[M] Change in osmo-msc[master]: vlr: add PS support

6 Jan 2026

lynxis lazus has submitted this change. ( https://gerrit.osmocom.org/c/osmo-msc/+/38490?usp=email )
Change subject: vlr: add PS support
......................................................................
vlr: add PS support
Add vlr_ra_update() similar to vlr_lu_update().
Implement resending of GMM PDUs. While CS has a reliable connection
between the MS and MSC, the MS and SGSN doesn't have such connection.
The PDU is resend N times before the LU fsm is failing.
Change-Id: Ie9ffeb140c9d354b3a0f4822e2619f623235add0
---
M src/libvlr/vlr.c
M src/libvlr/vlr_lu_fsm.c
2 files changed, 220 insertions(+), 2 deletions(-)
Approvals:
  fixeria: Looks good to me, but someone else must approve
  daniel: Looks good to me, approved
  Jenkins Builder: Verified

diff --git a/src/libvlr/vlr.c b/src/libvlr/vlr.c
index 21f9fc6..919def3 100644
--- a/src/libvlr/vlr.c
+++ b/src/libvlr/vlr.c
@@ -1487,6 +1487,15 @@
    }
 }
+/* SGSN->VLR: Subscriber has provided ATTACH/RAU Complete */
+int vlr_subscr_rx_rau_complete(struct vlr_subscr *vsub)
+{
+	if (!vsub->lu_fsm)
+		return -EINVAL;
+
+	return osmo_fsm_inst_dispatch(vsub->lu_fsm, VLR_ULA_E_NEW_TMSI_ACK, NULL);
+}
+
 bool vlr_subscr_expire(struct vlr_subscr *vsub)
 {
    if (vsub->lu_complete) {
diff --git a/src/libvlr/vlr_lu_fsm.c b/src/libvlr/vlr_lu_fsm.c
index ec459a1..4bed335 100644
--- a/src/libvlr/vlr_lu_fsm.c
+++ b/src/libvlr/vlr_lu_fsm.c
@@ -354,6 +354,7 @@
    uint8_t cause;
    bool assign_tmsi;
    enum vlr_lu_type lu_type;
+	int N; /*< counter of timeouts */
 };
static inline struct lu_compl_vlr_priv *lu_compl_vlr_fi_priv(struct osmo_fsm_inst *fi);
@@ -407,6 +408,7 @@
    OSMO_ASSERT(vlr);
OSMO_ASSERT(event == LU_COMPL_VLR_E_START);
+	lcvp->N = 0;
/* TODO: National Roaming restrictions? */
    /* TODO: Roaming restriction due to unsupported feature in subscriber
@@ -564,6 +566,47 @@
    vlr_lu_compl_fsm_success(fi);
 }
+static void vlr_lu_compl_fsm_reset_n(struct osmo_fsm_inst *fi, uint32_t prev_state)
+{
+	struct lu_compl_vlr_priv *lcvp = lu_compl_vlr_fi_priv(fi);
+	lcvp->N = 0;
+}
+
+static int lu_compl_vlr_timeout(struct osmo_fsm_inst *fi)
+{
+	struct lu_compl_vlr_priv *lcvp = lu_compl_vlr_fi_priv(fi);
+	struct vlr_instance *vlr = lcvp->vsub->vlr;
+	struct vlr_subscr *vsub = lcvp->vsub;
+
+	/* on cs: terminate the FSM */
+	if (vlr_is_cs(vlr))
+		return 1;
+
+	/* PS: we have to resend the complete message 5x times, before failing */
+	lcvp->N++;
+	if (lcvp->N >= 5)
+		return 1;
+
+	LOGPFSML(fi, LOGL_ERROR, "LU Compl timeout T%d / N%d\n", fi->T, lcvp->N);
+
+	switch (fi->state) {
+	case LU_COMPL_VLR_S_WAIT_IMEI:
+	case LU_COMPL_VLR_S_WAIT_IMEI_TMSI:
+		vlr->ops.tx_id_req(lcvp->msc_conn_ref, GSM_MI_TYPE_IMEI);
