[M] Change in libosmo-sigtran[master]: Propagate rx M3UA SCON -> MTP-STATUS.ind -> N-PCSTATE.ind - gerrit-log

11 Sep 2025

pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmo-sigtran/+/41092?usp=email )
Change subject: Propagate rx M3UA SCON -> MTP-STATUS.ind -> N-PCSTATE.ind
......................................................................
Propagate rx M3UA SCON -> MTP-STATUS.ind -> N-PCSTATE.ind
Change-Id: I82541612c039b1cc0191cb44d2eecdcbb07fae96
---
M include/osmocom/sigtran/protocol/mtp.h
M src/sccp_internal.h
M src/sccp_scmg.c
M src/xua_snm.c
4 files changed, 74 insertions(+), 17 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-sigtran refs/changes/92/41092/1

diff --git a/include/osmocom/sigtran/protocol/mtp.h b/include/osmocom/sigtran/protocol/mtp.h
index 2f0c7ac..408e442 100644
--- a/include/osmocom/sigtran/protocol/mtp.h
+++ b/include/osmocom/sigtran/protocol/mtp.h
@@ -24,11 +24,19 @@
 extern const struct value_string mtp_si_vals[];
-/* Chapter 15.17.5 of Q.705 */
+/* Chapter 15.17.5 of Q.704 */
 enum mtp_unavail_cause {
    MTP_UNAVAIL_C_UNKNOWN		= 0x0,
    MTP_UNAVAIL_C_UNEQUIP_REM_USER	= 0x1,
    MTP_UNAVAIL_C_INACC_REM_USER	= 0x2,
+	/* This field is not explicitly listed in Q.705 15.17.5, but it is
+	 * expicitly described as one of four options in:
+	 * Q.701 "TABLE 1" and 8.4
+	 * Q.704 2.4.2
+	 * Q.711 "Table 18" and 7.2.4
+	 * Q.714 "Figure D.4"
+	 */
+	MTP_UNAVAIL_C_CONGESTED		= 0x3,
    /* reserved */
 };
diff --git a/src/sccp_internal.h b/src/sccp_internal.h
index 045e49b..5b1b94d 100644
--- a/src/sccp_internal.h
+++ b/src/sccp_internal.h
@@ -80,5 +80,5 @@
 void sccp_scmg_rx_ssn_prohibited(struct osmo_sccp_instance *inst, uint32_t dpc, uint32_t ssn, uint32_t smi);
 void sccp_scmg_rx_mtp_pause(struct osmo_sccp_instance *inst, uint32_t dpc);
 void sccp_scmg_rx_mtp_resume(struct osmo_sccp_instance *inst, uint32_t dpc);
-void sccp_scmg_rx_mtp_status(struct osmo_sccp_instance *inst, uint32_t dpc, enum mtp_unavail_cause cause);
+void sccp_scmg_rx_mtp_status(struct osmo_sccp_instance *inst, uint32_t dpc, enum mtp_unavail_cause cause, uint8_t cong_level);
 int sccp_scmg_init(struct osmo_sccp_instance *inst);
diff --git a/src/sccp_scmg.c b/src/sccp_scmg.c
index 2ffedce..a0f9e1c 100644
--- a/src/sccp_scmg.c
+++ b/src/sccp_scmg.c
@@ -125,7 +125,8 @@
     * [this would require us to track SSNs at each PC, which we don't] */
 }
-void sccp_scmg_rx_mtp_status(struct osmo_sccp_instance *inst, uint32_t dpc, enum mtp_unavail_cause cause)
+/* ITU-T Q.701 8.4, ITU-T Q.711 7.2.4 */
+void sccp_scmg_rx_mtp_status(struct osmo_sccp_instance *inst, uint32_t dpc, enum mtp_unavail_cause cause, uint8_t cong_level)
 {
    struct osmo_scu_pcstate_param pcstate;
    /* 1) Informs the translation function to update the translation tables. */
@@ -142,20 +143,35 @@
    case MTP_UNAVAIL_C_UNKNOWN:
    case MTP_UNAVAIL_C_UNEQUIP_REM_USER:
    case MTP_UNAVAIL_C_INACC_REM_USER:
+		/* 4) local broadcast of "user-out-of-service" for each SSN at that dest
+		* [this would require us to track SSNs at each PC, which we don't] */
+
+		/* 6) local broadcast of "remote SCCP unavailable" */
+		pcstate = (struct osmo_scu_pcstate_param) {
+			.affected_pc = dpc,
+			/* cong_level/RIL doesn't apply here: */
+			.restricted_importance_level = 0,
+			.sp_status = OSMO_SCCP_SP_S_ACCESSIBLE,
+			.remote_sccp_status = OSMO_SCCP_REM_SCCP_S_UNAVAILABLE_UNKNOWN,
+		};
+		sccp_lbcs_local_bcast_pcstate(inst, &pcstate);
+		break;
+	case MTP_UNAVAIL_C_CONGESTED:
+		/* ITU-T Q.714 5.2.4 Signalling point congested
+		 * ITU-T Q.714 5.2.8 Inter- and Intra- SCCP management congestion reports procedure
+		 * ITU-T Q.714 5.3.6.6 Restricted importance level reporting
+		 * ITU-T Q.714 Figure D.4
