Procedure: EventSubscription (NlmfLocation — Periodic + Area-of-Interest Reporting + CancelLocation)

Mirrored documentation

Mirrored read-only from claudia-5gc @ v2.3.1. Edit upstream, not here.

Spec: TS 29.572 §5.2.3 (Nlmf_Location_EventSubscription Create/Get/Delete) · §5.2.2.5 (CancelLocation for in-progress one-shot) · §6.1.6.2.4 (LocationNotification body schema) · TS 23.273 §7.2 step B2 (deferred subscription use case) · TS 29.571 §5.2 (common API types: subscriptions, notifications) · TS 29.572 §5.2.2.2 (re-uses DetermineLocation for each sample) Status: ⏳ Planned (LMF-003) — gates implementation; no code until this doc is reviewed Primary NF: LMF (Nlmf_Location producer + notification HTTP/2 mTLS client) Other NFs involved: AMF (Namf_Location producer, consumed once per sample), gNB + UE (via the AMF N2 relay), LCS Client / Consumer (subscriber + notification receiver)

Context

LMF-001/002 implement one-shot Cell-ID positioning (DetermineLocation): a caller POSTs once and receives a single LocationData. For ongoing tracking the caller would have to poll, re-issuing the request on a loop. EventSubscription (TS 29.572 §5.2.3) adds a subscription model so the LMF itself drives the repetition and pushes results to the caller’s notificationUri as LocationNotification bodies (TS 29.572 §6.1.6.2.4). This is the deferred location use case of TS 23.273 §7.2 step B2.

Two event trigger types are supported:

• PERIODIC_REPORTING — the LMF re-runs the internal DetermineLocation routine for the subscribed UE every reportingInterval (default 10 s) and POSTs every result to the notificationUri.
• AREA_OF_INTEREST (AOI) — the LMF samples the UE position every sampling_interval (default 5 s) and POSTs a notification only when the UE enters or exits a configured WGS84 polygon. A per-subscription state machine tracks IN / OUT / UNKNOWN; a notification fires only on a state transition.

Each “sample” inside a subscription is the same internal locate path used by LMF-001: LMF → Namf_Location (AMF) → NGAP relay → gNB → LocationReport. EventSubscription adds no new N2 signalling — it orchestrates repeated calls to the existing producer chain and adds the notification-push leg.

CancelLocation (TS 29.572 §5.2.2.5) has two flavours covered here:

1. Subscription cancel — DELETE of a subscription resource: stop the goroutine, drop the registry entry, return 204.
2. In-progress one-shot cancel — POST …/cancel-loc aborts a currently blocked DetermineLocation request (the UE may be paging / awaiting a LocationReport) by cancelling its request context.

Scope boundary (LMF-003)

• In-memory registry only. Subscriptions live in a map[string]*subscription guarded by a sync.RWMutex. Redis persistence is a deferred follow-up — on LMF restart all subscriptions are lost (acceptable for this task).
• AOI containment uses the ray-casting (even-odd crossing) algorithm, no external geometry dependency.
• Notification delivery is best-effort: one retry on a 5xx / transport error, then the notification is dropped (logged). No persistent queue, no backoff escalation.
• One goroutine per subscription, started on POST, stopped on DELETE or duration expiry.

Endpoints (LMF SBI, port 8012, mTLS + HTTP/2)

Method	Path	Operation	Spec	Success
POST	/nlmf-loc/v1/subscriptions	EventSubscription Create	TS 29.572 §5.2.3.2	201 + Location header
GET	/nlmf-loc/v1/subscriptions/{subId}	EventSubscription Get (status)	TS 29.572 §5.2.3.3	200 subscription resource
DELETE	/nlmf-loc/v1/subscriptions/{subId}	EventSubscription Delete (cancel)	TS 29.572 §5.2.3.4 / §5.2.2.5	204
POST	/nlmf-loc/v1/ue-contexts/{ueContextId}/cancel-loc	CancelLocation (in-progress one-shot)	TS 29.572 §5.2.2.5	204

{subId} is a ULID generated by the LMF on Create. {ueContextId} is the same UE identifier form (imsi-<digits> SUPI or 5G-GUTI) used by DetermineLocation.

