NameResolution tests fail on tvos/Android devices - localhost resolves to non-loopback addresses

[kotlarmilos]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1362636
Build error leg or test failing: System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostAndSubdomain_BothReturnLoopback, System.Net.NameResolution.Tests.GetHostEntryTest.DnsGetHostEntry_LocalhostAndSubdomain_BothReturnLoopback
Pull request: #125441

Affected CI jobs: build_tvos_arm64_Release_AllSubsets_CoreCLR, build_android_arm64_Release_AllSubsets_CoreCLR

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": "Expected loopback address but got",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Summary

DnsGetHostAddresses_LocalhostAndSubdomain_BothReturnLoopback and DnsGetHostEntry_LocalhostAndSubdomain_BothReturnLoopback fail on tvos-arm64 and Android devices because localhost DNS resolution returns real device IP addresses instead of loopback (127.0.0.1/::1).

Error:

Assert.All() Failure: 16 out of 18 items in the collection did not pass.
[5]:  Item:  10.64.36.129
      Error: Expected loopback address but got: 10.64.36.129

Note

This issue was filed with the assistance of GitHub Copilot.

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1362636
Error message validated: [Expected loopback address but got]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 4/2/2026 10:16:51 AM UTC

Report

Build	Definition	Test	Pull Request
1406427	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1406235	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#127613
1405999	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1405703	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#127613
1404759	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1404470	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#127613
1403445	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#127498
1403076	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1402544	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#127578
1401195	dotnet/runtime	System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostSubdomain_ReturnsLoopback
1399604	dotnet/runtime	System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostSubdomain_ReturnsLoopback	#127498
1399212	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1398689	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#127465
1397424	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1396883	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1396313	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1391077	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#126838
1388819	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#126838

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
2	15	18

[dotnet-policy-service]

Tagging subscribers to 'arch-android': @vitek-karas, @simonrozsival, @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

[dotnet-policy-service]

Tagging subscribers to 'os-tvos': @vitek-karas, @kotlarmilos, @steveisok, @akoeplinger
See info in area-owners.md if you want to be subscribed.

[dotnet-policy-service]

Tagging subscribers to this area: @karelz, @dotnet/ncl
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