Bug #4703


ttcn3-bsc-test-latest: 108 of 196 tests fail reproducably since build nr 673

Added by neels over 1 year ago. Updated over 1 year ago.

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I recently broke the latest tests by introducing vty handling bugs (build 671 and 672),
and then after I fixed that, I see a different massive test failure of 'latest' osmo-bsc.
This time it is reproducable (673, 674) and seems unrelated to the vty, at least at first glance.

Actions #1

Updated by neels over 1 year ago

It seems that sometimes osmo-bsc drops a message because it has no MSC connection:

        var octetstring l3 := '00010203040506'O
        f_ipa_tx(0, ts_RSL_EST_IND(chan_nr, valueof(ts_RslLinkID_DCCH(0)), l3));
20200812212927495 DCHAN DEBUG lchan(0-0-0-CCCH_SDCCH4-0)[0x55f9b4f65630]{WAIT_RLL_RTP_ESTABLISH}: (type=SDCCH) SAPI=0 ESTABLISH INDICATION (abis_rsl.c:1647)
20200812212927495 DCHAN DEBUG lchan(0-0-0-CCCH_SDCCH4-0)[0x55f9b4f65630]{WAIT_RLL_RTP_ESTABLISH}: Received Event LCHAN_EV_RLL_ESTABLISH_IND (abis_rsl.c:1680)
20200812212927495 DCHAN DEBUG lchan(0-0-0-CCCH_SDCCH4-0)[0x55f9b4f65630]{WAIT_RLL_RTP_ESTABLISH}: state_chg to ESTABLISHED (lchan_fsm.c:805)
20200812212927495 DMSC DEBUG SUBSCR_CONN[0x55f9b4f64480]{INIT}: Allocated (fsm.c:461)
20200812212927495 DLCLS DEBUG LCLS[0x55f9b4f64640]{NO_LCLS}: Allocated (fsm.c:461)
20200812212927495 DLCLS DEBUG LCLS[0x55f9b4f64640]{NO_LCLS}: is child of SUBSCR_CONN[0x55f9b4f64480] (fsm.c:491)
20200812212927495 DMSC INFO Tx MSC COMPL L3 (gsm_08_08.c:369)
20200812212927495 DMSC NOTICE Initializing resources for new SIGTRAN connection to MSC: RI=NONE... (osmo_bsc_sigtran.c:306)
20200812212927495 DMSC ERROR MSC is not connected. Dropping. (osmo_bsc_sigtran.c:309)

Then the BSSAP.receive(tr_BSSAP_CONNECT_ind(?, ?, tr_BSSMAP_ComplL3(l3))); of course waits for ever for the COMPL L3 that was dropped.

Now to figure out why osmo-bsc latest sporadically considers MSCs as not connected.

Interesting is that the target MSC is usually is indicated by the SCCP address, but here it just says "RI=NONE":

20200812212927495 DMSC NOTICE Initializing resources for new SIGTRAN connection to MSC: RI=NONE... (osmo_bsc_sigtran.c:306)

The successful RESET->ACK happend some two seconds earlier:

20200812212925456 DMSC INFO Rx MSC UDT BSSMAP RESET (osmo_bsc_bssap.c:1013)
20200812212925456 DMSC NOTICE RESET from MSC: RI=SSN_PC,PC=0.23.1,SSN=BSSAP (osmo_bsc_bssap.c:96)
20200812212925456 DMSC NOTICE Sending RESET ACK to MSC: RI=SSN_PC,PC=0.23.1,SSN=BSSAP (osmo_bsc_sigtran.c:121)

So I would have expected the msc to print PC=0.23.1 upon forwarding the EST IND.
Instead osmo-bsc logs an empty SCCP address and concludes that that MSC is not connected.

(this log is from a manual test, but it is also visible in e.g. looking at 'gsm_abis_rsl || bssap || gsmtap_log.ident == OsmoBSC' )

Actions #2

Updated by neels over 1 year ago

OK damn, I figured it out. The failure DOES originate from the VTY changes in this way:

I set 'msc N' / 'allow-attach' flags and rely on the VTY handling code to ignore the 'allow-attach' command, which is not yet in the 'latest' build.
However, to get there, I enter the 'msc 0', 'msc 1' and 'msc 2' config scopes,
which actually then creates three MSCs to be available to osmo-bsc.

Since osmo-bsc latest does not yet properly ignore MSCs that are not even connected, the tests try to contact msc 1 and msc 2 in a sort of round-robin way,
i.e. establishing a new L3 fails two out of three times.

Now figuring out the simplest way to finally get a working 'latest' build...

Actions #3

Updated by neels over 1 year ago

  • Status changed from In Progress to Resolved
  • % Done changed from 0 to 100

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