, "-- T200 counter expired, What to do...\n");
		pri->solicitfbit = 1;
		/* Up to three retransmissions */
		if (pri->retrans < pri->timers[PRI_TIMER_N200]) {
			pri->retrans++;
			/* Reschedule t200_timer */
			if (pri->debug & PRI_DEBUG_Q921_DUMP)
				pri_message(pri, "-- Retransmitting %d bytes\n", pri->txqueue->len);
			if (pri->busy) 
				q921_rr(pri, 1, 1);
			else {
				if (!pri->txqueue->transmitted) 
					pri_error(pri, "!! Not good - head of queue has not been transmitted yet\n");
				/*Actually we need to retransmit the last transmitted packet, setting the poll bit */
				for (f=pri->txqueue; f; f = f->next) {
					if (f->transmitted)
						lastframe = f;
				}
				if (lastframe) {
					/* Force Poll bit */