+		break;
+	case LU_COMPL_VLR_S_WAIT_TMSI_CNF:
+		vlr->ops.tx_lu_acc(lcvp->msc_conn_ref, vsub->tmsi_new, lcvp->lu_type);
+		break;
+	default:
+		OSMO_ASSERT(0);
+		break;
+	}
+
+	osmo_timer_schedule(&fi->timer, vlr_timer_secs(vlr, fi->T, fi->T), 0);
+
+	return 0;
+}
+
 static const struct osmo_fsm_state lu_compl_vlr_states[] = {
    [LU_COMPL_VLR_S_INIT] = {
    	.in_event_mask = S(LU_COMPL_VLR_E_START),
@@ -586,6 +629,7 @@
    			 S(LU_COMPL_VLR_E_IMEI_CHECK_NACK),
    	.out_state_mask = S(LU_COMPL_VLR_S_DONE),
    	.name = OSMO_STRINGIFY(LU_COMPL_VLR_S_WAIT_IMEI),
+		.onenter = vlr_lu_compl_fsm_reset_n,
    	.action = lu_compl_vlr_wait_imei,
    },
    [LU_COMPL_VLR_S_WAIT_IMEI_TMSI] = {
@@ -594,12 +638,14 @@
    	.out_state_mask = S(LU_COMPL_VLR_S_DONE) |
    			  S(LU_COMPL_VLR_S_WAIT_TMSI_CNF),
    	.name = OSMO_STRINGIFY(LU_COMPL_VLR_S_WAIT_IMEI_TMSI),
+		.onenter = vlr_lu_compl_fsm_reset_n,
    	.action = lu_compl_vlr_wait_imei,
    },
    [LU_COMPL_VLR_S_WAIT_TMSI_CNF] = {
    	.in_event_mask = S(LU_COMPL_VLR_E_NEW_TMSI_ACK),
    	.out_state_mask = S(LU_COMPL_VLR_S_DONE),
    	.name = OSMO_STRINGIFY(LU_COMPL_VLR_S_WAIT_TMSI_CNF),
+		.onenter = vlr_lu_compl_fsm_reset_n,
    	.action = lu_compl_vlr_wait_tmsi,
    },
    [LU_COMPL_VLR_S_DONE] = {
@@ -616,6 +662,7 @@
    .allstate_action = NULL,
    .log_subsys = DLGLOBAL,
    .event_names = lu_compl_vlr_event_names,
+	.timer_cb = lu_compl_vlr_timeout,
 };
static inline struct lu_compl_vlr_priv *lu_compl_vlr_fi_priv(struct osmo_fsm_inst *fi)
@@ -711,6 +758,8 @@
    uint32_t tmsi;
    struct osmo_location_area_id old_lai;
    struct osmo_location_area_id new_lai;
+	struct osmo_routing_area_id old_rai;
+	struct osmo_routing_area_id new_rai;
    bool authentication_required;
    /* is_ciphering_to_be_attempted: true when any A5/n > 0 are enabled. Ciphering is allowed, always attempt to get Auth Info from
     * the HLR. */
@@ -722,6 +771,9 @@
    bool is_r99;
    bool is_utran;
    bool assign_tmsi;
+
+	/*! count times timer T timed out */
+	int N;
 };
@@ -1383,6 +1435,12 @@
    }
 }
+static void lu_fsm_wait_imsi_onenter(struct osmo_fsm_inst *fi, uint32_t prev_state)
+{
+	struct lu_fsm_priv *lfp = lu_fsm_fi_priv(fi);
+	lfp->N = 0;
+}
+
 static const struct osmo_fsm_state vlr_lu_fsm_states[] = {
    [VLR_ULA_S_IDLE] = {
    	.in_event_mask = S(VLR_ULA_E_UPDATE_LA),
@@ -1447,6 +1505,7 @@
    			  S(VLR_ULA_S_WAIT_HLR_UPD) |
    			  S(VLR_ULA_S_DONE),
    	.name = OSMO_STRINGIFY(VLR_ULA_S_WAIT_IMSI),
+		.onenter = lu_fsm_wait_imsi_onenter,
    	.action = lu_fsm_wait_imsi,
    },
    [VLR_ULA_S_WAIT_HLR_CHECK_IMEI_EARLY] = {
@@ -1508,6 +1567,59 @@
    	vsub->lu_fsm = NULL;
 }
+int fsm_lu_timer_cb(struct osmo_fsm_inst *fi)
+{
+	struct lu_fsm_priv *lfp = lu_fsm_fi_priv(fi);
