Tunnel Please

A lightweight SSH-based tunnel server written in Go that enables secure TCP and HTTP forwarding with an interactive terminal interface for managing connections and custom subdomains.

Features

• SSH interactive session with real-time command handling
• Custom subdomain management for HTTP tunnels
• Active connection control with drop functionality
• Dual protocol support: HTTP and TCP tunnels
• Real-time connection monitoring

Requirements

• Go 1.18 or higher
• Valid domain name for subdomain routing

Environment Variables

The following environment variables can be configured in the .env file:

Variable	Description	Default	Required
DOMAIN	Domain name for subdomain routing	localhost	No
PORT	SSH server port	2200	No
TLS_ENABLED	Enable TLS/HTTPS	false	No
TLS_REDIRECT	Redirect HTTP to HTTPS	false	No
CERT_LOC	Path to TLS certificate	certs/cert.pem	No
KEY_LOC	Path to TLS private key	certs/privkey.pem	No
SSH_PRIVATE_KEY	Path to SSH private key (auto-generated if missing)	certs/id_rsa	No
CORS_LIST	Comma-separated list of allowed CORS origins	-	No
ALLOWED_PORTS	Port range for TCP tunnels (e.g., 40000-41000)	40000-41000	No
BUFFER_SIZE	Buffer size for io.Copy operations in bytes (4096-1048576)	32768	No
PPROF_ENABLED	Enable pprof profiling server	false	No
PPROF_PORT	Port for pprof server	6060	No

Note: All environment variables now use UPPERCASE naming. The application includes sensible defaults for all variables, so you can run it without a .env file for basic functionality.

SSH Key Auto-Generation

If the SSH private key specified in SSH_PRIVATE_KEY doesn't exist, the application will automatically generate a new 4096-bit RSA key pair at the specified location. This makes it easier to get started without manually creating SSH keys.

Memory Optimization

The application uses a buffer pool with controlled buffer sizes to prevent excessive memory usage under high concurrent loads. The BUFFER_SIZE environment variable controls the size of buffers used for io.Copy operations:

• Default: 32768 bytes (32 KB) - Good balance for most scenarios
• Minimum: 4096 bytes (4 KB) - Lower memory usage, more CPU overhead
• Maximum: 1048576 bytes (1 MB) - Higher throughput, more memory usage

Recommended settings based on load:

• Low traffic (<100 concurrent): BUFFER_SIZE=32768 (default)
• High traffic (>100 concurrent): BUFFER_SIZE=16384 or BUFFER_SIZE=8192
• Very high traffic (>1000 concurrent): BUFFER_SIZE=8192 or BUFFER_SIZE=4096

The buffer pool reuses buffers across connections, preventing memory fragmentation and reducing garbage collection pressure.

Profiling with pprof

To enable profiling for performance analysis:

1. Set PPROF_ENABLED=true in your .env file
2. Optionally set PPROF_PORT to your desired port (default: 6060)
3. Access profiling data at http://localhost:6060/debug/pprof/

Common pprof endpoints:

• /debug/pprof/ - Index page with available profiles
• /debug/pprof/heap - Memory allocation profile
• /debug/pprof/goroutine - Stack traces of all current goroutines
• /debug/pprof/profile - CPU profile (30-second sample by default)
• /debug/pprof/trace - Execution trace

Example usage with go tool pprof:

# Analyze CPU profile
go tool pprof http://localhost:6060/debug/pprof/profile?seconds=30

# Analyze memory heap
go tool pprof http://localhost:6060/debug/pprof/heap

Contributing

Contributions are welcome!

If you'd like to contribute to this project, please follow the workflow below:

1. Fork the repository
2. Create a new branch for your changes
3. Commit and push your updates
4. Open a Pull Request targeting the staging branch
5. Clearly describe your changes and the reasoning behind them

License

This project is licensed under the Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) license.

Author

Bagas (fossyy)

• Website: fossy.my.id
• GitHub: @fossyy