LocalEndPointTestIPv6Sync.TcpAcceptSocket_WhenServerBoundToSpecificAddress_LocalEPIsSame failing

[runfoapp]

Runfo Tracking Issue: LocalEndPointTestIPv6Sync.TcpAcceptSocket_WhenServerBoundToSpecificAddress_LocalEPIsSame failing

Build	Definition	Kind	Run Name
1116477	runtime	PR 52128	net6.0-Linux-Debug-x64-Mono_release-(Centos.8.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:centos-8-helix-20201229003624-c1bf759
1113740	runtime	PR 52046	net6.0-Linux-Debug-x64-Mono_release-(Debian.10.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:debian-10-helix-amd64-bfcd90a-20200121150006

Build Result Summary

Day Hit Count	Week Hit Count	Month Hit Count
1	2	2

[ghost]

Tagging subscribers to this area: @dotnet/ncl
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Runfo Creating Tracking Issue (data being generated)

Author:	runfoapp[bot]
Assignees:	-
Labels:	area-System.Net, untriaged
Milestone:	-

[karelz]

Call stack:

Assert.Equal() Failure
Expected: [::1]:53046
Actual:   [::1]:53110
   at System.Net.Sockets.Tests.LocalEndPointTest`1.TcpAcceptSocket_WhenServerBoundToSpecificAddress_LocalEPIsSame() in /_/src/libraries/System.Net.Sockets/tests/FunctionalTests/LocalEndPointTest.cs:line 162
--- End of stack trace from previous location ---

Failures (3/12-7/22, incl. PRs):

Run	Date	OS
Official run	4/2	Debian.9.Amd64.Open - CoreCLR
PR #50929	4/9	Debian.9.Amd64.Open - Mono
PR #49526	4/24	Ubuntu.1804.ArmArch.Open - Mono
PR #52046	4/29	ubuntu.1604.amd64.open - Mono
PR #52003	4/29	RedHat.7.Amd64.Open - CoreCLR
PR #52128	4/30	Ubuntu.1604.Amd64.Open - Mono
PR #52475	5/8	Centos.8.Amd64.Open - Mono
PR #52510	6/7	Ubuntu.1804.ArmArch.Open - Mono
PR #53645	6/14	Ubuntu.1804.Amd64.Open - Mono
PR #54436	6/18	Fedora.30.Amd64.Open - Mono
PR #54822	7/1	SLES.15.Amd64.Open - Mono
PR #54253	7/2	Fedora.30.Amd64.Open - CoreCLR
PR #55101	7/11	Fedora.30.Amd64.Open - Mono
PR #52244	7/15	Fedora.32.Amd64.Open - Mono
PR #52244	7/19	Centos.8.Amd64.Open - CoreCLR

Alternative / related callstack:

System.Net.Internals.SocketExceptionFactory+ExtendedSocketException : Socket is already connected 127.0.0.1:54400
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) in /_/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs:line 3072
   at System.Net.Sockets.Socket.Connect(EndPoint remoteEP) in /_/src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs:line 860
   at System.Net.Sockets.Tests.SocketHelperArraySync.<>c__DisplayClass3_0.<ConnectAsync>b__0() in /_/src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketTestHelper.cs:line 61
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ExecutionContext.cs:line 294
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:line 2363
--- End of stack trace from previous location ---
   at System.Net.Sockets.Tests.LocalEndPointTest`1.TcpAcceptSocket_WhenServerBoundToSpecificAddress_LocalEPIsSame() in /_/src/libraries/System.Net.Sockets/tests/FunctionalTests/LocalEndPointTest.cs:line 159
--- End of stack trace from previous location ---

Failures (3/12-6/23, incl. PRs):

Run	Date	OS
PR #51763	4/27	OSX.1014.Amd64.Open - CoreCLR

[antonfirsov]

A possible explanation might be that this is yet another dual stack IPv4/IPv6 port-collision issue, caused by other test cases running in parallel.

runtime/src/libraries/System.Net.Sockets/tests/FunctionalTests/LocalEndPointTest.cs

Lines 152 to 165 in 01b7e73

	int serverPort = server.BindToAnonymousPort(Loopback);
	Assert.Equal(Loopback, GetLocalEPAddress(server)); // server -> specific before accept
	server.Listen();
	Task<Socket> acceptTask = AcceptAsync(server);
	await ConnectAsync(client, new IPEndPoint(Loopback, serverPort));
	Socket accept = await acceptTask;
	Assert.Equal(accept.RemoteEndPoint, client.LocalEndPoint);
	Assert.Equal(GetLocalEPAddress(server), GetLocalEPAddress(accept)); // accept -> same address
	Assert.Equal(serverPort, GetLocalEPPort(accept));

A dual-mode client in that other test that is intended to connect to it's matching IPv4-only listener may then connect to the server of the failing test case. Since the sync connection request kicks in slowly (AcceptAsync starting on a threadpool thread), the failing test then accepts that other connection request in Task<Socket> acceptTask = AcceptAsync(server); before accepting of it's own client-s connection.

We can move the sync tests classes to a non-parallel collection as a quick fix attempt.

[ghost]

Tagging subscribers to this area: @dotnet/ncl
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Runfo Tracking Issue: LocalEndPointTestIPv6Sync.TcpAcceptSocket_WhenServerBoundToSpecificAddress_LocalEPIsSame failing

Build	Definition	Kind	Run Name
1116477	runtime	PR 52128	net6.0-Linux-Debug-x64-Mono_release-(Centos.8.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:centos-8-helix-20201229003624-c1bf759
1113740	runtime	PR 52046	net6.0-Linux-Debug-x64-Mono_release-(Debian.10.Amd64.Open)[email protected]/dotnet-buildtools/prereqs:debian-10-helix-amd64-bfcd90a-20200121150006

Build Result Summary

Day Hit Count	Week Hit Count	Month Hit Count
1	2	2

Author:	runfoapp[bot]
Assignees:	antonfirsov
Labels:	area-System.Net.Sockets, test bug, test-run-core
Milestone:	6.0.0