IPV6 Support

[stephbu]

IPv6 Support

Support for:

• IPv6 listener bindings
• IPv6 DNS records (AAAA)

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Analysis Summary

Current State

Already Implemented ✅

• ResourceType.AAAA defined in ResourceType.cs (value 0x001c)
• BindZoneProvider parses AAAA records from zone files, stores IPv6 addresses, and generates ZoneRecord objects with Type = ResourceType.AAAA
• ZoneRecord uses IPAddress[] which handles both IPv4 and IPv6
• Tests exist for AAAA parsing in BindZoneProviderTests.cs
• Related task T29 in docs/task_list.md

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Gaps to Address

1. UdpListener IPv6 Binding (Critical)

Current code (UdpListener.cs):

_listener = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
IPEndPoint ep = new IPEndPoint(IPAddress.Any, port);

Problem: Hardcoded to AddressFamily.InterNetwork (IPv4 only) and IPAddress.Any (0.0.0.0)

Required:

• Add configuration for bind address(es)
• Support AddressFamily.InterNetworkV6 socket creation
• Consider dual-stack support or multiple listeners

2. No AAAANameRData Class (Critical)

Current code (RData.cs): Only ANameRData exists for IPv4

Problem:

• ANameRData.Length returns 4 (IPv4); IPv6 needs 16 bytes
• ANameRData.Parse() expects exactly 4 bytes

Required: Create AAAANameRData class (16-byte address handling)

3. DnsServer Response Handling (Critical)

Current code (DnsServer.cs):

message.Answers.Add(new ResourceRecord { 
    Type = ResourceType.A,  // Hardcoded!
    RData = new ANameRData { Address = address } 
});

Problem: Always creates A records with ANameRData, ignoring client's query type

Required:

• Check question.Type for A vs AAAA
• Use appropriate RData class based on address family

4. Configuration Schema Update

Current: No bind address configuration in AppConfig

Required: Add BindAddress or Addresses array to DnsListenerOptions

5. IPProbeZoneProvider IPv6 Support (Lower Priority)

Current: Always creates ResourceType.A records

Required: Detect address family and generate separate A/AAAA records

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Implementation Plan

Phase	Work Item	Files
1	Create AAAANameRData class	Dns/RData.cs
2	Update DnsServer.ProcessUdpRequest for AAAA queries	Dns/DnsServer.cs
3	Add integration tests for AAAA resolution	dnstest/
4	Extend UdpListener for IPv6 bindings	Dns/UdpListener.cs
5	Update configuration schema	Dns/Config/AppConfig.cs, appsettings.json
6	Update IPProbeZoneProvider for IPv6	Dns/ZoneProvider/IPProbe/
7	Documentation	README.md, docs/

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Open Questions

1. Listener Strategy: Dual-stack socket vs. multiple listeners vs. configurable bind addresses?
2. Backward Compatibility: Default IPv4-only with IPv6 opt-in?
3. IPProbe Scope: IPv6 health probing in this issue or separate?
4. Reverse DNS: Add ip6.arpa PTR support now or defer?