Debug.Assert when using ReceiveFrom on UnixDomainSocket

[wfurt]

I was adding new test like

 using (Socket server = new Socket(AddressFamily.Unix, SocketType.Dgram, ProtocolType.Unspecified))
 {
 server.Bind(new UnixDomainSocketEndPoint(serverAddress));
 using (Socket client = new Socket(AddressFamily.Unix, SocketType.Dgram, ProtocolType.Unspecified))
 {
 byte[] data = Encoding.ASCII.GetBytes(nameof(UnixDomainSocketEndPoint_SendToReceiveFrom_CorrectEndPoint));
 // Bind the client.
 client.Bind(new UnixDomainSocketEndPoint(clientAddress));

 var sender = new UnixDomainSocketEndPoint(GetRandomNonExistingFilePath());
 EndPoint senderRemote = (EndPoint)sender;
 client.SendTo(data, server.LocalEndPoint);

 byte[] buffer = new byte[data.Length * 2];
 int receivedBytes = server.ReceiveFrom(buffer, ref senderRemote);
 }
 }

and it will produce core with

 Starting: System.Net.Sockets.Tests (parallel test collections = off, max threads = 4)
 System.Net.Sockets.Tests.UnixDomainSocketTest.UnixDomainSocketEndPoint_SendToReceiveFrom_CorrectEndPoint(abstractAddress: False) [STARTING]
 dotnet: /home/furt/github/wfurt-runtime/src/native/libs/System.Native/pal_networking.c:1407: int32_t SystemNative_ReceiveMessage(intptr_t, MessageHeader *, int32_t, int64_t *): Assertion `(int32_t)header.msg_namelen <= messageHeader->SocketAddressLen' failed.
 /home/furt/github/wfurt-runtime/artifacts/bin/System.Net.Sockets.Tests/Debug/net7.0-unix/RunTests.sh: line 168: 79756 Aborted (core dumped) "$RUNTIME_PATH/dotnet" exec --runtimeconfig System.Net.Sockets.Tests.runtimeconfig.json --

While sockaddr_un has fixed size the actual path can vary

 struct sockaddr_un {
 sa_family_t sun_family; /* AF_UNIX */
 char sun_path[108]; /* Pathname */
 };

We seems to serialize only the actual size of the EndPoint so unless caller always creates string with maximum platform size they may have problems. (production code truncates the address)

Since the EndPoint is passed in as ref to be filled in it should not matter what the endpoint was. It would be nice if one could simply create empty UnixDomainSocketEndPoint from string.Empty but that fails in constructor.

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Issue Details

---

I was adding new test like

 using (Socket server = new Socket(AddressFamily.Unix, SocketType.Dgram, ProtocolType.Unspecified))
 {
 server.Bind(new UnixDomainSocketEndPoint(serverAddress));
 using (Socket client = new Socket(AddressFamily.Unix, SocketType.Dgram, ProtocolType.Unspecified))
 {
 byte[] data = Encoding.ASCII.GetBytes(nameof(UnixDomainSocketEndPoint_SendToReceiveFrom_CorrectEndPoint));
 // Bind the client.
 client.Bind(new UnixDomainSocketEndPoint(clientAddress));

 var sender = new UnixDomainSocketEndPoint(GetRandomNonExistingFilePath());
 EndPoint senderRemote = (EndPoint)sender;
 client.SendTo(data, server.LocalEndPoint);

 byte[] buffer = new byte[data.Length * 2];
 int receivedBytes = server.ReceiveFrom(buffer, ref senderRemote);
 }
 }

and it will produce core with

 Starting: System.Net.Sockets.Tests (parallel test collections = off, max threads = 4)
 System.Net.Sockets.Tests.UnixDomainSocketTest.UnixDomainSocketEndPoint_SendToReceiveFrom_CorrectEndPoint(abstractAddress: False) [STARTING]
 dotnet: /home/furt/github/wfurt-runtime/src/native/libs/System.Native/pal_networking.c:1407: int32_t SystemNative_ReceiveMessage(intptr_t, MessageHeader *, int32_t, int64_t *): Assertion `(int32_t)header.msg_namelen <= messageHeader->SocketAddressLen' failed.
 /home/furt/github/wfurt-runtime/artifacts/bin/System.Net.Sockets.Tests/Debug/net7.0-unix/RunTests.sh: line 168: 79756 Aborted (core dumped) "$RUNTIME_PATH/dotnet" exec --runtimeconfig System.Net.Sockets.Tests.runtimeconfig.json --

While sockaddr_un has fixed size the actual path can vary

 struct sockaddr_un {
 sa_family_t sun_family; /* AF_UNIX */
 char sun_path[108]; /* Pathname */
 };

We seems to serialize only the actual size of the EndPoint so unless caller always creates string with maximum platform size they may have problems. (production code truncates the address)

Since the EndPoint is passed in as ref to be filled in it should not matter what the endpoint was. It would be nice if one could simply create empty UnixDomainSocketEndPoint from string.Empty but that fails in constructor.

Author:	wfurt
Assignees:	-
Labels:	area-System.Net.Sockets
Milestone:	-