FrameRelay Emulation
Change-Id: I7a9c07bbf210c9ce18328ea39b2ef77d9f8dbd59
This commit is contained in:
parent
2bca644911
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9ea5e1f379
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module FrameRelay_Emulation {
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/* Frame Relay emulation layer on top of FrameRelay_CodecPort
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*
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* This implements de-multiplexing between per-DLCI client components and the
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* underlying FrameRelay_CodecPort / HLDC / AF_PACKET stack. It also implements
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* LMI as per ITU-T Q.933 on DLCI 0
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*/
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import from General_Types all;
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import from Osmocom_Types all;
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import from FrameRelay_CodecPort all;
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import from FrameRelay_Types all;
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import from Q933_Types all;
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/* Link status notification */
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type enumerated FRemu_LinkStatus {
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FR_LINK_STS_AVAILABLE,
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FR_LINK_STS_UNAVAILABLE
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};
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/* PVC status notification */
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type record FRemu_PvcStatus {
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integer dlci,
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boolean new,
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boolean delete,
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boolean active
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};
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/* Frame Relay Emulation notifies the user about some event */
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type union FRemu_Event {
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FRemu_LinkStatus link_status,
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FRemu_PvcStatus pvc_status
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};
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/* port type between FR emulation and per-DLCI components (like NS) */
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type port FRemu_PT message {
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inout FrameRelayFrame;
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in FRemu_Event;
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} with { extension "internal" };
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type port FRemu_asp_PT message {
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inout FrameRelayFrame;
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out FRemu_Event;
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} with { extension "internal" };
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/* port between FR emulation and per-DLCI client components (like NS) */
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type port FRemu_PROC_PT procedure {
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inout FRemu_register, FRemu_unregister;
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} with { extension "internal" };
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signature FRemu_register(integer dlci);
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signature FRemu_unregister(integer dlci);
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/* FR Emulation main component/dispatcher. Exists once per FR_CODEC_PT */
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type component FR_Emulation_CT {
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/* port towards the bottom (HDLC device) */
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port FR_CODEC_PT FR;
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/* port towards the user[s] (PVC specific) */
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port FRemu_PT CLIENT;
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port FRemu_PROC_PT PROC;
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var ConnectionData ConnectionTable[1024];
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var Q933em_State q933em;
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/* Polling verification timer */
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timer T391 := 10.0;
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/* Link integrity verification polling timer */
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timer T392 := 15.0;
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};
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/* FR Emulation user/client component/dispatcher. Exists once per FR_CODEC_PT */
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type component FR_Client_CT {
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/* message port towards the Frame Relay Emulation */
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port FRemu_asp_PT FR;
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/* procedure port towards the Frame Relay Emulation */
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port FRemu_PROC_PT FR_PROC;
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};
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type record ConnectionData {
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/* component refrence to the client component for the above DLCI */
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FR_Client_CT vc_conn
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};
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type record Q933em_State {
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/* configuration */
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Q933em_Config cfg,
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/* last transmitted sequence number */
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uint8_t tx_seq_nr,
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/* last received sequence number */
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uint8_t last_rx_seq_nr,
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/* error counter buckets; we use elements 0..N393 */
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boolean err_buckets[10],
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uint8_t err_bucket_idx,
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/* do we currently have a 'service affecting condition (true) or not? */
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boolean service_affecting_condition,
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/* did we receive a "full status" in the current T391 cycle? */
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boolean rx_status_in_cycle
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};
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type record Q933em_Config {
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/* Full status (status of all PVCs) polling counter (default: 6) */
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uint8_t N391,
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/* Error threshold */
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integer N392,
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/* Monitored events count */
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integer N393,
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/* is the ATS the user equipment (true) or network (false) */
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boolean ats_is_user,
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/* optional bidirectional network procedures */
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boolean bidirectional
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};
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template (value) Q933em_Config ts_Q933em_Config(boolean ats_is_user, boolean bidirectional) := {
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N391 := 6,
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N392 := 4,
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N393 := 10,
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ats_is_user := ats_is_user,
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bidirectional := bidirectional
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};
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private template (value) Q933em_State ts_Q933em_State(Q933em_Config cfg) := {
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cfg := cfg,
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tx_seq_nr := 0,
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last_rx_seq_nr := 0,
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err_buckets := { true, true, true, true, true, true, true, true, true, true },
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err_bucket_idx := 0,
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service_affecting_condition := true,
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rx_status_in_cycle := false
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}
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/* obtain the next sequence number following the one given as argument */
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private function q933_next_seq(uint8_t cur_seq) return uint8_t {
