Noise ripped out after the bench verdict (tightly-wrapped unshielded cables move victim SNR only 0.2-0.3 dB, recorded in measurement.md dead ends): noise.go deleted with the noiser, phase clock and panel lane; configureNoise/checkPrivFlag gone so the X710 pair is untouched; console noise column, NOISE links rows and lane colors removed; driverPair rehomed to system.go, carrierUp to phy.go; history anchors to run start (frame-rate sampling and draw-clock roll kept — they fix display latency for every lane); goals/hardware/state/nics docs updated; verified on hardware (20.00G, zero errors, ECD 41m, SNR +7.6)

docs/goals.md

@@ -7,10 +7,11 @@ The target of measurement is the cable, not throughput. Line rate is a means to
 ## Outputs, in priority order
 
 1. **Loss and error attribution** — reception gaps, link errors, NIC/driver counters as first-class output alongside application loss. Baseline loss must be exactly zero before a run counts; any host-side loss masks real cable faults.
-2. **Noise tolerance** — a deliberately-bad "noise" cable intertwined with the test cable, driven by link up/down cycling, stresses the cable under test with alien crosstalk.
+2. **Per-pair SNR** from the module PHYs — the leading indicator of a marginal cable before it drops frames. IEEE 802.3an standard registers on the Marvells; the BCM leaves those unpopulated and reports through its vendor command handler instead (modules/fs/). Shown as margin over the operating point, classified good/marginal/bad, so nobody needs the magic numbers to read it (`phy.go`).
-3. **Per-pair SNR** from the module PHYs — the leading indicator of a marginal cable before it drops frames. IEEE 802.3an standard registers on the Marvells; the BCM leaves those unpopulated and reports through its vendor command handler instead (modules/fs/). Shown as margin over the operating point, classified good/marginal/bad, so nobody needs the magic numbers to read it (`phy.go`).
+3. **Cable length** — sanity check and fault localization. The BCM ECD is the product path: per-pair lengths in meters, healthy pairs included, proven meter-accurate on the bench (modules/fs/); run at bringup and on every reset, with pair-swap and fault verdicts on the panel.
-4. **Cable length** — sanity check and fault localization. The BCM ECD is the product path: per-pair lengths in meters, healthy pairs included, proven meter-accurate on the bench (modules/fs/); run at bringup and on every reset, with pair-swap and fault verdicts on the panel.
+4. **Pre-FEC error visibility** — corrected-error counters that move before post-FEC loss appears. Vendor-specific; located on the Aquantia (modules/fibergaga/), unlocated elsewhere. Standard latched PCS counters (errored blocks, BER, block-lock loss) are the working proxy.
-5. **Pre-FEC error visibility** — corrected-error counters that move before post-FEC loss appears. Vendor-specific; located on the Aquantia (modules/fibergaga/), unlocated elsewhere. Standard latched PCS counters (errored blocks, BER, block-lock loss) are the working proxy under noise stress.
+
+Alien-crosstalk noise injection was an output here and is measured out (measurement.md, "Dead ends"): an intertwined noise cable moves the victim's SNR margin only 0.2–0.3 dB.
 
 ## Design preferences that shaped the tool
 

docs/hardware.md

@@ -5,7 +5,6 @@ Box contents, card placement, and interface assignments live in [state.md](state
 ## Interfaces
 
 - **Test pair**: the two ports whose modules hold the cable under test. Find by driver name, never by ethN — names shift with kernel link order.
-- **Noise pair**: driven bad on purpose, link up/down cycled, intertwined with the test cable to inject alien crosstalk.
 - **LAN uplink**: carries the default route. **Never repurpose or down it**; identify by default route, not name.
 - Test-path ports live in NetworkManager's unmanaged list (`/etc/NetworkManager/conf.d/99-unmanaged-10g.conf`), up with no IPv4.
 

docs/measurement.md

@@ -53,6 +53,7 @@ Measured in the E810 era; the binding constraint was total CPU across ~28 gorout
 - **CPU pinning** — the Go scheduler beats manual placement; E-cores are poor at TX.
 - **Batch sizes above 64** — no gain, worse loss.
 - **Chasing the TX `sendmmsg` busy-spin on ENOBUFS** — it only exists when the TX ring is full, which means the wire is the ceiling; recovering that CPU buys no packets. POLLOUT is inert under PACKET_QDISC_BYPASS (skb freed on ENOBUFS, socket always reports writable).
+- **Alien-crosstalk injection from an intertwined noise cable** — bench-measured: two unshielded cables tightly wrapped moved the victim's per-pair SNR margin only 0.2–0.3 dB, far too little to stress even a marginal cable; 10GBASE-T's alien-noise budget absorbs it. The noise pair, its link-cycling, and the panel lane are removed from the tool.
 