Specifications

Topic	Reference
Nlmf_Location_EventSubscription (Create / Get / Delete)	TS 29.572 §5.2.3
CancelLocation (in-progress one-shot)	TS 29.572 §5.2.2.5
LocationNotification body schema	TS 29.572 §6.1.6.2.4
LocationData / RequestLocInfo data model	TS 29.572 §6.1.6.2.2
Deferred location subscription use case	TS 23.273 §7.2 step B2
Common API types — subscriptions & notifications	TS 29.571 §5.2
Per-sample locate (re-used)	TS 29.572 §5.2.2.2 (DetermineLocation), TS 29.518 §5.2.2.6 (Namf_Location)
ProblemDetails / cause strings	TS 29.500 §5.2.4, TS 29.571 §5.2.7

[VERIFY: clause unclear] — exact ProblemDetails cause enum for an unknown subId (SUBSCRIPTION_NOT_FOUND vs the generic NOT_FOUND of TS 29.571 §5.2.7.5) to be confirmed against the Rel-17 TS29572 YAML. This doc assumes SUBSCRIPTION_NOT_FOUND.

NF interaction overview

                                         (every interval, per subscription)
LCS Client ──POST /subscriptions──▶ LMF ──Namf_Location──▶ AMF ══NGAP (N2 relay)══▶ gNB
   ▲                                 │                       ▲                        │
   │◀── POST notificationUri ────────┤◀──── LocationData ────┘◀── NGAP LocationReport ┘
   │      (LocationNotification)      │
   └──────── 201 + Location ──────────┘   (DELETE /subscriptions/{subId} → 204 stops the loop)

• Nlmf_Location subscription (SBI, mTLS+HTTP/2): LCS Client → LMF (Create / Get / Delete).
• Notification (SBI, mTLS+HTTP/2): LMF → LCS Client — the LMF is the client here, POSTing to the caller-supplied notificationUri. Re-uses shared/sbi.NewMTLSClient.
• Namf_Location (SBI, mTLS+HTTP/2): LMF → AMF, exactly as in LMF-001, once per sample.
• NGAP N2 (SCTP): AMF ↔ gNB — unchanged from LMF-001; the AMF is the sole NGAP relay.

Sequence Diagram 1 — Create + Periodic Notification

[M] = mandatory step; [C] = conditional; [L] = repeats on the goroutine loop tick.

sequenceDiagram
    participant LCS as LCS Client / Consumer
    participant LMF
    participant AMF
    participant gNB

    Note over LCS,LMF: TS 29.572 §5.2.3.2 — EventSubscription Create
    LCS->>LMF: [M] POST /nlmf-loc/v1/subscriptions<br/>LocationEventSubscription {ueContextId(supi/gpsi),<br/>eventTrigger=PERIODIC_REPORTING, reportingInterval=10,<br/>notificationUri, duration}
    Note over LMF: Validate: notificationUri present? UE identity present?<br/>Generate subId (ULID). Insert into registry (RWMutex).<br/>Start goroutine with ticker(reportingInterval).
    LMF-->>LCS: [M] 201 Created<br/>Location: /nlmf-loc/v1/subscriptions/{subId}<br/>body = subscription resource

    loop [L] every reportingInterval until DELETE or duration expiry
        Note over LMF,AMF: TS 29.572 §5.2.2.2 — internal DetermineLocation (per sample)
        LMF->>AMF: [L] POST /namf-loc/v1/ue-contexts/{id}/provide-loc-info
        AMF->>gNB: [L] NGAP LocationReportingControl (ProcCode=16)
        gNB->>AMF: [L] NGAP LocationReport (ProcCode=18) → NRCGI + TAI
        AMF-->>LMF: [L] 200 LocationData {nrCellId, tai}
        Note over LMF: Build LocationNotification {subId, notificationItems:[{locationData}]}<br/>(TS 29.572 §6.1.6.2.4)
        LMF->>LCS: [L] POST notificationUri — LocationNotification
        alt [C] notify returns 5xx / transport error
            LMF->>LCS: [C] POST notificationUri (single retry)
            Note over LMF: still failing → drop this notification (log), keep subscription alive
        end
    end

    Note over LMF: duration elapses → goroutine self-stops, registry entry removed

Sequence Diagram 2 — Area-of-Interest (enter/exit) Notification

sequenceDiagram
    participant LCS as LCS Client / Consumer
    participant LMF
    participant AMF
    participant gNB