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/* The network equipment increments the send sequence counter using modulo 256. The value zero is skipped. */
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if (cur_seq >= 255) {
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return 1;
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} else {
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return cur_seq + 1;
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}
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}
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private function fill_err_bucket(boolean has_error) runs on FR_Emulation_CT {
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var integer i, n_errors := 0;
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/* add current error status to bucket */
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q933em.err_buckets[q933em.err_bucket_idx] := has_error;
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/* check if thresholds are met */
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if (not q933em.service_affecting_condition) {
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for (i := 0; i < q933em.cfg.N393; i := i + 1) {
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if (q933em.err_buckets[i]) {
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n_errors := n_errors + 1;
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}
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}
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if (n_errors >= q933em.cfg.N392) {
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q933em.service_affecting_condition := true;
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log("Detecting service affecting condition after N392 errors during last N393 cycles");
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/* FIXME: notify all client components */
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}
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} else {
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/* if N392 consecutive 'good' cycles -> clear service_affecting_condition */
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var integer start_idx := (q933em.err_bucket_idx + q933em.cfg.N393 - q933em.cfg.N392) mod q933em.cfg.N393;
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var integer consecutive_good := 0;
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for (i := 0; i < q933em.cfg.N392; i := i+1) {
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if (q933em.err_buckets[(start_idx + i) mod q933em.cfg.N393] == false) {
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consecutive_good := consecutive_good + 1;
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}
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}
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if (consecutive_good == q933em.cfg.N392) {
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q933em.service_affecting_condition := false;
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log("Detecting no more service affecting condition after N392 consecutive good cycles");
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/* FIXME: notify all client components */
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}
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}
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/* increment index for next cycle */
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q933em.err_bucket_idx := (q933em.err_bucket_idx + 1) mod q933em.cfg.N393;
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}
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/* handle incoming Link Integrity Verification IE */
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private function q933_handle_rx_link_int(Q933_LinkIntegrityIE link_int) runs on FR_Emulation_CT {
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if (q933em.tx_seq_nr != link_int.recv_seq_nr) {
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log("Link Integrity IE with discontiguous sequence numbers: expected=",
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q933em.tx_seq_nr, " received=", link_int.recv_seq_nr);
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fill_err_bucket(true);
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/* FIXME */
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} else {
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fill_err_bucket(false);
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}
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q933em.last_rx_seq_nr := link_int.send_seq_nr;
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}
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/* generate outbound Link Integrity Verification IE */
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private function q933_gen_tx_link_int() runs on FR_Emulation_CT return Q933_LinkIntegrityIE {
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q933em.tx_seq_nr := q933_next_seq(q933em.tx_seq_nr);
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return valueof(ts_Q933_LinkIntIE(q933em.tx_seq_nr, q933em.last_rx_seq_nr));
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}
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/* generate outbound PVC Status Record */
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private function q933_gen_pvc_status_rec() runs on FR_Emulation_CT return Q933_PvcStatusRec {
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var Q933_PvcStatusRec ret := {};
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var integer i;
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for (i := 0; i < lengthof(ConnectionTable); i := i+1) {
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if (ConnectionTable[i].vc_conn == null) {
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continue;
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}
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var boolean active := not q933em.service_affecting_condition;
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/* TODO: set new? */
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ret := ret & {valueof(ts_Q933_PvcStatus(i, false, false, active))};
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}
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return ret;
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}
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/* transmit a Q.933 STATUS_ENQ and start T391 */
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private function q933_tx_status_enq() runs on FR_Emulation_CT {
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var Q933_TypeOfReport rep_type := Q933_REP_T_LINK_INTEG_VF_ONLY;
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var Q933_LinkIntegrityIE link_int := q933_gen_tx_link_int();
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/* every N391 cycles, request full status and not just link integrity */
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if ((link_int.send_seq_nr mod q933em.cfg.N391) == 0) {
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rep_type := Q993_REP_T_FULL_STATUS;
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}
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/* transmit STATUS ENQUIRY */
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q933_tx(ts_Q933_STATUS_ENQ(rep_type, q933_gen_tx_link_int()));
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/* re-start timer */
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q933em.rx_status_in_cycle := false;
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T391.start;
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}
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/* handle an incoming Q.933 message */
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private function handle_rx_q933(Q933_PDU rx_pdu) runs on FR_Emulation_CT {
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if (not q933em.cfg.ats_is_user or q933em.cfg.bidirectional) {
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/* network or bi-directional */
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select (rx_pdu) {
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case (tr_Q933_STATUS_ENQ(Q933_REP_T_LINK_INTEG_VF_ONLY)) {
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T392.stop;
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q933_handle_rx_link_int(rx_pdu.body.status_enq.link_int);
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q933_tx(ts_Q933_STATUS(Q933_REP_T_LINK_INTEG_VF_ONLY, q933_gen_tx_link_int()));
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T392.start;
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return;
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}
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case (tr_Q933_STATUS_ENQ(Q993_REP_T_FULL_STATUS)) {
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T392.stop;
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q933_handle_rx_link_int(rx_pdu.body.status_enq.link_int);
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/* create response message */
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var Q933_PvcStatusRec pvc_status_rec := q933_gen_pvc_status_rec();
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q933_tx(ts_Q933_STATUS(Q993_REP_T_FULL_STATUS, q933_gen_tx_link_int(), ts_Q933_PvcStatusIE(pvc_status_rec)));
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T392.start;
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return;
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}
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}