 ## rxnfc flow-rule programming — three traps (found on ice; 1 and 2 are kernel-ABI-generic)
 

docs/modules/fs/README.md

@@ -46,7 +46,7 @@ Protocol and full verified catalog: [bcm84891l-mdio-commands.md](bcm84891l-mdio-
 | Per-pair SNR | `CMD_GET_SNR` 0x8030, **invoked bare** (writing the documented DATA1 display flag returns zeros; IEEE 1.133–1.140 never populate — constant 0x8080) | DATA2–5 = SNR A–D ×0.1 dB; ≈ 27–32 dB absolute on bench, 0.1–0.4 dB jitter. 10GBASE-T operating point ≈ 26.5 dB, so margin ≈ value − 26.5 — a derived number that never proved actionable, so **cabletest does not poll it** (the panel's SNR comes from an IEEE-margin end — modules/wiitek/ — and each GET costs handler traffic on this µC). **Each training re-converges differently**: back-to-back retrains with identical roles, temperature and noise moved one pair by 3.6 dB (roles pinned, launch power pinned — the convergence itself is the variable, and the two bench modules differ in stability: ≤1.5 dB spread on one, 3.6 dB on the other). A single training's absolute SNR is a weak qualification number; qualification wants median-of-N trainings |
 | Die temperature | `CMD_GET_CURRENT_TEMP` 0x8031 | ~68–70 °C on bench |
 | Supply rails | `GET_CURRENT_VOLTAGE` 0x802F | 0.8 V and 1.88 V rails, tenths of mV |
-| Error counters | IEEE PCS 3.32/3.33 — block lock, latched errored-block/BER, clear-on-read | The noise-stress error proxy |
+| Error counters | IEEE PCS 3.32/3.33 — block lock, latched errored-block/BER, clear-on-read | The corrected-error channel cabletest polls |
 | Retrain on demand | IEEE AN restart `7.0 \|= 0x1200` (enable + restart — the ECD can leave the enable bit cleared, see below) | Relinks in ~5–6 s |
 
 ## Probed configuration states

docs/nics/README.md

@@ -18,7 +18,7 @@ Which card is where: [../state.md](../state.md).
 |---|---|---|---|
 | [X520 / 82599 (ixgbe)](x520/README.md) | Host bit-bangs — full control, **proven**, fast (<25 ms RollBall) | No (single serial latch; 1588-event frames only) — no longer required | **The product NIC** under the smoothed-bucket rate plan: only card with unmediated host I2C, and the FS links here (mixed FS+Wiitek pair proven) |
 | [ConnectX-4/5 (mlx5)](connectx-5/README.md) | Firmware MCIA — writes via VSC/ICMD only (fwctl read-only), every mailbox read quantized to ~150 ms steps by firmware module traffic | Yes (CQE-stamps everything) | Retired: its stamps are no longer needed and its I2C mediation is the cost; the FS never links on it either (host-interface deadlock, device page) |
-| [X710 (i40e)](x710/README.md) | 1-byte-offset only | No | RollBall oracle path; noise pair |
+| [X710 (i40e)](x710/README.md) | 1-byte-offset only | No | RollBall oracle path; in the box unused |
 | [E810 (ice)](e810/README.md) | Multi-byte framing, writes EPERM-blocked | Yes | Dead for diagnostics writes; the below-the-AQ bit-bang idea (device page) is retired with the timestamp requirement |
 
