<p>laforge <strong>submitted</strong> this change.</p><p><a href="https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/19212">View Change</a></p><div style="white-space:pre-wrap">Approvals:
laforge: Looks good to me, approved
Jenkins Builder: Verified
</div><pre style="font-family: monospace,monospace; white-space: pre-wrap;">library/GSM_SystemInformation: add dec_SystemInformationSafe()<br><br>Some types of System Information (mostly the Rest Octets) are not<br>fully implemented, so calling the generic dec_SystemInformation()<br>may result in a DTE. Let's add dec_SystemInformationSafeBT() with<br>"prototype(backtrack)", so it would return a non-zero integer if<br>decoding fails. Let's add a wrapper dec_SystemInformationSafe()<br>that would additionally check the RR Protocol Discriminator.<br><br>Change-Id: Id4d73e0f3347e1d4c4c77aec75b767311d662292<br>Related: OS#4662<br>---<br>M bts/BTS_Tests.ttcn<br>M library/GSM_SystemInformation.ttcn<br>2 files changed, 32 insertions(+), 15 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn</span><br><span>index 587e14a..47f8a29 100644</span><br><span>--- a/bts/BTS_Tests.ttcn</span><br><span>+++ b/bts/BTS_Tests.ttcn</span><br><span>@@ -3534,7 +3534,6 @@</span><br><span> repeat;</span><br><span> }</span><br><span> [] L1CTL.receive(tr_L1CTL_DATA_IND(t_RslChanNr_PCH_AGCH(0), ?)) -> value l1_dl {</span><br><span style="color: hsl(0, 100%, 40%);">- /* somehow dec_SystemInformation will try to decode even non-RR as SI */</span><br><span> var GsmRrMessage rr := dec_GsmRrMessage(l1_dl.payload.data_ind.payload);</span><br><span> if (not match(rr, tr_IMM_ASS(42, ?, 5, ?, ?))) {</span><br><span> /* FIXME: Why are we seeing paging requests on PCH/AGCH? */</span><br><span>@@ -3936,15 +3935,12 @@</span><br><span> T.start;</span><br><span> alt {</span><br><span> [] pt.receive(tr_L1CTL_DATA_IND(t_RslChanNr_BCCH(0), ?)) -> value l1_dl {</span><br><span style="color: hsl(0, 100%, 40%);">- /* somehow dec_SystemInformation will try to decode even non-RR as SI */</span><br><span style="color: hsl(0, 100%, 40%);">- if (not (l1_dl.payload.data_ind.payload[1] == '06'O)) {</span><br><span style="color: hsl(0, 100%, 40%);">- log("Ignoring non-RR SI ", l1_dl);</span><br><span style="color: hsl(120, 100%, 40%);">+ var SystemInformationFn sig := { frame_number := l1_dl.dl_info.frame_nr };</span><br><span style="color: hsl(120, 100%, 40%);">+ if (dec_SystemInformationSafe(l1_dl.payload.data_ind.payload, sig.si) != 0) {</span><br><span style="color: hsl(120, 100%, 40%);">+ log("Ignoring non-RR or invalid SI ", l1_dl);</span><br><span> repeat;</span><br><span> }</span><br><span style="color: hsl(0, 100%, 40%);">- var SystemInformationFn sig := {</span><br><span style="color: hsl(0, 100%, 40%);">- frame_number := l1_dl.dl_info.frame_nr,</span><br><span style="color: hsl(0, 100%, 40%);">- si := dec_SystemInformation(l1_dl.payload.data_ind.payload)</span><br><span style="color: hsl(0, 100%, 40%);">- }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> var integer tc := f_gsm_compute_tc(sig.frame_number);</span><br><span> log("SI received at TC=", tc, ": ", sig.si);</span><br><span> /* append to the per-TC bucket */</span><br><span>@@ -5227,17 +5223,13 @@</span><br><span> runs on test_CT return SystemInformation {</span><br><span> var L1ctlDlMessage l1_dl;</span><br><span> var SystemInformation si;</span><br><span style="color: hsl(120, 100%, 40%);">+ var integer rc;</span><br><span> timer T := 5.0;</span><br><span> T.start;</span><br><span> alt {</span><br><span> [] pt.receive(tr_L1CTL_DATA_IND(t_RslChanNr_BCCH(0), ?)) -> value l1_dl {</span><br><span style="color: hsl(0, 100%, 40%);">- /* somehow dec_SystemInformation will try to decode even non-RR as SI */</span><br><span style="color: hsl(0, 100%, 40%);">- if (not (l1_dl.payload.data_ind.payload[1] == '06'O)) {</span><br><span style="color: hsl(0, 100%, 40%);">- log("Ignoring