NEMO

NEMO is an Android network conditioner for testing apps under degraded mobile and Wi-Fi conditions.

It runs as a local VpnService, forwards traffic through a userspace datapath, and applies configurable network degradation without requiring root.

Features

• preset network profiles
• one custom profile
• latency
• jitter
• uplink and downlink bandwidth limiting
• packet loss
• temporary traffic stalls
• per-app targeting

Build

Clone with submodules:

git clone --recurse-submodules <repo-url>
cd <repo-directory>

If you already cloned the repo:

git submodule update --init --recursive

Build a debug APK:

./gradlew :app:buildDebug

The APK will be produced under:

app/build/outputs/apk/debug/

Release Build

Create a signing keystore:

keytool -genkeypair -v \
  -keystore nemo-release.keystore \
  -alias nemo \
  -keyalg RSA \
  -keysize 2048 \
  -validity 10000

Create a local keystore.properties from the example:

cp keystore.properties.example keystore.properties

Then set:

• storeFile
• storePassword
• keyAlias
• keyPassword

Build a signed release APK:

./gradlew :app:assembleRelease

Or an Android App Bundle:

./gradlew :app:bundleRelease

Project Notes

• Android app code lives in app/src/main/java
• native datapath and conditioner code lives in app/src/main/jni
• zdtun is included as a git submodule in submodules/zdtun
• synthetic TCP loss is asymmetric by design: downlink TCP packets are not dropped directly; instead loss is modeled through uplink ACK loss to produce more realistic TCP degradation in the local VPN datapath

Acknowledgements

NEMO builds on ideas explored in:

• PCAPdroid by Emanuele Faranda
• Network Link Conditioner by Apple

It also depends on:

• zdtun
• CustomActivityOnCrash