[OSX] ip_mreqn struct is not supported for IPv4 Multicast by liveans · Pull Request #119354 · dotnet/runtime

liveans · 2025-09-04T14:45:48Z

With this fix we can set MulticastInterface socket option successfully, I tested the Multicast capabilities, and it seems to be working as expected.

Seems like Apple doesn't support ip_mreqn struct with IPv4 Sockets. Kernel header file description

sw_vers
ProductName:		macOS
ProductVersion:		26.0
BuildVersion:		25A5349a
../../../../../dotnet.sh build /t:test /p:outerloop=true /p:xunitoptions="-method System.Net.Sockets.Tests.SocketOptionNameTest.MulticastInterface_Set_AnyInterface_Succeeds"

  Determining projects to restore...
  All projects are up-to-date for restore.
  TestUtilities -> /Users/liveans/Desktop/dotnet-runtime/artifacts/bin/TestUtilities/Debug/net8.0/TestUtilities.dll
  StreamConformanceTests -> /Users/liveans/Desktop/dotnet-runtime/artifacts/bin/StreamConformanceTests/Debug/net10.0/StreamConformanceTests.dll
  System.Net.Sockets.Tests -> /Users/liveans/Desktop/dotnet-runtime/artifacts/bin/System.Net.Sockets.Tests/Debug/net10.0-unix/System.Net.Sockets.Tests.dll
  ========================= Begin custom configuration settings ==============================
  export __IsXUnitLogCheckerSupported=1
  export XUNIT_HIDE_PASSING_OUTPUT_DIAGNOSTICS=1
  ========================== End custom configuration settings ===============================
  ----- start Thu Sep 4 17:36:24 +03 2025 =============== To repro directly: =====================================================
  pushd /Users/liveans/Desktop/dotnet-runtime/artifacts/bin/System.Net.Sockets.Tests/Debug/net10.0-unix
  /Users/liveans/Desktop/dotnet-runtime/artifacts/bin/testhost/net10.0-osx-Debug-arm64/dotnet exec --runtimeconfig System.Net.Sockets.Tests.runtimeconfig.json --depsfile System.Net.Sockets.Tests.deps.json /Users/liveans/.nuget/packages/microsoft.dotnet.xunitconsolerunner/2.9.3-beta.25420.121/build/../tools/net/xunit.console.dll System.Net.Sockets.Tests.dll -xml testResults.xml -nologo -notrait category=failing -method System.Net.Sockets.Tests.SocketOptionNameTest.MulticastInterface_Set_AnyInterface_Succeeds 
  popd
  ===========================================================================================================
  ~/Desktop/dotnet-runtime/artifacts/bin/System.Net.Sockets.Tests/Debug/net10.0-unix ~/Desktop/dotnet-runtime/src/libraries/System.Net.Sockets/tests/FunctionalTests
    Discovering: System.Net.Sockets.Tests (method display = ClassAndMethod, method display options = None)
    Discovered:  System.Net.Sockets.Tests (found 1 of 1875 test case)
    Starting:    System.Net.Sockets.Tests (parallel test collections = on [16 threads], stop on fail = off)
    Finished:    System.Net.Sockets.Tests
  === TEST EXECUTION SUMMARY ===
     System.Net.Sockets.Tests  Total: 1, Errors: 0, Failed: 0, Skipped: 0, Time: 0,041s
  ~/Desktop/dotnet-runtime/src/libraries/System.Net.Sockets/tests/FunctionalTests
  ----- end Thu Sep 4 17:36:24 +03 2025 ----- exit code 0 ----------------------------------------------------------
  exit code 0 means Exited Successfully

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:03.15

/cc @vcsjones @wfurt

dotnet-policy-service · 2025-09-04T14:47:27Z

Tagging subscribers to this area: @dotnet/ncl
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Pull Request Overview

This PR fixes a macOS compatibility issue where the ip_mreqn struct is not supported for IPv4 multicast socket operations. The fix prevents the use of ip_mreqn on Apple platforms, resolving exceptions when setting the MulticastInterface socket option.

