library/GSM_SystemInformation: add dec_SystemInformationSafe()
Some types of System Information (mostly the Rest Octets) are not fully implemented, so calling the generic dec_SystemInformation() may result in a DTE. Let's add dec_SystemInformationSafeBT() with "prototype(backtrack)", so it would return a non-zero integer if decoding fails. Let's add a wrapper dec_SystemInformationSafe() that would additionally check the RR Protocol Discriminator. Change-Id: Id4d73e0f3347e1d4c4c77aec75b767311d662292 Related: OS#4662
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@ -3534,7 +3534,6 @@ private function f_TC_imm_ass(integer num_total, float sleep_s, float exp_pass)
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repeat;
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}
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[] L1CTL.receive(tr_L1CTL_DATA_IND(t_RslChanNr_PCH_AGCH(0), ?)) -> value l1_dl {
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/* somehow dec_SystemInformation will try to decode even non-RR as SI */
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var GsmRrMessage rr := dec_GsmRrMessage(l1_dl.payload.data_ind.payload);
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if (not match(rr, tr_IMM_ASS(42, ?, 5, ?, ?))) {
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/* FIXME: Why are we seeing paging requests on PCH/AGCH? */
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@ -3936,15 +3935,12 @@ return SystemInformationVectorPerTc {
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T.start;
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alt {
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[] pt.receive(tr_L1CTL_DATA_IND(t_RslChanNr_BCCH(0), ?)) -> value l1_dl {
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/* somehow dec_SystemInformation will try to decode even non-RR as SI */
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if (not (l1_dl.payload.data_ind.payload[1] == '06'O)) {
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log("Ignoring non-RR SI ", l1_dl);
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var SystemInformationFn sig := { frame_number := l1_dl.dl_info.frame_nr };
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if (dec_SystemInformationSafe(l1_dl.payload.data_ind.payload, sig.si) != 0) {
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log("Ignoring non-RR or invalid SI ", l1_dl);
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repeat;
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}
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var SystemInformationFn sig := {
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frame_number := l1_dl.dl_info.frame_nr,
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si := dec_SystemInformation(l1_dl.payload.data_ind.payload)
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}
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var integer tc := f_gsm_compute_tc(sig.frame_number);
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log("SI received at TC=", tc, ": ", sig.si);
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/* append to the per-TC bucket */
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@ -5227,17 +5223,13 @@ private function f_get_si(L1CTL_PT pt, RrMessageType si_type)
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runs on test_CT return SystemInformation {
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var L1ctlDlMessage l1_dl;
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var SystemInformation si;
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var integer rc;
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timer T := 5.0;
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T.start;
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alt {
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[] pt.receive(tr_L1CTL_DATA_IND(t_RslChanNr_BCCH(0), ?)) -> value l1_dl {
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/* somehow dec_SystemInformation will try to decode even non-RR as SI */
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if (not (l1_dl.payload.data_ind.payload[1] == '06'O)) {
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log("Ignoring non-RR SI ", l1_dl);
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repeat;
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}
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si := dec_SystemInformation(l1_dl.payload.data_ind.payload)
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if (si.header.message_type != si_type) {
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rc := dec_SystemInformationSafe(l1_dl.payload.data_ind.payload, si);
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if (rc != 0 or si.header.message_type != si_type) {
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repeat;
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}
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}
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@ -264,4 +264,29 @@ module GSM_SystemInformation {
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}
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}
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external function dec_SystemInformationSafeBT(in octetstring stream, out SystemInformation si)
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return integer /* Decoding result: successful (0) or unsuccessful (1) */
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with { extension "prototype(backtrack) decode(RAW)" };
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/* Some types of System Information (mostly the Rest Octets) are not fully implemented,
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* so calling the generic dec_SystemInformation() may result in a DTE. This function
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* additionally checks RR Protocol Discriminator, and should be used in the most cases. */
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function dec_SystemInformationSafe(in octetstring stream, out SystemInformation si)
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return integer {
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/* Try to decode a given octetstring as System Information */
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if (dec_SystemInformationSafeBT(stream, si) != 0) {
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log("Failed to decode (RR) System Information: ", stream);
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return 1;
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}
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/* Check the protocol discriminator (we expect RR messages) */
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if (si.header.rr_protocol_discriminator != bit2int('0110'B)) {
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log("Protocol discriminator is not RR (!= '0110'B): ",
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si.header.rr_protocol_discriminator);
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return 1;
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}
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return 0;
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}
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} with { encode "RAW"; variant "FIELDORDER(msb)" }
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