[Kernel] Preserve socket descriptors after failed connect (#343)

Keep ownership of a socket descriptor with the guest when connect fails, and route generic close calls through the socket table. Add a deterministic regression test for the failure and close sequence.

Signed-off-by: missatjuhvdk1 <177474143+missatjuhvdk1@users.noreply.github.com>
Co-authored-by: missatjuhvdk1 <177474143+missatjuhvdk1@users.noreply.github.com>

src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs

@@ -1966,6 +1966,12 @@ public static partial class KernelMemoryCompatExports
             return (int)OrbisGen2Result.ORBIS_GEN2_OK;
         }
 
+        if (KernelSocketCompatExports.TryCloseSocketFd(fd))
+        {
+            ctx[CpuRegister.Rax] = 0;
+            return (int)OrbisGen2Result.ORBIS_GEN2_OK;
+        }
+
         FileStream? stream;
         lock (_fdGate)
         {

src/SharpEmu.Libs/Kernel/KernelSocketCompatExports.cs

@@ -160,7 +160,6 @@ internal static class KernelSocketCompatExports
         if (!TryParseGuestSockaddrIn(sockaddrAddress, addrlen, ctx, out var ipAddress, out var port))
         {
             LogNet($"connect sockaddr parse failed: fd={fd} addr=0x{sockaddrAddress:X} len={addrlen}");
-            RemoveEmulatedSocketFd(fd);
             ctx[CpuRegister.Rax] = unchecked((ulong)0xFFFFFFFFFFFFFFFF);
             return (int)OrbisGen2Result.ORBIS_GEN2_OK;
         }
@@ -174,7 +173,6 @@ internal static class KernelSocketCompatExports
         if (!IsGuestTcpOutboundAllowed(ipAddress, redirectApplied))
         {
             LogNet($"connect denied by outbound policy: fd={fd} ip={ipAddress} port={port}");
-            RemoveEmulatedSocketFd(fd);
             ctx[CpuRegister.Rax] = unchecked((ulong)0xFFFFFFFFFFFFFFFF);
             return (int)OrbisGen2Result.ORBIS_GEN2_OK;
         }
@@ -182,7 +180,6 @@ internal static class KernelSocketCompatExports
         if (!TryEstablishHostTcpConnection(ipAddress, port, out var client, out var stream))
         {
             LogNet($"connect failed: fd={fd} ip={ipAddress} port={port}");
-            RemoveEmulatedSocketFd(fd);
             ctx[CpuRegister.Rax] = unchecked((ulong)0xFFFFFFFFFFFFFFFF);
             return (int)OrbisGen2Result.ORBIS_GEN2_OK;
         }
@@ -418,17 +415,6 @@ internal static class KernelSocketCompatExports
         state.Connected = false;
     }
 
-    private static void RemoveEmulatedSocketFd(int fd)
-    {
-        lock (Gate)
-        {
-            if (Sockets.Remove(fd, out var socketState))
-            {
-                DisposeEmulatedSocket(socketState);
-            }
-        }
-    }
-
     private static void LogNet(string message)
     {
         if (string.Equals(Environment.GetEnvironmentVariable("SHARPEMU_LOG_NET"), "1", StringComparison.Ordinal))

tests/SharpEmu.Libs.Tests/Kernel/KernelSocketCompatExportsTests.cs

@@ -0,0 +1,50 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.HLE;
+using SharpEmu.Libs.Kernel;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.Kernel;
+
+public sealed class KernelSocketCompatExportsTests
+{
+    [Fact]
+    public void Connect_InvalidSockaddrLeavesFdOpenForGuestClose()
+    {
+        const ulong memoryBase = 0x0000_7FFF_3000_0000;
+        var context = new CpuContext(new FakeCpuMemory(memoryBase, 0x1000), Generation.Gen5);
+        context[CpuRegister.Rdi] = 2;
+        context[CpuRegister.Rsi] = 1;
+        context[CpuRegister.Rdx] = 6;
+
+        Assert.Equal(0, KernelSocketCompatExports.Socket(context));
+        Assert.NotEqual(ulong.MaxValue, context[CpuRegister.Rax]);
+        var guestFd = checked((int)context[CpuRegister.Rax]);
+
+        try
+        {
+            context[CpuRegister.Rdi] = unchecked((ulong)guestFd);
+            context[CpuRegister.Rsi] = memoryBase;
+            context[CpuRegister.Rdx] = 0;
+
+            Assert.Equal(0, KernelSocketCompatExports.Connect(context));
+            Assert.Equal(ulong.MaxValue, context[CpuRegister.Rax]);
+
+            context[CpuRegister.Rdi] = unchecked((ulong)guestFd);
+            Assert.Equal(
+                (int)OrbisGen2Result.ORBIS_GEN2_OK,
+                KernelMemoryCompatExports.PosixClose(context));
+            Assert.Equal(0UL, context[CpuRegister.Rax]);
+
+            context[CpuRegister.Rdi] = unchecked((ulong)guestFd);
+            Assert.Equal(
+                (int)OrbisGen2Result.ORBIS_GEN2_ERROR_NOT_FOUND,
+                KernelMemoryCompatExports.PosixClose(context));
+        }
+        finally
+        {
+            KernelSocketCompatExports.TryCloseSocketFd(guestFd);
+        }
+    }
+}