 ## Architecture

docs/state.md

@@ -22,7 +22,7 @@ Indices shift as stashes are pushed/popped — match by message, not number.
 | Interface | Device | Role (rules: hardware.md) |
 |---|---|---|
 | `enp1s0f0` + second port | X520 (ixgbe) | Test pair — FS + Wiitek, dispatched by EEPROM PN so either port may hold either module. **Stock ixgbe refuses the FS's honest EEPROM and its port has no netdev until `./load-ixgbe`** (allow_unsupported_sfp=1 + the sff_i2c/ETQF patches); the tool needs exactly 2 ixgbe interfaces |
-| `enp3s0f0np0` / `enp3s0f1np1` | X710 (i40e) | Noise pair (has been `enp4s0f*` across reboots) — two Wiiteks, both qualified by the X710. The FS cannot live here (firmware rejects the honest EEPROM, no `allow_unsupported_sfp` in i40e) |
+| `enp3s0f0np0` / `enp3s0f1np1` | X710 (i40e) | Unused by the tool (was the noise pair; alien crosstalk measured ineffective — measurement.md). Two Wiiteks still seated (has been `enp4s0f*` across reboots). The FS cannot live here (firmware rejects the honest EEPROM, no `allow_unsupported_sfp` in i40e) |
 | `enp88s0` | igc | LAN uplink, default route; sibling `enp89s0` is dark |
 
 ## Hardware
@@ -32,7 +32,7 @@ Indices shift as stashes are pushed/popped — match by message, not number.
 | X520-DA2 | **Installed** in the single PCIe slot — **the product NIC** (nics/x520/) | Unmediated bit-bang I2C (patched-ixgbe `sff_i2c`), <25 ms RollBall, FS links and the ECD length path is proven; the smoothed-bucket rate design removes the need for hardware RX stamps |
 | ConnectX-5 | Out of the box — retired | Ran the two-Wiitek pair at near line rate with dual-end SNR (stashed `phy_mcia.go` MCIA transport), but the firmware quantizes every module mailbox read to ~150 ms steps and the FS never links behind mlx5 — nics/connectx-5/, "Status" |
 | FS SFP-10G-T-100 ×2 | One in the X520 test pair, one on the shelf | BCM84891L, documented, robust; ixgbe-only (unlinkable behind mlx5 — host-interface deadlock, confirmed module-typed, nics/connectx-5/ — and rejected by the X710). The FS+Wiitek mixed pair (FS length via ECD + Wiitek SNR) is the product configuration |
-| Replacement Wiiteks | One in the X520 test pair, two in the X710 noise pair, rest on the shelf | Originals bricked by register exploration — modules/wiitek/ trap first. IEEE-standard registers only (modules/README.md safe set); VCT templates are single-shot candidates on a sacrificial unit only |
+| Replacement Wiiteks | One in the X520 test pair, two seated in the unused X710, rest on the shelf | Originals bricked by register exploration — modules/wiitek/ trap first. IEEE-standard registers only (modules/README.md safe set); VCT templates are single-shot candidates on a sacrificial unit only |
 | Fibergaga SFP-10G-T-30M | On the shelf | Aquantia, RollBall, the documented oracle; the alternate length path if the pair mix ever changes |
 | 10Gtek | In hand | Claims SFP-10G-SR, still copper RJ45; filler, not in the test set |
 | E810 | Out of the box | Patched ice + `sff_i2c` remains useful only if it returns for read-side work |

history.go

@@ -140,8 +140,8 @@ type histView struct {
 }
 
 // The window's newest column is the slot containing now, taken from the draw
-// clock rather than the last sample: the grid then rolls on the slot boundary
+// clock rather than the last sample, so the grid rolls on the slot boundary
-// itself — the same instant the noise cycle flips.
+// itself.
 func (h *history) view(now time.Time) histView {
 	h.mu.Lock()
 	defer h.mu.Unlock()

main.go

@@ -69,7 +69,6 @@ var intervalCols = []colSpec{
 	{group: "NOW", title: "link", width: 7, right: true},
 	{group: "NOW", title: "internal", width: 8, right: true},
 	{group: "NOW", title: "corrected", width: 9, right: true},
-	{group: "NOW", title: "noise", width: 7, right: true},
 	{group: "OVERALL", title: "elapsed", width: 9, right: true},
 	{group: "OVERALL", title: "packets", width: 9, right: true},
 	{group: "OVERALL", title: "bytes", width: 9, right: true},
@@ -82,9 +81,8 @@ var intervalCols = []colSpec{
 }
 
