Native CDC-NCM USB tethering for Nothing phones on macOS

README.md

Nothing NCM Tether

A fire-and-forget macOS shell command that makes a supported Nothing phone expose native CDC-NCM USB Ethernet. It installs nothing and runs no background process.

Quick start

Install ADB once, enable USB debugging on the unlocked phone, connect it, and accept its authorization prompt:

brew install android-platform-tools
git clone https://gist.github.com/bdd3faf8990d1aa15d39bb92a7c9ac2e.git nothing-ncm-tether
cd nothing-ncm-tether
bash build.sh
sh nothing-tether

With multiple Android devices connected, use sh nothing-tether SERIAL. Re-run it after rebooting the phone or whenever tethering does not return. Android keeps using its normal upstream—phone Wi-Fi or mobile data—and the script does not change Wi-Fi settings on either device.

What it does

The thin shell script performs exactly three ADB phases:

1. Push ncmtether.jar to /data/local/tmp/.
2. Save NCM as the unlocked USB mode and reset USB so usb0 is absent.
3. Request Ethernet tethering through Android's shell identity, then enable NCM.

The ordering prevents Android's Ethernet client from claiming usb0 before the tethering service does. Plain svc usb setFunctions ncm is insufficient on the affected Nothing build because its NCM resource overlay targets the wrong package.

Everything is visible in nothing-tether and NcmTether.java. The JAR is compiled Android DEX, not a Mac executable. Run bash build.sh to reproduce it from source when Android SDK/build-tools 36.1 and a JDK are installed. Without those, build.sh keeps the checked-in precompiled JAR and still validates it.

No Go, root, sudo, proxy, VPN, macOS driver, or installation is involved.

build.sh

#!/bin/bash
set -euo pipefail

root="$(cd "$(dirname "$0")" && pwd)"
sdk="${ANDROID_SDK_ROOT:-$HOME/Library/Android/sdk}"
platform="${ANDROID_PLATFORM:-$sdk/platforms/android-36.1/android.jar}"
d8="${D8:-$sdk/build-tools/36.1.0/d8}"
studio_jdk="/Applications/Android Studio.app/Contents/jbr/Contents/Home"
java_compiler="${JAVAC:-$studio_jdk/bin/javac}"
bridge="$root/ncmtether.jar"

[ -x "$java_compiler" ] || java_compiler="$(command -v javac 2>/dev/null || true)"
[ "$java_compiler" != "$studio_jdk/bin/javac" ] || export JAVA_HOME="$studio_jdk"

if [ -f "$platform" ] && [ -x "$d8" ] && [ -x "$java_compiler" ] && "$java_compiler" -version >/dev/null 2>&1; then
  work="$(mktemp -d)"
  trap 'rm -rf "$work"' EXIT
  mkdir -p "$work/classes" "$work/dex"
  "$java_compiler" -source 11 -target 11 -cp "$platform" -d "$work/classes" "$root/NcmTether.java"
  "$d8" --lib "$platform" --output "$work/dex" "$work/classes"/*.class
  touch -t 198001010000 "$work/dex/classes.dex"
  (cd "$work/dex" && zip -X -q "$bridge" classes.dex)
  echo "Rebuilt Android bridge from source."
else
  [ -s "$bridge" ] || base64 -D < "$root/ncmtether.jar.b64" > "$bridge"
  [ -s "$bridge" ] || { echo "Missing Android toolchain and precompiled bridge." >&2; exit 1; }
  echo "Using precompiled Android bridge."
fi

shasum -a 256 "$bridge"

ncmtether.jar.b64

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NcmTether.java

import android.content.Context;
import android.content.ContextWrapper;
import android.net.TetheringManager;
import android.os.Looper;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 * Complete source for the Android tethering bridge embedded by the Go CLI.
 * It runs as the real ADB shell UID and requests Ethernet tethering.
 */
public final class NcmTether {
    public static void main(String[] args) throws Exception {
        Looper.prepareMainLooper();
        Class<?> activityThread = Class.forName("android.app.ActivityThread");
        Object thread = activityThread.getMethod("systemMain").invoke(null);
        Context system = (Context) activityThread.getMethod("getSystemContext").invoke(thread);
        Context shell = system.createPackageContext("com.android.shell", 0);
        TetheringManager manager = shell.getSystemService(TetheringManager.class);
        if (manager == null) throw new IllegalStateException("No TetheringManager");

        Context shellIdentity = new ContextWrapper(shell) {
            @Override public String getOpPackageName() { return "com.android.shell"; }
            @Override public String getAttributionTag() { return null; }
        };
        Field contextField = TetheringManager.class.getDeclaredField("mContext");
        contextField.setAccessible(true);
        contextField.set(manager, shellIdentity);

        boolean stopping = args.length > 0 && "stop".equals(args[0]);
        int type = Integer.parseInt(args[stopping ? 1 : 0]);
        TetheringManager.TetheringRequest.Builder builder =
                new TetheringManager.TetheringRequest.Builder(type);
        Method setScope = builder.getClass().getMethod("setConnectivityScope", int.class);
        setScope.invoke(builder, 1); // CONNECTIVITY_SCOPE_GLOBAL
        Method exempt = builder.getClass().getMethod("setExemptFromEntitlementCheck", boolean.class);
        exempt.invoke(builder, true);
        Method showUi = builder.getClass().getMethod("setShouldShowEntitlementUi", boolean.class);
        showUi.invoke(builder, false);
        TetheringManager.TetheringRequest request = builder.build();

        CountDownLatch done = new CountDownLatch(1);
        int[] result = {-1};
        if (stopping) {
            manager.stopTethering(request, Runnable::run,
                    new TetheringManager.StopTetheringCallback() {
                        @Override public void onStopTetheringSucceeded() {
                            result[0] = 0;
                            done.countDown();
                        }
                        @Override public void onStopTetheringFailed(int error) {
                            result[0] = error;
                            done.countDown();
                        }
                    });
        } else {
            manager.startTethering(request, Runnable::run,
                    new TetheringManager.StartTetheringCallback() {
                        @Override public void onTetheringStarted() {
                            result[0] = 0;
                            done.countDown();
                        }
                        @Override public void onTetheringFailed(int error) {
                            result[0] = error;
                            done.countDown();
                        }
                    });
        }

        if (!done.await(15, TimeUnit.SECONDS)) System.exit(2);
        System.exit(result[0] == 0 ? 0 : 1);
    }
}

nothing-tether

#!/bin/sh
set -e

bridge_jar="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)/ncmtether.jar"
serial="${1:-$(adb get-serialno)}"
phone() { adb -s "$serial" "$@"; }

# 1. Put the auditable Android bridge on the phone.
phone push "$bridge_jar" /data/local/tmp/ncmtether.jar >/dev/null

# 2. Remove usb0 after saving NCM as the unlocked USB mode.
phone shell 'for type in 1 4 5; do CLASSPATH=/data/local/tmp/ncmtether.jar app_process /system/bin NcmTether stop $type >/dev/null 2>&1 || :; done
settings put global tether_force_usb_functions 1; svc usb setScreenUnlockedFunctions ncm; svc usb setFunctions' >/dev/null 2>&1 || :
sleep 1
phone wait-for-device

# 3. Request tethering before recreating usb0 as native NCM.
phone shell 'CLASSPATH=/data/local/tmp/ncmtether.jar app_process /system/bin NcmTether 5 && svc usb setFunctions ncm' >/dev/null 2>&1 || :
sleep 1
phone wait-for-device
echo "NCM tethering ready"