R-1247: the weekly upload line test — the agent's own iperf3 client to ep0's tunnel-only server, Tuesday 10:00-15:59 after 10 quiet minutes, under the heavy-op gate, best of 3; line_test stanza + GET /host/line-test; 15 tests red-proved; unreleased (next v0.164.0)

2026-10-24 08:59:42 +02:00
parent 2d4b1930df
commit f7e1dcbb27
16 changed files with 1474 additions and 1 deletions
@@ -1,3 +1,32 @@
+## Unreleased (next: v0.164.0; 2026-10-24 attended release run) — the weekly upload line test (R-1247)
+
+Operator ruling 2026-10-24 07:26: once a week the box's HOST measures its upload line with a 10-second iperf3 upload to an
+iperf3 server on ep0 that answers **only inside the WireGuard tunnel** (felhom.eu `scripts/ep0-iperf3/`; installed the same
+day). The agent speaks the iperf3 protocol itself (operator's pick, 2026-10-24: nothing is installed on any host).
+**No sudoers or config-bundle change.** **MinController: none** — the controller (≥ 0.342.0) reads the new route and
+treats a 404 as „not measured".
+
+- **`internal/linetest`** — `Client` (the iperf3 3.x client protocol: cookie, params, N data streams, TEST_END, results
+  exchange; the value is the SERVER's received bytes) and `Tester` (the schedule): due weekly from Tuesday 10:00 local,
+  starts 10:00–15:59 only (never in the night chain), from a per-host slot spread over 10:00–13:59; only after 10 quiet
+  minutes (every one-minute transmit rate of the host's physical uplink below 2 Mbit/s); under the one-heavy-op gate
+  (`line-test`); 3 runs of 10 s with 4 streams, 30 s apart, the highest counts; each run bounded by 25 s; „server busy" →
+  tried again at the next tick the same day, at most 6 tries a day; no operational tunnel → no test, no value. The last
+  result is persisted (`<oob state dir>/line-test.json`).
+- **Report:** a `line_test` stanza (`schedule`, `last_ok_at`, `mbps`, `runs_mbps`, `server`, `last_attempt_at`,
+  `last_error`). **Local API:** `GET /host/line-test` → `{present, mbps, measured_at, method:"iperf3-tunnel"}`.
+- `wgtunnel.Manager.LineTestTarget()` — the desired block's `pbs_tunnel_ip`, only while the tunnel is operational
+  (cached, no exec). Config `line_test.disable` (default on).
+- **Proven live** (felhom.eu `audits/line-test-2026-10-24/`): a probe built from this package on demo-hp's host read
+  **90.7 Mbit/s** in 10.4 s (the push floor said „at least 10"); a second test 2 s later → „server busy" in 0.1 s while the
+  first went on undisturbed (90.6).
+- Tests, each red-proved by a mutation (15): `TestClientSpeaksTheProtocolAndCountsTheServersBytes` (against a fake
+  iperf3 server), `TestClientBusyServerIsErrBusy`, `TestClientHonoursTheDeadlineAgainstAStalledServer`,
+  `TestEligibleWindowNeverInTheNightChain`, `TestNeverTestsInTheNightOrBeforeTuesday`, `TestBusyServerIsRetriedLaterTheSameDay`,
+  `TestTriesPerDayAreBounded`, `TestNoTunnelNoTest`, `TestBusyUplinkOrHeavyOpWaits`, `TestTickMeasuresTheHighestOfThreeRuns`,
+  `TestStateSurvivesARestartAndReportsIt`, `TestUplinkCountsTheBridgesPhysicalPortsOnly`, `TestLineTestRoute`,
+  `TestLineTestTargetOnlyWhileOperational`, `TestMainWiresTheLineTest`.
+
 ## v0.163.0 — the tunnel heals itself after a clock that ran ahead (D30, R-1204); root SSH from the LAN by key only (D4, R-982) (2026-10-23) — RELEASED on the operator's yes (day brief); the vouch is the operator's

 Binary sha256 `561b5316cd511de9fa9d8b8be4553da7add684f715d3bea533ca330ff7f3763c`; config bundle sha256 `3afb88d9fbbc4adc16083fa52a98cd4974583c6378a77a1a6e0ed8ae6d1b80c8`. Built from `1109092` (CI 2246 green). Both sections below are in it.
@@ -1,5 +1,11 @@
 # CONTEXT — felhom-agent working state

+> **2026-10-24 (attended release run) — v0.164.0: the weekly upload line test (R-1247; operator ruling 07:26).**
+> `internal/linetest`: the agent's own iperf3 client (operator's pick — nothing installed on hosts) to ep0's tunnel-only
+> server `10.77.0.1:5201`, Tuesday 10:00-15:59, after 10 quiet minutes, under the heavy-op gate, best of 3; `line_test`
+> stanza + `GET /host/line-test` (the controller's qBittorrent limit, D41 = 50 %). demo-hp measured 90.7 Mbit/s. Release
+> needs the operator's vouch.
+
 > **2026-10-22/23 night — D30 on `main` (`ae69ad4`), unreleased; the D4 patches v2 ready.** Operator ruling D30
 > (2026-10-22): a handshake stamped in the future for 15 min → a new WG key pair (`wgtunnel/rekey.go`; old key kept as
 > `wg/private.key.prev`), registered on `POST /hosts/<id>/wg` (the hub re-keys in place; its full-list push swaps the
@@ -171,6 +171,7 @@
 | `localapi.GuestAPI` / `BackupService` / `BackupStore` / `TokenAuthority` | internal/localapi/server.go | `*proxmox.Client`, `*backup.BackupRunner`, `*backup.Store`, `*TokenStore` | `fakeGuests`/`fakeBackups`/`fakeStore` internal/localapi/server_test.go |
 | `backup.InFlight` | internal/backup/inflight.go | `TryAcquire(what) (release, busy, ok)` / `Busy()` | THE host-wide "one heavy guest operation at a time" gate — shared by the local-API backup path and the restore-test scheduler (R-85) | A **LINK** guard, not a lock one: the scratch VMID never touches the live guest's vzdump lock, but an offsite restore PULLS multi-GB over the tunnel a backup PUSHES one. Callers **DEFER, never cancel** — a deferred restore-test costs coverage, a cancelled backup costs the backup. A nil gate is ungated (pre-R-85 callers). |
 | `fstrim.Trimmer` (R-444) | internal/fstrim/fstrim.go | `New(runner, guests, gate, statePath, logger)` / `Pass(ctx)` / `GuestDiskTrimStatus(ctx)` / `ParseTrimmed(out)` | the weekly `pct fstrim <vmid>` of owned running guests (Wednesday from 10:00 local, starts 10:00-20:59 only), under `backup.InFlight`; last result per guest persisted and reported as `guest_disk_trim` | A busy gate DEFERS to the next hourly tick, never waits; a failed trim retries at most `MaxAttemptsPerWeek`; the report reads the persisted record, it never runs pct |
+| `linetest.Tester` + `linetest.Client` (R-1247) | internal/linetest/linetest.go · internal/linetest/iperf.go | `New(runner, target, gate, uplink, hostID, statePath, logger)` / `Tick(ctx)` / `Value()` / `LineTestStatus(ctx)`; `Client{Streams, Time}.Run(ctx, addr)` | the weekly upload line test: a 10-second iperf3 upload (the agent speaks the iperf3 protocol — nothing installed on the host) to ep0's tunnel-only server (`wgtunnel.Manager.LineTestTarget`), Tuesday 10:00-15:59 local from a per-host slot, after 10 quiet minutes of the PHYSICAL uplink (`SysUplinkTx`: the bridge's ports with a `device` link — the bridge counter misses bridged guest traffic), under `backup.InFlight`; best of 3; reported as `line_test`, served as GET /host/line-test | **The value is the SERVER's received bytes**, never the client's written ones (the send buffer). `Run` refuses a context without a deadline. iperf3 numbers streams 1, 3, 4, 5 — the server matches results by those ids. „server busy" (ACCESS_DENIED) stops the measurement and is retried at the next tick, at most `MaxTriesPerDay` |
 | `capability` store-grant probe (`storeGrantStatuses` / `storeGrantVerdict` / `Client.Permissions`) | cmd/felhom-agent/main.go, internal/proxmox/query.go | *"may the agent READ this backup tier?"*, one `capability.Status` per configured tier | R-185. **Never infer permission from an empty content listing** — `{"data":[]}` is what a FORBIDDEN tier and a NEWBORN tier both return, and that ambiguity hid an unreadable host tier on both demo boxes. Ask `/access/permissions` **as the agent's own token** (root always says yes). **The ungranted answer is not empty and not a 403** — it carries the privileges inherited from the box-wide `/` grant, so test for **`Datastore.AllocateSpace`** specifically; path-presence or `Datastore.Audit` reports a blinded storage healthy. Probed set comes from `BackupTiers()`, never a fixed list. Critical except the `local` fallback. Composes AROUND the sudo prober (the `poolReadStatus` precedent); `Status`'s wire shape is untouched so the hub alert is free. Unreachable PVE ⇒ degraded, never ok. |
 | `backup.RestoreTestState` | internal/backup/restoretest_state.go | `RecordSuccess(target,archive,tier,verified,t)` / `ProvenArchive(target)` / `ProvenRestoreTests(ctx)` / `LastSuccess(target)` / `OldestFirst(targets)` | Per-tier restore-test PROOF state, persisted (atomic tmp+rename) — **which archive** was proven, and when (R-86) | **Credit ONLY on success** — a permanently failing tier must keep sorting first, or it looks freshly proven and stops being retried. Ties break on target id: without it, two tiers proven in the same second rotate by Go's randomised map order. **This one NEEDS persistence unlike R-84** — R-84 had ground truth to consult (the archive is still on the storage); a restore-test destroys its scratch and leaves no artifact. **R-86: the ARCHIVE is the state, the time is metadata** — a time alone cannot answer "have we proven THIS archive", which is the due-check's whole question. A pre-R-86 file (bare RFC3339 per target) keeps its time and yields NO proven archive, so each tier is due once after the upgrade; reading a legacy time as proof of the current archive would invent a guarantee. **R-189: it is also the REPORTABLE half of the restore-test signal.** The in-memory `backup.Store` holds only this process's latest run, and under per-archive due-ness the agent will not re-test a proven archive — so a proof lost to a restart is not repeated for a whole archive generation (observed live: a passing 14.5 GB offsite restore reached no host-report). `ProvenRestoreTests` renders the stored proofs as `hub.RestoreTest` entries and the collector merges them; a record missing the archive or the tier is NOT emitted, because an unproven tier reading as proven is worse than the defect. **Only successes are stored, deliberately:** a success suppresses future work, a failure causes it. |
 | `backup.BackupSuccessState` | internal/backup/backup_state.go | `RecordBackupSuccess(target, b)` / `LastKnownSuccess(target, vmid)` | Newest SUCCESSFUL backup per tier+guest, persisted (atomic tmp+rename) — the due-check's fallback when the tier's storage cannot be read after a restart (R-894) | **Read ONLY when the storage cannot be read** — a storage that answers is the ground truth (R-84), and an archive absent there must make the tier due even when this file remembers one. A saved copy older than the cadence still reads due. Only successes are written. |
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"testing"
+)
+
+// R-1247: the weekly line test has the fstrim shape (component + reporter seam + goroutine) plus a local-API reader,
+// so its wiring is asserted from the AST. It must share the ONE heavy-op gate (heavyOps) — or it could run beside a
+// backup — and take its server from the tunnel manager, never a literal address.