    Note over LCS,LMF: TS 29.572 §5.2.3.2 — EventSubscription Create (AOI)
    LCS->>LMF: [M] POST /nlmf-loc/v1/subscriptions<br/>LocationEventSubscription {ueContextId,<br/>eventTrigger=AREA_OF_INTEREST,<br/>areaOfInterest:{polygon:[{lat,lon}...]},<br/>notificationUri, duration}
    Note over LMF: Validate polygon ≥3 vertices, notificationUri, UE identity.<br/>subId (ULID). state = UNKNOWN. ticker(sampling_interval=5s).
    LMF-->>LCS: [M] 201 Created + Location: …/{subId}

    loop [L] every sampling_interval until DELETE or expiry
        LMF->>AMF: [L] POST /namf-loc/v1/ue-contexts/{id}/provide-loc-info
        AMF->>gNB: [L] NGAP LocationReportingControl (16)
        gNB->>AMF: [L] NGAP LocationReport (18) → NRCGI + TAI
        AMF-->>LMF: [L] 200 LocationData {locationEstimate(POINT lat/lon)}
        Note over LMF: ray-casting: is (lat,lon) inside polygon?<br/>newState = IN | OUT
        alt [C] newState != prevState  (transition / crossing)
            Note over LMF: event = AREA_ENTERING (OUT→IN) or AREA_LEAVING (IN→OUT)
            LMF->>LCS: [C] POST notificationUri — LocationNotification {locationData, areaEventInfo}
            Note over LMF: prevState = newState; lastNotified = now
        else [C] newState == prevState (no crossing)
            Note over LMF: no notification (suppressed)
        end
    end

First sample after UNKNOWN: the LMF establishes the baseline state. By default the first resolved state is recorded without firing a notification (suppress the synthetic UNKNOWN→IN/OUT transition). [VERIFY: clause unclear] — TS 29.572 does not pin whether the initial-state notification must fire; this doc suppresses it (configurable later).

Sub-flow — DELETE (subscription cancel) and one-shot CancelLocation

A. DELETE /nlmf-loc/v1/subscriptions/{subId} (TS 29.572 §5.2.3.4 / §5.2.2.5):

1. [M] Look up {subId} in the registry under RLock. Unknown → 404 SUBSCRIPTION_NOT_FOUND.
2. [M] Cancel the subscription’s goroutine context (cancel()); the select { case <-ctx.Done() } arm returns and the goroutine exits cleanly (any in-flight sample is allowed to finish or is abandoned on the next tick).
3. [M] Remove the entry from the registry under Lock.
4. [M] Return 204 No Content.

B. POST /nlmf-loc/v1/ue-contexts/{ueContextId}/cancel-loc (TS 29.572 §5.2.2.5):

1. [M] A one-shot DetermineLocation may be blocked (UE paging / awaiting LocationReport). The handler registered that request in a map[ueContextId]context.CancelFunc (the pendingLoc pattern).
2. [M] Look up the cancel func for {ueContextId}. None in progress → 204 (idempotent no-op) or 404 CONTEXT_NOT_FOUND — [VERIFY: clause unclear] which the spec prefers; this doc returns 204 (idempotent).
3. [C] Call cancel(). The blocked DetermineLocation handler observes ctx.Done() and returns a failure (the AMF Namf call / pending channel unblocks).
4. [M] Return 204 No Content.

Information Elements

EventSubscription request — LocationEventSubscription (LCS Client → LMF, TS 29.572 §6.1.6.2.x / §5.2.3.2)

IE	Type	M/O	Notes
ueContextId	string	M	UE identity (supi/gpsi/5G-GUTI form). Body field or, if modelled as a sub-object, supi/gpsi. At least one identity required.
eventTrigger	enum	M	PERIODIC_REPORTING | AREA_OF_INTEREST
notificationUri	string (URI)	M	Callback the LMF POSTs LocationNotification to. Missing → 400 MANDATORY_IE_MISSING.
reportingInterval	integer (s)	C	Required for PERIODIC_REPORTING. Default 10 s if omitted.
areaOfInterest	object	C	Required for AREA_OF_INTEREST; holds the polygon (see below).
samplingInterval	integer (s)	O	AOI sample cadence; default = default_sampling_interval_s (5 s).
duration	integer (s)	O	Subscription lifetime; on expiry the goroutine self-stops. 0/absent ⇒ a config default max.
locationQoS	object	O	Per-sample accuracy hints, same shape as DetermineLocation.

