https://osmocom.org/https://osmocom.org/favicon.ico?16647414092018-03-11T23:03:25ZOpen Source Mobile CommunicationsOpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81582018-03-11T23:03:25Zlaforge
<ul><li><strong>Related to</strong> <i><a class="issue tracker-1 status-3 priority-2 priority-default closed" href="/issues/3057">Bug #3057</a>: OsmoBTS fails to schedule SACCH filling like SI5</i> added</li></ul> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81602018-03-11T23:03:40Zlaforge
<ul><li><strong>Related to</strong> <i><a class="issue tracker-1 status-3 priority-2 priority-default closed" href="/issues/2963">Bug #2963</a>: Measurement Reports cease to be useful some time into a voice call / after handover (not sure which project has the bug / bugs yet)</i> added</li></ul> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81622018-03-11T23:13:34Zlaforge
<ul><li><strong>Status</strong> changed from <i>New</i> to <i>In Progress</i></li><li><strong>% Done</strong> changed from <i>0</i> to <i>10</i></li></ul><p>the interesting question is: how does the format look on Abis? According to my reading of the specs:</p>
<ul>
<li>L3 Info TLV length given by TS 48.058 for SACCH FILLING is "22", where 1 byte is tag, and 2 bytes are length, i.e. 19 bytes left for actual payload
<ul>
<li>this indicates the full 19 bytes <em>including pseudo-length</em> are to be included</li>
</ul>
</li>
<li>The actual SI5 / SI6 definitions in TS 44.018 also include the L2 pseodo length as part of the SI message</li>
</ul>
<p>I also found some old pcap files of a proprietary ip.access BSC, which confirms that assumption.</p>
So it seems to me that
<ul>
<li>OsmoBSC is lacking the L2 pseudo-length field as first byte of the L3 INFO</li>
<li>the wireshark packet-rsl.c decoder is broken as it assumes no l2 plen</li>
<li>we impleemnted our code to comply with wireshark, inheriting the bug</li>
<li>the wireshark LAPDm decoder was "fixed" by me to also comply with that broken assumption</li>
</ul>
<p>So now, wiershark RSL, wiershark GSMTAP/LAPDm and OsmoBSC are all broken. yay. :(</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81632018-03-11T23:19:13Zlaforge
<ul></ul><p>This appears to be the root of all evil:</p>
<pre>
commit 6f0e50c8337355eb59033903ede9ab6528890835
Author: Max <msuraev@sysmocom.de>
Date: Wed Apr 12 15:30:54 2017 +0200
Prepare for extended SI2quater support
</pre>
<p>as it overwrites the l2_plen just after it was written.</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81642018-03-11T23:30:03Zlaforge
<ul><li><strong>Assignee</strong> changed from <i>laforge</i> to <i>neels</i></li><li><strong>% Done</strong> changed from <i>10</i> to <i>30</i></li></ul><p>proposed (but yet untested) patch at <a class="external" href="https://gerrit.osmocom.org/7220">https://gerrit.osmocom.org/7220</a></p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81652018-03-11T23:33:48Zlaforge
<ul><li><strong>Project</strong> changed from <i>Cellular Network Infrastructure</i> to <i>OsmoBSC</i></li></ul> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81662018-03-12T02:05:17Zneelsnhofmeyr@sysmocom.de
<ul><li><strong>Project</strong> changed from <i>OsmoBSC</i> to <i>Cellular Network Infrastructure</i></li><li><strong>Assignee</strong> changed from <i>neels</i> to <i>laforge</i></li><li><strong>% Done</strong> changed from <i>30</i> to <i>80</i></li></ul><p>Just tested with this patch as well as <a class="external" href="https://gerrit.osmocom.org/#/c/7218/">https://gerrit.osmocom.org/#/c/7218/</a> (it's already merged to osmo-bts master, but let me mention that it was used in the test) and: YES! Finally the measurement reports survive a handover! No matter what I do, the neighbor lists are reliably populated. Excellent! Let me add a few percent there.</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81712018-03-12T06:42:26Zfixeria
