q921.c

Q.931/Q.921 source code compiles

	/* Discard anything waiting to go out */
	q921_discard_retransmissions(pri);
}

static void q921_tei_release_and_reacquire(struct pri *master)
{
	/* Make sure the master is passed into this function */
	q921_dchannel_down(master->subchannel);
	__pri_free_tei(master->subchannel);
	master->subchannel = NULL;
	master->ev.gen.e = PRI_EVENT_DCHAN_DOWN;
	master->schedev = 1;
	q921_start(master, master->localtype == PRI_CPE);
}

static pri_event *q921_receive_MDL(struct pri *pri, q921_u *h, int len)
{
	int ri;
	struct pri *sub;
	int tei;
	if (pri->debug & PRI_DEBUG_Q921_STATE)
		pri_message(pri, "Received MDL message\n");
	if (h->data[0] != 0x0f) {
		pri_error(pri, "Received MDL with unsupported management entity %02x\n", h->data[0]);
		return NULL;
	}
	if (!(h->data[4] & 0x01)) {
		pri_error(pri, "Received MDL with multibyte TEI identifier\n");
		return NULL;
	}
	ri = (h->data[1] << 8) | h->data[2];
	tei = (h->data[4] >> 1);
	switch(h->data[3]) {
	case Q921_TEI_IDENTITY_REQUEST:
		if (tei != 127) {
			pri_error(pri, "Received TEI identity request with invalid TEI %d\n", tei);
			q921_send_tei(pri, Q921_TEI_IDENTITY_DENIED, ri, tei, 1);
		}
		/* Go to master */
		for (sub = pri; sub->master; sub = sub->master);
		tei = 64;
		while(sub->subchannel) {
			if(sub->subchannel->tei == tei)
				++tei;
		}
		sub->subchannel = __pri_new_tei(-1, pri->localtype, pri->switchtype, pri, NULL, NULL, NULL, tei, 1);
		if (!sub->subchannel) {
			pri_error(pri, "Unable to allocate D-channel for new TEI %d\n", tei);
			return NULL;
		}
		q921_send_tei(pri, Q921_TEI_IDENTITY_ASSIGNED, ri, tei, 1);
		break;
	case Q921_TEI_IDENTITY_ASSIGNED:
		if (ri != pri->ri) {
			pri_message(pri, "TEI assignment received for invalid Ri %02x (our is %02x)\n", ri, pri->ri);
			return NULL;
		}
		if (pri->t202_timer) {
			pri_schedule_del(pri, pri->t202_timer);
			pri->t202_timer = 0;
		}
		if (pri->subchannel && (pri->subchannel->tei == tei)) {
			pri_error(pri, "TEI already assigned (new is %d, current is %d)\n", tei, pri->subchannel->tei);
			q921_tei_release_and_reacquire(pri);
			return NULL;
		}

		pri_message(pri, "TEI assiged to %d\n", tei);
		pri->subchannel = __pri_new_tei(-1, pri->localtype, pri->switchtype, pri, NULL, NULL, NULL, tei, 1);
		if (!pri->subchannel) {
			pri_error(pri, "Unable to allocate D-channel for new TEI %d\n", tei);
			return NULL;
		}
		pri->q921_state = Q921_TEI_ASSIGNED;
		break;
	case Q921_TEI_IDENTITY_CHECK_REQUEST:
		/* We're assuming one TEI per PRI in TE PTMP mode */

		/* If no subchannel (TEI) ignore */
		if (!pri->subchannel)
			return NULL;

		/* If it's addressed to the group TEI or to our TEI specifically, we respond */
		if ((tei == Q921_TEI_GROUP) || (tei == pri->subchannel->tei))
			q921_send_tei(pri, Q921_TEI_IDENTITY_CHECK_RESPONSE, random() % 65535, pri->subchannel->tei, 1);

		break;
	case Q921_TEI_IDENTITY_REMOVE:
		/* XXX: Assuming multiframe mode has been disconnected already */
		if (!pri->subchannel)
			return NULL;

		if ((tei == Q921_TEI_GROUP) || (tei == pri->subchannel->tei)) {
			q921_tei_release_and_reacquire(pri);
		}
	}
	return NULL;	/* Do we need to return something??? */
}

