[M] Change in osmo-msc[master]: msc: Initial implementation of N-PCSTATE.ind

15 Jul 2025

pespin has submitted this change. ( https://gerrit.osmocom.org/c/osmo-msc/+/40630?usp=email )
Change subject: msc: Initial implementation of N-PCSTATE.ind
......................................................................
msc: Initial implementation of N-PCSTATE.ind
Related: OS#5917
Change-Id: Ice1b2c163b1b0d134fcaa1c8bf543038a35fabdf
---
M include/osmocom/msc/ran_peer.h
M src/libmsc/ran_peer.c
M src/libmsc/sccp_ran.c
3 files changed, 158 insertions(+), 0 deletions(-)
Approvals:
  osmith: Looks good to me, but someone else must approve
  pespin: Looks good to me, approved
  Jenkins Builder: Verified
  laforge: Looks good to me, but someone else must approve

diff --git a/include/osmocom/msc/ran_peer.h b/include/osmocom/msc/ran_peer.h
index ea6187a..cf6097c 100644
--- a/include/osmocom/msc/ran_peer.h
+++ b/include/osmocom/msc/ran_peer.h
@@ -1,5 +1,6 @@
 #pragma once
+#include <stdint.h>
 #include <osmocom/core/linuxlist.h>
 #include <osmocom/gsm/gsm0808.h>
 #include <osmocom/sigtran/sccp_sap.h>
@@ -80,6 +81,8 @@
    RAN_PEER_EV_MSG_DOWN_CO,
    RAN_PEER_EV_RX_RESET,
    RAN_PEER_EV_RX_RESET_ACK,
+	RAN_PEER_EV_AVAILABLE,
+	RAN_PEER_EV_UNAVAILABLE
 };
struct ran_peer_ev_ctx {
@@ -90,6 +93,7 @@
struct ran_peer *ran_peer_find_or_create(struct sccp_ran_inst *sri, const struct osmo_sccp_addr *peer_addr);
 struct ran_peer *ran_peer_find_by_addr(const struct sccp_ran_inst *sri, const struct osmo_sccp_addr *peer_addr);
+struct ran_peer *ran_peer_find_by_pc(const struct sccp_ran_inst *sri, uint32_t pc);
void ran_peer_cells_seen_add(struct ran_peer *ran_peer, const struct gsm0808_cell_id *id);
diff --git a/src/libmsc/ran_peer.c b/src/libmsc/ran_peer.c
index a33608d..26cd7cd 100644
--- a/src/libmsc/ran_peer.c
+++ b/src/libmsc/ran_peer.c
@@ -98,6 +98,21 @@
    return NULL;
 }
+/* Find a ran_peer (BSC/RNC) by its remote Point Code */
+struct ran_peer *ran_peer_find_by_pc(const struct sccp_ran_inst *sri, uint32_t pc)
+{
+	struct ran_peer *rp;
+	struct osmo_ss7_instance *cs7 = osmo_sccp_get_ss7(sri->sccp);
+	struct osmo_sccp_addr rem_addr;
+
+	osmo_sccp_make_addr_pc_ssn(&rem_addr, pc, sri->ran->ssn);
+	rp = ran_peer_find_by_addr(sri, &rem_addr);
+	if (rp)
+		return rp;
+	LOGP(DMSC, LOGL_DEBUG, "No ran_peer found under remote address: %s\n", osmo_sccp_addr_name(cs7, &rem_addr));
+	return NULL;
+}
+
 void ran_peer_cells_seen_add(struct ran_peer *ran_peer, const struct gsm0808_cell_id *cid)
 {
    if (!cell_id_list_add_cell(ran_peer, &ran_peer->cells_seen, cid))
@@ -292,6 +307,15 @@
    	ran_peer_rx_reset(rp, msg);
    	return;
+	case RAN_PEER_EV_AVAILABLE:
+		/* Send a RESET to the peer. */
+		ran_peer_reset(rp);
+		return;
+
+	case RAN_PEER_EV_UNAVAILABLE:
+		/* Do nothing, wait for peer to come up again. */
+		return;
+
    default:
    	LOG_RAN_PEER(rp, LOGL_ERROR, "Unhandled event: %s\n", osmo_fsm_event_name(&ran_peer_fsm, event));
    	return;
@@ -327,6 +351,15 @@
    	ran_peer_rx_reset(rp, msg);
    	return;
+	case RAN_PEER_EV_AVAILABLE:
+		/* Send a RESET to the peer. */
+		ran_peer_reset(rp);
+		return;
+
+	case RAN_PEER_EV_UNAVAILABLE:
+		ran_peer_state_chg(rp, RAN_PEER_ST_WAIT_RX_RESET);
+		return;
+
    default:
    	LOG_RAN_PEER(rp, LOGL_ERROR, "Unhandled event: %s\n", osmo_fsm_event_name(&ran_peer_fsm, event));