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} else if (q933em.cfg.ats_is_user or q933em.cfg.bidirectional) {
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select (rx_pdu) {
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case (tr_Q933_STATUS(Q933_REP_T_LINK_INTEG_VF_ONLY)) {
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q933_handle_rx_link_int(rx_pdu.body.status.link_int);
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q933em.rx_status_in_cycle := true;
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return;
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}
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case (tr_Q933_STATUS(Q993_REP_T_FULL_STATUS)) {
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q933_handle_rx_link_int(rx_pdu.body.status.link_int);
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q933em.rx_status_in_cycle := true;
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/* process inbound PVC status and dispatch to users */
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return;
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}
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}
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}
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/* if we reach here, something unsupported was received */
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setverdict(fail, "Unexpected Q933 received: ", rx_pdu);
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}
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/* Encode + Transmit a Q.933 message over DLCI 0 */
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private function q933_tx(template (value) Q933_PDU tx) runs on FR_Emulation_CT {
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var octetstring q933_bin := enc_Q933_PDU(valueof(tx));
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/* Add Q.921 LAPD UI frame header */
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FR.send(ts_FR(0, '03'O & q933_bin, false));
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}
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function main(Q933em_Config q933_cfg) runs on FR_Emulation_CT {
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var FrameRelayFrame rx_fr;
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var integer dlci;
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var FR_Client_CT vc_conn;
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q933em := valueof(ts_Q933em_State(q933_cfg));
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if (q933em.cfg.ats_is_user or q933em.cfg.bidirectional) {
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q933_tx_status_enq();
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}
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for (var integer i:= 0; i < sizeof(ConnectionTable); i := i + 1) {
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ConnectionTable[i] := { vc_conn := null };
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}
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while (true) {
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alt {
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/* FR PORT */
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/* Handle DLCI=0 wihh UI frame and ITU-T LMI */
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[] FR.receive(tr_FR(0, '03*'O)) -> value rx_fr {
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/* strip one-byte FR header */
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var Q933_PDU rx_q933 := dec_Q933_PDU(substr(rx_fr.payload, 1, lengthof(rx_fr.payload)-1));
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handle_rx_q933(rx_q933);
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}
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[] FR.receive(tr_FR(0, ?)) -> value rx_fr {
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setverdict(fail, "Unsupported DLCI 0 frame received: ", rx_fr);
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mtc.stop;
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}
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[q933em.cfg.ats_is_user or q933em.cfg.bidirectional] T391.timeout {
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if (not q933em.rx_status_in_cycle) {
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/* increase error count */
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fill_err_bucket(true);
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}
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/* again request status; re-start timer */
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q933_tx_status_enq();
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}
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[not q933em.cfg.ats_is_user or q933em.cfg.bidirectional] T392.timeout {
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/* increase error count */
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fill_err_bucket(true);
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/* re-start timer */
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T392.start;
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}
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/* Handle all other DLCIs */
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[not q933em.service_affecting_condition] FR.receive(tr_FR(?, ?)) -> value rx_fr {
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/* find user for DLCI; dispatch */
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vc_conn := ConnectionTable[rx_fr.hdr.dlci].vc_conn;
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if (vc_conn == null) {
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log("Dropping Rx FR for unequipped user DLCI ", rx_fr.hdr.dlci);
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repeat;
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}
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CLIENT.send(rx_fr) to vc_conn;
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}
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[q933em.service_affecting_condition] FR.receive(tr_FR(?, ?)) -> value rx_fr {
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log("Dropping Rx FR frame while service affecting condition exists");
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}
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/* CLIENT PORT */
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[not q933em.service_affecting_condition] CLIENT.receive(rx_fr) {
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FR.send(rx_fr);
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}
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[q933em.service_affecting_condition] CLIENT.receive(rx_fr) {
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log("Dropping Tx FR frame while service affecting condition exists");
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}
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/* PROCEDURE PORT */
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[] PROC.getcall(FRemu_register:{?}) -> param(dlci) sender vc_conn {
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if (ConnectionTable[dlci].vc_conn != null and ConnectionTable[dlci].vc_conn != vc_conn) {
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setverdict(fail, "DLCI ", dlci, " already registred by ", ConnectionTable[dlci].vc_conn,
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" when ", vc_conn, " tries to register for it");
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mtc.stop;
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}
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ConnectionTable[dlci].vc_conn := vc_conn;
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/* optionally send async Q.933 STATUS? */
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}
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[] PROC.getcall(FRemu_unregister:{?}) -> param(dlci) sender vc_conn {
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if (ConnectionTable[dlci].vc_conn != vc_conn) {
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setverdict(fail, "Component ", vc_conn, " tries to unregister DLCI ", dlci,
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" registered by ", ConnectionTable[dlci].vc_conn);
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mtc.stop;
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}
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ConnectionTable[dlci].vc_conn := null;
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/* optionally send async Q.933 STATUS? */
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}
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}
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}
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}
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function f_fremu_register(integer dlci) runs on FR_Client_CT {
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FR_PROC.call(FRemu_register:{dlci}) {
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[] FR_PROC.getreply(FRemu_register:{dlci}) {}
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}
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}
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function f_fremu_unregister(integer dlci) runs on FR_Client_CT {
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FR_PROC.call(FRemu_unregister:{dlci}) {
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[] FR_PROC.getreply(FRemu_unregister:{dlci}) {}
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}
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}
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}
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