+func TestMainWiresTheLineTest(t *testing.T) {
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "main.go", nil, 0)
+	if err != nil {
+		t.Fatalf("parse main.go: %v", err)
+	}
+	var withGate, withTunnelTarget, reporterWired, localAPIWired, started bool
+	ast.Inspect(f, func(n ast.Node) bool {
+		switch node := n.(type) {
+		case *ast.CallExpr:
+			if fn, ok := node.Fun.(*ast.SelectorExpr); ok {
+				switch fn.Sel.Name {
+				case "New":
+					if pkg, ok := fn.X.(*ast.Ident); ok && pkg.Name == "linetest" && len(node.Args) >= 3 {
+						if id, ok := node.Args[2].(*ast.Ident); ok && id.Name == "heavyOps" {
+							withGate = true
+						}
+						if sel, ok := node.Args[1].(*ast.SelectorExpr); ok && sel.Sel.Name == "LineTestTarget" {
+							withTunnelTarget = true
+						}
+					}
+				case "SetLineTestReporter":
+					reporterWired = true
+				case "SetLineTest":
+					localAPIWired = true
+				}
+			}
+		case *ast.GoStmt:
+			if sel, ok := node.Call.Fun.(*ast.SelectorExpr); ok && sel.Sel.Name == "Run" {
+				if id, ok := sel.X.(*ast.Ident); ok && id.Name == "lineTest" {
+					started = true
+				}
+			}
+		}
+		return true
+	})
+	if !withGate {
+		t.Error("main.go never calls linetest.New(..., heavyOps, ...) — no line test, or one outside the heavy-op gate")
+	}
+	if !withTunnelTarget {
+		t.Error("linetest.New does not take its server from wgMgr.LineTestTarget")
+	}
+	if !reporterWired {
+		t.Error("main.go never calls collector.SetLineTestReporter — the line_test stanza never reaches the hub")
+	}
+	if !localAPIWired {
+		t.Error("main.go never calls localSrv.SetLineTest — the controller's GET /host/line-test always reads present:false")
+	}
+	if !started {
+		t.Error("main.go never starts the line test with `go lineTest.Run(ctx)`")
+	}
+}
@@ -43,6 +43,7 @@ import (
 	"gitea.dooplex.hu/admin/felhom-agent/internal/guestnet"
 	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
 	"gitea.dooplex.hu/admin/felhom-agent/internal/lanresolver"
+	"gitea.dooplex.hu/admin/felhom-agent/internal/linetest"
 	"gitea.dooplex.hu/admin/felhom-agent/internal/localapi"
 	applog "gitea.dooplex.hu/admin/felhom-agent/internal/log"
 	"gitea.dooplex.hu/admin/felhom-agent/internal/mgmtplane"
@@ -1641,6 +1642,24 @@ func runDaemon(cfg config.Config, logger *slog.Logger, logRing *applog.Ring) int
 	} else {
 		logger.Info("fstrim: weekly guest disk trim disabled by config (disk_trim.disable)")
 	}
+	// R-1247 (operator ruling 2026-10-24 07:26): the weekly upload line test — a 10-second iperf3 upload from this host
+	// to ep0's tunnel-only server, Tuesday 10:00-15:59 local, after 10 quiet minutes, under the one-heavy-op gate. Only
+	// with the offsite tunnel (the server is reachable nowhere else). Not part of the errc fan-out.
+	switch {
+	case !cfg.LineTest.Enabled():
+		logger.Info("linetest: weekly upload line test disabled by config (line_test.disable)")
+	case wgMgr == nil:
+		logger.Info("linetest: weekly upload line test off — no offsite tunnel on this host")
+	default:
+		lineTest := linetest.New(linetest.Client{Streams: linetest.Streams, Time: linetest.TestTime}, wgMgr.LineTestTarget,
+			heavyOps, linetest.SysUplinkTx("/"), cfg.Hub.HostID,
+			filepath.Join(cfg.OOB.WithDefaults().StateDir, "line-test.json"), logger)
+		collector.SetLineTestReporter(lineTest)
+		if localSrv != nil {
+			localSrv.SetLineTest(lineTest)
+		}
+		go lineTest.Run(ctx)
+	}
 	if lanLoop != nil {
 		lanServers = 1
 		go func() { errc <- lanLoop.Run(ctx) }()
@@ -34,6 +34,7 @@ type Config struct {
 	WGTunnel    WGTunnelConfig    `json:"wg_tunnel"`
 	GuestNet    GuestNetConfig    `json:"guest_net"`
 	DiskTrim    DiskTrimConfig    `json:"disk_trim"`
+	LineTest    LineTestConfig    `json:"line_test"`
 	OOB         OOBConfig         `json:"oob"`
 	SelfUpdate  SelfUpdateConfig  `json:"selfupdate"`
 	LogLevel    string            `json:"log_level"` // debug|info|warn|error (default info)
@@ -150,6 +151,16 @@ type DiskTrimConfig struct {
 // Enabled reports whether the weekly trim should run.
 func (d DiskTrimConfig) Enabled() bool { return !d.Disable }

+// LineTestConfig configures the R-1247 weekly upload line test (internal/linetest). DEFAULT-ON: it reaches only ep0's
+// tunnel-only iperf3 server, so it runs only on a box that already has an operational offsite tunnel (operator
+// ruling 2026-10-24 07:26: every box with a tunnel measures its line weekly).
+type LineTestConfig struct {
+	Disable bool `json:"disable"`
+}
+
+// Enabled reports whether the weekly line test should run.
+func (l LineTestConfig) Enabled() bool { return !l.Disable }
+
 // GuestNetConfig configures the R-54 guest-network watchdog (internal/guestnet).
 //
 // **This is the repo's first DEFAULT-ON feature gate, and the inversion is deliberate.** Every other
@@ -104,6 +104,12 @@ type GuestDiskTrimReporter interface {
 	GuestDiskTrimStatus(ctx context.Context) *GuestDiskTrimStatus
 }

+// LineTestReporter is the R-1247 seam the weekly line test plugs into (hub does not import linetest). nil → no
+// line_test stanza.
+type LineTestReporter interface {
+	LineTestStatus(ctx context.Context) *LineTestStatus
+}
+
 // Collector builds a HostReport from read-only sources. All deps are behind narrow
 // interfaces for unit testing.
 type Collector struct {
@@ -124,6 +130,7 @@ type Collector struct {
 	ctrlSup          ControllerSupervisorReporter                  // R-523: in-guest controller supervisor (nil → stanza omitted)
 	guestNet         GuestNetReporter                              // R-54: per-guest network watchdog (nil → stanza omitted)
 	diskTrim         GuestDiskTrimReporter                         // R-444: weekly guest disk trim (nil → stanza omitted)
+	lineTest         LineTestReporter                              // R-1247: weekly upload line test (nil → stanza omitted)
 	deliberateOff    func() *DeliberateOff                         // R-998: household power-off record of this boot (nil → omitted)
 	foreignKey       ForeignKeyArchiveReporter                     // R-366 slice 2 (nil → omitted)
 	selfUpdate       SelfUpdateReporter                            // D1: agent self-update pending status (nil → false)
@@ -259,6 +266,12 @@ func (c *Collector) SetGuestDiskTrimReporter(r GuestDiskTrimReporter) *Collector
 	return c
 }

+// SetLineTestReporter wires the R-1247 weekly line test as a report source (nil-safe → stanza omitted).