    	return;
@@ -441,6 +474,15 @@
    	ran_peer_rx_reset(rp, msg);
    	return;
+	case RAN_PEER_EV_AVAILABLE:
+		/* Do nothing, we were already up. */
+		return;
+
+	case RAN_PEER_EV_UNAVAILABLE:
+		ran_peer_discard_all_conns(rp);
+		ran_peer_state_chg(rp, RAN_PEER_ST_WAIT_RX_RESET);
+		return;
+
    default:
    	LOG_RAN_PEER(rp, LOGL_ERROR, "Unhandled event: %s\n", osmo_fsm_event_name(&ran_peer_fsm, event));
    	return;
@@ -470,6 +512,8 @@
    OSMO_VALUE_STRING(RAN_PEER_EV_MSG_DOWN_CO),
    OSMO_VALUE_STRING(RAN_PEER_EV_RX_RESET),
    OSMO_VALUE_STRING(RAN_PEER_EV_RX_RESET_ACK),
+	OSMO_VALUE_STRING(RAN_PEER_EV_AVAILABLE),
+	OSMO_VALUE_STRING(RAN_PEER_EV_UNAVAILABLE),
    {}
 };
@@ -483,6 +527,8 @@
    		| S(RAN_PEER_EV_RX_RESET)
    		| S(RAN_PEER_EV_MSG_UP_CO_INITIAL)
    		| S(RAN_PEER_EV_MSG_UP_CO)
+			| S(RAN_PEER_EV_AVAILABLE)
+			| S(RAN_PEER_EV_UNAVAILABLE)
    		,
    	.out_state_mask = 0
    		| S(RAN_PEER_ST_WAIT_RX_RESET)
@@ -499,6 +545,8 @@
    		| S(RAN_PEER_EV_RX_RESET_ACK)
    		| S(RAN_PEER_EV_MSG_UP_CO_INITIAL)
    		| S(RAN_PEER_EV_MSG_UP_CO)
+			| S(RAN_PEER_EV_AVAILABLE)
+			| S(RAN_PEER_EV_UNAVAILABLE)
    		,
    	.out_state_mask = 0
    		| S(RAN_PEER_ST_WAIT_RX_RESET)
@@ -517,6 +565,8 @@
    		| S(RAN_PEER_EV_MSG_DOWN_CO_INITIAL)
    		| S(RAN_PEER_EV_MSG_DOWN_CO)
    		| S(RAN_PEER_EV_MSG_DOWN_CL)
+			| S(RAN_PEER_EV_AVAILABLE)
+			| S(RAN_PEER_EV_UNAVAILABLE)
    		,
    	.out_state_mask = 0
    		| S(RAN_PEER_ST_WAIT_RX_RESET)
diff --git a/src/libmsc/sccp_ran.c b/src/libmsc/sccp_ran.c
index 9907f20..71d250e 100644
--- a/src/libmsc/sccp_ran.c
+++ b/src/libmsc/sccp_ran.c
@@ -29,6 +29,7 @@
 #include <osmocom/msc/debug.h>
 #include <osmocom/msc/sccp_ran.h>
 #include <osmocom/msc/ran_infra.h>
+#include <osmocom/msc/ran_peer.h>
struct osmo_tdef g_sccp_tdefs[] = {
    {}
@@ -59,6 +60,96 @@
    return sri;
 }
+static void handle_pcstate_ind(struct sccp_ran_inst *sri, const struct osmo_scu_pcstate_param *pcst)
+{
+	struct osmo_ss7_instance *cs7 = osmo_sccp_get_ss7(sri->sccp);
+	struct ran_peer *rp;
+	bool connected;
+	bool disconnected;
+
+	LOGP(DMSC, LOGL_DEBUG, "N-PCSTATE ind: affected_pc=%u=%s sp_status=%s remote_sccp_status=%s\n",
+	     pcst->affected_pc, osmo_ss7_pointcode_print(cs7, pcst->affected_pc),
+	     osmo_sccp_sp_status_name(pcst->sp_status),
+	     osmo_sccp_rem_sccp_status_name(pcst->remote_sccp_status));
+
+	/* If we don't care about that point-code, ignore PCSTATE. */
+	rp = ran_peer_find_by_pc(sri, pcst->affected_pc);
+	if (!rp) {
+		LOGP(DMSC, LOGL_DEBUG, "No ran_peer found under pc=%u=s%s\n",
+		     pcst->affected_pc, osmo_ss7_pointcode_print(cs7, pcst->affected_pc));
+		return;
+	}
+
+	/* See if this marks the point code to have become available, or to have been lost.
+	 *
+	 * I want to detect two events:
+	 * - connection event (both indicators say PC is reachable).
+	 * - disconnection event (at least one indicator says the PC is not reachable).
+	 *
+	 * There are two separate incoming indicators with various possible values -- the incoming events can be:
+	 *
+	 * - neither connection nor disconnection indicated -- just indicating congestion
+	 *   connected == false, disconnected == false --> do nothing.
+	 * - both incoming values indicate that we are connected
+	 *   --> trigger connected