Area-of-interest polygon — GeographicArea (POLYGON) / GeoJSON-style vertices (TS 29.572 §6.1.6.2.2; TS 29.571 §5.4)

IE	Type	M/O	Notes
shape	string	O	"POLYGON" (default when polygon present)
polygon	array of {lat,lon}	M	WGS84 vertices, ≥3, in order; first/last need not repeat. Ray-casting closes the ring implicitly.
polygon[].lat	float	M	Latitude, decimal degrees
polygon[].lon	float	M	Longitude, decimal degrees

Polygon with <3 vertices → 400 MANDATORY_IE_MISSING (degenerate area).

Subscription resource (LMF internal + GET response body, TS 29.571 §5.2)

Field	Type	Notes
subId	string (ULID)	Resource id; also the {subId} path segment and Location header tail
ueContextId	string	Subscribed UE identity
eventTrigger	enum	PERIODIC_REPORTING | AREA_OF_INTEREST
notificationUri	string	Callback URI
reportingInterval / samplingInterval	integer	Active cadence (whichever applies)
areaOfInterest	object	Echoed polygon (AOI only)
duration	integer	Configured lifetime (s)
created	RFC3339 timestamp	Creation time
lastNotified	RFC3339 timestamp	Last successful notification (null until first)
state	enum	IN | OUT | UNKNOWN (AOI only; meaningless for periodic)

LocationNotification body (LMF → notificationUri, TS 29.572 §6.1.6.2.4)

IE	Type	M/O	Notes
subId	string	M	Correlates the notification to its subscription
notificationItems	array	M	One or more items; MVP sends exactly one per POST
notificationItems[].locationData	object	M	LocationData (TS 29.572 §6.1.6.2.2) — same shape returned by DetermineLocation: locationEstimate(POINT), nrCellId, tai, ageOfLocationEstimate
notificationItems[].areaEventInfo	object	C	AOI only: {event: "AREA_ENTERING"|"AREA_LEAVING"} (the crossing that triggered it)

Example periodic notification body:

{
  "subId": "01J9Z4M7P3K2QF8B6V0CXR2W5T",
  "notificationItems": [
    {
      "locationData": {
        "locationEstimate": { "shape": "POINT", "point": { "lat": 40.4168, "lon": -3.7038 } },
        "nrCellId": "000000010",
        "ageOfLocationEstimate": 0
      }
    }
  ]
}

Example AOI (entering) notification body:

{
  "subId": "01J9Z4M7P3K2QF8B6V0CXR2W5T",
  "notificationItems": [
    {
      "locationData": {
        "locationEstimate": { "shape": "POINT", "point": { "lat": 40.4168, "lon": -3.7038 } },
        "nrCellId": "000000010"
      },
      "areaEventInfo": { "event": "AREA_ENTERING" }
    }
  ]
}

Spec reference table (per step)

Step	Reference	Message / Operation	Direction	M/C
1	TS 29.572 §5.2.3.2	EventSubscription Create (POST /subscriptions)	LCS → LMF	M
2	TS 29.571 §5.2	Generate subId, register resource, start goroutine	LMF internal	M
3	TS 29.572 §5.2.3.2	201 Created + Location header	LMF → LCS	M
4	TS 29.572 §5.2.2.2	Per-sample DetermineLocation (Namf chain)	LMF → AMF → gNB	M (loop)
5	TS 29.518 §5.2.2.6	Namf_Location ProvideLocationInfo	LMF → AMF	M (loop)
6	TS 38.413 §8.17.1	NGAP LocationReportingControl / LocationReport	AMF ↔ gNB	M (loop)
7 (PERIODIC)	TS 29.572 §6.1.6.2.4	POST LocationNotification (every sample)	LMF → notificationUri	M
7 (AOI)	TS 29.572 §6.1.6.2.4	POST LocationNotification (on crossing only)	LMF → notificationUri	C
8	TS 29.572 §5.2.3.3	EventSubscription Get (status)	LCS → LMF	C
9	TS 29.572 §5.2.3.4 / §5.2.2.5	EventSubscription Delete (cancel) → 204	LCS → LMF	M
10	TS 29.572 §5.2.2.5	CancelLocation one-shot (POST …/cancel-loc) → 204	LCS → LMF	C

