fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/36502?usp=email )

Change subject: msc: fix race condition in TC_mm_id_resp_no_identity ......................................................................

msc: fix race condition in TC_mm_id_resp_no_identity

This testcase is failing sporadically ever since it was introduced back in 2019, during 36C3. The problem is that osmo-msc does not react to the malformed MM IDENTITY RESPONSE immediately, but only after timeout of timer X1 (5 seconds, by default); while the testsuite expects the LU REJECT to be received within 5 seconds.

We should ideally fix osmo-msc to react immediately, but for now let's enlarge the LU REJECT waiting timeout in the testcase.

Change-Id: I5d2b5d49df8f7ae1eb12fc137f4256fe6fab9117 Related: OS#6426, OS#4340 --- M msc/BSC_ConnectionHandler.ttcn M msc/MSC_Tests.ttcn 2 files changed, 28 insertions(+), 8 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-ttcn3-hacks refs/changes/02/36502/1

diff --git a/msc/BSC_ConnectionHandler.ttcn b/msc/BSC_ConnectionHandler.ttcn index be12fae..6f8078b 100644 --- a/msc/BSC_ConnectionHandler.ttcn +++ b/msc/BSC_ConnectionHandler.ttcn @@ -916,11 +916,11 @@ } }

-function f_expect_lu_reject(template OCT1 cause := ?) runs on BSC_ConnHdlr { +function f_expect_lu_reject(template OCT1 cause := ?, float Tval := 5.0) runs on BSC_ConnHdlr { var PDU_DTAP_MT dtap_mt; - timer T := 5.0; + timer T;

- T.start; + T.start(Tval); alt { [] BSSAP.receive(tr_PDU_DTAP_MT(tr_ML3_MT_LU_Rej(cause))) { setverdict(pass); diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn index 52a5c2f..513e346 100644 --- a/msc/MSC_Tests.ttcn +++ b/msc/MSC_Tests.ttcn @@ -6616,15 +6616,13 @@ vc_conn.done; }

+/* Test how the MSC handles a malformed MM IDENTITY RESPONSE with no identity. */ friend function f_tc_mm_id_resp_no_identity(charstring id, BSC_ConnHdlrPars pars) runs on BSC_ConnHdlr { - pars.tmsi := 'FFFFFFFF'O; f_init_handler(pars);

- f_create_gsup_expect(hex2str(g_pars.imsi)); - /* Initiate Location Updating using an unknown TMSI */ - f_bssap_compl_l3(f_build_lu_tmsi(pars.tmsi)); + f_bssap_compl_l3(f_build_lu_tmsi('FFFFFFFF'O));

/* Expect an Identity Request, send response with no identity */ BSSAP.receive(tr_PDU_DTAP_MT(tr_ML3_MT_MM_ID_Req(CM_ID_TYPE_IMSI))); @@ -6641,7 +6639,10 @@ } })));

- f_expect_lu_reject(); + /* XXX: Current osmo-msc does not react on bad/malformed MM IDENTITY RESPONSE immediately. + * It instead relies on expiry of timer X1, which is set to 5.0 seconds by default. This + * is not good (DoS vector) and should ideally be fixed, but for now just work it around. */ + f_expect_lu_reject(Tval := 5.0 + 1.0); f_expect_clear(); } testcase TC_mm_id_resp_no_identity() runs on MTC_CT {