non-RR SI ", l1_dl);</span><br><span style="color: hsl(0, 100%, 40%);">- repeat;</span><br><span style="color: hsl(0, 100%, 40%);">- }</span><br><span style="color: hsl(0, 100%, 40%);">- si := dec_SystemInformation(l1_dl.payload.data_ind.payload)</span><br><span style="color: hsl(0, 100%, 40%);">- if (si.header.message_type != si_type) {</span><br><span style="color: hsl(120, 100%, 40%);">+ rc := dec_SystemInformationSafe(l1_dl.payload.data_ind.payload, si);</span><br><span style="color: hsl(120, 100%, 40%);">+ if (rc != 0 or si.header.message_type != si_type) {</span><br><span> repeat;</span><br><span> }</span><br><span> }</span><br><span>diff --git a/library/GSM_SystemInformation.ttcn b/library/GSM_SystemInformation.ttcn</span><br><span>index 3c3d96c..9113583 100644</span><br><span>--- a/library/GSM_SystemInformation.ttcn</span><br><span>+++ b/library/GSM_SystemInformation.ttcn</span><br><span>@@ -264,4 +264,29 @@</span><br><span> }</span><br><span> }</span><br><span> </span><br><span style="color: hsl(120, 100%, 40%);">+ external function dec_SystemInformationSafeBT(in octetstring stream, out SystemInformation si)</span><br><span style="color: hsl(120, 100%, 40%);">+ return integer /* Decoding result: successful (0) or unsuccessful (1) */</span><br><span style="color: hsl(120, 100%, 40%);">+ with { extension "prototype(backtrack) decode(RAW)" };</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Some types of System Information (mostly the Rest Octets) are not fully implemented,</span><br><span style="color: hsl(120, 100%, 40%);">+ * so calling the generic dec_SystemInformation() may result in a DTE. This function</span><br><span style="color: hsl(120, 100%, 40%);">+ * additionally checks RR Protocol Discriminator, and should be used in the most cases. */</span><br><span style="color: hsl(120, 100%, 40%);">+ function dec_SystemInformationSafe(in octetstring stream, out SystemInformation si)</span><br><span style="color: hsl(120, 100%, 40%);">+ return integer {</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Try to decode a given octetstring as System Information */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (dec_SystemInformationSafeBT(stream, si) != 0) {</span><br><span style="color: hsl(120, 100%, 40%);">+ log("Failed to decode (RR) System Information: ", stream);</span><br><span style="color: hsl(120, 100%, 40%);">+ return 1;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* Check the protocol discriminator (we expect RR messages) */</span><br><span style="color: hsl(120, 100%, 40%);">+ if (si.header.rr_protocol_discriminator != bit2int('0110'B)) {</span><br><span style="color: hsl(120, 100%, 40%);">+ log("Protocol discriminator is not RR (!= '0110'B): ",</span><br><span style="color: hsl(120, 100%, 40%);">+ si.header.rr_protocol_discriminator);</span><br><span style="color: hsl(120, 100%, 40%);">+ return 1;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ return 0;</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span> } with { encode "RAW"; variant "FIELDORDER(msb)" }</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/19212">change 19212</a>. 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<div style="display:none"> Gerrit-Project: osmo-ttcn3-hacks </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: Id4d73e0f3347e1d4c4c77aec75b767311d662292 </div>
<div style="display:none"> Gerrit-Change-Number: 19212 </div>
<div style="display:none"> Gerrit-PatchSet: 3 </div>
<div style="display:none"> Gerrit-Owner: fixeria <vyanitskiy@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: Jenkins Builder </div>
<div style="display:none"> Gerrit-Reviewer: fixeria <vyanitskiy@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-Reviewer: neels <nhofmeyr@sysmocom.de> </div>
<div style="display:none"> Gerrit-Reviewer: pespin <pespin@sysmocom.de> </div>
<div style="display:none"> Gerrit-MessageType: merged </div>