+	struct vlr_instance *vlr = lfp->vlr;
+	struct vlr_subscr *vsub = lfp->vsub;
+
+	/* only PS requires resending, CS terminate FSM */
+	if (vlr_is_cs(vlr))
+		return 1;
+
+	/* PS: we have to resend the complete message 5x times, before failing */
+	if (++lfp->N >= 5) {
+		/* LU reject and terminate FSM */
+		uint8_t gsm48_cause;
+
+		switch (fi->state) {
+		case VLR_ULA_S_WAIT_IMSI:
+		case VLR_ULA_S_WAIT_CIPH:
+			gsm48_cause = GSM48_REJECT_MS_IDENTITY_NOT_DERVIVABLE;
+			break;
+		case VLR_ULA_S_WAIT_AUTH: /* HLR/GSUP timeout */
+		default:
+			gsm48_cause = GSM48_REJECT_NETWORK_FAILURE;
+			break;
+		}
+
+		lfp->vlr->ops.tx_lu_rej(lfp->msc_conn_ref, gsm48_cause, lfp->lu_type);
+		/* 1 will terminate the fsm */
+		return 1;
+	}
+
+	switch (fi->state) {
+	case VLR_ULA_S_WAIT_CIPH:
+		if (vlr_set_ciph_mode(vsub->vlr, fi, lfp->msc_conn_ref,
+				  vsub->sec_ctx,
+				  vsub->vlr->cfg.retrieve_imeisv_ciphered)) {
+			LOGPFSML(fi, LOGL_ERROR,
+				 "Failed to re-send Ciphering Mode Command\n");
+			lu_fsm_failure(fi, GSM48_REJECT_NETWORK_FAILURE);
+			return 0;
+		}
+		break;
+	case VLR_ULA_S_WAIT_IMSI:
+		vlr->ops.tx_id_req(lfp->msc_conn_ref, GSM_MI_TYPE_IMSI);
+		break;
+	}
+
+	osmo_timer_schedule(&fi->timer, vlr_timer_secs(vlr, fi->T, fi->T), 0);
+
+	return 0;
+}
+
+
 static struct osmo_fsm vlr_lu_fsm = {
    .name = "vlr_lu_fsm",
    .states = vlr_lu_fsm_states,
@@ -1517,6 +1629,7 @@
    .log_subsys = DLGLOBAL,
    .event_names = fsm_lu_event_names,
    .cleanup = fsm_lu_cleanup,
+	.timer_cb = fsm_lu_timer_cb,
 };
static inline struct lu_fsm_priv *lu_fsm_fi_priv(struct osmo_fsm_inst *fi)
@@ -1525,8 +1638,8 @@
    return (struct lu_fsm_priv*)fi->priv;
 }
-struct osmo_fsm_inst *
-vlr_loc_update(struct osmo_fsm_inst *parent,
+static struct osmo_fsm_inst *
+_vlr_loc_update(struct osmo_fsm_inst *parent,
           uint32_t parent_event_success,
           uint32_t parent_event_failure,
           void *parent_event_data,
@@ -1575,6 +1688,102 @@
    }
    fi->priv = lfp;
+	return fi;
+}
+
+struct osmo_fsm_inst *
+vlr_loc_update(struct osmo_fsm_inst *parent,
+	       uint32_t parent_event_success,
+	       uint32_t parent_event_failure,
+	       void *parent_event_data,
+	       struct vlr_instance *vlr, void *msc_conn_ref,
+	       enum vlr_lu_type type, uint32_t tmsi, const char *imsi,
+	       const struct osmo_location_area_id *old_lai,
+	       const struct osmo_location_area_id *new_lai,
+	       bool authentication_required,
+	       bool is_ciphering_to_be_attempted,
+	       bool is_ciphering_required,
+	       uint8_t key_seq,
+	       bool is_r99, bool is_utran,
+	       bool assign_tmsi)
+{
+	struct osmo_fsm_inst *fi = _vlr_loc_update(
+		parent,
+		parent_event_success,
+		parent_event_failure,
