Implement RFC6761 reserved DNS names handling #6924
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Pull Request Overview
This PR implements RFC 6761 compliant handling of reserved DNS names by extending special-case treatment beyond just "localhost" to include its subdomains (e.g., "service.localhost") and the "invalid" domain. The implementation centralizes reserved name checking and ensures DNS servers are not contacted for these special cases.
Key Changes:
- Refactored localhost resolution logic into a shared
CheckIsReservedDnsNamemethod that handles both "localhost" and "invalid" domains plus their subdomains - Added comprehensive test coverage for reserved name resolution including subdomain variants and explicit root labels
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/Libraries/Microsoft.Extensions.ServiceDiscovery.Dns/Resolver/DnsResolver.cs | Refactored hardcoded localhost checks into centralized RFC 6761 reserved name handling with support for subdomains and the "invalid" domain |
| test/Libraries/Microsoft.Extensions.ServiceDiscovery.Dns.Tests/Resolver/ResolveAddressesTests.cs | Added test cases for subdomain variants of reserved names and renamed test to reflect broader scope |
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rzikm
commented
Oct 15, 2025
.../Libraries/Microsoft.Extensions.ServiceDiscovery.Dns.Tests/Resolver/ResolveAddressesTests.cs
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Replaces dotnet/aspire#10311 since the code moved to this repo.
The Managed DNS implementation correctly special-cased "localhost" and resolved to loopback without contacting DNS server, but the authoritative RFC 6761 requires the same for subdomains as well (e.g. service.localhost). Ths PR fills the gap, including the other special-cased name "invalid".