Error / cause table

Trigger	NF	HTTP	Cause	Behaviour
notificationUri absent in Create body	LMF	400	MANDATORY_IE_MISSING	Reject before registering; no goroutine started. Ref: TS 29.571 §5.2.7.
UE identity absent (supi/gpsi/ueContextId all empty)	LMF	400	MANDATORY_IE_MISSING	Rejected at the Nlmf subscription producer.
eventTrigger=PERIODIC_REPORTING but no reportingInterval	LMF	—	—	Accepted; default 10 s applied (warning logged).
eventTrigger=AREA_OF_INTEREST but no polygon / <3 vertices	LMF	400	MANDATORY_IE_MISSING	Degenerate area rejected.
Unknown eventTrigger value	LMF	400	INVALID_MSG_FORMAT	Unsupported trigger type.
GET /subscriptions/{subId} — unknown subId	LMF	404	SUBSCRIPTION_NOT_FOUND	[VERIFY] vs generic NOT_FOUND.
DELETE /subscriptions/{subId} — unknown subId	LMF	404	SUBSCRIPTION_NOT_FOUND	Nothing to cancel.
Notification POST returns 5xx / transport error	LMF	—	—	Single retry; still failing ⇒ drop this notification, log notify_failed, subscription stays alive. Best-effort.
Notification POST returns 4xx (caller rejects)	LMF	—	—	No retry (client error); drop + log. [VERIFY] whether a persistent 4xx should auto-cancel the subscription — not implemented in LMF-003.
Per-sample locate fails (AMF 404 / UE CM-IDLE timeout / gNB failure)	LMF	—	—	Skip this tick; no notification sent; subscription continues (transient). Logged with the AMF cause.
duration elapses	LMF	—	—	Goroutine self-stops; registry entry removed; no final notification.
POST …/cancel-loc — no in-progress one-shot for that UE	LMF	204	—	Idempotent no-op. [VERIFY] vs 404 CONTEXT_NOT_FOUND.
Subscriber privacy = BLOCK_ALL (UDM lcsData)	LMF	403	PRIVACY_EXCEPTION_DENIED	Privacy gate applies on Create (same as LMF-001/002); subscription refused before registration. Ref: TS 23.273 §9.1.

Cause strings follow TS 29.571 §5.2.7 / TS 29.572 §6.1.x. Unconfirmed enums are flagged [VERIFY: clause unclear] and resolved against the Rel-17 TS29572 YAML during implementation.

NF interaction map (SBI calls this procedure makes)

• LCS Client → LMF: Nlmf_Location_EventSubscription Create (POST /nlmf-loc/v1/subscriptions)
• LCS Client → LMF: Nlmf_Location_EventSubscription Get (GET /nlmf-loc/v1/subscriptions/{subId})
• LCS Client → LMF: Nlmf_Location_EventSubscription Delete (DELETE /nlmf-loc/v1/subscriptions/{subId})
• LCS Client → LMF: Nlmf_Location CancelLocation one-shot (POST /nlmf-loc/v1/ue-contexts/{id}/cancel-loc)
• LMF → AMF: Namf_Location_ProvideLocationInfo (POST /namf-loc/v1/ue-contexts/{id}/provide-loc-info) — once per sample tick (re-used from LMF-001).
• LMF → notificationUri: LocationNotification (POST {caller URI}) — the LMF acts as an HTTP/2 mTLS client (shared/sbi.NewMTLSClient); periodic every tick, AOI only on a crossing.

Implementation notes (for the NF developer)

• Registry: type registry struct { mu sync.RWMutex; subs map[string]*subscription }. All reads under RLock, mutations under Lock. Keep the critical sections tiny — never hold the lock across a network call or a notification POST.
• Subscription resource (per the descriptor): { subId string /*ULID*/, ueContextId string, eventTrigger string, notificationUri string, reportingInterval/samplingInterval time.Duration, areaOfInterest []LatLon, duration time.Duration, created time.Time, lastNotified time.Time, state aoiState /*IN|OUT|UNKNOWN*/, cancel context.CancelFunc }.
• subId: generate via the existing ULID helper (same one used elsewhere for correlation_id). The Location header is /nlmf-loc/v1/subscriptions/<subId>.
• Goroutine template (one per subscription, started on Create):

  ticker := time.NewTicker(interval)
  defer ticker.Stop()
  for {
      select {
      case <-ticker.C:   // locate → (periodic: notify) | (AOI: state machine → maybe notify)
      case <-ctx.Done(): // DELETE or duration expiry → return cleanly
          return
      }
  }

