[ci-scan] Test failure: DnsGetHostAddresses_LocalhostSubdomainWithTrailingDot_ReturnsLoopback on android

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Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1413202
Build error leg or test failing: android-arm64 Release AllSubsets_CoreCLR - System.Net.NameResolution.Functional.Tests

Error Message

{
  "ErrorMessage": "[FAIL] System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Additional Context

Summary: GetHostAddressesTest.DnsGetHostAddresses_LocalhostSubdomainWithTrailingDot_ReturnsLoopback fails on android-arm64 because DNS resolution of foo.localhost. and bar.test.localhost. returns non-loopback addresses (host network interfaces) instead of loopback.

Failed in (10+):

• runtime-extra-platforms 1413202 (2026-05-08)
• runtime-extra-platforms 1411505 (2026-05-07)
• All 10 checked builds have android-arm64 CoreCLR failing (test is part of the failing work item)

Console Log: android-arm64 Console Log

Failed tests:

runtime-extra-platforms (android-arm64 Release AllSubsets_CoreCLR)
- Windows.11.Amd64.Android.Open
  - System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostSubdomainWithTrailingDot_ReturnsLoopback(hostName: "foo.localhost.")
  - System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostSubdomainWithTrailingDot_ReturnsLoopback(hostName: "bar.test.localhost.")

Error Message:

[FAIL] System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostSubdomainWithTrailingDot_ReturnsLoopback(hostName: "foo.localhost.")
Assert.All() Failure: 7 out of 8 items in the collection did not pass.
     Error: Expected loopback address but got: fe80::2dd7:ff44:eff:c764%30
     Error: Expected loopback address but got: 10.64.33.196

Impact on platforms:

• runtime-extra-platforms + android-arm64 + Windows.11.Amd64.Android.Open + exit code 1

First build it occurred: First seen in build 1396313 (2026-04-25) within the scanned window. 10/10 builds affected. Note: this is the earliest in the scanned window and may not be the true origin.

Recommended action: Android DNS resolution does not treat *.localhost subdomains as loopback per RFC 6761 the same way desktop OSes do. The test assumptions about foo.localhost. resolving to loopback are not valid on Android. The test should be annotated with [ActiveIssue] for Android or the test should skip when PlatformDetection.IsAndroid is true. Area owners: @dotnet/ncl.

Generated by CI Outer-Loop Failure Scanner · ● 26.1M · ◷

Report

Build	Definition	Test	Pull Request
1427615	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1427030	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#125437
1426342	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#125437
1426173	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128284
1425947	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1424920	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128068
1424079	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1423593	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1423053	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1422120	dotnet/runtime	System.Net.NameResolution.Tests.GetHostEntryTest.DnsGetHostEntry_LocalhostSubdomain_RespectsAddressFamily	#127498
1421640	dotnet/runtime	System.Net.NameResolution.Tests.GetHostEntryTest.DnsGetHostEntry_LocalhostSubdomain_RespectsAddressFamily
1422048	dotnet/runtime	System.Net.NameResolution.Tests.GetHostEntryTest.DnsGetHostEntry_LocalhostSubdomain_RespectsAddressFamily	#128068
1420484	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128068
1420480	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128188
1420407	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128135
1420376	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#125437
1420047	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1418805	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#124173
1418956	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#125437
1417637	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128068
1416787	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1416322	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#128049
1415929	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution	#125437
1415126	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1414719	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1414320	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution
1396313	dotnet/runtime	System.Net.NameResolution.Functional.Tests.WorkItemExecution

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
2	19	27

[jkotas]

"ErrorMessage": "DnsGetHostAddresses_LocalhostSubdomainWithTrailingDot_ReturnsLoopback",

@kotlarmilos These error matching patterns are not specific enough. This string is going to match even when unrelated test fails and this one passes (names of passing tests are often in the test logs as well).

[kotlarmilos]

I updated this and other issues manually, and based on feedback, created #127961. We might need a few more iterations to get it right. Let me know when/if it starts generating too much noise and I'll reduce the scope to a subset of tests for the additional iterations.

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