q921.c

This a software PBX driver

		Q921_INC(pri->v_r);
		/* Handle their ACK */
		pri->sentrej = 0;
		ev = q921_ack_rx(pri, i->n_r);
		if (ev)
			return ev;
		if (i->p_f) {
			/* If the Poll/Final bit is set, immediate send the RR */
			q921_rr(pri, 1, 0);
		} else if (pri->busy) {
			q921_rr(pri, 0, 0);
		}
		/* Receive Q.931 data */
		res = q931_receive(pri, (q931_h *)i->data, len - 4);
		/* Send an RR if one wasn't sent already */
		if (pri->v_na != pri->v_r) 
			q921_rr(pri, 0, 0);
		if (res == -1) {
			return NULL;
		}
		if (res & Q931_RES_HAVEEVENT)
			return &pri->ev;
	} else {
		/* If we haven't already sent a reject, send it now, otherwise
		   we are obliged to RR */
		if (!pri->sentrej)
			q921_reject(pri, i->p_f);
		else if (i->p_f)
			q921_rr(pri, 1, 0);
	}
	return NULL;
}

void q921_dump(q921_h *h, int len, int showraw, int txrx)
{
	int x;
        char *type;
	char direction_tag;
	
	direction_tag = txrx ? '>' : '<';
	if (showraw) {
		char *buf = malloc(len * 3 + 1);
		int buflen = 0;
		if (buf) {
			for (x=0;x<len;x++) 
				buflen += sprintf(buf + buflen, "%02x ", h->raw[x]);
			pri_message("\n%c [ %s]\n", direction_tag, buf);
			free(buf);
		}
	}

	switch (h->h.data[0] & Q921_FRAMETYPE_MASK) {
	case 0:
	case 2:
		pri_message("\n%c Informational frame:\n", direction_tag);
		break;
	case 1:
		pri_message("\n%c Supervisory frame:\n", direction_tag);
		break;
	case 3:
		pri_message("\n%c Unnumbered frame:\n", direction_tag);
		break;
	}
	
	pri_message(
"%c SAPI: %02d  C/R: %d EA: %d\n"
"%c  TEI: %03d        EA: %d\n", 
    	direction_tag,
	h->h.sapi, 
	h->h.c_r,
	h->h.ea1,
    	direction_tag,
	h->h.tei,
	h->h.ea2);
	switch (h->h.data[0] & Q921_FRAMETYPE_MASK) {
	case 0:
	case 2:
		/* Informational frame */
		pri_message(
"%c N(S): %03d   0: %d\n"
"%c N(R): %03d   P: %d\n"
"%c %d bytes of data\n",
    	direction_tag,
	h->i.n_s,
	h->i.ft,
    	direction_tag,
	h->i.n_r,
	h->i.p_f, 
    	direction_tag,
	len - 4);
		break;
	case 1:
		/* Supervisory frame */
		type = "???";
		switch (h->s.ss) {
		case 0:
			type = "RR (receive ready)";
			break;
		case 1:
			type = "RNR (receive not ready)";
			break;
		case 2:
			type = "REJ (reject)";
			break;
		}
		pri_message(
"%c Zero: %d     S: %d 01: %d  [ %s ]\n"
"%c N(R): %03d P/F: %d\n"
"%c %d bytes of data\n",
    	direction_tag,
	h->s.x0,
	h->s.ss,
	h->s.ft,
	type,
	direction_tag,
	h->s.n_r,
	h->s.p_f, 
	direction_tag,
	len - 4);
		break;
	case 3:		
		/* Unnumbered frame */
		type = "???";
		if (h->u.ft == 3) {
			switch (h->u.m3) {
			case 0:
				if (h->u.m2 == 3)
					type = "DM (disconnect mode)";
				else if (h->u.m2 == 0)
					type = "UI (unnumbered information)";
				break;
			case 2:
				if (h->u.m2 == 0)
					type = "DISC (disconnect)";
				break;
			case 3:
			       	if (h->u.m2 == 3)
					type = "SABME (set asynchronous balanced mode extended)";
				else if (h->u.m2 == 0)
					type = "UA (unnumbered acknowledgement)";
				break;
			case 4:
				if (h->u.m2 == 1)
					type = "FRMR (frame reject)";
				break;
			case 5:
				if (h->u.m2 == 3)
					type = "XID (exchange identification note)";
				break;
			}
		}
		pri_message(
"%c   M3: %d   P/F: %d M2: %d 11: %d  [ %s ]\n"
"%c %d bytes of data\n",
	direction_tag,
	h->u.m3,
	h->u.p_f,
	h->u.m2,
	h->u.ft,
	type,
	direction_tag,
	len - 3);
		break;
	};
}

static pri_event *q921_dchannel_up(struct pri *pri)
{
	/* Reset counters, etc */
	q921_reset(pri);
	
	/* Stop any SABME retransmissions */
	pri_schedule_del(pri, pri->sabme_timer);
	pri->sabme_timer = 0;
	
	/* Reset any rejects */
	pri->sentrej = 0;
	
	/* Go into connection established state */
	pri->q921_state = Q921_LINK_CONNECTION_ESTABLISHED;

	/* Start the T203 timer */
	pri->t203_timer = pri_schedule_event(pri, T_203, t203_expire, pri);
	
	/* Report event that D-Channel is now up */
	pri->ev.gen.e = PRI_EVENT_DCHAN_UP;
	return &pri->ev;
}

static pri_event *q921_dchannel_down(struct pri *pri)
{
	/* Reset counters, reset sabme timer etc */
	q921_reset(pri);
	