Key changes:

Excludes Apple platforms from using the ip_mreqn struct in IPv4 multicast operations
Allows the code to fall back to alternative multicast handling approaches on macOS

wfurt · 2025-09-04T15:55:48Z

Looking at the code, we will throw if the interface index is set since ip_mreq does not have a filed, right? We can perhaps document that but it would be nice to actually verify that the multicast subscription works as expected and one can pin the interface using SocketOptionName.MulticastInterface.

liveans · 2025-09-05T02:05:49Z

While reading the kernel code to understand how to make it work, I stumbled upon IP_MULTICAST_IFINDEX and it seems to be specific to Apple platforms. Tested it through Wireshark it works as expected. I can make condition even more specified to check for both Addresses should be zero etc, but in this way, if we provide a InterfaceIndex, it will take over priority.

/cc @wfurt

vcsjones · 2025-09-05T11:59:07Z

Do we think this will fix it for iOS too?

The test MulticastInterface_Set_AnyInterface_Succeeds has been disabled on iOS for quite a while now. It would be interesting to try removing the ActiveIssue and running the iOS pipelines and seeing what happens if we think there is a chance this chance will apply to iOS as well.

liveans · 2025-09-05T12:09:57Z

/azp list

azure-pipelines · 2025-09-05T12:10:03Z

CI/CD Pipelines for this repository: runtime-coreclr outerloop runtime-coreclr jitstress runtime-coreclr jitstressregs runtime-coreclr jitstress2-jitstressregs runtime-coreclr gcstress0x3-gcstress0xc runtime-coreclr gcstress-extra runtime-coreclr r2r-extra runtime-coreclr jitstress-isas-x86 runtime-coreclr jitstress-isas-arm runtime-coreclr jitstressregs-x86 runtime-coreclr libraries-jitstressregs runtime-coreclr libraries-jitstress2-jitstressregs runtime-coreclr r2r runtime-coreclr runincontext runtime-coreclr crossgen2 runtime-libraries-coreclr outerloop runtime-libraries-coreclr outerloop-windows runtime-libraries-coreclr outerloop-linux runtime-libraries-coreclr outerloop-osx runtime runtime-libraries enterprise-linux runtime-libraries stress-http runtime-libraries stress-ssl runtime-dev-innerloop runtime-coreclr crossgen2 outerloop coreclr-release-outerloop-nightly runtime-coreclr crossgen2-composite runtime-jit-experimental runtime-coreclr libraries-jitstress dotnet-linker-tests runtime-coreclr ilasm runtime-coreclr crossgen2-composite gcstress runtime-coreclr pgo runtime-coreclr libraries-pgo Antigen runtime-community Fuzzlyn runtime-coreclr superpmi-replay runtime-wasm runtime-coreclr superpmi-diffs runtime-coreclr superpmi-asmdiffs-checked-release runtime-extra-platforms jit-cfg runtime-wasm-perf runtime-llvm runtime-coreclr jitstress-random runtime-coreclr libraries-jitstress-random runtime-android-grpc-client-tests runtime-wasm-non-libtests runtime-android runtime-androidemulator runtime-ioslike runtime-ioslikesimulator runtime-linuxbionic runtime-coreclr pgostress runtime-coreclr jitstress-isas-avx512 runtime-libraries-mono outerloop runtime-sanitized runtime-wasm-dbgtests runtime-wasm-optional runtime-nativeaot-outerloop runtime-coreclr superpmi-collect-test runtime-diagnostics runtime-interpreter

liveans · 2025-09-05T12:10:58Z

Should I run ioslike pipeline for it ? @vcsjones

vcsjones · 2025-09-05T12:54:46Z

/azp run runtime-extra-platforms

azure-pipelines · 2025-09-05T12:55:06Z

Azure Pipelines successfully started running 1 pipeline(s).

liveans · 2025-09-06T11:31:28Z

This PR also fixes the issue for other Apple platforms, only left issue is:

MacCatalyst test returns "SocketException: No route to host". (This might be due to reason of missing entitlement).

wfurt · 2025-09-06T18:05:39Z

note that the routing error sometimes happens on other platforms as well.. #90491
(IPv6 but essentially same problem)

Also since you at multicast can you please check following issues? Maybe there is some hope for them as well.
#53767
#110889

…IFINDEX for interface index specification

wfurt

LGTM. thanks @liveans for diffing in.