<ul></ul><p>Hi Harald,</p>
<p>this is probably related to:</p>
<p><a class="external" href="https://lists.osmocom.org/pipermail/openbsc/2017-December/011545.html">https://lists.osmocom.org/pipermail/openbsc/2017-December/011545.html</a></p>
<p>my plan is to revert the:</p>
<p><a class="external" href="https://git.osmocom.org/osmocom-bb/commit/?id=1a8a80aeae4c2e5c870ae5b032d9a6ae60b67ac8">https://git.osmocom.org/osmocom-bb/commit/?id=1a8a80aeae4c2e5c870ae5b032d9a6ae60b67ac8</a></p>
<p>because I was referring an outdated spec version and the way of Osmocom stack.</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81752018-03-12T10:16:36Zlaforge
<ul><li><b>Checklist item</b> <input type='checkbox' class='checklist-checkbox' disabled> <i>wireshark patch for RSL</i> added</li><li><b>Checklist item</b> <input type='checkbox' class='checklist-checkbox' disabled> <i>wireshark patch for SACCH/LAPDm</i> added</li><li><strong>Project</strong> changed from <i>Cellular Network Infrastructure</i> to <i>OpenBSC</i></li><li><strong>% Done</strong> changed from <i>80</i> to <i>90</i></li></ul><p>ok, have merged the related patch now. Let's abuse this ticket until wireshark patches are written + tested.</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81762018-03-12T10:26:29Zlaforge
<ul><li><b>Checklist item</b> <input type='checkbox' class='checklist-checkbox' checked disabled> <i>patch for legacy openbsc.git</i> added</li></ul><p>openbsc.git fix submitted in <a class="external" href="https://gerrit.osmocom.org/#/c/7226/">https://gerrit.osmocom.org/#/c/7226/</a></p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81782018-03-12T13:16:53Zfixeria
<ul></ul><p>My question was lost because the 7226 was merged, but anyway,<br /><a class="user active" href="https://osmocom.org/users/7">laforge</a>, what do you think about introducing a new structure with l2_plen?</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=81792018-03-12T13:50:10Zlaforge
<ul></ul><p>On Mon, Mar 12, 2018 at 01:16:53PM +0000, fixeria [REDMINE] wrote:</p>
<blockquote>
<p>My question was lost because the 7226 was merged, but anyway,</p>
</blockquote>
<p>it wasn't lost, I read it ;)</p>
<blockquote>
<p><a class="user active" href="https://osmocom.org/users/7">laforge</a>, what do you think about introducing a new structure with l2_plen?</p>
</blockquote>
<p>I don't think it's worth it. Too much confusion?</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=87252018-04-07T22:43:24Zlaforge
<ul><li><b>Checklist item</b> <input type='checkbox' class='checklist-checkbox' checked disabled> <i>wireshark patch for RSL</i> set to Done</li></ul> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=87262018-04-07T22:43:48Zlaforge
<ul></ul><p>wireshark patch for RSL now proposed as <a class="external" href="https://code.wireshark.org/review/#/c/26797/">https://code.wireshark.org/review/#/c/26797/</a></p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=87272018-04-07T23:12:24Zlaforge
<ul><li><b>Checklist item</b> <input type='checkbox' class='checklist-checkbox' checked disabled> <i>wireshark patch for SACCH/LAPDm</i> set to Done</li><li><strong>Status</strong> changed from <i>In Progress</i> to <i>Stalled</i></li></ul><p>LAPDm patch submitted at <a class="external" href="https://code.wireshark.org/review/#/c/26798/1">https://code.wireshark.org/review/#/c/26798/1</a> - waiting for review.</p> OpenBSC - Bug #3059: System Information on SACCH missing L2 Pseudo-Lengthhttps://osmocom.org/issues/3059?journal_id=90612018-04-29T08:35:17Zlaforge
<ul><li><strong>Status</strong> changed from <i>Stalled</i> to <i>Resolved</i></li><li><strong>% Done</strong> changed from <i>90</i> to <i>100</i></li></ul><p>both wireshark patches merged.</p>