+func (c *Collector) SetLineTestReporter(r LineTestReporter) *Collector {
+	c.lineTest = r
+	return c
+}
+
 // SetDeliberateOffSource wires the R-998 power-off record (poweroff.State.Current, adapted).
 func (c *Collector) SetDeliberateOffSource(f func() *DeliberateOff) *Collector {
 	c.deliberateOff = f
@@ -427,6 +440,10 @@ func (c *Collector) Collect(ctx context.Context) (*HostReport, error) {
 	if c.diskTrim != nil {
 		report.GuestDiskTrim = c.diskTrim.GuestDiskTrimStatus(ctx)
 	}
+	// R-1247: the last weekly line test (nil reporter = not wired → stanza omitted).
+	if c.lineTest != nil {
+		report.LineTest = c.lineTest.LineTestStatus(ctx)
+	}
 	// R-366 slice 2: archives the restore-test skipped as another key's (nil → not evaluated yet → omitted).
 	if c.foreignKey != nil {
 		report.ForeignKeyArchives = c.foreignKey.ForeignKeyArchives(ctx)
@@ -129,6 +129,11 @@ type HostReport struct {
 	// wired; an empty `guests` list means the job runs and no guest has been trimmed yet. No secret.
 	GuestDiskTrim *GuestDiskTrimStatus `json:"guest_disk_trim,omitempty"`

+	// LineTest is the weekly upload line test stanza (R-1247; operator ruling 2026-10-24): the schedule, the last
+	// measured upload line (best of the runs, Mbit/s, as ep0's iperf3 server counted it) and the last attempt. Present
+	// only when the job is wired. No secret.
+	LineTest *LineTestStatus `json:"line_test,omitempty"`
+
 	// ForeignKeyArchives (R-366 slice 2, `09` §3 decision 168): per backup tier, the whole-guest archives the
 	// restore-test SKIPPED because they were written with another key (an earlier install of this box). This box
 	// cannot open them; the hub turns a CHANGE of this list into one operator event. Absent = not evaluated yet since
@@ -232,6 +237,19 @@ type GuestDiskTrimStatus struct {
 	Guests   []GuestDiskTrim `json:"guests,omitempty"`
 }

+// LineTestStatus is the R-1247 weekly upload line test stanza. `last_ok_at` + `mbps` are the last SUCCESSFUL
+// measurement ("" / 0 = never); `last_attempt_at` + `last_error` the last attempt, whatever its verdict — never read
+// the attempt time as a result.
+type LineTestStatus struct {
+	Schedule      string    `json:"schedule"`
+	LastOKAt      string    `json:"last_ok_at,omitempty"`
+	Mbps          float64   `json:"mbps,omitempty"`
+	RunsMbps      []float64 `json:"runs_mbps,omitempty"`
+	Server        string    `json:"server,omitempty"`
+	LastAttemptAt string    `json:"last_attempt_at,omitempty"`
+	LastError     string    `json:"last_error,omitempty"`
+}
+
 // GuestDiskTrim is one guest's LAST trim attempt. `ok` with `last_attempt_at` is the verdict of that attempt — never
 // read the time alone as success; `last_ok_at` is the last attempt that succeeded ("" = never). `bytes_trimmed` is
 // the sum of the "(N bytes) trimmed" lines `pct fstrim` printed, over `mounts` mount points.
@@ -0,0 +1,294 @@
+package linetest
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// A minimal iperf3 CLIENT for one TCP upload test (client → server), speaking the iperf3 control protocol (3.x) to the
+// stock `iperf3 --server` on ep0 (operator ruling 2026-10-24: the agent speaks iperf3 itself, nothing is installed on
+// the host). The number that counts is the SERVER's: the bytes it received, from its results JSON — bytes the client
+// handed to its socket include what still sat in the send buffer when the timer ended.
+//
+// The protocol, as the server drives it (one state byte at a time on the control connection):
+//
+//	client → 37-byte cookie
+//	server → PARAM_EXCHANGE(9)      client → params JSON (4-byte big-endian length + bytes)
+//	server → CREATE_STREAMS(10)     client opens N data connections, each starts with the same cookie
+//	server → TEST_START(1), TEST_RUNNING(2)   client sends for the test time, then → TEST_END(4)
+//	server → EXCHANGE_RESULTS(13)   client → its results JSON; server → its results JSON
+//	server → DISPLAY_RESULTS(14)    client → IPERF_DONE(16)
+//
+// A server already running a test answers ACCESS_DENIED(-1) and closes: that is ErrBusy (another box is testing; try
+// again later the same day). SERVER_ERROR(-3) / SERVER_TERMINATE(-2) end the test with an error.
+
+const (
+	stParamExchange   = 9
+	stCreateStreams   = 10
+	stTestStart       = 1
+	stTestRunning     = 2
+	stTestEnd         = 4
+	stExchangeResults = 13
+	stDisplayResults  = 14
+	stIperfDone       = 16
+	stAccessDenied    = -1
+	stServerTerminate = -2
+	stServerError     = -3
+
+	cookieSize   = 37 // 36 characters + NUL
+	blockSize    = 128 * 1024
+	maxJSONBytes = 1 << 20
+)
+
+// ErrBusy: the server is running another client's test.
+var ErrBusy = errors.New("iperf3 server busy")
+
+// Result is one upload test.
+type Result struct {
+	Mbps          float64 // the server's received bits per second / 1e6
+	ServerBytes   int64   // bytes the server received, all streams
+	ClientBytes   int64   // bytes the client wrote (diagnostics only)
+	ServerSeconds float64 // the server's measured duration
+}
+
+// Dialer opens a TCP connection (net.Dialer in production; a seam for tests).
+type Dialer interface {
+	DialContext(ctx context.Context, network, address string) (net.Conn, error)
+}
+
+// Client runs one test. The whole run is bounded by ctx; Run sets every connection's deadline from it.
+type Client struct {
+	Dialer  Dialer
+	Streams int           // parallel streams (-P)
+	Time    time.Duration // test time (-t)
+}
+
+func (c Client) dialer() Dialer {
+	if c.Dialer != nil {
+		return c.Dialer
+	}
+	return &net.Dialer{Timeout: 5 * time.Second}
+}
+
+func newCookie() ([]byte, error) {
+	const alphabet = "abcdefghijklmnopqrstuvwxyz234567"
+	b := make([]byte, cookieSize)
+	if _, err := rand.Read(b[:cookieSize-1]); err != nil {
+		return nil, err
+	}
+	for i := 0; i < cookieSize-1; i++ {
+		b[i] = alphabet[int(b[i])%len(alphabet)]
+	}
+	b[cookieSize-1] = 0
+	return b, nil
+}
+
+func writeJSON(w io.Writer, v any) error {
+	data, err := json.Marshal(v)
+	if err != nil {
+		return err
+	}
+	var hdr [4]byte
+	binary.BigEndian.PutUint32(hdr[:], uint32(len(data)))
+	if _, err := w.Write(append(hdr[:], data...)); err != nil {
+		return err
+	}
+	return nil
+}
+
+func readJSON(r io.Reader, v any) error {
+	var hdr [4]byte
+	if _, err := io.ReadFull(r, hdr[:]); err != nil {
+		return err
+	}
+	n := binary.BigEndian.Uint32(hdr[:])
+	if n == 0 || n > maxJSONBytes {
+		return fmt.Errorf("iperf3: results JSON of %d bytes refused", n)
+	}
+	buf := make([]byte, n)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		return err
+	}
+	return json.Unmarshal(buf, v)
+}
+
+type streamResult struct {
+	ID             int     `json:"id"`
+	Bytes          int64   `json:"bytes"`
+	Retransmits    int64   `json:"retransmits"`
+	Jitter         float64 `json:"jitter"`
+	Errors         int64   `json:"errors"`
+	OmittedErrors  int64   `json:"omitted_errors"`
+	Packets        int64   `json:"packets"`
+	OmittedPackets int64   `json:"omitted_packets"`
+	StartTime      float64 `json:"start_time"`
+	EndTime        float64 `json:"end_time"`
+}
+
+type results struct {
+	CPUTotal             float64        `json:"cpu_util_total"`
+	CPUUser              float64        `json:"cpu_util_user"`
+	CPUSystem            float64        `json:"cpu_util_system"`
+	SenderHasRetransmits int            `json:"sender_has_retransmits"`
+	CongestionUsed       string         `json:"congestion_used,omitempty"`
+	Streams              []streamResult `json:"streams"`
+}
+
+// streamIDs are the ids iperf3 gives its streams: the first is 1, every later one is (streams so far) + 2 — so 1, 3,
+// 4, 5 … (iperf_add_stream). The server matches our results by these ids.
+func streamIDs(n int) []int {
+	ids := make([]int, n)
+	for i := range ids {
+		if i == 0 {
+			ids[i] = 1
+		} else {
+			ids[i] = i + 2
+		}
+	}
+	return ids
+}
+
+// Run performs one upload test to addr ("10.77.0.1:5201").
