Cellular Network Infrastructure » Radio Access Network » OsmoPCU

actually, it seems it even forwards GMM-PDUs over a blocked BVC.

I think it would be best to block all transmission of BSSGP or higher layer messages on the NS level if the NS-VC is not UNBLOCKED.

That's odd: bssgp_tx_bvc_reset() is using gprs_ns_sendmsg() which checks that NS is alive and unblocked via gprs_active_nsvc_by_nsei(). Seems like we somehow set the flags too early.

I'm unable to reproduce this locally with current master of libosmocore, OsmoPCU and OsmoSGSN (I'm using osmo-bts-virtual):

20171129154912764 <0008> gprs_ns.c:266 NSVCI=65534 Creating NS-VC
20171129154912765 <0008> gprs_ns.c:1622 Listening for nsip packets from 10.9.1.105:23000 on 0.0.0.0:23100
20171129154912765 <0008> gprs_ns.c:1641 NS UDP socket at 0.0.0.0:23100
20171129154912765 <0008> gprs_ns.c:266 NSVCI=101 Creating NS-VC
20171129154912765 <0008> gprs_ns.c:1659 NSEI=101 RESET procedure based on API request
20171129154912765 <0008> gprs_ns.c:449 NSEI=101 Tx NS RESET (NSVCI=101, cause=O&M intervention)
20171129154912765 <0008> gprs_ns.c:1523 recv error Connection refused during NSIP recv
20171129154915765 <0008> gprs_ns.c:449 NSEI=101 Tx NS RESET (NSVCI=101, cause=O&M intervention)
20171129154915765 <0008> gprs_ns.c:1523 recv error Connection refused during NSIP recv
20171129154918765 <0008> gprs_ns.c:449 NSEI=101 Tx NS RESET (NSVCI=101, cause=O&M intervention)
20171129154918766 <0008> gprs_ns.c:998 NSVCI=101 Rx NS RESET ACK (NSEI=101, NSVCI=101)
20171129154918766 <0008> gprs_ns.c:558 NSEI=101 Tx NS UNBLOCK (NSVCI=101)
20171129154918766 <0008> gprs_ns.c:1420 NSEI=101 Rx NS UNBLOCK ACK
20171129154918767 <000a> gprs_bssgp_pcu.cpp:541 NS-VC 101 is unblocked.
20171129154918768 <0009> gprs_bssgp_bss.c:292 BSSGP (BVCI=0) Tx BVC-RESET CAUSE=O&M intervention
20171129154918768 <0009> gprs_bssgp_pcu.cpp:299 Rx BSSGP BVCI=-1 (SIGN) BVC_RESET_ACK
20171129154918768 <0009> gprs_bssgp_bss.c:292 BSSGP (BVCI=2) Tx BVC-RESET CAUSE=O&M intervention
20171129154918768 <0009> gprs_bssgp_pcu.cpp:299 Rx BSSGP BVCI=-1 (SIGN) BVC_RESET_ACK
20171129154918768 <0009> gprs_bssgp_bss.c:272 BSSGP (BVCI=2) Tx BVC-BLOCK
20171129154918769 <0009> gprs_bssgp_pcu.cpp:310 Rx BSSGP BVCI=-1 (SIGN) BVC_UNBLOCK_ACK

What kind of configs were used while taking this capture?
Which version were used?
Is there test system available?

this was done on a sysmoBTS while working on interconnection with a Quortus SGSN. Nobody made claims that this can be reproduced with unmodified OsmoSGSN.

You have to re-create the scenario yourself, i.e. make sure that the real or simulated SGSN performs NS-RESET and NS-ALIVE but never NS-UNBLOCKS. If you cannot reproduce then, and/or cannot see based on code review how this might happen, close/reject the ticket.

Seems like a good candidate for TTCN3 test. Although maybe it would be quicker to alter OsmoSGSN - not sure yet.

Likely related to: https://gerrit.osmocom.org/c/libosmocore/+/11833

Should be fixed by above patch which has been merged.