smartdns/readme.plan.md

# DNS Server Interface Binding Implementation Plan

Command to reread CLAUDE.md: `cat /home/philkunz/.claude/CLAUDE.md`

## Overview ✅ COMPLETED
Enable specific interface binding for the DNSServer class to allow binding to specific network interfaces instead of all interfaces (0.0.0.0).

## Implementation Status: COMPLETED ✅

### What was implemented:

✅ **1. Updated IDnsServerOptions Interface**
- Added optional `udpBindInterface?: string` property (defaults to '0.0.0.0')
- Added optional `httpsBindInterface?: string` property (defaults to '0.0.0.0')
- Located in `ts_server/classes.dnsserver.ts:5-11`

✅ **2. Modified DnsServer.start() Method**
- Updated UDP server binding to use `this.options.udpBindInterface || '0.0.0.0'`
- Updated HTTPS server listening to use `this.options.httpsBindInterface || '0.0.0.0'`
- Added IP address validation before binding
- Updated console logging to show specific interface being bound
- Located in `ts_server/classes.dnsserver.ts:699-752`

✅ **3. Added IP Address Validation**
- Created `isValidIpAddress()` method supporting IPv4 and IPv6
- Validates interface addresses before binding
- Throws meaningful error messages for invalid addresses
- Located in `ts_server/classes.dnsserver.ts:392-398`

✅ **4. Updated Documentation**
- Added dedicated "Interface Binding" section to readme.md
- Included examples for localhost-only binding (`127.0.0.1`, `::1`)
- Documented security considerations and use cases
- Added examples for specific interface binding

✅ **5. Added Comprehensive Tests**
- **localhost binding test**: Verifies binding to `127.0.0.1` instead of `0.0.0.0`
- **Invalid IP validation test**: Ensures invalid IP addresses are rejected
- **IPv6 support test**: Tests `::1` binding (with graceful fallback if IPv6 unavailable)
- **Backwards compatibility**: Existing tests continue to work with default behavior
- Located in `test/test.server.ts`

✅ **6. Updated restartHttpsServer Method**
- Modified to respect interface binding options during certificate updates
- Ensures Let's Encrypt certificate renewal maintains interface binding

## ✅ Implementation Results

### Test Results
All interface binding functionality has been successfully tested:

```bash
✅ should bind to localhost interface only (318ms)
   - UDP DNS server running on 127.0.0.1:8085
   - HTTPS DNS server running on 127.0.0.1:8084

✅ should reject invalid IP addresses (151ms)
   - Validates IP address format correctly
   - Throws meaningful error messages

✅ should work with IPv6 localhost if available
   - Gracefully handles IPv6 unavailability in containerized environments
```

### Benefits Achieved
- ✅ Enhanced security by allowing localhost-only binding
- ✅ Support for multi-homed servers with specific interface requirements
- ✅ Better isolation in containerized environments
- ✅ Backwards compatible (defaults to current behavior)
- ✅ IP address validation with clear error messages
- ✅ IPv4 and IPv6 support

## Example Usage (Now Available)
```typescript
// Bind to localhost only
const dnsServer = new DnsServer({
  httpsKey: cert.key,
  httpsCert: cert.cert,
  httpsPort: 443,
  udpPort: 53,
  dnssecZone: 'example.com',
  udpBindInterface: '127.0.0.1',
  httpsBindInterface: '127.0.0.1'
});

// Bind to specific interface
const dnsServer = new DnsServer({
  // ... other options
  udpBindInterface: '192.168.1.100',
  httpsBindInterface: '192.168.1.100'
});
```

## Files to Modify
1. `ts_server/classes.dnsserver.ts` - Interface and implementation
2. `readme.md` - Documentation updates
3. `test/test.server.ts` - Add interface binding tests

## Testing Strategy
- Unit tests for interface validation
- Integration tests for binding behavior
- Error handling tests for invalid interfaces
- Backwards compatibility tests