+func (c Client) Run(ctx context.Context, addr string) (Result, error) {
+	var res Result
+	streams, dur := c.Streams, c.Time
+	if streams < 1 {
+		streams = 1
+	}
+	if dur <= 0 {
+		dur = 10 * time.Second
+	}
+	deadline, ok := ctx.Deadline()
+	if !ok {
+		return res, errors.New("iperf3: Run needs a context with a deadline")
+	}
+	cookie, err := newCookie()
+	if err != nil {
+		return res, err
+	}
+	ctrl, err := c.dialer().DialContext(ctx, "tcp", addr)
+	if err != nil {
+		return res, fmt.Errorf("iperf3: connect: %w", err)
+	}
+	defer ctrl.Close()
+	ctrl.SetDeadline(deadline)
+	if _, err := ctrl.Write(cookie); err != nil {
+		return res, fmt.Errorf("iperf3: cookie: %w", err)
+	}
+
+	var data []net.Conn
+	defer func() {
+		for _, d := range data {
+			d.Close()
+		}
+	}()
+	var sent atomic.Int64
+	var server results
+	var wg sync.WaitGroup
+	for {
+		var st [1]byte
+		if _, err := io.ReadFull(ctrl, st[:]); err != nil {
+			return res, fmt.Errorf("iperf3: control read: %w", err)
+		}
+		switch int8(st[0]) {
+		case stParamExchange:
+			params := map[string]any{"tcp": true, "omit": 0, "time": int(dur / time.Second), "num": 0, "blockcount": 0,
+				"parallel": streams, "len": blockSize, "pacing_timer": 1000, "client_version": "3.18"}
+			if err := writeJSON(ctrl, params); err != nil {
+				return res, fmt.Errorf("iperf3: params: %w", err)
+			}
+		case stCreateStreams:
+			for i := 0; i < streams; i++ {
+				d, err := c.dialer().DialContext(ctx, "tcp", addr)
+				if err != nil {
+					return res, fmt.Errorf("iperf3: data stream %d: %w", i+1, err)
+				}
+				d.SetDeadline(deadline)
+				data = append(data, d)
+				if _, err := d.Write(cookie); err != nil {
+					return res, fmt.Errorf("iperf3: data stream %d cookie: %w", i+1, err)
+				}
+			}
+		case stTestStart:
+		case stTestRunning:
+			stopAt := time.Now().Add(dur)
+			if stopAt.After(deadline) {
+				return res, errors.New("iperf3: no time left for the test inside the deadline")
+			}
+			buf := make([]byte, blockSize)
+			for _, d := range data {
+				d.SetWriteDeadline(stopAt)
+				wg.Add(1)
+				go func(d net.Conn) {
+					defer wg.Done()
+					for {
+						n, err := d.Write(buf)
+						sent.Add(int64(n))
+						if err != nil {
+							return
+						}
+					}
+				}(d)
+			}
+			wg.Wait()
+			if _, err := ctrl.Write([]byte{stTestEnd}); err != nil {
+				return res, fmt.Errorf("iperf3: test end: %w", err)
+			}
+		case stExchangeResults:
+			ids := streamIDs(len(data))
+			mine := results{SenderHasRetransmits: -1, CongestionUsed: "cubic"}
+			per := sent.Load() / int64(max(len(data), 1))
+			for _, id := range ids {
+				mine.Streams = append(mine.Streams, streamResult{ID: id, Bytes: per, Retransmits: -1, EndTime: dur.Seconds()})
+			}
+			if err := writeJSON(ctrl, mine); err != nil {
+				return res, fmt.Errorf("iperf3: send results: %w", err)
+			}
+			if err := readJSON(ctrl, &server); err != nil {
+				return res, fmt.Errorf("iperf3: read server results: %w", err)
+			}
+		case stDisplayResults:
+			ctrl.Write([]byte{stIperfDone})
+			return summarize(server, sent.Load(), dur)
+		case stAccessDenied:
+			return res, ErrBusy
+		case stServerTerminate, stServerError:
+			var codes [8]byte
+			io.ReadFull(ctrl, codes[:])
+			return res, fmt.Errorf("iperf3: server error (state %d, iperf errno %d, errno %d)", int8(st[0]),
+				int32(binary.BigEndian.Uint32(codes[:4])), int32(binary.BigEndian.Uint32(codes[4:])))
+		default:
+			return res, fmt.Errorf("iperf3: unexpected state %s", strconv.Itoa(int(int8(st[0]))))
+		}
+	}
+}
+
+// summarize turns the server's results into a Result. No stream bytes is an error, never a zero line.
+func summarize(server results, clientBytes int64, dur time.Duration) (Result, error) {
+	res := Result{ClientBytes: clientBytes}
+	for _, s := range server.Streams {
+		res.ServerBytes += s.Bytes
+		if s.EndTime > res.ServerSeconds {
+			res.ServerSeconds = s.EndTime
+		}
+	}
+	if res.ServerBytes <= 0 {
+		return res, errors.New("iperf3: the server reported no received bytes")
+	}
+	secs := res.ServerSeconds
+	if secs <= 0 {
+		secs = dur.Seconds()
+	}
+	res.Mbps = float64(res.ServerBytes) * 8 / secs / 1e6
+	return res, nil
+}
@@ -0,0 +1,439 @@
+// Package linetest is the weekly upload line-speed test (R-1247; operator ruling 2026-10-24 07:26).
+//
+// Why: the controller's upload watch and qBittorrent's default limit (50 % of the line, D41) need the household's
+// upload line. The passive reading — the nightly off-site push — is only a low floor (2026-10-24 night: demo-hp „at
+// least 10 Mbit/s"; this test read 90.7 on the same line). So once a week the HOST (the tunnel lives on the host)
+// runs a 10-second iperf3 upload to ep0's tunnel-only iperf3 server (felhom.eu scripts/ep0-iperf3). No file is left
+// anywhere and nothing counts against the household's storage.
+//
+// The rule, each part pinned by a test in linetest_test.go:
+//   - Weekly: due from Tuesday 10:00 local until one measurement succeeded since then (a box that was off catches up
+//     on a later day, inside the window).
+//   - Daytime only: a test starts only 10:00–15:59 local — never in the night chain's window (01:00–06:59), and each
+//     host starts from its own minute (SlotMinute, spread over 10:00–13:59) so the fleet does not test at once.
+//   - Never beside a backup, a restore-test, an OS update or a trim: the test holds the host-wide one-heavy-op gate.
+//   - Only after QuietMinutes of quiet uplink: every one-minute transmit rate of the host's physical uplink below
+//     QuietMbps — so neither the family's upload nor a restore is measured against itself.
+//   - Up to RunsPerMeasurement runs of TestTime each; the highest counts. A run is bounded by RunTimeout.
+//   - „Server busy" (another box is testing) → tried again at the next tick the same day; at most MaxTriesPerDay.
+//   - No tunnel (no operational wg-felhom with a server address) → no test and no value; the controller then keeps its
+//     passive floor and sets no qBittorrent limit.
+//   - The last result is persisted, so a restart neither loses it nor re-tests.
+package linetest
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"hash/fnv"
+	"log/slog"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
+)
+
+const (
+	Weekday            = time.Tuesday
+	StartHour          = 10 // first eligible local hour (inclusive)
+	EndHour            = 16 // first NOT-eligible local hour: the last start is 15:59
+	SlotSpreadMinutes  = 240
+	QuietMinutes       = 10
+	QuietMbps          = 2.0
+	RunsPerMeasurement = 3
+	TestTime           = 10 * time.Second
+	Streams            = 4
+	RunTimeout         = 25 * time.Second
+	RunGap             = 30 * time.Second
+	MaxTriesPerDay     = 6
+	ServerPort         = 5201
+	TickInterval       = time.Minute
+	FirstTickDelay     = 5 * time.Minute
+	GateName           = "line-test"
+)
+
+// ScheduleText is carried on the host report.
+const ScheduleText = "weekly, due Tuesday from 10:00 host-local time; starts 10:00-15:59 after 10 quiet minutes; never beside a backup, restore-test or update"
+
+// Gate is the host-wide one-heavy-operation gate (*backup.InFlight).
+type Gate interface {
+	TryAcquire(what string) (release func(), busy string, ok bool)
+}
+
+// Target answers the iperf3 server's tunnel address, ok=false when the tunnel is not operational.
+type Target func() (netip.Addr, bool)
+
+// Runner runs one upload test (Client in production).
+type Runner interface {
+	Run(ctx context.Context, addr string) (Result, error)
+}
+
+// UplinkTx reads the host's physical-uplink transmit byte counter.
+type UplinkTx func() (uint64, error)
+
+// State is what is persisted (line-test.json).
+type State struct {
+	LastOKAt      time.Time `json:"last_ok_at,omitempty"`
+	Mbps          float64   `json:"mbps,omitempty"`
+	RunsMbps      []float64 `json:"runs_mbps,omitempty"`
+	Server        string    `json:"server,omitempty"`
+	LastAttemptAt time.Time `json:"last_attempt_at,omitempty"`
+	LastError     string    `json:"last_error,omitempty"`
+	TriesDay      string    `json:"tries_day,omitempty"` // local date of TriesToday
+	TriesToday    int       `json:"tries_today,omitempty"`
+}
+
+type txSample struct {
+	at time.Time
+	tx uint64
+}
+
+// Tester is the weekly job.
+type Tester struct {
+	runner    Runner
+	target    Target
+	gate      Gate
+	uplink    UplinkTx
+	statePath string
+	slot      int // minutes after StartHour:00 this host may first start
+	logger    *slog.Logger
+	loc       *time.Location
+	now       func() time.Time
+	sleep     func(context.Context, time.Duration) bool
+
+	mu      sync.Mutex
+	st      State
+	samples []txSample
+}
+
+// New builds the job and loads the persisted state (missing = empty; corrupt = logged, empty — the cost is one extra
+// test, never a lost value elsewhere).
+func New(runner Runner, target Target, gate Gate, uplink UplinkTx, hostID, statePath string, logger *slog.Logger) *Tester {
+	if logger == nil {
+		logger = slog.Default()
+	}
+	t := &Tester{runner: runner, target: target, gate: gate, uplink: uplink, statePath: statePath,
+		slot: SlotMinute(hostID), logger: logger, loc: time.Local, now: time.Now, sleep: sleepCtx}
+	t.load()
+	return t
+}
+
+func sleepCtx(ctx context.Context, d time.Duration) bool {
+	tm := time.NewTimer(d)
+	defer tm.Stop()
+	select {
+	case <-ctx.Done():
+		return false
+	case <-tm.C:
+		return true
+	}
+}
+
+// SlotMinute spreads hosts over the first SlotSpreadMinutes of the window, stable per host id.