static int is_command(struct pri *pri, q921_h *h)
{
	int	command =0;
	int c_r = h->s.h.c_r;

	if ((pri->localtype == PRI_NETWORK && c_r == 0) ||
		(pri->localtype == PRI_CPE && c_r == 1))
		command = 1;

	return( command );
}

static pri_event *__q921_receive_qualified(struct pri *pri, q921_h *h, int len)
{
	q921_frame *f;
	pri_event *ev;
	int sendnow;

	switch(h->h.data[0] & Q921_FRAMETYPE_MASK) {
	case 0:
	case 2:
		if (pri->q921_state != Q921_LINK_CONNECTION_ESTABLISHED) {
			pri_error(pri, "!! Got I-frame while link state %d\n", pri->q921_state);
			return NULL;
		}
		/* Informational frame */
		if (len < 4) {
			pri_error(pri, "!! Received short I-frame (expected 4, got %d)\n", len);
			break;
		}
		return q921_handle_iframe(pri, &h->i, len);	
		break;
	case 1:
		if (pri->q921_state != Q921_LINK_CONNECTION_ESTABLISHED) {
			pri_error(pri, "!! Got S-frame while link down\n");
			return NULL;
		}
		if (len < 4) {
			pri_error(pri, "!! Received short S-frame (expected 4, got %d)\n", len);
			break;
		}
		switch(h->s.ss) {
		case 0:
			/* Receiver Ready */
			pri->busy = 0;
			/* Acknowledge frames as necessary */
			ev = q921_ack_rx(pri, h->s.n_r, 1);
			if (ev)
				return ev;
			if (is_command(pri, h))
				pri->solicitfbit = 0;
			if (h->s.p_f) {
				/* If it's a p/f one then send back a RR in return with the p/f bit set */
				if (!is_command(pri, h)) {
					if (pri->debug & PRI_DEBUG_Q921_DUMP)
						pri_message(pri, "-- Got RR response to our frame\n");
					pri->retrans = 0;
				} else {
					if (pri->debug & PRI_DEBUG_Q921_DUMP)
						pri_message(pri, "-- Unsolicited RR with P/F bit, responding\n");
						q921_rr(pri, 1, 0);
				}
			}
			break;
 		case 1:
 			/* Receiver not ready */
 			if (pri->debug & PRI_DEBUG_Q921_STATE)
 				pri_message(pri, "-- Got receiver not ready\n");
 			pri->busy = 1;
			ev = q921_ack_rx(pri, h->s.n_r, 0);
			if (ev)
				return ev;
			if (h->s.p_f && is_command(pri, h))
				q921_rr(pri, 1, 0);
			pri->solicitfbit = 1;
			pri->retrans = 0;
			if (pri->t203_timer) {
				if (pri->debug & PRI_DEBUG_Q921_DUMP)
					pri_message(pri, "Stopping T_203 timer\n");
				pri_schedule_del(pri, pri->t203_timer);
				pri->t203_timer = 0;
			}
			if (pri->debug & PRI_DEBUG_Q921_DUMP)
				pri_message(pri, "Restarting T_200 timer\n");
			reschedule_t200(pri);			
 			break;   
 		case 2:
 			/* Just retransmit */
 			if (pri->debug & PRI_DEBUG_Q921_STATE)
 				pri_message(pri, "-- Got reject requesting packet %d...  Retransmitting.\n", h->s.n_r);
			if (pri->busy && !is_command(pri, h))
				pri->solicitfbit = 0;
			pri->busy = 0;
			if (is_command(pri, h) && h->s.p_f)
					q921_rr(pri, 1, 0);
			q921_ack_rx(pri, h->s.n_r, 0);
			/*Resend only if we are in the Multiple Frame Established state or when
			  we are in the Time Recovery state and received responce with bit F=1*/
			if ((pri->solicitfbit == 0) || (pri->solicitfbit && !is_command(pri, h) && h->s.p_f)) {
				pri->solicitfbit = 0;
				pri->retrans = 0;
				sendnow = 0;
				/* Resend I-frames starting from frame where f->h.n_s == h->s.n_r */
				for (f = pri->txqueue; f && (f->h.n_s != h->s.n_r); f = f->next);
				while (f) {
					sendnow = 1;
					if (f->transmitted || (!f->transmitted && (pri->windowlen < pri->window))) {
			 			if (pri->debug & PRI_DEBUG_Q921_STATE)
							pri_error(pri, "!! Got reject for frame %d, retransmitting frame %d now, updating n_r!\n", h->s.n_r, f->h.n_s);
						f->h.n_r = pri->v_r;
						f->h.p_f = 0;
						if (!f->transmitted && (pri->windowlen < pri->window))
							pri->windowlen++;
						q921_transmit(pri, (q921_h *)(&f->h), f->len);
					}
					f = f->next; 
				} 
				if (!sendnow) {
					if (pri->txqueue) {
						/* This should never happen */
						if (!h->s.p_f || h->s.n_r) {
							pri_error(pri, "!! Got reject for frame %d, but we only have others!\n", h->s.n_r);
						}
					} else {
						/* Hrm, we have nothing to send, but have been REJ'd.  Reset v_a, v_s, etc */
						pri_error(pri, "!! Got reject for frame %d, but we have nothing -- resetting!\n", h->s.n_r);
						pri->v_a = h->s.n_r;
						pri->v_s = h->s.n_r;
					}
				}
				/* Reset t200 timer if it was somehow going */
				if (pri->t200_timer) {
					pri_schedule_del(pri, pri->t200_timer);
					pri->t200_timer = 0;
				}
				/* Reset and restart t203 timer */
				reschedule_t203(pri);
			}
 			break;
		default:
			pri_error(pri, "!! XXX Unknown Supervisory frame ss=0x%02x,pf=%02xnr=%02x vs=%02x, va=%02x XXX\n", h->s.ss, h->s.p_f, h->s.n_r,
					pri->v_s, pri->v_a);
		}
		break;
	case 3:
		if (len < 3) {
			pri_error(pri, "!! Received short unnumbered frame\n");
			break;
		}
		switch(h->u.m3) {
		case 0:
			if (h->u.m2 == 3) {
				if (h->u.p_f) {
					/* Section 5.7.1 says we should restart on receiving a DM response with the f-bit set to
					   one, but we wait T200 first */
					if (pri->debug & (PRI_DEBUG_Q921_STATE | PRI_DEBUG_Q921_DUMP))
						pri_message(pri, "-- Got DM Mode from peer.\n");
					/* Disconnected mode, try again after T200 */
					ev = q921_dchannel_down(pri);
					q921_restart(pri, 0);
					return ev;
						