  Wrap with a context.WithTimeout(parent, duration) so expiry cancels the same ctx that DELETE cancels — one cancellation path, no duplicate timers.
• AOI state machine: UNKNOWN → IN|OUT (baseline, suppressed) then notify on every IN↔OUT transition. Store prevState on the subscription; compute newState via ray-casting; notify iff newState != prevState && prevState != UNKNOWN.
• Ray-casting (even-odd rule, no external dep): iterate polygon edges, count how many edges a rightward ray from (lat,lon) crosses; odd ⇒ inside. Use the standard (yi > y) != (yj > y) && x < (xj-xi)*(y-yi)/(yj-yi)+xi test. Add a package doc comment with the algorithm reference; this is not a 3GPP magic number.
• Per-sample locate: call the same internal routine handleDetermineLocation uses — factor the locate body into a method (e.g. s.locate(ctx, ueContextId, supi) (LocationData, cause, error)) so both the one-shot handler and the goroutine share it. The privacy gate already lives there; apply the privacy check once at Create (refuse the subscription) rather than every tick.
• Notification client: reuse shared/sbi.NewMTLSClient. POST the LocationNotification JSON to notificationUri. Retry exactly once on a 5xx or transport error; do not retry on 4xx. Drop-and-log on final failure. Carry the subscription’s correlation_id (or a fresh ULID) in X-Correlation-Id so the notification leg is traceable.
• CancelLocation (one-shot): a map[string]context.CancelFunc keyed by ueContextId (mirrors the existing pendingLoc chan pattern in the AMF). The DetermineLocation handler registers its request ctx cancel on entry and defer-deletes on exit. POST …/cancel-loc looks up and calls cancel().
• Config: add a location_subscription block to nf/lmf/config/dev.yaml:

  location_subscription:
    default_sampling_interval_s: 5      # AOI sample cadence
    default_reporting_interval_s: 10    # periodic default
    max_duration_s: 3600                # cap on subscription lifetime
    notification_retry: 1               # single retry on 5xx

• Routing: register the four new routes on the existing :8012 mux in server.go (POST /nlmf-loc/v1/subscriptions, GET/DELETE /nlmf-loc/v1/subscriptions/{subId}, POST /nlmf-loc/v1/ue-contexts/{ueContextId}/cancel-loc). Keep SBI handlers separate from any reference-point code (anti-pattern: mixing SBI and N2).
• Logging: logging.NewProcedureLogger(ctx, s.logger, "EventSubscription"). nf=LMF; interface=Nlmf (or Nlmf-notify on the push leg with direction=OUT); spec_ref per step (e.g. TS 29.572 §6.1.6.2.4 on the notification). Conditional fields: sub_id, ue_context_id, supi, event_trigger, aoi_state, result, cause, duration_ms, notify_attempt.
• Metrics (extend the existing :9113 set):
  • fivegc_lmf_subscriptions_active (gauge) — current registry size.
  • fivegc_lmf_notifications_total{event_trigger,result} (counter) — result ∈ OK/RETRIED/DROPPED.
  • fivegc_lmf_subscription_create_total{result} (counter).
• Graceful shutdown: on LMF stop, cancel every subscription context so all goroutines exit before http.Server.Shutdown returns; no leaked goroutines.

Validation approach

Unit (in-process, httptest, no TLS — srv.Handler()):

1. Ray-casting correctness: a fixed polygon; points clearly inside, clearly outside, and on an edge/vertex (document the boundary convention). Table-driven.
2. AOI state machine: feed a scripted sequence of positions; assert a notification fires only on IN↔OUT transitions and the UNKNOWN→x baseline is suppressed.
3. Notification body shape matches TS 29.572 §6.1.6.2.4 (subId + notificationItems[].locationData, and areaEventInfo.event for AOI).
4. Notification retry: a mock notificationUri server returns 503 then 200 ⇒ exactly two POSTs, result=RETRIED. Returns 503 twice ⇒ dropped, subscription still active.
5. Registry lifecycle: Create inserts + starts a goroutine; Delete cancels + removes; duration expiry self-removes (use a short duration + a fake/short ticker).

Functional (godog, ≥5 scenarios):

1. Create periodic subscription → 201 + Location header; a mock notification sink receives ≥1 LocationNotification within reportingInterval + slack.
2. Create AOI subscription; drive the UE’s synthetic position across the polygon boundary (mobility model) → exactly one AREA_ENTERING then one AREA_LEAVING notification.
3. GET /subscriptions/{subId} returns the resource with the current state/lastNotified; unknown subId → 404 SUBSCRIPTION_NOT_FOUND.
4. DELETE /subscriptions/{subId} → 204; the notification sink receives no further POSTs after the delete; unknown subId → 404.
5. Create with missing notificationUri → 400 MANDATORY_IE_MISSING; create with missing UE identity → 400.
6. (One-shot cancel) POST …/cancel-loc while a DetermineLocation is blocked → the blocked request returns a failure and the cancel returns 204.

mTLS + HTTP/2: the four new routes share the existing :8012 server (ALPN invariant already satisfied). The notification client uses shared/sbi.NewMTLSClient (mutual TLS, h2).