 // The same figures the panel draws, in the same order: the last second as
-// rates and error flags with the noise cable riding at the end of them, then
+// rates and error flags, then everything since the reset.
-// everything since the reset.
+func totalRow(elapsed time.Duration, v view, target float64, phy phyDisplay) []string {
-func totalRow(elapsed time.Duration, v view, target float64, phy phyDisplay, nv noiseView) []string {
 	return []string{
 		rateCell(v.rxGbps*1e9, target*1e9),
 		scaleSI(v.rxPPS),
@@ -94,7 +92,6 @@ func totalRow(elapsed time.Duration, v view, target float64, phy phyDisplay, nv
 		flagCell(v.window.link),
 		flagCell(v.window.internal),
 		correctedFlag(phy.recent),
-		noiseCell(nv),
 		scaleTime(elapsed),
 		scaleCount(v.rxFrames),
 		scaleCount(v.rxBytes),
@@ -202,14 +199,7 @@ func run(aName, bName string) (err error) {
 	if err != nil {
 		return err
 	}
-	noise, err := newNoiser()
-	if err != nil {
-		return err
-	}
-	defer noise.close()
-
 	a.tag, b.tag = "TEST A", "TEST B"
-	noise.eps[0].tag, noise.eps[1].tag = "NOISE A", "NOISE B"
 	ifnames := []string{a.name, b.name}
 
 	ethertypes := make([]uint16, numStreams)
@@ -224,7 +214,6 @@ func run(aName, bName string) (err error) {
 
 	checks := configureSystem(ifnames, ethertypes)
 	checks = append(checks, moduleChecks(modules, [2]string{a.name, b.name})...)
-	checks = append(checks, configureNoise(noise.names())...)
 	if err := reportChecks("SETTINGS", checks); err != nil {
 		return err
 	}
@@ -261,13 +250,9 @@ func run(aName, bName string) (err error) {
 	}()
 
 	var linkRows [][]string
-	for i, e := range []endpoint{a, b, noise.eps[0], noise.eps[1]} {
+	for i, e := range []endpoint{a, b} {
-		mod := ""
-		if i < len(moduleIDs) {
-			mod = moduleIDs[i]
-		}
 		linkRows = append(linkRows, []string{
-			paint(e.tag, cCyan), e.name, e.macString(), fmt.Sprintf("%d", e.mtu), mod,
+			paint(e.tag, cCyan), e.name, e.macString(), fmt.Sprintf("%d", e.mtu), moduleIDs[i],
 		})
 	}
 	fmt.Println(renderBox("LINKS",
@@ -295,14 +280,6 @@ func run(aName, bName string) (err error) {
 		defer holdPanic()
 		samp.run(&done, startTx)
 	}()
-	// Not gated on startTx: the cycle and the connected verdict are wanted the
-	// moment the panel is, and nothing it does touches the measurement.
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
-		defer holdPanic()
-		noise.run(&done)
-	}()
 	for _, m := range modules {
 		wg.Add(1)
 		go func() {
@@ -359,9 +336,7 @@ func run(aName, bName string) (err error) {
 	}
 
 	start := time.Now()
-	// Anchored to the same clock as the noise cycle, so slot boundaries and
+	hist := newHistory(start)
-	// phase transitions coincide.
-	hist := newHistory(rateEpochStart)
 	// A reset resets at the press, then re-measures; the measure's failures
 	// are suppressed at their sources while it runs, so there is nothing to
 	// hide or revert afterwards.
@@ -405,7 +380,7 @@ func run(aName, bName string) (err error) {
 			phy, measuring := phyView(diag, modules)
 			hist.sample(now, v, phy, measuring, target)
 			if err := disp.render(v, now.Sub(start), phy, measuring,
-				noise.view(), hist.view(now), target); err != nil {
+				hist.view(now), target); err != nil {
 				return err
 			}
 		case now := <-tick.C:
@@ -420,8 +395,7 @@ func run(aName, bName string) (err error) {
 					fmt.Println(stats.rule(n))
 				}
 			}
-			for _, line := range stats.emit(totalRow(elapsed, v, target, phy,
+			for _, line := range stats.emit(totalRow(elapsed, v, target, phy)) {
-				noise.view())) {
 				fmt.Println(line)
 			}
 		}