+	 * - both indicate we are disconnected
+	 *   --> trigger disconnected
+	 * - one value indicates 'connected', the other indicates 'disconnected'
+	 *   --> trigger disconnected
+	 *
+	 * Congestion could imply that we're connected, but it does not indicate that a PC's reachability changed, so no need to
+	 * trigger on that.
+	 */
+	connected = false;
+	disconnected = false;
+
+	switch (pcst->sp_status) {
+	case OSMO_SCCP_SP_S_ACCESSIBLE:
+		connected = true;
+		break;
+	case OSMO_SCCP_SP_S_INACCESSIBLE:
+		disconnected = true;
+		break;
+	default:
+	case OSMO_SCCP_SP_S_CONGESTED:
+		/* Neither connecting nor disconnecting */
+		break;
+	}
+
+	switch (pcst->remote_sccp_status) {
+	case OSMO_SCCP_REM_SCCP_S_AVAILABLE:
+		if (!disconnected)
+			connected = true;
+		break;
+	case OSMO_SCCP_REM_SCCP_S_UNAVAILABLE_UNKNOWN:
+	case OSMO_SCCP_REM_SCCP_S_UNEQUIPPED:
+	case OSMO_SCCP_REM_SCCP_S_INACCESSIBLE:
+		disconnected = true;
+		connected = false;
+		break;
+	default:
+	case OSMO_SCCP_REM_SCCP_S_CONGESTED:
+		/* Neither connecting nor disconnecting */
+		break;
+	}
+
+	if (disconnected) {
+		LOG_RAN_PEER(rp, LOGL_NOTICE,
+			     "now unreachable: N-PCSTATE ind: pc=%u=%s sp_status=%s remote_sccp_status=%s\n",
+			     pcst->affected_pc, osmo_ss7_pointcode_print(cs7, pcst->affected_pc),
+			     osmo_sccp_sp_status_name(pcst->sp_status),
+			     osmo_sccp_rem_sccp_status_name(pcst->remote_sccp_status));
+		osmo_fsm_inst_dispatch(rp->fi, RAN_PEER_EV_UNAVAILABLE, NULL);
+	} else if (connected) {
+		LOG_RAN_PEER(rp, LOGL_NOTICE,
+			     "now available: N-PCSTATE ind: pc=%u=%s sp_status=%s remote_sccp_status=%s\n",
+			     pcst->affected_pc, osmo_ss7_pointcode_print(cs7, pcst->affected_pc),
+			     osmo_sccp_sp_status_name(pcst->sp_status),
+			     osmo_sccp_rem_sccp_status_name(pcst->remote_sccp_status));
+		osmo_fsm_inst_dispatch(rp->fi, RAN_PEER_EV_AVAILABLE, NULL);
+	}
+}
+
 static int sccp_ran_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 {
    struct osmo_sccp_user *scu = _scu;
@@ -141,6 +232,19 @@
    	rc = sri->ran->sccp_ran_ops.up_l2(sri, peer_addr, false, 0, oph->msg);
    	break;
+	case OSMO_PRIM(OSMO_SCU_PRIM_N_PCSTATE, PRIM_OP_INDICATION):
+		handle_pcstate_ind(sri, &prim->u.pcstate);
+		rc = 0;
+		break;
+
+	case OSMO_PRIM(OSMO_SCU_PRIM_N_STATE, PRIM_OP_INDICATION):
+		LOG_SCCP_RAN_CL(sri, NULL, LOGL_INFO,
+				"SCCP-User-SAP: Ignoring %s.%s\n",
+				osmo_scu_prim_type_name(oph->primitive),
+				get_value_string(osmo_prim_op_names, oph->operation));
+		rc = 0;
+		break;
+
    default:
    	LOG_SCCP_RAN_CL(sri, NULL, LOGL_DEBUG, "%s(%s)\n", __func__, osmo_scu_prim_name(oph));
    	rc = -1;
-- 
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Gerrit-MessageType: merged
Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-Change-Id: Ice1b2c163b1b0d134fcaa1c8bf543038a35fabdf
Gerrit-Change-Number: 40630
Gerrit-PatchSet: 4
Gerrit-Owner: pespin pespin@sysmocom.de
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria vyanitskiy@sysmocom.de
Gerrit-Reviewer: laforge laforge@osmocom.org
Gerrit-Reviewer: neels nhofmeyr@sysmocom.de
Gerrit-Reviewer: osmith osmith@sysmocom.de
Gerrit-Reviewer: pespin pespin@sysmocom.de



    

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[M] Change in osmo-msc[master]: msc: Initial implementation of N-PCSTATE.ind