				} else {
					if (pri->debug & PRI_DEBUG_Q921_DUMP)
						pri_message(pri, "-- Ignoring unsolicited DM with p/f set to 0\n");
#if 0
					/* Requesting that we start */
					q921_restart(pri, 0);
#endif					
				}
				break;
			} else if (!h->u.m2) {
				if ((pri->sapi == Q921_SAPI_LAYER2_MANAGEMENT) && (pri->tei == Q921_TEI_GROUP))
					q921_receive_MDL(pri, (q921_u *)h, len);
				else {
					int res;

					res = q931_receive(pri, (q931_h *) h->u.data, len - 3);
					if (res == -1) {
						return NULL;
					}
					if (res & Q931_RES_HAVEEVENT)
						return &pri->ev;
				}
			}
			break;
		case 2:
			if (pri->debug & (PRI_DEBUG_Q921_STATE | PRI_DEBUG_Q921_DUMP))
				pri_message(pri, "-- Got Disconnect from peer.\n");
			/* Acknowledge */
			q921_send_ua(pri, h->u.p_f);
			ev = q921_dchannel_down(pri);
			q921_restart(pri, 0);
			return ev;
		case 3:
			if (h->u.m2 == 3) {
				/* SABME */
				if (pri->debug & (PRI_DEBUG_Q921_STATE | PRI_DEBUG_Q921_DUMP)) {
					pri_message(pri, "-- Got SABME from %s peer.\n", h->h.c_r ? "network" : "cpe");
				}
				if (h->h.c_r) {
					pri->remotetype = PRI_NETWORK;
					if (pri->localtype == PRI_NETWORK) {
						/* We can't both be networks */
						return pri_mkerror(pri, "We think we're the network, but they think they're the network, too.");
					}
				} else {
					pri->remotetype = PRI_CPE;
					if (pri->localtype == PRI_CPE) {
						/* We can't both be CPE */
						return pri_mkerror(pri, "We think we're the CPE, but they think they're the CPE too.\n");
					}
				}
				/* Send Unnumbered Acknowledgement */
				q921_send_ua(pri, h->u.p_f);
				return q921_dchannel_up(pri);
			} else if (h->u.m2 == 0) {
					/* It's a UA */
				if (pri->q921_state == Q921_AWAITING_ESTABLISH) {
					if (pri->debug & (PRI_DEBUG_Q921_STATE | PRI_DEBUG_Q921_DUMP)) {
						pri_message(pri, "-- Got UA from %s peer  Link up.\n", h->h.c_r ? "cpe" : "network");
					}
					return q921_dchannel_up(pri);
				} else if ((pri->q921_state >= Q921_TEI_ASSIGNED) && pri->bri) {
					/* Possible duplicate TEI assignment */
					if (pri->master)
						q921_tei_release_and_reacquire(pri->master);
					else
						pri_error(pri, "Huh!? no master found\n");
				} else {
					/* Since we're not in the AWAITING_ESTABLISH STATE, it's unsolicited */
					pri_error(pri, "!! Got a UA, but i'm in state %d\n", pri->q921_state);