noise.go

@@ -1,227 +0,0 @@
-package main
-
-import (
-	"encoding/binary"
-	"fmt"
-	"os"
-	"path/filepath"
-	"sort"
-	"strings"
-	"sync/atomic"
-	"time"
-	"unsafe"
-
-	"golang.org/x/sys/unix"
-)
-
-// The noise cable: a deliberately bad cable twisted around the one under test,
-// there to radiate into it. Its ports are driven for the interference they
-// produce, not measured: nothing is ever received from them, and nothing they
-// count reaches the error columns.
-//
-// The wire cannot be quieted by going idle, because without EEE the PHYs
-// signal at full power whether or not frames flow, and these PHYs live inside
-// the SFP+ modules where no EEE control reaches them. Closing the port is the
-// one switch the host actually has, so the cycle is built on it: links up and
-// carrying frames for a spell, then administratively down for one. Every wake
-// re-runs 10GBASE-T training, which is as loud as this wire ever gets.
-const (
-	noiseDriver   = "i40e"
-	noiseFrameLen = 1514
-	noiseFrameGap = 10 * time.Millisecond
-
-	noiseEther uint16 = etherBase + numStreams
-)
-
-// Kernel names shift with which drivers are built in, since ethN is handed out
-// in link order rather than by slot. The driver name is the one label a port
-// keeps across kernel configs, so pairs are found by it rather than named.
-func driverPair(driver string) (string, string, error) {
-	ents, err := os.ReadDir("/sys/class/net")
-	if err != nil {
-		return "", "", err
-	}
-	var names []string
-	for _, e := range ents {
-		link, err := os.Readlink("/sys/class/net/" + e.Name() + "/device/driver")
-		if err != nil {
-			continue
-		}
-		if filepath.Base(link) == driver {
-			names = append(names, e.Name())
-		}
-	}
-	if len(names) != 2 {
-		return "", "", fmt.Errorf("want 2 %s interfaces, found %d [%s]",
-			driver, len(names), strings.Join(names, " "))
-	}
-	sort.Strings(names)
-	return names[0], names[1], nil
-}
-
-type noisePort struct {
-	name  string
-	fd    int
-	frame []byte
-}
-
-// The cycle is a pure function of the shared slot clock: even slots up — ports
-// admin-up and the wire loud, training or frames — odd slots down. Everything
-// that shows the phase computes it from the clock through here rather than
-// sampling the actuator, whose ioctls lag the boundary.
-func slotUp(seq int64) bool { return seq%2 == 0 }
-
-func noiseUp(now time.Time) bool {
-	return slotUp(int64(now.Sub(rateEpochStart) / histSlotSpan))
-}
-
-type noiser struct {
-	eps   [2]endpoint
-	ports [2]noisePort
-
-	// Whether the cable is judged present: both carriers seen during an up
-	// phase. Latched across the down phase, where the missing carrier is our
-	// own doing and says nothing about the cable.
-	connected atomic.Bool
-}
-
-func newNoiser() (*noiser, error) {
-	aName, bName, err := driverPair(noiseDriver)
-	if err != nil {
-		return nil, fmt.Errorf("noise: %w", err)
-	}
-	a, err := lookupEndpoint(aName)
-	if err != nil {
-		return nil, fmt.Errorf("noise: %w", err)
-	}
-	b, err := lookupEndpoint(bName)
-	if err != nil {
-		return nil, fmt.Errorf("noise: %w", err)
-	}
-
-	n := &noiser{eps: [2]endpoint{a, b}}
-	// The grid-locked cycle can start mid-down-slot, where absence would be
-	// our own doing: presence is granted until the first up phase delivers a
-	// verdict.
-	n.connected.Store(true)
-	for i, p := range [][2]endpoint{{a, b}, {b, a}} {
-		fd, err := openTxSocket(p[0].idx)
-		if err != nil {
-			return nil, fmt.Errorf("noise tx socket %s: %w", p[0].name, err)
-		}
-		// The payload is left zero: the PCS scrambles everything on the wire,
-		// so no pattern radiates differently from any other. The frame exists
-		// to occupy the link, not to say anything.
