this is probably a better idea.

include/fdlist.h

@@ -24,6 +24,7 @@ extern MODVAR FDEntry fd_table[MAXCONNECTIONS + 1];
 
 extern int fd_open(int fd, const char *desc);
 extern void fd_close(int fd);
+extern int fd_unmap(int fd);
 extern void fd_unnotify(int fd);
 extern int fd_socket(int family, int type, int protocol, const char *desc);
 extern int fd_accept(int sockfd);

src/fdlist.c

@@ -89,7 +89,7 @@ int fd_fileopen(const char *path, unsigned int flags)
 	return fd_open(fd, comment);
 }
 
-void fd_close(int fd)
+int fd_unmap(int fd)
 {
 	FDEntry *fde;
 	unsigned int befl;
@@ -100,7 +100,7 @@ void fd_close(int fd)
 				fd, MAXCONNECTIONS);
 		ircd_log(LOG_ERROR, "[BUG] trying to close fd #%d in fd table, but MAXCONNECTIONS is %d",
 				fd, MAXCONNECTIONS);
-		return;
+		return 0;
 	}
 
 	fde = &fd_table[fd];
@@ -110,7 +110,7 @@ void fd_close(int fd)
 				fd);
 		ircd_log(LOG_ERROR, "[BUG] trying to close fd #%d in fd table, but this FD isn't reported open",
 				fd);
-		return;
+		return 0;
 	}
 
 	befl = fde->backend_flags;
@@ -121,6 +121,17 @@ void fd_close(int fd)
 	/* only notify the backend if it is actively tracking the FD */
 	if (befl)
 		fd_refresh(fd);
+	
+	return 1;
+}
+
+void fd_close(int fd)
+{
+	FDEntry *fde;
+	unsigned int befl;
+
+	if (!fd_unmap(fd))
+		return;
 
 	CLOSE_SOCK(fd);
 }

src/res.c

@@ -105,6 +105,15 @@ static void unrealdns_sock_state_cb(void *data, ares_socket_t fd, int read, int
 {
 	int selflags = 0;
 
+	if (!read && !write)
+	{
+		/* Socket is going to be closed *BY C-ARES*..
+		 * so don't call fd_close() but fd_unmap().
+		 */
+		fd_close(fd);
+//		return;
+	}
+	
 	if (read)
 		selflags |= FD_SELECT_READ;