+func SlotMinute(hostID string) int {
+	h := fnv.New32a()
+	h.Write([]byte(hostID))
+	return int(h.Sum32() % SlotSpreadMinutes)
+}
+
+func (t *Tester) load() {
+	data, err := os.ReadFile(t.statePath)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			t.logger.Warn("linetest: state read failed — starting empty", "path", t.statePath, "err", err)
+		}
+		return
+	}
+	if err := json.Unmarshal(data, &t.st); err != nil {
+		t.logger.Warn("linetest: state file corrupt — starting empty", "path", t.statePath, "err", err)
+		t.st = State{}
+	}
+}
+
+func (t *Tester) saveLocked() error {
+	data, err := json.MarshalIndent(t.st, "", "  ")
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(t.statePath), 0o755); err != nil {
+		return err
+	}
+	tmp := t.statePath + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o600); err != nil {
+		os.Remove(tmp)
+		return err
+	}
+	return os.Rename(tmp, t.statePath)
+}
+
+// EligibleAt reports whether a test may START at local time lt for a host whose slot is slot minutes after
+// StartHour:00 on the due day. On a catch-up day (anchorDay=false) the slot is not waited for again.
+func EligibleAt(lt time.Time, slot int, anchorDay bool) bool {
+	h := lt.Hour()
+	if h < StartHour || h >= EndHour {
+		return false
+	}
+	if anchorDay {
+		mins := (h-StartHour)*60 + lt.Minute()
+		return mins >= slot
+	}
+	return true
+}
+
+// weekAnchor is the most recent Tuesday StartHour:00 at or before lt.
+func weekAnchor(lt time.Time) time.Time {
+	daysBack := (int(lt.Weekday()) - int(Weekday) + 7) % 7
+	d := lt.AddDate(0, 0, -daysBack)
+	a := time.Date(d.Year(), d.Month(), d.Day(), StartHour, 0, 0, 0, lt.Location())
+	if a.After(lt) {
+		d = d.AddDate(0, 0, -7)
+		a = time.Date(d.Year(), d.Month(), d.Day(), StartHour, 0, 0, 0, lt.Location())
+	}
+	return a
+}
+
+// Due reports whether a measurement is due at lt given the state.
+func Due(st State, lt time.Time) bool {
+	return st.LastOKAt.IsZero() || st.LastOKAt.In(lt.Location()).Before(weekAnchor(lt))
+}
+
+// sample records the uplink counter (once a minute) and keeps QuietMinutes+1 samples.
+func (t *Tester) sample() {
+	if t.uplink == nil {
+		return
+	}
+	tx, err := t.uplink()
+	if err != nil {
+		t.logger.Debug("linetest: uplink counter unreadable", "err", err)
+		t.mu.Lock()
+		t.samples = nil // a gap is not quiet
+		t.mu.Unlock()
+		return
+	}
+	t.mu.Lock()
+	t.samples = append(t.samples, txSample{at: t.now(), tx: tx})
+	if len(t.samples) > QuietMinutes+1 {
+		t.samples = t.samples[len(t.samples)-(QuietMinutes+1):]
+	}
+	t.mu.Unlock()
+}
+
+// quiet reports whether the last QuietMinutes minutes each sent below QuietMbps, and the highest minute seen.
+func quiet(samples []txSample) (bool, float64) {
+	if len(samples) < QuietMinutes+1 {
+		return false, 0
+	}
+	worst := 0.0
+	for i := 1; i < len(samples); i++ {
+		dt := samples[i].at.Sub(samples[i-1].at).Seconds()
+		if dt <= 0 || dt > 3*TickInterval.Seconds() || samples[i].tx < samples[i-1].tx {
+			return false, worst // a gap or a counter reset is not proof of quiet
+		}
+		mbps := float64(samples[i].tx-samples[i-1].tx) * 8 / dt / 1e6
+		if mbps > worst {
+			worst = mbps
+		}
+	}
+	return worst < QuietMbps, worst
+}
+
+// Run ticks every TickInterval until ctx ends. It never returns an error: a failed test is a reported fact.
+func (t *Tester) Run(ctx context.Context) {
+	t.logger.Info("linetest: weekly upload line test starting", "schedule", ScheduleText, "slot_minute", t.slot)
+	if !t.sleep(ctx, FirstTickDelay) {
+		return
+	}
+	for {
+		t.sample()
+		t.Tick(ctx)
+		if !t.sleep(ctx, TickInterval) {
+			return
+		}
+	}
+}
+
+// Tick is one look.
+func (t *Tester) Tick(ctx context.Context) {
+	lt := t.now().In(t.loc)
+	t.mu.Lock()
+	st := t.st
+	samples := append([]txSample(nil), t.samples...)
+	t.mu.Unlock()
+	if !Due(st, lt) {
+		return
+	}
+	anchor := weekAnchor(lt)
+	anchorDay := lt.YearDay() == anchor.YearDay() && lt.Year() == anchor.Year()
+	if !EligibleAt(lt, t.slot, anchorDay) {
+		return
+	}
+	day := lt.Format("2006-01-02")
+	if st.TriesDay == day && st.TriesToday >= MaxTriesPerDay {
+		return
+	}
+	ip, ok := t.target()
+	if !ok {
+		t.logger.Debug("linetest: no operational tunnel — no test")
+		return
+	}
+	if q, worst := quiet(samples); !q {
+		t.logger.Debug("linetest: uplink not quiet — waiting", "worst_minute_mbps", fmt.Sprintf("%.1f", worst), "samples", len(samples))
+		return
+	}
+	release, busy, ok := t.gate.TryAcquire(GateName)
+	if !ok {
+		t.logger.Info("linetest: deferred — a heavy operation is in flight", "busy", busy)
+		return
+	}
+	defer release()
+	t.measure(ctx, netip.AddrPortFrom(ip, ServerPort).String(), day)
+}
+
+func (t *Tester) measure(ctx context.Context, addr, day string) {
+	start := t.now()
+	var runs []float64
+	var lastErr error
+	busy := false
+	for i := 0; i < RunsPerMeasurement; i++ {
+		if i > 0 && !t.sleep(ctx, RunGap) {
+			break
+		}
+		rctx, cancel := context.WithTimeout(ctx, RunTimeout)
+		r, err := t.runner.Run(rctx, addr)
+		cancel()
+		if errors.Is(err, ErrBusy) {
+			busy, lastErr = true, err
+			break
+		}
+		if err != nil {
+			lastErr = err
+			t.logger.Warn("linetest: run failed", "run", i+1, "server", addr, "err", err)
+			continue
+		}
+		runs = append(runs, r.Mbps)
+		t.logger.Info(fmt.Sprintf("linetest: run %d: %.1f Mbit/s", i+1, r.Mbps), "server", addr,
+			"server_bytes", r.ServerBytes, "server_seconds", r.ServerSeconds)
+	}
+
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.st.TriesDay != day {
+		t.st.TriesDay, t.st.TriesToday = day, 0
+	}
+	t.st.TriesToday++
+	t.st.LastAttemptAt = start.UTC()
+	if len(runs) > 0 {
+		best := runs[0]
+		for _, r := range runs {
+			if r > best {
+				best = r
+			}
+		}
+		t.st.LastOKAt, t.st.Mbps, t.st.RunsMbps, t.st.Server, t.st.LastError = start.UTC(), best, runs, addr, ""
+		t.logger.Info(fmt.Sprintf("linetest: upload line measured: %.1f Mbit/s (best of %d)", best, len(runs)),
+			"server", addr, "runs", len(runs), "duration_s", t.now().Sub(start).Seconds())
+	} else {
+		msg := "no run succeeded"
+		if lastErr != nil {
+			msg = lastErr.Error()
+		}
+		if len(msg) > 300 {
+			msg = msg[:300]
+		}
+		t.st.LastError = msg
+		if busy {
+			t.logger.Info("linetest: the test server is busy — trying again later today", "server", addr, "tries_today", t.st.TriesToday)
+		} else {
+			t.logger.Warn("linetest: measurement failed", "server", addr, "tries_today", t.st.TriesToday, "err", msg)
+		}
+	}
+	if err := t.saveLocked(); err != nil {
+		t.logger.Warn("linetest: state save failed — the result will not survive a restart", "path", t.statePath, "err", err)
+	}
+}
+
+// Value is the measured line (ok=false: never measured).
+func (t *Tester) Value() (mbps float64, at time.Time, ok bool) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.st.LastOKAt.IsZero() || t.st.Mbps <= 0 {
+		return 0, time.Time{}, false
+	}
+	return t.st.Mbps, t.st.LastOKAt, true
+}
+
+// LineTestStatus implements hub.LineTestReporter: a pure read of the persisted state.
+func (t *Tester) LineTestStatus(context.Context) *hub.LineTestStatus {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	out := &hub.LineTestStatus{Schedule: ScheduleText, Mbps: t.st.Mbps, RunsMbps: t.st.RunsMbps, Server: t.st.Server,
+		LastError: t.st.LastError}
+	if !t.st.LastOKAt.IsZero() {
+		out.LastOKAt = t.st.LastOKAt.UTC().Format(time.RFC3339)
+	}
+	if !t.st.LastAttemptAt.IsZero() {
+		out.LastAttemptAt = t.st.LastAttemptAt.UTC().Format(time.RFC3339)
+	}
+	return out
+}
+
+// ── the host's physical uplink counter ──────────────────────────────────────────────────────────────────────────
+
+// SysUplinkTx reads the transmit bytes of the host's physical uplink under root (normally "/"): the interface of the
+// default route in /proc/net/route, and — when it is a bridge (vmbr0), as on every Proxmox host — the sum of its
+// PHYSICAL member ports (those with a `device` link). The bridge's own counter does not see the guests' bridged
+// traffic, which is the traffic this check exists for.
