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sccp: Handle N-NOTICE.ind (Routing Failure of SCCP CL messages)

ITU Q.714 2.8:
"""
When an end node is informed of a routing failure, this information
is forwarded towards the SCCP user by using the N-DISCONNECT primitive
(refer to reason for release in 2.1.1.2.4/Q.711) or the N-NOTICE primitive
(refer to reason for return in 2.2.2.2.4/Q.711)
"""

We are already handling N-DISCONNECT.ind for CO messages, but
N-NOTICE.ind for CL messages was not being handled.

If CL messages are not arriving to the peer (cnlink), then reset the link
and mark the peer as disconnected, until a new RESET can successfully fo
through.

Related: OS#5917
Change-Id: Ie5f643ba9ac8c443ce95c7f0a89a198fb804c94d
---
M include/osmocom/hnbgw/cnlink.h
M src/osmo-hnbgw/cnlink.c
M src/osmo-hnbgw/hnbgw_sccp.c
3 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/include/osmocom/hnbgw/cnlink.h b/include/osmocom/hnbgw/cnlink.h
index 1d413a9..5571396 100644
--- a/include/osmocom/hnbgw/cnlink.h
+++ b/include/osmocom/hnbgw/cnlink.h
@@ -32,6 +32,7 @@
 	/* SCCP Counters: */
 	CNLINK_CTR_SCCP_N_UNITDATA_REQ,
 	CNLINK_CTR_SCCP_N_UNITDATA_IND,
+	CNLINK_CTR_SCCP_N_NOTICE_IND,
 	CNLINK_CTR_SCCP_N_CONNECT_REQ,
 	CNLINK_CTR_SCCP_N_CONNECT_CNF,
 	CNLINK_CTR_SCCP_N_DATA_REQ,
diff --git a/src/osmo-hnbgw/cnlink.c b/src/osmo-hnbgw/cnlink.c
index 83ca51f..c927c90 100644
--- a/src/osmo-hnbgw/cnlink.c
+++ b/src/osmo-hnbgw/cnlink.c
@@ -84,6 +84,10 @@
 		"sccp:n_unit_data:ind",
 		"Received SCCP N-UNITDATA.ind (DL)"
 	},
+	[CNLINK_CTR_SCCP_N_NOTICE_IND] = {
+		"sccp:n_notice:ind",
+		"Received SCCP N-NOTICE.ind"
+	},
 	[CNLINK_CTR_SCCP_N_CONNECT_REQ] = {
 		"sccp:n_connect:req",
 		"Submit SCCP N-CONNECT.req (UL SCCP CR)"
diff --git a/src/osmo-hnbgw/hnbgw_sccp.c b/src/osmo-hnbgw/hnbgw_sccp.c
index 2020f40..5baef06 100644
--- a/src/osmo-hnbgw/hnbgw_sccp.c
+++ b/src/osmo-hnbgw/hnbgw_sccp.c
@@ -32,6 +32,7 @@
 #include <osmocom/sigtran/sccp_sap.h>
 #include <osmocom/sigtran/sccp_helpers.h>
 #include <osmocom/sigtran/protocol/sua.h>
+#include <osmocom/sccp/sccp_types.h>
 
 #include <osmocom/hnbgw/hnbgw_cn.h>
 #include <osmocom/hnbgw/context_map.h>
@@ -111,6 +112,38 @@
 	return hnbgw_ranap_rx_udt_dl(cnlink, param, msgb_l2(oph->msg), msgb_l2len(oph->msg));
 }
 
+static void handle_notice_ind(struct hnbgw_sccp_user *hsu,
+			      const struct osmo_scu_notice_param *param,
+			      const struct osmo_prim_hdr *oph)
+{
+	struct hnbgw_cnlink *cnlink;
+
+	cnlink = cnlink_from_addr(hsu, &param->calling_addr, oph);
+	if (!cnlink) {
+		LOGP(DCN, LOGL_DEBUG, "(calling_addr=%s) N-NOTICE.ind cause=%u='%s' importance=%u didn't match any cnlink, ignoring\n",
+		     osmo_sccp_addr_dump(&param->calling_addr),
+		     param->cause, osmo_sccp_return_cause_name(param->cause),
+		     param->importance);
+		return;
+	}
+
+	LOG_CNLINK(cnlink, DCN, LOGL_NOTICE, "N-NOTICE.ind cause=%u='%s' importance=%u\n",
+		   param->cause, osmo_sccp_return_cause_name(param->cause),
+		   param->importance);
+	CNLINK_CTR_INC(cnlink, CNLINK_CTR_SCCP_N_NOTICE_IND);
+	switch (param->cause) {
+	case SCCP_RETURN_CAUSE_SUBSYSTEM_CONGESTION:
+	case SCCP_RETURN_CAUSE_NETWORK_CONGESTION:
+		/* Transient failures (hopefully), keep going. */
+		return;
+	default:
+		break;
+	}
+
+	/* Messages are not arriving to destination of cnlink. Kick it back to DISC state. */
+	cnlink_set_disconnected(cnlink);
+}
+
 static int handle_cn_conn_conf(struct hnbgw_sccp_user *hsu,
 			       const struct osmo_scu_connect_param *param,
 			       struct osmo_prim_hdr *oph)
@@ -318,6 +351,9 @@
 	case OSMO_PRIM(OSMO_SCU_PRIM_N_UNITDATA, PRIM_OP_INDICATION):
 		rc = handle_cn_unitdata(hsu, &prim->u.unitdata, oph);
 		break;
+	case OSMO_PRIM(OSMO_SCU_PRIM_N_NOTICE, PRIM_OP_INDICATION):
+		handle_notice_ind(hsu, &prim->u.notice, oph);
+		break;
 	case OSMO_PRIM(OSMO_SCU_PRIM_N_CONNECT, PRIM_OP_CONFIRM):
 		rc = handle_cn_conn_conf(hsu, &prim->u.connect, oph);
 		break;

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