Malformed packet sending an SMS
While running the "sms" test from osmo-gsm-tester with 2 Sierra Wireless modems and a SysmoBTS+NITB. Scenario: 2 modems register to the network, one sends an SMS to the other one.
Sometimes the test fails and the receiving modem gets unregistered from the network without receiving the SMS.
I was trying to find out the differences between the PASS case and the FAIL case. I attach now the run directory for both cases. THey contain a pcap file from the NITB + GSMTAP enabled on the BTS.
Strangely enough, the malformed packet is on the test run which PASSed, while the same packet on the FAILed is not malformed. See frame number 1406 in run-good/osmo-nitb_10.42.42.1/pcap/*.pcap for the malformed packet: length inside CP-DATA should be 59 but it's 60.
The issue about the MS not registering or becoming unregistered is almost 100% the issue already tracked (and for now it seems already solved by using incremental LAC) in #2456.
However, it may still be helpful to leave the ticket open to investigate whether the CP-DATA sent by the SMS is wrong or if there's a bug in wireshark not handling the data in there correctly.