FlashTunnel

High-performance, lightweight TCP stealth tunnel designed for secure, low-latency relay connections.

Features

• Native Zig Core: Minimal memory footprint (<0.5MB baseline) with zero garbage collection overhead.
• Multi-Tunnel Engine: Create, monitor, restart, and manage multiple independent tunnels concurrently.
• Built-in Connectivity & Latency Checker: Direct TCP RTT (ping) measurement and port status inspection.
• TLS 1.3 Record Carrier: Streams are encapsulated within standard TLS records for protocol masking.
• Integrated Anti-DPI Segmentation: Out-of-order TCP segmentation with sequence overlap and urgent flag signaling directly at the transport layer.
• ChaCha20-Poly1305 AEAD: Authenticated end-to-end encryption with vectorized processing.
• Multi-Port Redirection: Native iptables support for mapping alternative ports (e.g., 8443, 2087, 8080) to the primary entry port.
• Built-in Interactive Management: Terminal dashboard for configuration, service control, and live monitoring.

Installation

Run the one-command installer on your Linux server (x86_64):

bash <(curl -sSL https://raw.githubusercontent.com/Lagtor-code/flashtunnel/main/install.sh)

Or clone the repository manually:

git clone https://github.com/Lagtor-code/flashtunnel.git /opt/flashtunnel && bash /opt/flashtunnel/install.sh

After installation, access the management menu anytime by running:

flashtunnel

Quick Start

1. Server Setup (Upstream / Destination)

1. Run flashtunnel on your remote destination server.
2. Select option 1 (Configure Server).
3. Set the tunnel listen port (default: 4433), local target service port (default: 443), and a security key.
4. The service will start automatically via systemd.

2. Client Setup (Relay / Local Entry)

1. Run flashtunnel on your local relay server.
2. Select option 2 (Configure Client).
3. Enter the remote server IP, tunnel port, incoming listen port (default: 443), optional redirect ports, and the matching security key.
4. The relay service will start immediately.

3. Client Configuration

Point your proxy client (e.g., VLESS / Trojan / Shadowsocks) to the relay server's IP address and chosen port.

Command-Line Usage

# Run server directly
flashtunnel server --listen 0.0.0.0:4433 --target 127.0.0.1:443 --tcp --key <SECRET_KEY>

# Run client directly
flashtunnel client --server <REMOTE_IP>:4433 --listen 0.0.0.0:443 --tcp --key <SECRET_KEY>

# Run cryptographic and transport self-tests
flashtunnel test

Repository Structure

flashtunnel/
├── bin/
│   └── flashtunnel             # Precompiled static Linux x86_64 binary
├── src/                        # Complete Zig source code
│   ├── main.zig                # CLI entrypoint
│   ├── tcp/
│   │   ├── tunnel_server.zig   # Server listener and decryptor
│   │   ├── tunnel_client.zig   # Client relay and desync injector
│   │   └── tunnel_protocol.zig # Protocol frame framing and AEAD
│   ├── protocol/
│   │   └── desync.zig          # Packet desynchronization engine
│   └── crypto/
│       └── chacha20poly1305.zig# ChaCha20-Poly1305 implementation
├── build.zig                   # Zig build configuration
├── flashtunnel.sh              # Management TUI script
├── install.sh                  # One-command installer
├── flashtunnel-server.service  # Systemd unit template for server
├── flashtunnel-client.service  # Systemd unit template for client
└── README.md                   # Documentation

License

Open-source under the MIT License.