[Fix] Duplicated sockets need to be closed properly.

If the child process exists without closing the socket first, a socket read
error occurs on both the parent process and the connected slave.

src/Win32_Interop/Win32_FDAPI.cpp

@@ -143,6 +143,23 @@ BOOL FDAPI_WSAGetOverlappedResult(int rfd, LPWSAOVERLAPPED lpOverlapped, LPDWORD
     return SOCKET_ERROR;
 }
 
+/* This method should only be called to close the sockets duplicated
+ * by the child process.
+ */
+BOOL FDAPI_CloseDuplicatedSocket(int rfd) {
+    try {
+        SOCKET socket = RFDMap::getInstance().lookupSocket(rfd);
+        if (socket != INVALID_SOCKET) {
+            RFDMap::getInstance().removeRFDToSocketInfo(rfd);
+            RFDMap::getInstance().removeSocketToRFD(socket);
+            return f_closesocket(socket);
+        }
+    } CATCH_AND_REPORT();
+
+    errno = EBADF;
+    return FALSE;
+}
+
 int FDAPI_WSADuplicateSocket(int rfd, DWORD dwProcessId, LPWSAPROTOCOL_INFO lpProtocolInfo) {
     try {
         SOCKET socket = RFDMap::getInstance().lookupSocket(rfd);

src/Win32_Interop/Win32_FDAPI.h

@@ -199,6 +199,7 @@ int     FDAPI_WSAIoctl(int rfd, DWORD dwIoControlCode, LPVOID lpvInBuffer, DWORD
 int     FDAPI_WSASend(int rfd, LPWSABUF lpBuffers, DWORD dwBufferCount, LPDWORD lpNumberOfBytesSent, DWORD dwFlags, LPWSAOVERLAPPED lpOverlapped, LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine);
 int     FDAPI_WSARecv(int rfd, LPWSABUF lpBuffers, DWORD dwBufferCount, LPDWORD lpNumberOfBytesRecvd, LPDWORD lpFlags, LPWSAOVERLAPPED lpOverlapped, LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine);
 BOOL    FDAPI_WSAGetOverlappedResult(int rfd, LPWSAOVERLAPPED lpOverlapped, LPDWORD lpcbTransfer, BOOL fWait, LPDWORD lpdwFlags);
+BOOL    FDAPI_CloseDuplicatedSocket(int rfd);
 int     FDAPI_WSADuplicateSocket(int rfd, DWORD dwProcessId, LPWSAPROTOCOL_INFO lpProtocolInfo);
 int     FDAPI_WSASocket(int af, int type, int protocol, LPWSAPROTOCOL_INFO lpProtocolInfo, GROUP g, DWORD dwFlags);
 int     FDAPI_WSAGetLastError(void);

src/Win32_Interop/Win32_QFork.cpp

@@ -363,6 +363,12 @@ BOOL QForkChildInit(HANDLE QForkControlMemoryMapHandle, DWORD ParentProcessID) {
                                             g_pQForkControl->globalData.numfds,
                                             g_pQForkControl->globalData.clientids,
                                             pipe_write_fd);
+            // After the socket replication has finished, close the duplicated sockets.
+            // Failing to close the sockets properly will produce a socket read error
+            // on both the parent process and the slave.
+            for (int i = 0; i < g_pQForkControl->globalData.numfds; i++) {
+                FDAPI_CloseDuplicatedSocket(g_pQForkControl->globalData.fds[i]);
+            }
         } else {
             throw runtime_error("unexpected operation type");
         }