+func SysUplinkTx(root string) UplinkTx {
+	return func() (uint64, error) {
+		ifc, err := defaultRouteIface(filepath.Join(root, "proc/net/route"))
+		if err != nil {
+			return 0, err
+		}
+		sys := filepath.Join(root, "sys/class/net")
+		ports := []string{ifc}
+		if ents, err := os.ReadDir(filepath.Join(sys, ifc, "brif")); err == nil {
+			ports = ports[:0]
+			for _, e := range ents {
+				if _, err := os.Stat(filepath.Join(sys, e.Name(), "device")); err == nil {
+					ports = append(ports, e.Name())
+				}
+			}
+			if len(ports) == 0 {
+				return 0, fmt.Errorf("linetest: bridge %s has no physical port", ifc)
+			}
+		}
+		var sum uint64
+		for _, p := range ports {
+			b, err := os.ReadFile(filepath.Join(sys, p, "statistics/tx_bytes"))
+			if err != nil {
+				return 0, err
+			}
+			n, err := strconv.ParseUint(strings.TrimSpace(string(b)), 10, 64)
+			if err != nil {
+				return 0, err
+			}
+			sum += n
+		}
+		return sum, nil
+	}
+}
+
+func defaultRouteIface(path string) (string, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return "", err
+	}
+	for _, line := range strings.Split(string(b), "\n")[1:] {
+		f := strings.Fields(line)
+		if len(f) >= 8 && f[1] == "00000000" && f[7] == "00000000" {
+			return f[0], nil
+		}
+	}
+	return "", errors.New("linetest: no default route")
+}
@@ -0,0 +1,433 @@
+package linetest
+
+import (
+	"context"
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+	"io"
+	"net"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
+)
+
+// ── a fake iperf3 server (the server half of the protocol, as `iperf3 --server` drives it) ─────────────────────────
+
+type fakeServer struct {
+	ln          net.Listener
+	busy        bool    // answer ACCESS_DENIED
+	stall       bool    // accept the cookie, then never answer
+	recvSeconds float64 // what the server reports as its duration
+	gotIDs      []int   // the stream ids the client reported
+	gotParams   map[string]any
+	mu          sync.Mutex
+	received    int64
+}
+
+func newFakeServer(t *testing.T) *fakeServer {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := &fakeServer{ln: ln, recvSeconds: 1}
+	t.Cleanup(func() { ln.Close() })
+	go s.serve()
+	return s
+}
+
+func (s *fakeServer) addr() string { return s.ln.Addr().String() }
+
+func wjson(w io.Writer, v any) {
+	b, _ := json.Marshal(v)
+	var h [4]byte
+	binary.BigEndian.PutUint32(h[:], uint32(len(b)))
+	w.Write(append(h[:], b...))
+}
+
+func (s *fakeServer) serve() {
+	ctrl, err := s.ln.Accept()
+	if err != nil {
+		return
+	}
+	defer ctrl.Close()
+	cookie := make([]byte, cookieSize)
+	if _, err := io.ReadFull(ctrl, cookie); err != nil {
+		return
+	}
+	if s.busy {
+		ctrl.Write([]byte{0xff})
+		return
+	}
+	if s.stall {
+		time.Sleep(5 * time.Second)
+		return
+	}
+	ctrl.Write([]byte{stParamExchange})
+	var params map[string]any
+	if readJSON(ctrl, &params) != nil {
+		return
+	}
+	s.gotParams = params
+	n := int(params["parallel"].(float64))
+	ctrl.Write([]byte{stCreateStreams})
+	var wg sync.WaitGroup
+	var conns []net.Conn
+	for i := 0; i < n; i++ {
+		d, err := s.ln.Accept()
+		if err != nil {
+			return
+		}
+		c := make([]byte, cookieSize)
+		io.ReadFull(d, c)
+		conns = append(conns, d)
+		wg.Add(1)
+		go func(d net.Conn) {
+			defer wg.Done()
+			k, _ := io.Copy(io.Discard, d)
+			s.mu.Lock()
+			s.received += k
+			s.mu.Unlock()
+		}(d)
+	}
+	ctrl.Write([]byte{stTestStart, stTestRunning})
+	var st [1]byte
+	if _, err := io.ReadFull(ctrl, st[:]); err != nil || st[0] != stTestEnd {
+		return
+	}
+	ctrl.Write([]byte{stExchangeResults})
+	var theirs results
+	if readJSON(ctrl, &theirs) != nil {
+		return
+	}
+	for _, x := range theirs.Streams {
+		s.gotIDs = append(s.gotIDs, x.ID)
+	}
+	// The server counts what it RECEIVED; report a fixed figure so the test can tell it from the client's own count.
+	wjson(ctrl, results{Streams: []streamResult{{ID: 1, Bytes: 12_500_000, EndTime: s.recvSeconds}}})
+	ctrl.Write([]byte{stDisplayResults})
+	io.ReadFull(ctrl, st[:])
+	for _, d := range conns {
+		d.Close()
+	}
+	wg.Wait()
+}
+
+func TestClientSpeaksTheProtocolAndCountsTheServersBytes(t *testing.T) {
+	s := newFakeServer(t)
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	r, err := Client{Streams: 4, Time: 300 * time.Millisecond}.Run(ctx, s.addr())
+	if err != nil {
+		t.Fatalf("Run: %v", err)
+	}
+	if r.ServerBytes != 12_500_000 || r.Mbps != 100 {
+		t.Fatalf("result = %+v; want the SERVER's 12.5 MB in 1 s = 100 Mbit/s", r)
+	}
+	if want := []int{1, 3, 4, 5}; len(s.gotIDs) != 4 || s.gotIDs[0] != want[0] || s.gotIDs[1] != want[1] || s.gotIDs[3] != want[3] {
+		t.Fatalf("stream ids sent = %v, want %v (iperf3 numbers its streams 1, 3, 4, 5)", s.gotIDs, want)
+	}
+	if s.gotParams["tcp"] != true || s.gotParams["parallel"].(float64) != 4 {
+		t.Fatalf("params = %v", s.gotParams)
+	}
+}
+
+func TestClientBusyServerIsErrBusy(t *testing.T) {
+	s := newFakeServer(t)
+	s.busy = true
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	if _, err := (Client{Streams: 4, Time: time.Second}).Run(ctx, s.addr()); !errors.Is(err, ErrBusy) {
+		t.Fatalf("err = %v, want ErrBusy", err)
+	}
+}
+
+func TestClientHonoursTheDeadlineAgainstAStalledServer(t *testing.T) {
+	s := newFakeServer(t)
+	s.stall = true
+	ctx, cancel := context.WithTimeout(context.Background(), 400*time.Millisecond)
+	defer cancel()
+	start := time.Now()
+	_, err := Client{Streams: 4, Time: time.Second}.Run(ctx, s.addr())
+	if err == nil {
+		t.Fatal("a stalled server gave no error")
+	}
+	if took := time.Since(start); took > 1500*time.Millisecond {
+		t.Fatalf("Run took %v against a stalled server; the deadline is 400 ms", took)
+	}
+}
+
+func TestClientRefusesAContextWithoutDeadline(t *testing.T) {
+	if _, err := (Client{}).Run(context.Background(), "127.0.0.1:1"); err == nil {
+		t.Fatal("Run without a deadline must refuse (an unbounded test is the thing RunTimeout exists to prevent)")
+	}
+}
+
+// ── the schedule ────────────────────────────────────────────────────────────────────────────────────────────────
+
+func TestEligibleWindowNeverInTheNightChain(t *testing.T) {
+	loc := time.FixedZone("CET", 3600)
+	start := time.Date(2026, 10, 19, 0, 0, 0, 0, loc) // a Monday
+	for m := 0; m < 7*24*60; m++ {
+		lt := start.Add(time.Duration(m) * time.Minute)
+		for _, anchorDay := range []bool{true, false} {
+			if !EligibleAt(lt, 0, anchorDay) {
+				continue
+			}
+			if h := lt.Hour(); h < StartHour || h >= EndHour || (h >= 1 && h <= 6) {
+				t.Fatalf("eligible at %s — outside 10:00-15:59 or inside the night chain (01:00-06:59)", lt.Format("Mon 15:04"))
+			}
+		}
+	}
+}
+
+func TestSlotDelaysTheFirstStartOnTheDueDayOnly(t *testing.T) {
+	loc := time.UTC
+	tue := time.Date(2026, 10, 20, 10, 30, 0, 0, loc)
+	if EligibleAt(tue, 45, true) {
+		t.Fatal("10:30 with slot 45 must wait until 10:45 on the due day")
+	}
+	if !EligibleAt(tue.Add(15*time.Minute), 45, true) {
+		t.Fatal("10:45 with slot 45 must be eligible")
+	}
+	if !EligibleAt(tue.Add(24*time.Hour), 45, false) {
+		t.Fatal("a catch-up day does not wait for the slot again")
+	}
+	if a, b := SlotMinute("demo-hp-bb76ea"), SlotMinute("demo-felhom-8363b5"); a < 0 || a >= SlotSpreadMinutes || b < 0 || b >= SlotSpreadMinutes {
+		t.Fatalf("slots out of range: %d %d", a, b)
+	}
+}
+
+func TestDueWeeklyFromTuesday(t *testing.T) {
+	loc := time.UTC
+	mon := time.Date(2026, 10, 19, 12, 0, 0, 0, loc)
+	tue := time.Date(2026, 10, 20, 12, 0, 0, 0, loc)
+	if !Due(State{}, mon) {
+		t.Fatal("never measured is due")
+	}
+	st := State{LastOKAt: time.Date(2026, 10, 14, 11, 0, 0, 0, loc)} // last Wednesday
+	if Due(st, mon) {
+		t.Fatal("measured after last Tuesday 10:00 is not due on Monday")
+	}
+	if !Due(st, tue) {
+		t.Fatal("from Tuesday 10:00 a new measurement is due")
+	}
+}
+
+// ── the job ─────────────────────────────────────────────────────────────────────────────────────────────────────
+
+type fakeRunner struct {
+	mu    sync.Mutex
+	calls int
+	out   []runOut
+}
+type runOut struct {
+	mbps float64
+	err  error
+}
+
+func (f *fakeRunner) Run(ctx context.Context, addr string) (Result, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	i := f.calls
+	f.calls++
+	if i >= len(f.out) {
+		return Result{}, errors.New("no more scripted runs")
+	}
+	return Result{Mbps: f.out[i].mbps, ServerBytes: 1}, f.out[i].err
+}
+
+type fakeGate struct{ busy string }
+
+func (g *fakeGate) TryAcquire(what string) (func(), string, bool) {
+	if g.busy != "" {
+		return nil, g.busy, false
+	}
+	return func() {}, "", true
+}
+
+type rig struct {
+	t      *Tester
+	run    *fakeRunner
+	gate   *fakeGate
+	now    time.Time
+	tx     uint64
+	tunnel bool
+}
+
+// newRig: Tuesday 12:00 UTC (eligible, any slot), tunnel up, 11 quiet samples taken.
