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Bug #2388

OsmoPCU sends BVC-RESET over NS-VC which is still in state BLOCKED

Added by laforge about 1 year ago. Updated 5 months ago.

Status:
Stalled
Priority:
Normal
Assignee:
Target version:
-
Start date:
07/23/2017
Due date:
% Done:

0%

Spec Reference:

Description

When looking at the sequence of events:
  • OsmoPCU is performing the NS-RESET procedure successfully
  • OsmoPCU is performing the NS-ALIVE procedure successfully
  • OsmoPCU is sending the BVC-RESET message before the NS-VC is unblocked using the NS-UNBLOCK procedure

This is too soon. A spec compliant implementation of the SGSN side will thus reject the (first) BVC-RESET due to this too early transmission

History

#1 Updated by laforge about 1 year ago

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

#2 Updated by laforge about 1 year ago

  • Assignee changed from laforge to msuraev

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.

#3 Updated by laforge about 1 year ago

  • Priority changed from Normal to High

#4 Updated by msuraev 11 months ago

  • Status changed from New to In Progress

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.

#5 Updated by msuraev 11 months ago

  • Status changed from In Progress to Feedback
  • Assignee changed from msuraev to laforge

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?

#6 Updated by laforge 11 months ago

  • Status changed from Feedback to New
  • Assignee changed from laforge to msuraev

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.

#7 Updated by msuraev 11 months ago

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

#8 Updated by msuraev 10 months ago

  • Status changed from New to In Progress

#9 Updated by msuraev 9 months ago

  • Status changed from In Progress to Stalled

#10 Updated by laforge 8 months ago

  • Assignee deleted (msuraev)

#11 Updated by laforge 5 months ago

  • Assignee set to stsp
  • Priority changed from High to Normal

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