-		frame := make([]byte, noiseFrameLen)
-		copy(frame[0:6], p[1].mac[:])
-		copy(frame[6:12], p[0].mac[:])
-		binary.BigEndian.PutUint16(frame[12:14], noiseEther)
-		n.ports[i] = noisePort{name: p[0].name, fd: fd, frame: frame}
-	}
-	return n, nil
-}
-
-func (n *noiser) names() []string {
-	return []string{n.eps[0].name, n.eps[1].name}
-}
-
-type noiseView struct {
-	missing uint64
-	on      bool
-}
-
-// missing is zero while the cable was there at the last verdict, one while it
-// was not: the shape the error cells already colour by, so absence paints as
-// the fault it is. on is the commanded phase, straight from the clock.
-func (n *noiser) view() noiseView {
-	v := noiseView{on: noiseUp(time.Now())}
-	if !n.connected.Load() {
-		v.missing = 1
-	}
-	return v
-}
-
-// The ports were reachable when the noiser was built, so one that stops taking
-// the ioctl now is the interface going away underneath us, the same fault the
-// counter reads stop for.
-func (n *noiser) setLinks(fd int, up bool) {
-	for i := range n.ports {
-		var ifr flagsIfreq
-		copy(ifr.name[:], n.ports[i].name)
-		if _, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd),
-			uintptr(unix.SIOCGIFFLAGS), uintptr(unsafe.Pointer(&ifr))); errno != 0 {
-			panic(fmt.Sprintf("reading %s flags: %v", n.ports[i].name, errno))
-		}
-		if up {
-			ifr.flags |= unix.IFF_UP
-		} else {
-			ifr.flags &^= unix.IFF_UP
-		}
-		if _, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd),
-			uintptr(unix.SIOCSIFFLAGS), uintptr(unsafe.Pointer(&ifr))); errno != 0 {
-			panic(fmt.Sprintf("setting %s flags: %v", n.ports[i].name, errno))
-		}
-	}
-}
-
-// Down reads as EINVAL rather than zero, and either way the answer is the
-// same: no carrier here now.
-func carrierUp(name string) bool {
-	v, ok := readUint("/sys/class/net/" + name + "/carrier")
-	return ok && v == 1
-}
-
-func (n *noiser) bothUp() bool {
-	return carrierUp(n.ports[0].name) && carrierUp(n.ports[1].name)
-}
-
-// Send results are deliberately dropped: the cable is bad on purpose, the link
-// comes and goes under the cycle, and a frame this side declined to send is as
-// good as one the wire mangled. What matters is only ever what the test cable
-// counted.
-//
-// The cycle is locked to the panel's history grid — up on even 5 s slots,
-// down on odd, transitions on the shared slot boundaries — so a history cell
-// never straddles a phase and flickers between the two answers.
-func (n *noiser) run(done *atomic.Bool) {
-	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
-	if err != nil {
-		panic(fmt.Sprintf("noise ioctl socket: %v", err))
-	}
-	defer unix.Close(fd)
-
-	tick := time.NewTicker(noiseFrameGap)
-	defer tick.Stop()
-
-	applied, wasUp, linked := false, false, false
-	for !done.Load() {
-		<-tick.C
-		up := noiseUp(time.Now())
-		if !applied || up != wasUp {
-			// A whole up phase with no link is many times the ~1s the wire
-			// needs to train, so at its end the silence is the cable's answer.
-			if applied && wasUp {
-				n.connected.Store(linked)
-			}
-			n.setLinks(fd, up)
-			applied, wasUp, linked = true, up, false
-		}
-		if !up || !n.bothUp() {
-			continue
-		}
-		linked = true
-		n.connected.Store(true)
-		for i := range n.ports {
-			unix.Write(n.ports[i].fd, n.ports[i].frame)
-		}
-	}
-	// Left up rather than wherever the cycle stopped, so a run never strands
-	// the ports down for whoever looks next.
-	n.setLinks(fd, true)
-}
-
-func (n *noiser) close() {
-	for i := range n.ports {
-		unix.Close(n.ports[i].fd)
-	}
-}

phy.go

@@ -506,6 +506,13 @@ func openModules(names [2]string) ([]*phyModule, [2]string, error) {
 	return mods, idents, nil
 }
 