	/* Report event that D-Channel is now up */
	pri->ev.gen.e = PRI_EVENT_DCHAN_DOWN;
	return &pri->ev;
}

void q921_reset(struct pri *pri)
{
	/* Having gotten a SABME we MUST reset our entire state */
	pri->v_s = 0;
	pri->v_a = 0;
	pri->v_r = 0;
	pri->v_na = 0;
	pri->window = 7;
	pri->windowlen = 0;
	pri_schedule_del(pri, pri->sabme_timer);
	pri_schedule_del(pri, pri->t203_timer);
	pri_schedule_del(pri, pri->t200_timer);
	pri->sabme_timer = 0;
	pri->t203_timer = 0;
	pri->t200_timer = 0;
	pri->busy = 0;
	pri->solicitfbit = 0;
	pri->q921_state = Q921_LINK_CONNECTION_RELEASED;
	pri->retrans = 0;
	pri->sentrej = 0;
	
	/* Discard anything waiting to go out */
	q921_discard_retransmissions(pri);
}

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("!! Got I-frame while link state %d\n", pri->q921_state);
			return NULL;
		}
		/* Informational frame */
		if (len < 4) {
			pri_error("!! 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("!! Got S-frame while link down\n");
			return NULL;
		}
		if (len < 4) {
			pri_error("!! 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);
			if (ev)
				return ev;
			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 (pri->solicitfbit) {
					if (pri->debug & PRI_DEBUG_Q921_STATE) 
						pri_message("-- Got RR response to our frame\n");
				} else {
					if (pri->debug & PRI_DEBUG_Q921_STATE) 
						pri_message("-- Unsolicited RR with P/F bit, responding\n");
						q921_rr(pri, 1, 0);
				}
				pri->solicitfbit = 0;
			}
			break;
      case 1:
         /* Receiver not ready */
         if (pri->debug & PRI_DEBUG_Q921_STATE)
            pri_message("-- Got receiver not ready\n");
	 if(h->s.p_f) {
		/* Send RR if poll bit set */
		q921_rr(pri, h->s.p_f, 0);
	 }
         pri->busy = 1;
         break;   
      case 2:
         /* Just retransmit */
         if (pri->debug & PRI_DEBUG_Q921_STATE)
            pri_message("-- Got reject requesting packet %d...  Retransmitting.\n", h->s.n_r);
         if (h->s.p_f) {
            /* If it has the poll bit set, send an appropriate supervisory response */
            q921_rr(pri, 1, 0);
         }
		 sendnow = 0;
         /* Resend the proper I-frame */
         for(f=pri->txqueue;f;f=f->next) {
               if ((sendnow || (f->h.n_s == h->s.n_r)) && f->transmitted) {
                     /* Matches the request, or follows in our window, and has
					    already been transmitted. */
					 sendnow = 1;
					 pri_error("!! 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;
                     q921_transmit(pri, (q921_h *)(&f->h), f->len);
               }
         }
         if (!sendnow) {
               if (pri->txqueue) {
                     /* This should never happen */
		     if (!h->s.p_f || h->s.n_r) {
			pri_error("!! 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("!! 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 */
                     if (pri->t203_timer)
                           pri_schedule_del(pri, pri->t203_timer);
                     pri->t203_timer = pri_schedule_event(pri, T_203, t203_expire, pri);
               }
         }
         break;
		default:
			pri_error("!! 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("!! 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_message("-- Got DM Mode from peer.\n");
					/* Disconnected mode, try again after T200 */
					ev = q921_dchannel_down(pri);
					q921_start(pri, 0);
					return ev;
						
				} else {
					if (pri->debug & PRI_DEBUG_Q921_STATE)
						pri_message("-- Ignoring unsolicited DM with p/f set to 0\n");
#if 0
					/* Requesting that we start */
					q921_start(pri, 0);
#endif					
				}
				break;
			} else if (!h->u.m2) {
				pri_message("XXX Unnumbered Information not implemented XXX\n");
			}
			break;
		case 2:
			if (pri->debug &  PRI_DEBUG_Q921_STATE)
				pri_message("-- Got Disconnect from peer.\n");
			/* Acknowledge */
			q921_send_ua(pri, h->u.p_f);
			ev = q921_dchannel_down(pri);
			q921_start(pri, 0);
			return ev;
		case 3:
			if (h->u.m2 == 3) {
				/* SABME */
				if (pri->debug & PRI_DEBUG_Q921_STATE) {
					pri_message("-- 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_message("-- Got UA from %s peer  Link up.\n", h->h.c_r ? "cpe" : "network");
					}
					return q921_dchannel_up(pri);
				} else 
					pri_error("!! Got a UA, but i'm in state %d\n", pri->q921_state);
			} else 
				pri_error("!! Weird frame received (m3=3, m2 = %d)\n", h->u.m2);
			break;
		case 4:
			pri_error("!! Frame got rejected!\n");
			break;
		case 5:
			pri_error("!! XID frames not supported\n");
			break;
		default:
			pri_error("!! 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)
		q921_dump(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;

	/* Check for broadcasts - not yet handled */
	if (h->h.tei == Q921_TEI_GROUP)
		return NULL;

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

	}
	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;
}

void q921_start(struct pri *pri, int now)
{
	if (pri->q921_state != Q921_LINK_CONNECTION_RELEASED) {
		pri_error("!! 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);
}