+		 * ITU-T Q.715 9.5 Coordination of congestion control measures between SCCP and other MTP users */
+		pcstate = (struct osmo_scu_pcstate_param) {
+			.affected_pc = dpc,
+			.restricted_importance_level = cong_level,
+			.sp_status = OSMO_SCCP_SP_S_CONGESTED,
+			.remote_sccp_status = (cong_level == 0) ? OSMO_SCCP_REM_SCCP_S_AVAILABLE :
+								  OSMO_SCCP_REM_SCCP_S_CONGESTED,
+		};
+		sccp_lbcs_local_bcast_pcstate(inst, &pcstate);
    	break;
    }
-
-	/* 4) local broadcast of "user-out-of-service" for each SSN at that dest
-	 * [this would require us to track SSNs at each PC, which we don't] */
-
-	/* 6) local broadcast of "remote SCCP unavailable" */
-	pcstate = (struct osmo_scu_pcstate_param) {
-		.affected_pc = dpc,
-		.restricted_importance_level = 0,
-		.sp_status = OSMO_SCCP_SP_S_ACCESSIBLE,
-		.remote_sccp_status = OSMO_SCCP_REM_SCCP_S_UNAVAILABLE_UNKNOWN,
-	};
-	sccp_lbcs_local_bcast_pcstate(inst, &pcstate);
 }
const struct value_string sccp_scmg_msgt_names[] = {
diff --git a/src/xua_snm.c b/src/xua_snm.c
index 344cc63..fd2ef24 100644
--- a/src/xua_snm.c
+++ b/src/xua_snm.c
@@ -309,7 +309,7 @@
/* Translate to MTP-STATUS.ind towards SCCP (will create N-PCSTATE.ind to SCU) */
    if (s7i->sccp && user == MTP_SI_SCCP)
-		sccp_scmg_rx_mtp_status(s7i->sccp, dpc, cause);
+		sccp_scmg_rx_mtp_status(s7i->sccp, dpc, cause, 0);
/* inform remote ASPs via DUPU */
    llist_for_each_entry(asp, &s7i->asp_list, list) {
@@ -331,6 +331,34 @@
    }
 }
+/* ITU Q.701 8.4 "The level value is included if national options with congestion priorities or multiple signalling link states
+without congestion priorities as in Recommendation Q.704 are implemented" */
+static void xua_snm_scon_to_sccp(struct osmo_sccp_instance *sccp,
+				 const uint32_t *aff_pc, unsigned int num_aff_pc,
+				 uint8_t cong_level)
+{
+	int i;
+
+	for (i = 0; i < num_aff_pc; i++) {
+		/* 32bit "Affected Point Code" consists of a 7-bit mask followed by 14/16/24-bit SS7 PC,
+		 * see RFC 4666 3.4.1 */
+		uint32_t _aff_pc = ntohl(aff_pc[i]);
+		uint32_t pc = _aff_pc & 0xffffff;
+		uint8_t mask = _aff_pc >> 24;
+
+		if (!mask) {
+			sccp_scmg_rx_mtp_status(sccp, pc, MTP_UNAVAIL_C_CONGESTED, cong_level);
+		} else {
+			/* we have to send one MTP primitive for each individual point
+			 * code within that mask */
+			uint32_t maskbits = (1 << mask) - 1;
+			uint32_t fullpc;
+			for (fullpc = (pc & ~maskbits); fullpc <= (pc | maskbits); fullpc++)
+				sccp_scmg_rx_mtp_status(sccp, fullpc, MTP_UNAVAIL_C_CONGESTED, cong_level);
+		}
+	}
+}
+
 static void xua_snm_scon(struct osmo_ss7_as *as, const uint32_t *aff_pc, unsigned int num_aff_pc,
    		 const uint32_t *concerned_dpc, const uint8_t *cong_level, const char *info_string)
 {
@@ -339,7 +367,12 @@
    uint32_t rctx[OSMO_SS7_MAX_RCTX_COUNT];
    unsigned int num_rctx;
-	/* TODO: Translate to MTP-STATUS.ind towards SCCP (will create N-PCSTATE.ind to SCU) */
+	/* TODO: Change Congested level/state of related routes,
+	 * see ITU Q.704 3.8.4 "Congestion status of signalling route sets" */
+
+	/* Translate to MTP-STATUS.ind towards SCCP (will create N-PCSTATE.ind to SCU) */
+	if (s7i->sccp)
+		xua_snm_scon_to_sccp(s7i->sccp, aff_pc, num_aff_pc, cong_level ? *cong_level : 0);
/* RFC4666 1.4.6: "When an SG receives a congestion message (SCON) from an ASP and the SG
     * determines that an SPMC is now encountering congestion, it MAY trigger SS7 MTP3 Transfer
-- 
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Gerrit-MessageType: newchange
Gerrit-Project: libosmo-sigtran
Gerrit-Branch: master
Gerrit-Change-Id: I82541612c039b1cc0191cb44d2eecdcbb07fae96
Gerrit-Change-Number: 41092
Gerrit-PatchSet: 1
Gerrit-Owner: pespin pespin@sysmocom.de



    