+// Down reads as EINVAL rather than zero, and either way the answer is the
+// same: no carrier here now.
+func carrierUp(name string) bool {
+	v, ok := readUint("/sys/class/net/" + name + "/carrier")
+	return ok && v == 1
+}
+
 func waitCarrier(names [2]string, done *atomic.Bool) {
 	deadline := time.Now().Add(linkWaitSpan)
 	for !(carrierUp(names[0]) && carrierUp(names[1])) {

render.go

@@ -304,18 +304,6 @@ func correctedFlag(v uint64) string {
 	return paint("warn", cYellow)
 }
 
-// Green either way while the cable is present — the cycle's phase is state,
-// not health. Red stays what it was: the cable missing.
-func noiseCell(nv noiseView) string {
-	switch {
-	case nv.missing > 0:
-		return paint("ERR", cRed)
-	case nv.on:
-		return paint("on", cGreen)
-	}
-	return paint("off", cGreen)
-}
-
 // Per-interval rates jitter by a couple of percent at line rate, so green has
 // to cover that. Yellow means a real shortfall, red means badly off.
 const (

system.go

@@ -6,12 +6,39 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
 
+// Kernel names shift with which drivers are built in, since ethN is handed out
+// in link order rather than by slot. The driver name is the one label a port
+// keeps across kernel configs, so pairs are found by it rather than named.
+func driverPair(driver string) (string, string, error) {
+	ents, err := os.ReadDir("/sys/class/net")
+	if err != nil {
+		return "", "", err
+	}
+	var names []string
+	for _, e := range ents {
+		link, err := os.Readlink("/sys/class/net/" + e.Name() + "/device/driver")
+		if err != nil {
+			continue
+		}
+		if filepath.Base(link) == driver {
+			names = append(names, e.Name())
+		}
+	}
+	if len(names) != 2 {
+		return "", "", fmt.Errorf("want 2 %s interfaces, found %d [%s]",
+			driver, len(names), strings.Join(names, " "))
+	}
+	sort.Strings(names)
+	return names[0], names[1], nil
+}
+
 const (
 	ethtoolGRXRINGS    = 0x2d
 	ethtoolGRXCLSRLCNT = 0x2e
@@ -366,9 +393,8 @@ func getCoalesce(fd int, ifname string) (ethtoolCoalesce, error) {
 }
 
 const (
-	ethSSStats     = 1
+	ethSSStats    = 1
-	ethSSPrivFlags = 2
+	ethGstringLen = 32
-	ethGstringLen  = 32
 )
 
 // Each of these has a __u32 or __u8 tail the kernel fills past the end of the
@@ -660,67 +686,6 @@ func withIoctlSocket(fn func(fd int) []checkResult) []checkResult {
 	return fn(fd)
 }
 
-type ethtoolValue struct {
-	cmd  uint32
-	data uint32
-}
-
-// i40e leaves the module transmitting when a port is closed, so the peer never
-// sees anything happen and the copper stays trained. This flag is what makes
-// an administrative down reach the wire, and the noise cycle is switched
-// entirely through it.
-func checkPrivFlag(fd int, ifname, flag string) checkResult {
-	res := checkResult{item: ifname + " " + flag}
-	names, err := stringSetNames(fd, ifname, ethSSPrivFlags)
-	if err != nil {
-		res.err = err
-		return res
-	}
-	bit := -1
-	for i, s := range names {
-		if s == flag {
-			bit = i
-			break
-		}
-	}
-	if bit < 0 {
-		res.err = fmt.Errorf("driver has no private flag %q", flag)
-		return res
-	}
-	v := ethtoolValue{cmd: unix.ETHTOOL_GPFLAGS}
-	if err := ethtoolCall(fd, ifname, unsafe.Pointer(&v)); err != nil {
-		res.err = err
-		return res
-	}
-	if v.data&(1<<bit) != 0 {
-		res.state = "on"
-		return res
-	}
-	v.cmd = unix.ETHTOOL_SPFLAGS
-	v.data |= 1 << bit
-	if err := ethtoolCall(fd, ifname, unsafe.Pointer(&v)); err != nil {
-		res.err = err
-		res.state = "could not set"
-		return res
-	}
-	res.fixed = true
-	res.state = "was off, now on"
-	return res
-}
-
-// The noise ports get none of the test pair's tuning: nothing is measured on
-// them, so rings, coalescing and steering are all beside the point. All they
-// need is for a closed port to really drop the link.
-func configureNoise(ifnames []string) []checkResult {
-	return withIoctlSocket(func(fd int) []checkResult {
-		var out []checkResult
-		for _, ifname := range ifnames {
-			out = append(out, checkPrivFlag(fd, ifname, "link-down-on-close"))
-		}
-		return out
-	})
-}
-
 // Nothing here waits for a carrier: the two ports are the two ends of the cable
 // under test, so with no cable there is never going to be one.
 func configureSystem(ifnames []string, ethertypes []uint16) []checkResult {

