[codecs filter] use filter result in MT DTAP CC Setup

So far, we just forwarded the Bearer Capabilities received in MNCC from
the remote MO call leg, and omitted Bearer Cap if the remote call leg
did not provide any.

Instead, always include Bearer Cap, and compose it from the codecs
filter result. Hence the Bearer Cap is now an intersection of MS, BSS
and remote call leg, instead of just the remote call leg.

Related: SYS#5066
Change-Id: I9586221ef56352b7ce4b2604ae0dc04554145a78

3 files changed, 40 insertions, 12 deletions

diff --git a/src/libmsc/gsm_04_08_cc.c b/src/libmsc/gsm_04_08_cc.c
index 269fd5709..f0aca9cc3 100644
--- a/src/libmsc/gsm_04_08_cc.c
+++ b/src/libmsc/gsm_04_08_cc.c
@@ -695,6 +695,7 @@ static int gsm48_cc_tx_setup(struct gsm_trans *trans, void *arg)
 	struct gsm48_hdr *gh;
 	struct gsm_mncc *setup = arg;
 	int rc, trans_id;
+	struct gsm_mncc_bearer_cap bearer_cap;
 
 	gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh));
 
@@ -759,15 +760,42 @@ static int gsm48_cc_tx_setup(struct gsm_trans *trans, void *arg)
 	codec_filter_run(&trans->cc.codecs);
 	LOG_TRANS(trans, LOGL_DEBUG, "codecs: %s\n", codec_filter_to_str(&trans->cc.codecs));
 
-	/* NEAR FUTURE: upcoming patch will use the codecs filter to determine the Bearer Cap to send to the MS.
-	 * So far just gathering information in the new codecs filter. */
-	/* bearer capability */
-	if (setup->fields & MNCC_F_BEARER_CAP) {
-		/* Create a copy of the bearer capability in the transaction struct, so we
-		 * can use this information later */
-		memcpy(&trans->bearer_cap, &setup->bearer_cap, sizeof(trans->bearer_cap));
-		gsm48_encode_bearer_cap(msg, 0, &setup->bearer_cap);
+	/* Compose Bearer Capability information that reflects only the codecs (Speech Versions) remaining after
+	 * intersecting MS, BSS and remote call leg restrictions. To store in trans for later use, and to include in
+	 * the outgoing CC Setup message. */
+	bearer_cap = (struct gsm_mncc_bearer_cap){
+		.speech_ver = { -1 },
+	};
+	sdp_audio_codecs_to_bearer_cap(&bearer_cap, &trans->cc.codecs.result.audio_codecs);
+	rc = bearer_cap_set_radio(&bearer_cap);
+	if (rc) {
+		LOG_TRANS(trans, LOGL_ERROR, "Error composing Bearer Capability for CC Setup\n");
+		trans_free(trans);
+		msgb_free(msg);
+		return rc;
+	}
+	/* Create a copy of the bearer capability in the transaction struct, so we can use this information later */
+	/* TODO: we should be able to drop trans->bearer_cap, replaced by the codecs filter. Verify this.
+	 * So far let's just store it there like previous code did. */
+	trans->bearer_cap = bearer_cap;
+	/* If no resulting codecs remain, error out. We cannot find a codec that matches both call legs. If the MGW were
+	 * able to transcode, we could use non-identical codecs on each conn of the MGW endpoint, but we are aiming for
+	 * finding a matching codec. */
+	if (bearer_cap.speech_ver[0] == -1) {
+		LOG_TRANS(trans, LOGL_ERROR, "%s: no codec match possible: %s\n",
+			  get_mncc_name(setup->msg_type), codec_filter_to_str(&trans->cc.codecs));
+
+		/* incompatible codecs */
+		rc = mncc_release_ind(trans->net, trans, trans->callref,
+				      GSM48_CAUSE_LOC_PRN_S_LU,
+				      GSM48_CC_CAUSE_INCOMPAT_DEST /* TODO: correct cause code? */);
+		trans->callref = 0;
+		trans_free(trans);
+		msgb_free(msg);
+		return rc;
 	}
+	gsm48_encode_bearer_cap(msg, 0, &bearer_cap);
+
 	/* facility */
 	if (setup->fields & MNCC_F_FACILITY)
 		gsm48_encode_facility(msg, 0, &setup->facility);
diff --git a/tests/msc_vlr/msc_vlr_test_call.c b/tests/msc_vlr/msc_vlr_test_call.c
index 06602f7bc..6c7a8ad4e 100644
--- a/tests/msc_vlr/msc_vlr_test_call.c
+++ b/tests/msc_vlr/msc_vlr_test_call.c
@@ -316,7 +316,7 @@ static void test_call_mt()
 	VERBOSE_ASSERT(security_mode_ctrl_sent, == true, "%d");
 