E2E (UERANSIM): make ueransim → register a UE → POST a periodic subscription pointing notificationUri at the management-portal LCS sink (or a local debug receiver) → observe repeated LocationNotification POSTs in the LMF logs (grep EventSubscription); DELETE and confirm they stop. AOI E2E rides the LMF synthetic mobility model used in LMF-006, so the UE’s coordinate drifts across a test polygon over time.

Out of scope (deferred — follow-up tasks)

• Redis persistence of the subscription registry (survive LMF restart). LMF-003 is in-memory only.
• Notification reliability beyond one retry — persistent queue, exponential backoff, dead-letter handling.
• Multi-item notifications (batching several notificationItems per POST).
• Subscription PATCH / modify (TS 29.572 §5.2.3 update operation) — only Create/Get/Delete.
• LPP/NRPPa-based positioning for the samples (still Cell-ID via the LMF-001 chain).
• GMLC / N56 forwarding of notifications (TS 29.515).

Conformance Notes — 2026-06-24 (SPEC-VERIFIER audit, LMF-003)

Verdict: CONFORMANT-WITH-NOTES.

Audited against TS 29.572 §5.2.3 (EventSubscription Create/Get/Delete), §5.2.2.5 (CancelLocation), §6.1.6.2.x (LocationNotification / GeographicArea), TS 23.273 §7.2 step B2, TS 29.571 §5.2. The Rel-17 TS29572_Nlmf_Location.yaml is NOT present locally (specs/3gpp-openapi/ holds only README.md; make sync-openapi has not been run). All field/enum findings below are therefore raised against the TS prose + the existing DetermineLocation conformance precedent, not a byte-diff of the YAML. They must be re-verified against the YAML when it is synced. No production Go was modified.

Routes / status codes — CONFORMANT

Route	Method	Code	Verdict
/nlmf-loc/v1/subscriptions	POST	201 + Location	OK
/nlmf-loc/v1/subscriptions/{subId}	GET	200	OK
/nlmf-loc/v1/subscriptions/{subId}	DELETE	204	OK
/nlmf-loc/v1/ue-contexts/{ueContextId}/cancel-loc	POST	204	OK

The subscriptions collection + Location header + 204-on-delete shape matches the TS 29.571 §5.2 subscription/notification convention and the implemented row precedent (Nudm_SDM Subscribe/Notify, Nnef Create). No route or status-code divergence found.

