Firestack is a userspace TCP/UDP connection monitor, firewall, DNS resolver, and multi-hop WireGuard client for Android.

Firestack is built specifically for Rethink DNS + Firewall + VPN. gVisor/netstack provides a SOCKS-like interface (similar to badvpn's tun2socks) for TCP/UDP over a TUN device.

Firestack is a hard-fork of Google's outline-go-tun2socks project.

DNS

Firestack supports DNS over HTTPS, DNS over TLS, Oblivious DNS over HTTPS, DNS over WireGuard / SOCKS5 / Tor, DNSCrypt, and plain old DNS upstreams.

WireGuard

Firestack runs WireGuard in userspace. When running multiple WireGuard tunnels at once, only ICMP, DNS, TCP and UDP are forwarded through them. ARP / IGMP / SCTP / RTP and other IP protocols are not forwarded to WireGuard tunnels.

Firestack supports multi-hop / multi-relay WireGuard, where multiple tunnels can be chained together, provided that the outer tunnel (hop/relay) can route to the inner tunnel's (exit) endpoint.

WireGuard integration was sponsored by FOSS United; and Multi-hop / Multi-relay WireGuard by FLOSS/fund.

Releases

Firestack is released as an Android Library (aar) and can be integrated into your Android builds via Jitpack (ref) or Maven Central (OSSRH).

    // add this to your project's build.gradle
    allprojects {
        repositories {
            ...
            // if consuming from maven central
            // ref: central.sonatype.org/consume
            mavenCentral()
            ...
            // if consuming from jitpack
            // ref: docs.jitpack.io/android/#installing
            maven { url 'https://jitpack.io' }
            ...
        }
    }

    // add the dep to your app's build.gradle
    dependencies {
        ...
        // maven central (stripped)
        implementation 'com.celzero:firestack:Tag@aar'
        ...
        // jitpack (stripped)
        implementation 'com.github.celzero:firestack:Tag@aar'
        // jitpack (debug symbols)
        implementation 'com.github.celzero:firestack:Tag:debug@aar'
        ...
    }

API

The APIs aren't stable and hence left undocumented, but you can look at Rethink DNS + Firewall + VPN codebase: (GoVpnAdapter, BraveVpnService) to see how to integrate with Firestack on Android.

Build

Firestack only supports Android. Instructions for other platforms are left as-is, but they may or may not work.

Prerequisites

• macOS host (iOS, macOS)
• make
• Go >= 1.25
• A C compiler (e.g.: clang, gcc)

Firestack APIs are available only on Android builds for now. iOS and Linux support planned but nothing concrete yet.

Android

• sdkmanager
  1. Download the command line tools from developer.android.com.
  2. Unzip the pacakge as ~/Android/Sdk/cmdline-tools/latest/. Make sure sdkmanager is located at ~/Android/Sdk/cmdline-tools/latest/bin/sdkmanager
• Android NDK 28+

  # Install the NDK (exact NDK version obtained from `sdkmanager --list`)
  ~/Android/Sdk/cmdline-tools/latest/bin/sdkmanager "platforms;android-36" "ndk;28.2.13676358"
  # Set up the environment variables:
  export ANDROID_NDK_HOME=~/Android/Sdk/ndk/28.2.13676358 ANDROID_HOME=~/Android/Sdk

• gomobile (installed as needed by make)

Apple (iOS and macOS)

• Xcode
• gomobile (installed as needed by make)

Linux and Windows

We build binaries for Linux and Windows from source without any custom integrations. xgo and Docker are required to support cross-compilation.

• Docker (for XGO)
• xgo (installed as needed by make)
• ghcr.io/crazy-max/xgo Docker image (~6.8GB pulled by xgo).

Make

# creates build/intra/{tun2socks.aar,tun2socks-sources.jar}
make clean && make intra

If needed, you can extract the jni files into build/android/jni with:

unzip build/android/tun2socks.aar 'jni/*' -d build/android