+		parent_event_data,
+		vlr, msc_conn_ref,
+		type, tmsi, imsi,
+		old_lai,
+		new_lai,
+		authentication_required,
+		is_ciphering_to_be_attempted,
+		is_ciphering_required,
+		key_seq,
+		is_r99, is_utran,
+		assign_tmsi);
+
+	if (!fi)
+		return NULL;
+
+	LOGPFSM(fi, "rev=%s net=%s%s%s\n",
+		is_r99 ? "R99" : "GSM",
+		is_utran ? "UTRAN" : "GERAN",
+		(authentication_required || is_ciphering_to_be_attempted) ?
+		    " Auth" : " (no Auth)",
+		(authentication_required || is_ciphering_to_be_attempted) ?
+		    (is_ciphering_to_be_attempted ? "+Ciph" : " (no Ciph)")
+									  : "");
+
+	if (is_utran && !authentication_required)
+		LOGPFSML(fi, LOGL_ERROR,
+			 "Authentication off on UTRAN network. Good luck.\n");
+
+	osmo_fsm_inst_dispatch(fi, VLR_ULA_E_UPDATE_LA, NULL);
+
+	return fi;
+}
+
+struct osmo_fsm_inst *
+vlr_ra_update(struct osmo_fsm_inst *parent,
+	      uint32_t parent_event_success,
+	      uint32_t parent_event_failure,
+	      void *parent_event_data,
+	      struct vlr_instance *vlr, void *msc_conn_ref,
+	      enum vlr_lu_type type, uint32_t tmsi, const char *imsi,
+	      const struct osmo_routing_area_id *old_rai,
+	      const struct osmo_routing_area_id *new_rai,
+	      bool authentication_required,
+	      bool is_ciphering_to_be_attempted,
+	      bool is_ciphering_required,
+	      uint8_t key_seq,
+	      bool is_r99, bool is_utran,
+	      bool assign_tmsi)
+{
+	struct lu_fsm_priv *lfp;
+	struct osmo_fsm_inst *fi = _vlr_loc_update(
+		parent,
+		parent_event_success,
+		parent_event_failure,
+		parent_event_data,
+		vlr, msc_conn_ref,
+		type, tmsi, imsi,
+		&old_rai->lac,
+		&new_rai->lac,
+		authentication_required,
+		is_ciphering_to_be_attempted,
+		is_ciphering_required,
+		key_seq,
+		is_r99, is_utran,
+		assign_tmsi);
+
+	if (!fi)
+		return NULL;
+
+	lfp = fi->priv;
+	lfp->old_rai = *old_rai;
+	lfp->new_rai = *new_rai;
+
    LOGPFSM(fi, "rev=%s net=%s%s%s\n",
    	is_r99 ? "R99" : "GSM",
    	is_utran ? "UTRAN" : "GERAN",
-- 
To view, visit https://gerrit.osmocom.org/c/osmo-msc/+/38490?usp=email
To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings?usp=email

Gerrit-MessageType: merged
Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-Change-Id: Ie9ffeb140c9d354b3a0f4822e2619f623235add0
Gerrit-Change-Number: 38490
Gerrit-PatchSet: 14
Gerrit-Owner: lynxis lazus lynxis@fe80.eu
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: daniel dwillmann@sysmocom.de
Gerrit-Reviewer: fixeria vyanitskiy@sysmocom.de
Gerrit-Reviewer: laforge laforge@osmocom.org
Gerrit-Reviewer: lynxis lazus lynxis@fe80.eu
Gerrit-Reviewer: neels nhofmeyr@sysmocom.de
Gerrit-Reviewer: pespin pespin@sysmocom.de



    

2026

2025

2024

2023

2022

[M] Change in osmo-msc[master]: vlr: add PS support