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JNetRuntime BPF VM

Welcome to the JNetRuntime BPF Virtual Machine module documentation. This module provides a high-performance, thread-safe Berkeley Packet Filter (BPF) interpreter with support for standard BPF bytecode and extensible instruction sets.

🚀 Key Features

• Full BPF Compatibility

  • Supports standard BPF instruction set
  • Compatible with tcpdump-generated bytecode
  • Kernel BPF-compatible execution semantics

• Extensible Architecture

  • Runtime-loadable custom instructions
  • Pluggable optimization modules
  • Custom context handlers

• High Performance Design

  • Zero-copy packet processing
  • Thread-safe execution model
  • Stateless VM architecture
  • Minimal garbage collection impact

• Concurrent Execution Support

  • Thread-local execution contexts
  • Multiple program instances
  • Parallel packet processing

🎯 Purpose

The BPF VM module serves as a pure Java implementation of the Berkeley Packet Filter virtual machine, providing:

1. Flexible Execution Environment

   • User-space BPF execution
   • Platform-independent operation
   • Kernel BPF fallback support

2. Performance-Critical Processing

   • High-speed packet filtering
   • Real-time network monitoring
   • Large-scale traffic analysis

3. Integration Capabilities

   • Works with JNetRuntime Compiler
   • Supports external BPF bytecode
   • Extensible for custom protocols

🔧 Quick Start

// Create VM instance (stateless)
BPFVirtualMachine vm = new BPFVirtualMachine();

// Create execution context
BPFContext context = new BPFContext();

// Load BPF program
byte[] bytecode = getBytecode();  // from compiler or external source
BPFProgram program = BPFProgram.load(bytecode);

// Process packets
void processPacket(byte[] packet) {
    context.reset();              // Reset state for new execution
    context.setPacket(packet);    // Set packet data
    boolean matches = program.execute(context);
}

📚 Core Components

Virtual Machine Architecture

┌─────────────────────────────┐
│     BPF Virtual Machine     │
├─────────────────────────────┤
│  ┌─────────┐   ┌─────────┐ │
│  │Instruction │ │Register │ │
│  │  Decoder  │ │   Set   │ │
│  └─────────┘   └─────────┘ │
│  ┌─────────┐   ┌─────────┐ │
│  │ Memory  │   │ Context │ │
│  │ Manager │   │ Handler │ │
│  └─────────┘   └─────────┘ │
└─────────────────────────────┘

Execution Model

[BPF Program] → [Context Setup] → [VM Execution] → [Result]
                      ↑                 ↓
                  [Context Reset] ← [Next Packet]

🔄 Thread-Safe Usage

public class PacketProcessor {
    private final BPFProgram program;
    private final ThreadLocal<BPFContext> contextHolder;
    
    public PacketProcessor(byte[] bytecode) {
        this.program = BPFProgram.load(bytecode);
        this.contextHolder = ThreadLocal.withInitial(BPFContext::new);
    }
    
    public boolean processPacket(byte[] packet) {
        BPFContext context = contextHolder.get();
        context.reset();
        context.setPacket(packet);
        return program.execute(context);
    }
}

🛠️ Extending the VM

Custom Instructions

public class CustomInstruction implements BPFInstruction {
    @Override
    public int execute(BPFContext ctx) {
        // Custom instruction logic
        return BPF_OK;
    }
}

// Register custom opcode
BPFVirtualMachine.registerOpcode(0xF0, new CustomInstruction());

Custom Context Data

public class EnhancedContext extends BPFContext {
    private Map<String, Object> metadata;
    
    @Override
    public void reset() {
        super.reset();
        metadata.clear();
    }
}

📊 Performance Considerations

• Context reuse within threads
• Batch processing capabilities
• Memory allocation optimization
• Instruction cache efficiency
• Zero-copy operation modes

📚 Documentation

• Architecture Overview
• Instruction Set Reference
• Performance Tuning
• API Reference
• Extension Guide

🔄 Integration

Works seamlessly with other JNetRuntime components:

[BPF Compiler] → [BPF Bytecode] → [BPF VM]
                                    ↓
                              [Packet Processing]
                                    ↓
                              [Application Logic]

🛠️ Next Steps

• Getting Started
• Examples
• Best Practices
• Contributing

📮 Support

• GitHub Issues
• Discussions
• Mailing List

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Check out our API Documentation for detailed information about using the VM.

Have questions? Join our Community Discussion!