ui.go

@@ -19,8 +19,6 @@ var (
 	uiCrit   = rgb{0xd0, 0x3b, 0x3b}
 	uiCellOK = rgb{0x0a, 0x5d, 0x0a}
 	uiCellNA = rgb{0x3a, 0x3a, 0x37}
-	uiNoise  = rgb{0x1c, 0x5c, 0xab}
-	uiNoise0 = rgb{0x24, 0x24, 0x23}
 	uiAccent = rgb{0x39, 0x87, 0xe5}
 )
 
@@ -58,10 +56,9 @@ const (
 )
 
 // The panel is the heat matrix: one row per check, columns for now, the last
-// 90 seconds at 5 s a cell, and since reset. Noise rides at the bottom as
+// 90 seconds at 5 s a cell, and since reset.
-// context — state, not a verdict.
 var panelRows = []string{
-	"line rate", "lost", "corrupt", "link", "internal", "corrected", "SNR dB", "noise",
+	"line rate", "lost", "corrupt", "link", "internal", "corrected", "SNR dB",
 }
 
 type rect struct {
@@ -418,7 +415,7 @@ func okOr(bad bool, c rgb) rgb {
 	return uiCellOK
 }
 
-func (d *display) drawRows(v view, phy phyDisplay, measuring bool, nv noiseView,
+func (d *display) drawRows(v view, phy phyDisplay, measuring bool,
 	hv histView, target float64) {
 	nowR := d.nowX + d.nowW
 	resetR := d.resetX + d.resetW
@@ -473,33 +470,6 @@ func (d *display) drawRows(v view, phy phyDisplay, measuring bool, nv noiseView,
 			} else {
 				d.colText(d.text, resetR, y, "-", uiMuted)
 			}
-		case "noise":
-			state := "off"
-			if nv.on {
-				state = "on"
-			}
-			if nv.missing > 0 {
-				d.colMark(nowR, y, markCross, uiCrit)
-			} else {
-				d.colText(d.text, nowR, y, state, uiInk2)
-			}
-			// The lane shows the commanded phase, a pure function of each
-			// slot's parity; only slots the run never lived through are unknown.
-			for k, s := range hv.slots {
-				c := uiCellNA
-				if s.sampled {
-					c = uiNoise0
-					if slotUp(s.seq) {
-						c = uiNoise
-					}
-				}
-				d.heatCell(y, k, c)
-			}
-			if nv.missing > 0 {
-				d.colMark(resetR, y, markCross, uiCrit)
-			} else {
-				d.colMark(resetR, y, markCheck, uiGood)
-			}
 		default:
 			f := -1
 			for j, c := range faultClasses {
@@ -553,14 +523,14 @@ func (d *display) drawFooter(v view, elapsed time.Duration) {
 }
 
 func (d *display) render(v view, elapsed time.Duration, phy phyDisplay,
-	measuring bool, nv noiseView, hv histView, target float64) error {
+	measuring bool, hv histView, target float64) error {
 	fb := d.fb
 	fb.fill(uiBg)
 
 	d.drawHeader(v, phy, hv, measuring, time.Now())
 	d.hairline(d.headerH - 1)
 	d.drawColHeaders()
-	d.drawRows(v, phy, measuring, nv, hv, target)
+	d.drawRows(v, phy, measuring, hv, target)
 	d.drawAxis()
 	d.drawFooter(v, elapsed)
 	d.drawResetButton()