Findings

#	Severity	Field / route	Expected per TS	Actual (impl)	Recommendation
1	MAJOR	eventTrigger enum	TS 29.572 §6.1.6.3 LocationEventType is EMERGENCY_CALL_ORIGINATION / EMERGENCY_CALL_RELEASE / EMERGENCY_CALL_HANDOVER / UE_AVAILABLE / PERIODIC_LOCATION / MOTION / AREA_EVENT. There is no PERIODIC_REPORTING or AREA_OF_INTEREST token.	PERIODIC_REPORTING, AREA_OF_INTEREST	Map periodic→PERIODIC_LOCATION and AOI→AREA_EVENT (or model AOI via the LdrType/AreaEventInfo IE) when the YAML is synced. Current tokens are LMF-internal, not spec tokens. Not a runtime blocker (LMF is both producer and the only consumer here), but it is a wire-format divergence an external LCS consumer would reject.
2	MAJOR	Subscription request body type	TS 29.572 models the EventSubscription request as InputData / LocationEventSubscription containing an externalClientType/ldrType/hgmlcCallBackURI/ldrReference group, with the UE in supi/gpsi. The flat {ueContextId, eventTrigger, notificationUri, reportingInterval, samplingInterval, areaOfInterest, duration} body is an LMF-internal shape.	flat custom body	Document explicitly as an LMF-internal simplification (as DetermineLocation’s nlmfRequest already is). Acceptable for an in-house producer/consumer; flag before any external N L1/N L g interop.
3	MAJOR	LocationNotification.subId + notificationItems[]	TS 29.572 §6.1.6.2.x names the notification body NotifiedPosInfo / EventReportMessage with fields like notifyCorrelationId, locationEstimate (a GeographicArea), achievedQos, ageOfLocationEstimate, servingNode. There is no {subId, notificationItems:[{locationData, areaEventInfo}]} envelope in the canonical Nlmf body.	{subId, notificationItems:[{locationData, areaEventInfo}]}	The chosen envelope follows the generic TS 29.571 §5.2 notification convention rather than the Nlmf-specific NotifiedPosInfo. Re-map field names against the YAML. Functionally self-consistent today (LMF produces and the mock sink consumes), so not a blocker for LMF-003 scope.
4	MINOR	areaEventInfo.event enum values	TS 29.572 §6.1.6.3 AreaEventType uses UE_INSIDE_AREA / UE_OUTSIDE_AREA (and the LDR area-event model uses occurrence ENTERING_INTO_AREA / LEAVING_FROM_AREA in some IE variants).	AREA_ENTERING / AREA_LEAVING	Align the two crossing tokens with the YAML enum (UE_INSIDE_AREA/UE_OUTSIDE_AREA or ENTERING_INTO_AREA/LEAVING_FROM_AREA). Cosmetic until external interop.
5	INFO	areaOfInterest.polygon shape	TS 29.572 §6.1.6.2.2 references GeographicArea / GadShape (TS 29.572 §6.1.6.2.13) where a polygon is shape=POLYGON with a pointList of GeographicalCoordinates (lon,lat order, with degrees-encoded fields).	{shape, polygon:[{lat,lon}]} flat WGS84 decimal	Simplified WGS84 decimal pair vs the GAD GeographicalCoordinates encoding. Same simplification already accepted for DetermineLocation locationEstimate.point. Consistent with existing precedent — INFO only.
6	INFO	Cause SUBSCRIPTION_NOT_FOUND (404)	TS 29.571 §5.2.7 application errors do not define a SUBSCRIPTION_NOT_FOUND; the generic is NOT_FOUND / SUBSCRIPTION_NOT_FOUND appears in some service-specific tables but is not pinned for Nlmf. Doc already carries a [VERIFY] marker (§“Error / cause table”).	SUBSCRIPTION_NOT_FOUND	Resolve the [VERIFY] against the YAML; NOT_FOUND is the safe generic. Implemented value is plausible and internally consistent.
7	INFO	Cancel-loc 204 on no-op	Doc [VERIFY]: 204 idempotent vs 404 CONTEXT_NOT_FOUND.	204 idempotent	Acceptable design choice; matches REST idempotency. Leave [VERIFY] until YAML confirms.
8	OK	MANDATORY_IE_MISSING (400), INVALID_MSG_FORMAT (400), PRIVACY_EXCEPTION_DENIED (403)	All three are valid TS 29.571 §5.2.7 / TS 29.572 application-error causes.	same	Conformant. PRIVACY_EXCEPTION_DENIED matches the LMF-001/002 privacy-gate precedent (TS 23.273 §9.1).
9	OK	AOI ray-casting containment	Not spec-prescribed (TS leaves geometry to implementation).	PNPOLY even-odd	Implementation detail; flat-Cartesian approximation is documented and bounded to small polygons. No conformance issue.
10	OK	Privacy gate applied once at Create	TS 23.273 §9.1 — check before disclosure; subscription refused before registration.	applied at Create, fail-open on UDM error	Conformant; consistent with DetermineLocation precedent.

Blockers

None. All MAJOR findings (1–3) are wire-format/naming divergences from the canonical Nlmf_Location data model, not behavioural or security defects. Because the LMF is simultaneously the producer and (in LMF-003 scope) drives the only consumer via its own mock/portal sink, the custom envelope is internally self-consistent and the service is functional and testable. They are recorded as deferred interop debt: the enum/field names MUST be reconciled against TS29572_Nlmf_Location.yaml (run make sync-openapi) before any external LCS/GMLC consumer (LMF-007, N56) is integrated. This mirrors the DetermineLocation precedent, where nlmfRequest/LocationData are likewise LMF-internal shapes accepted into the matrix with an explicit deferral note.

Required follow-up (track in BACKLOG)

• ☐ Sync TS29572_Nlmf_Location.yaml and re-verify findings 1–7 byte-for-byte.
• ☐ Reconcile eventTrigger → LocationEventType (PERIODIC_LOCATION/AREA_EVENT).
• ☐ Reconcile notification body → NotifiedPosInfo field names.
• ☐ Reconcile AOI crossing enum → AreaEventType (UE_INSIDE_AREA/UE_OUTSIDE_AREA).