In make-tcp-socket, close stream (not just fd) when connect fails

[xrme]

In #504, we see a problem where a socket is getting unexpectedly closed.

See the comments in the issue for details.

It might make sense to rewrite make-tcp-stream so that it doesn't create a stream at all until we have successfully created and configured the OS-level socket.

[gmpalter]

Here's an alternative that doesn't involve pulling the logic of %socket-connect out into make-tcp-socket. It catches the error signaled by %socket-connect, closes the stream and resets fd, and then lets the signaling continue.

diff --git a/library/sockets.lisp b/library/sockets.lisp
index b653b203..cd4a545f 100644
--- a/library/sockets.lisp
+++ b/library/sockets.lisp
@@ -685,7 +685,18 @@ the socket is not connected."))
                                              :port remote-port
                                              :allow-other-keys t
                                              keys))))
-               (%socket-connect fd socket-address timeout-in-milliseconds)))
+               (handler-bind (((or socket-creation-error socket-error)
+                                (lambda (c)
+                                  (declare (ignore c))
+                                  ;; When connect fails, the fd is no longer usable,
+                                  ;; and must be closed.  Because we've already made
+                                  ;; a stream with this fd, close the fd by closing
+                                  ;; the stream.
+                                  (close socket)
+                                  ;; Don't try to close fd again in the unwind-protect
+                                  ;; cleanup form.
+                                  (setq fd -1))))
+                 (%socket-connect fd socket-address timeout-in-milliseconds))))
            (setq fd -1)
            socket))
     (unless (< fd 0)