				}
			} else 
				pri_error(pri, "!! Weird frame received (m3=3, m2 = %d)\n", h->u.m2);
			break;
		case 4:
			pri_error(pri, "!! Frame got rejected!\n");
			break;
		case 5:
			pri_error(pri, "!! XID frames not supported\n");
			break;
		default:
			pri_error(pri, "!! Don't know what to do with M3=%d u-frames\n", h->u.m3);
		}
		break;
				
	}
	return NULL;
}

static pri_event *__q921_receive(struct pri *pri, q921_h *h, int len)
{
	pri_event *ev;
	/* Discard FCS */
	len -= 2;
	
	if (!pri->master && pri->debug & (PRI_DEBUG_Q921_DUMP | PRI_DEBUG_Q921_RAW))
		q921_dump(pri, h, len, pri->debug & PRI_DEBUG_Q921_RAW, 0);

	/* Check some reject conditions -- Start by rejecting improper ea's */
	if (h->h.ea1 || !(h->h.ea2))
		return NULL;

#if 0 /* Will be rejected by subchannel analyzis */
	/* Check for broadcasts - not yet handled */
	if (h->h.tei == Q921_TEI_GROUP)
		return NULL;
#endif

	if (!((h->h.sapi == pri->sapi) && ((h->h.tei == pri->tei) || (h->h.tei == Q921_TEI_GROUP)))) {
		/* Check for SAPIs we don't yet handle */
		/* If it's not us, try any subchannels we have */
		if (pri->subchannel)
			return q921_receive(pri->subchannel, h, len + 2);
		else {
			return NULL;
		}

	}
	if (pri->debug & PRI_DEBUG_Q921_DUMP)
		pri_message(pri, "Handling message for SAPI/TEI=%d/%d\n", h->h.sapi, h->h.tei);
	ev = __q921_receive_qualified(pri, h, len);
	reschedule_t203(pri);
	return ev;
}

pri_event *q921_receive(struct pri *pri, q921_h *h, int len)
{
	pri_event *e;
	e = __q921_receive(pri, h, len);
#ifdef LIBPRI_COUNTERS
	pri->q921_rxcount++;
#endif
	return e;
}

static void q921_restart(struct pri *pri, int now)
{
	if (pri->q921_state != Q921_LINK_CONNECTION_RELEASED) {
		pri_error(pri, "!! q921_start: Not in 'Link Connection Released' state\n");
		return;
	}
	/* Reset our interface */
	q921_reset(pri);
	/* Do the SABME XXX Maybe we should implement T_WAIT? XXX */
	q921_send_sabme(pri, now);
}

void q921_start(struct pri *pri, int isCPE)
{
	q921_reset(pri);
	if ((pri->sapi == Q921_SAPI_LAYER2_MANAGEMENT) && (pri->tei == Q921_TEI_GROUP)) {
		pri->q921_state = Q921_DOWN;
		if (isCPE)
			q921_tei_request(pri);
	} else {
		q921_send_sabme(pri, isCPE);
	}
}