DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback - SocketException : Name or service not known

[pavelsavara]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1440366
Build error leg or test failing: System.Net.NameResolution.Tests.GetHostAddressesTest

Log

Starting:    System.Net.NameResolution.Functional.Tests (parallel test collections = on [2 threads], stop on fail = off)
    System.Net.NameResolution.Tests.GetHostEntryTest.DnsGetHostEntry_LocalhostWithTrailingDot_ReturnsLoopback [FAIL]
      System.Net.Sockets.SocketException : Name or service not known
      Stack Trace:
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(526,0): at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, Nullable`1 activityOrDefault)
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(385,0): at System.Net.Dns.GetHostEntryCore(String hostName, AddressFamily addressFamily, Nullable`1 activityOrDefault)
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(87,0): at System.Net.Dns.GetHostEntry(String hostNameOrAddress, AddressFamily family)
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(59,0): at System.Net.Dns.GetHostEntry(String hostNameOrAddress)
        /_/src/libraries/System.Net.NameResolution/tests/FunctionalTests/GetHostEntryTest.cs(413,0): at System.Net.NameResolution.Tests.GetHostEntryTest.DnsGetHostEntry_LocalhostWithTrailingDot_ReturnsLoopback()
        --- End of stack trace from previous location ---
        --- End of stack trace from previous location ---
    System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback [FAIL]
      System.Net.Sockets.SocketException : Name or service not known
      Stack Trace:
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(526,0): at System.Net.Dns.GetHostEntryOrAddressesCore(String hostName, Boolean justAddresses, AddressFamily addressFamily, Nullable`1 activityOrDefault)
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(388,0): at System.Net.Dns.GetHostAddressesCore(String hostName, AddressFamily addressFamily, Nullable`1 activityOrDefault)
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(217,0): at System.Net.Dns.GetHostAddresses(String hostNameOrAddress, AddressFamily family)
        /_/src/libraries/System.Net.NameResolution/src/System/Net/Dns.cs(189,0): at System.Net.Dns.GetHostAddresses(String hostNameOrAddress)
        /_/src/libraries/System.Net.NameResolution/tests/FunctionalTests/GetHostAddressesTest.cs(377,0): at System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback()
        --- End of stack trace from previous location ---
        --- End of stack trace from previous location ---
  Finished:    System.Net.NameResolution.Functional.Tests
=== TEST EXECUTION SUMMARY ===
   System.Net.NameResolution.Functional.Tests  Total: 139, Errors: 0, Failed: 2, Skipped: 0, Time: 6.884s

{
  "ErrorMessage": "SocketException : Name or service not known",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1440366
Error message validated: [SocketException : Name or service not known]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 5/29/2026 11:49:34 AM UTC

Report

Build	Repository	Test	Pull Request
1503909	dotnet/runtime	System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback	#130415
1502921	dotnet/runtime	System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback	#130168
1502742	dotnet/runtime	System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback	#130463
1494467	dotnet/runtime	System.Net.NameResolution.Tests.GetHostAddressesTest.DnsGetHostAddresses_LocalhostWithTrailingDot_ReturnsLoopback	#130221

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	0	4

[pavelsavara]

Probably related #127965 and #128068

[dotnet-policy-service]

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

I'm a bot. Here is a possible related and/or duplicate issue (I may be wrong):

• System.Net.NameResolution.Tests DNS failures: Name or service not known #126641

[wfurt]

This looks like Ubuntu 26 container. The linked Android issues have different root cause IMHO e.g. different way how resolver works. We should investigate.

[wfurt]

no recent failures. This looks like infra problem where the OS fails to resolve names.