liveans · 2025-09-09T06:27:45Z

/ba-g xml test failure is not related

liveans · 2025-09-09T06:28:21Z

/backport to release/10.0

github-actions · 2025-09-09T06:28:30Z

Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17573854114

liveans · 2025-09-09T06:40:55Z

/backport to release/9.0-staging

liveans · 2025-09-09T06:41:00Z

/backport to release/8.0-staging

github-actions · 2025-09-09T06:41:07Z

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/17574101803

github-actions · 2025-09-09T06:41:09Z

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/17574100129

github-actions · 2025-09-09T06:42:54Z

@liveans backporting to "release/8.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix IPv4 multicast on macOS by handling ip_mreqn struct compatibility
Applying: Remove Active Issue for iOS
Using index info to reconstruct a base tree...
M	src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs
Falling back to patching base and 3-way merge...
Auto-merging src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs
CONFLICT (content): Merge conflict in src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0002 Remove Active Issue for iOS
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

github-actions · 2025-09-09T06:42:54Z

@liveans backporting to "release/9.0-staging" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Fix IPv4 multicast on macOS by handling ip_mreqn struct compatibility
Applying: Remove Active Issue for iOS
Using index info to reconstruct a base tree...
M	src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs
Falling back to patching base and 3-way merge...
Auto-merging src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs
CONFLICT (content): Merge conflict in src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0002 Remove Active Issue for iOS
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!

) * Fix IPv4 multicast on macOS by handling ip_mreqn struct compatibility * Remove Active Issue for iOS * Add support for IP_MULTICAST_IFINDEX * Refactor IPv4 multicast option handling to directly use IP_MULTICAST_IFINDEX for interface index specification * Accept 0 interface as valid --------- Co-authored-by: Tomas Weinfurt <tweinfurt@yahoo.com>

Copilot AI review requested due to automatic review settings September 4, 2025 14:45

github-actions Bot added the needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners label Sep 4, 2025

dotnet-policy-service Bot assigned liveans Sep 4, 2025

liveans changed the title ~~On OSX ip_mreqn struct is not supported for IPv4~~ [OSX] ip_mreqn struct is not supported for IPv4 Multicast Sep 4, 2025

liveans added area-System.Net.Sockets and removed needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners labels Sep 4, 2025

Copilot AI reviewed Sep 4, 2025

View reviewed changes

Fix IPv4 multicast on macOS by handling ip_mreqn struct compatibility

5cc12a8

liveans force-pushed the ipv4_multicast_osx_fix branch from 8cbb38d to 5cc12a8 Compare September 5, 2025 02:37

liveans requested a review from wfurt September 5, 2025 02:52

Remove Active Issue for iOS

a408dd6

wfurt reviewed Sep 5, 2025

View reviewed changes

Comment thread src/native/libs/System.Native/pal_networking.c Outdated

Add support for IP_MULTICAST_IFINDEX

46c56f1

build-analysis Bot mentioned this pull request Sep 8, 2025

[browser] HalfTests.ExplicitConversion_FromSingle failing due to NaN != NaN #103347

Closed

wfurt reviewed Sep 8, 2025

View reviewed changes

Comment thread src/native/libs/System.Native/pal_networking.c Outdated

Refactor IPv4 multicast option handling to directly use IP_MULTICAST_…

3be47f1

…IFINDEX for interface index specification

Accept 0 interface as valid

9089eb0

liveans requested a review from wfurt September 8, 2025 18:44

wfurt approved these changes Sep 8, 2025

View reviewed changes

Merge branch 'main' into ipv4_multicast_osx_fix

dc68628

liveans merged commit 0e3562e into dotnet:main Sep 9, 2025
159 of 161 checks passed

github-actions Bot mentioned this pull request Sep 9, 2025

[release/10.0] [OSX] ip_mreqn struct is not supported for IPv4 Multicast #119480

Merged

karelz added this to the 11.0.0 milestone Sep 9, 2025

karelz mentioned this pull request Sep 9, 2025

[iOS][MacCatalyst] Invalid SocketOption in MulticastInterface on new macOS versions (14.7, 15.2) #113827

Closed

This was referenced Sep 9, 2025

[9.0][OSX] ip_mreqn struct is not supported for IPv4 Multicast #119481

Closed

[8.0][OSX] ip_mreqn struct is not supported for IPv4 Multicast (#119354) #119482

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