 	btw("MS sends SecurityModeControl acceptance, VLR accepts, sends CC Setup");
-	dtap_expect_tx("0305" /* CC: Setup */);
+	dtap_expect_tx("0305" /* CC: Setup */ "04 07 60 04 05 0b 06 08 87" /* Bearer Cap */);
 	ms_sends_security_mode_complete(1);
 
 	btw("MS confirms call, we create a RAN-side RTP and forward MNCC_CALL_CONF_IND");
@@ -419,7 +419,7 @@ static void test_call_mt2()
 	VERBOSE_ASSERT(security_mode_ctrl_sent, == true, "%d");
 
 	btw("MS sends SecurityModeControl acceptance, VLR accepts, sends CC Setup");
-	dtap_expect_tx("0305" /* CC: Setup */);
+	dtap_expect_tx("0305" /* CC: Setup */ "04 07 60 04 05 0b 06 08 87" /* Bearer Cap */);
 	ms_sends_security_mode_complete(1);
 
 	btw("MS confirms call, we create a RAN-side RTP and forward MNCC_CALL_CONF_IND");
diff --git a/tests/msc_vlr/msc_vlr_test_call.err b/tests/msc_vlr/msc_vlr_test_call.err
index d97806d5d..e1d2f4df6 100644
--- a/tests/msc_vlr/msc_vlr_test_call.err
+++ b/tests/msc_vlr/msc_vlr_test_call.err
@@ -761,7 +761,7 @@ DCC trans(CC:NULL IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAG
 DCC trans(CC:NULL IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP callref-0x423 tid-0) new state NULL -> CALL_PRESENT
 DIUCS msc_a(IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP){MSC_A_ST_COMMUNICATING}: Sending DTAP: CC GSM48_MT_CC_SETUP
 DMSC msc_a(IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP){MSC_A_ST_COMMUNICATING}: RAN encode: DTAP on UTRAN-Iu
-- DTAP --UTRAN-Iu--> MS: GSM48_MT_CC_SETUP: 0305
+- DTAP --UTRAN-Iu--> MS: GSM48_MT_CC_SETUP: 030504076004050b060887
 - DTAP matches expected message
 DMSC dummy_msc_i(IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP){0}: Received Event MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST
 DREF VLR subscr IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100 - Paging: now used by 3 (attached,CC,active-conn)
@@ -1230,7 +1230,7 @@ DCC trans(CC:NULL IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAG
 DCC trans(CC:NULL IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP callref-0x423 tid-0) new state NULL -> CALL_PRESENT
 DIUCS msc_a(IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP){MSC_A_ST_COMMUNICATING}: Sending DTAP: CC GSM48_MT_CC_SETUP
 DMSC msc_a(IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP){MSC_A_ST_COMMUNICATING}: RAN encode: DTAP on UTRAN-Iu
-- DTAP --UTRAN-Iu--> MS: GSM48_MT_CC_SETUP: 0305
+- DTAP --UTRAN-Iu--> MS: GSM48_MT_CC_SETUP: 030504076004050b060887
 - DTAP matches expected message
 DMSC dummy_msc_i(IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100:UTRAN-Iu:PAGING_RESP){0}: Received Event MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST
 DREF VLR subscr IMSI-901700000010650:MSISDN-42342:TMSI-0x03020100 - Paging: now used by 3 (attached,CC,active-conn)