+func newRig(t *testing.T, outs ...runOut) *rig {
+	r := &rig{run: &fakeRunner{out: outs}, gate: &fakeGate{}, now: time.Date(2026, 10, 20, 12, 0, 0, 0, time.UTC), tunnel: true}
+	r.t = New(r.run, func() (netip.Addr, bool) { return netip.MustParseAddr("10.77.0.1"), r.tunnel }, r.gate,
+		func() (uint64, error) { return r.tx, nil }, "host-x", filepath.Join(t.TempDir(), "line-test.json"), nil)
+	r.t.loc = time.UTC
+	r.t.now = func() time.Time { return r.now }
+	r.t.sleep = func(context.Context, time.Duration) bool { return true }
+	r.quietMinutes(QuietMinutes + 1)
+	return r
+}
+
+func (r *rig) minute(bytes uint64) {
+	r.now = r.now.Add(time.Minute)
+	r.tx += bytes
+	r.t.sample()
+}
+
+func (r *rig) quietMinutes(n int) {
+	for i := 0; i < n; i++ {
+		r.minute(1_000_000) // 1 MB/min = 0.13 Mbit/s
+	}
+}
+
+func TestTickMeasuresTheHighestOfThreeRuns(t *testing.T) {
+	r := newRig(t, runOut{mbps: 88}, runOut{mbps: 91.5}, runOut{mbps: 90})
+	r.t.Tick(context.Background())
+	mbps, _, ok := r.t.Value()
+	if !ok || mbps != 91.5 || r.run.calls != RunsPerMeasurement {
+		t.Fatalf("value %.1f ok=%v calls=%d; want the highest of 3 runs = 91.5", mbps, ok, r.run.calls)
+	}
+	r.t.Tick(context.Background())
+	if r.run.calls != RunsPerMeasurement {
+		t.Fatal("a measured week must not test again")
+	}
+}
+
+func TestBusyServerIsRetriedLaterTheSameDay(t *testing.T) {
+	r := newRig(t, runOut{err: ErrBusy}, runOut{mbps: 90}, runOut{mbps: 89}, runOut{mbps: 92})
+	r.t.Tick(context.Background())
+	if _, _, ok := r.t.Value(); ok || r.run.calls != 1 {
+		t.Fatalf("busy: ok=%v calls=%d; want no value and the measurement stopped after the busy answer", ok, r.run.calls)
+	}
+	if r.t.st.TriesToday != 1 || r.t.st.LastError == "" {
+		t.Fatalf("busy attempt not recorded: %+v", r.t.st)
+	}
+	r.quietMinutes(1)
+	r.t.Tick(context.Background())
+	if mbps, _, ok := r.t.Value(); !ok || mbps != 92 {
+		t.Fatalf("retry later the same day: value %.1f ok=%v", mbps, ok)
+	}
+}
+
+func TestTriesPerDayAreBounded(t *testing.T) {
+	outs := make([]runOut, 20)
+	for i := range outs {
+		outs[i] = runOut{err: ErrBusy}
+	}
+	r := newRig(t, outs...)
+	for i := 0; i < 10; i++ {
+		r.quietMinutes(1)
+		r.t.Tick(context.Background())
+	}
+	if r.run.calls != MaxTriesPerDay {
+		t.Fatalf("calls = %d in one day, want at most %d", r.run.calls, MaxTriesPerDay)
+	}
+}
+
+func TestNoTunnelNoTest(t *testing.T) {
+	r := newRig(t, runOut{mbps: 90})
+	r.tunnel = false
+	r.t.Tick(context.Background())
+	if r.run.calls != 0 {
+		t.Fatal("tested without an operational tunnel")
+	}
+	if _, _, ok := r.t.Value(); ok {
+		t.Fatal("a value without a test")
+	}
+}
+
+func TestBusyUplinkOrHeavyOpWaits(t *testing.T) {
+	r := newRig(t, runOut{mbps: 90}, runOut{mbps: 90}, runOut{mbps: 90})
+	r.minute(60_000_000) // one minute at 8 Mbit/s: the family is uploading
+	r.t.Tick(context.Background())
+	if r.run.calls != 0 {
+		t.Fatal("tested while the uplink was busy in the last 10 minutes")
+	}
+	r.quietMinutes(QuietMinutes)
+	r.gate.busy = "backup:felhom-pbs"
+	r.t.Tick(context.Background())
+	if r.run.calls != 0 {
+		t.Fatal("tested beside a heavy operation")
+	}
+	r.gate.busy = ""
+	r.t.Tick(context.Background())
+	if r.run.calls == 0 {
+		t.Fatal("never tested once the uplink was quiet and the gate free")
+	}
+}
+
+func TestNeverTestsInTheNightOrBeforeTuesday(t *testing.T) {
+	r := newRig(t, runOut{mbps: 90}, runOut{mbps: 90}, runOut{mbps: 90})
+	r.now = time.Date(2026, 10, 20, 3, 0, 0, 0, time.UTC) // Tuesday 03:00 — the night chain
+	r.quietMinutes(QuietMinutes + 1)
+	r.t.Tick(context.Background())
+	r.t.st.LastOKAt = time.Date(2026, 10, 14, 12, 0, 0, 0, time.UTC)
+	r.now = time.Date(2026, 10, 19, 12, 0, 0, 0, time.UTC) // Monday noon, measured last week
+	r.quietMinutes(QuietMinutes + 1)
+	r.t.Tick(context.Background())
+	if r.run.calls != 0 {
+		t.Fatalf("tested %d times at night or when not due", r.run.calls)
+	}
+}
+
+func TestStateSurvivesARestartAndReportsIt(t *testing.T) {
+	r := newRig(t, runOut{mbps: 90.7}, runOut{err: errors.New("reset")}, runOut{mbps: 80})
+	r.t.Tick(context.Background())
+	again := New(r.run, nil, r.gate, nil, "host-x", r.t.statePath, nil)
+	mbps, at, ok := again.Value()
+	if !ok || mbps != 90.7 || at.IsZero() {
+		t.Fatalf("after a restart: %.1f %v %v", mbps, at, ok)
+	}
+	b, _ := json.Marshal(again.LineTestStatus(context.Background()))
+	var back hub.LineTestStatus
+	json.Unmarshal(b, &back)
+	if back.Mbps != 90.7 || back.LastOKAt == "" || len(back.RunsMbps) != 2 || back.Schedule == "" {
+		t.Fatalf("report stanza = %s", b)
+	}
+}
+
+// ── the uplink counter ──────────────────────────────────────────────────────────────────────────────────────────
+
+func TestUplinkCountsTheBridgesPhysicalPortsOnly(t *testing.T) {
+	root := t.TempDir()
+	w := func(p, s string) {
+		os.MkdirAll(filepath.Dir(filepath.Join(root, p)), 0o755)
+		os.WriteFile(filepath.Join(root, p), []byte(s), 0o644)
+	}
+	w("proc/net/route", "Iface\tDestination\tGateway\tFlags\tRefCnt\tUse\tMetric\tMask\n"+
+		"wg-felhom\t0000004D\t00000000\t0001\t0\t0\t0\tFFFFFFFF\n"+
+		"vmbr0\t00000000\t0100A8C0\t0003\t0\t0\t0\t00000000\n")
+	w("sys/class/net/vmbr0/statistics/tx_bytes", "5\n")
+	w("sys/class/net/vmbr0/brif/enp1s0/.keep", "")
+	w("sys/class/net/vmbr0/brif/veth9201i0/.keep", "")
+	w("sys/class/net/enp1s0/device/.keep", "")
+	w("sys/class/net/enp1s0/statistics/tx_bytes", "1000\n")
+	w("sys/class/net/veth9201i0/statistics/tx_bytes", "777777\n")
+	got, err := SysUplinkTx(root)()
+	if err != nil || got != 1000 {
+		t.Fatalf("uplink tx = %d, %v; want 1000 (the physical port only — not the bridge, not the guest's veth)", got, err)
+	}
+}
+
+func TestQuietNeedsTenFullMinutes(t *testing.T) {
+	base := time.Date(2026, 10, 20, 12, 0, 0, 0, time.UTC)
+	var s []txSample
+	for i := 0; i <= QuietMinutes; i++ {
+		s = append(s, txSample{at: base.Add(time.Duration(i) * time.Minute), tx: uint64(i) * 1_000_000})
+	}
+	if q, _ := quiet(s); !q {
+		t.Fatal("ten quiet minutes must read quiet")
+	}
+	if q, _ := quiet(s[1:]); q {
+		t.Fatal("nine minutes of samples must not read quiet")
+	}
+	gap := append([]txSample(nil), s...)
+	gap[5].at = gap[5].at.Add(-10 * time.Minute)
+	if q, _ := quiet(gap); q {
+		t.Fatal("a gap in the samples must not read quiet")
+	}
+}
@@ -0,0 +1,37 @@
+package localapi
+
+import (
+	"net/http"
+	"time"
+)
+
+// LineTestReader is the R-1247 weekly upload line test (internal/linetest.Tester) as the local API reads it.
+type LineTestReader interface {
+	Value() (mbps float64, at time.Time, ok bool)
+}
+
+// LineTestResponse is GET /host/line-test. Present=false: never measured, or the job is not wired (no tunnel, disabled,
+// or an agent before the route answers 404 — the controller reads all three as „unknown").
+type LineTestResponse struct {
+	Present    bool    `json:"present"`
+	Mbps       float64 `json:"mbps,omitempty"`
+	MeasuredAt string  `json:"measured_at,omitempty"` // RFC3339 UTC
+	Method     string  `json:"method,omitempty"`      // "iperf3-tunnel": a 10-second upload to ep0 inside the tunnel
+}
+
+// SetLineTest wires the weekly line test (main.go builds it after the local API server).
+func (s *Server) SetLineTest(r LineTestReader) { s.lineTest = r }
+
+func (s *Server) handleLineTest(w http.ResponseWriter, r *http.Request, vmid int) {
+	if s.lineTest == nil {
+		writeOK(w, LineTestResponse{Present: false})
+		return
+	}
+	mbps, at, ok := s.lineTest.Value()
+	if !ok {
+		writeOK(w, LineTestResponse{Present: false})
+		return
+	}
+	s.logger.Debug("local-api: /host/line-test served", "vmid", vmid, "mbps", mbps, "measured_at", at.UTC().Format(time.RFC3339))
+	writeOK(w, LineTestResponse{Present: true, Mbps: mbps, MeasuredAt: at.UTC().Format(time.RFC3339), Method: "iperf3-tunnel"})
+}
@@ -0,0 +1,51 @@
+package localapi
+
+import (
+	"encoding/json"
+	"log/slog"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+type fixedLine struct {
+	mbps float64
+	ok   bool
+}
+
+func (f fixedLine) Value() (float64, time.Time, bool) {
+	return f.mbps, time.Date(2026, 10, 24, 6, 31, 0, 0, time.UTC), f.ok
+}
+
+func lineTestBody(t *testing.T, s *Server) LineTestResponse {
+	t.Helper()
+	rec := httptest.NewRecorder()
+	s.handleLineTest(rec, httptest.NewRequest("GET", "/host/line-test", nil), 9201)
+	var env struct {
+		OK   bool             `json:"ok"`
+		Data LineTestResponse `json:"data"`
+	}
+	if err := json.Unmarshal(rec.Body.Bytes(), &env); err != nil {
+		t.Fatalf("decode %q: %v", rec.Body.String(), err)
+	}
+	return env.Data
+}
+
+// R-1247: the controller sets qBittorrent's limit only from a PRESENT value; never measured and not wired must both
+// read present:false, never a zero line.
+func TestLineTestRoute(t *testing.T) {
+	s := &Server{logger: slog.Default()}
+	if got := lineTestBody(t, s); got.Present {
+		t.Fatalf("not wired: %+v, want present:false", got)
+	}
+	s.SetLineTest(fixedLine{ok: false})
+	if got := lineTestBody(t, s); got.Present || got.Mbps != 0 {
+		t.Fatalf("never measured: %+v, want present:false", got)
+	}
+	s.SetLineTest(fixedLine{mbps: 90.7, ok: true})
+	got := lineTestBody(t, s)
+	if !got.Present || got.Mbps != 90.7 || got.Method != "iperf3-tunnel" || !strings.HasPrefix(got.MeasuredAt, "2026-10-24T06:31") {
+		t.Fatalf("measured: %+v", got)
+	}
+}
@@ -336,6 +336,7 @@ type Server struct {
 	formatJobs        *FormatJobStore                     // F20-BUG3 detached-format job record (optional)
 	staleLock         StaleLockController                 // F2-b startup stale-lock recovery (optional)
 	partialSweep      func(ctx context.Context, vmid int) // R-1006 start-up sweep of dead vzdump leftovers (optional)
+	lineTest          LineTestReader                      // R-1247 weekly line test (optional; nil → present:false)
 	// guestPower (F-REBOOT) is per-guest start-attempt state for the guest-power watchdog.
 	// Guarded by guestPowerMu in guestpower.go; in-memory on purpose (see guestPowerState).
 	guestPower map[int]guestPowerState
@@ -573,6 +574,9 @@ func (s *Server) Handler() http.Handler {
 	// R-856 (`09` §3 decision 143): the host crash guard's record of the last HOST boot — the controller
 	// waits ~15 min with app mails after an unclean one. Read-only; a missing/garbled file = present:false.
 	mux.HandleFunc("GET /host/crash-guard", s.withGuest(s.handleCrashGuard))
+	// R-1247: the weekly upload line test's last measurement — the controller's qBittorrent limit and upload watch
+	// read it. Read-only; never measured (or the job not wired) = present:false.
+	mux.HandleFunc("GET /host/line-test", s.withGuest(s.handleLineTest))
 	// Disk management (slice 8C) — self-scoped; format routes through the data-bearing classifier+gate.
 	mux.HandleFunc("GET /disks", s.withGuest(s.handleDisks))
 	mux.HandleFunc("GET /disks/candidates", s.withGuest(s.handleDiskCandidates))
@@ -0,0 +1,32 @@
+package wgtunnel
+
+import (
+	"context"
+	"testing"
+)
+
+// R-1247: the line test's server is the desired block's pbs_tunnel_ip, and ONLY while the tunnel is operational
+// (registered + unit active) — „no tunnel → no test" rests on this answer.
+func TestLineTestTargetOnlyWhileOperational(t *testing.T) {
+	m, _, active, _ := testManager(t, &fakeHub{})
+	ctx := context.Background()
+	if _, ok := m.LineTestTarget(); ok {
+		t.Fatal("a target before any Apply")
+	}
+	m.Apply(ctx, false, nil) // registers
+	pub := localPub(t, m)
+	m.Apply(ctx, true, testBlock(pub)) // installs; the unit is not active yet
+	if _, ok := m.LineTestTarget(); ok {
+		t.Fatal("a target while the unit is not active")
+	}
+	*active = true
+	m.Apply(ctx, true, testBlock(pub))
+	ip, ok := m.LineTestTarget()
+	if !ok || ip.String() != "10.77.0.1" {
+		t.Fatalf("operational tunnel: target %v ok=%v, want 10.77.0.1", ip, ok)
+	}
+	m.Apply(ctx, true, nil) // revoked
+	if _, ok := m.LineTestTarget(); ok {
+		t.Fatal("a target after the hub revoked the tunnel")
+	}
+}
@@ -128,6 +128,7 @@ type Manager struct {
 type convSnapshot struct {
 	wgBlockDesired bool
 	operational    bool
+	serverIP       netip.Addr // the desired block's pbs_tunnel_ip (R-1247 line test target); invalid when none
 }

 // TunnelConvergence returns the cached (desired, operational) snapshot without any exec (fast-tick
@@ -139,6 +140,17 @@ func (m *Manager) TunnelConvergence() (desired, operational bool) {
 	return m.conv.wgBlockDesired, m.conv.operational
 }

+// LineTestTarget is the R-1247 line test's server: ep0's tunnel address, ok only while the tunnel is operational
+// (registered + unit active, as of the last Apply). Cached — no exec.
+func (m *Manager) LineTestTarget() (netip.Addr, bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if !m.conv.operational || !m.conv.serverIP.IsValid() {
+		return netip.Addr{}, false
+	}
+	return m.conv.serverIP, true
+}
+
 // NewManager builds a Manager. stateDir is the agent state dir (default /var/lib/felhom-agent —
 // note the FELHOM_WG sudoers install entry hard-codes the staged path under it).
 func NewManager(runner proxmox.Runner, registrar Registrar, stateDir string, logger *slog.Logger) *Manager {
@@ -348,7 +360,13 @@ func (m *Manager) Apply(ctx context.Context, fetched bool, block *hub.WireWiregu
 				operational = m.isActive(ctx)
 			}
 		}
-		m.conv = convSnapshot{wgBlockDesired: desired, operational: operational}
+		var server netip.Addr
+		if desired {
+			if a, err := netip.ParseAddr(block.Endpoint.PBSTunnelIP); err == nil && a.Is4() {
+				server = a
+			}
+		}
+		m.conv = convSnapshot{wgBlockDesired: desired, operational: operational, serverIP: server}
 	}()

 	keyExists := false