sockets and close-on-exec (F_SETFD)

["Fifer, Eric" <EFifer at sanwaint dot com>]

I have some socket code that does the typical series of
socket, bind, listen, accept, connect, and close calls.
The sockets are marked for close-on-exec with
fcntl(fd, F_SETFD, 1).  Unfortunately, in some circumstances,
not entirely deterministic, a bind fails with EINVAL
(which according to MSDN means the socket is already
bound to an address).

After a lot of tracing, I found that the close-on-exec flag
uses code in set_inheritance that does a CloseHandle (after
a DuplicateHandle) instead of a closesocket.  In my code,
handles end up getting reused because they have been previously
closed (either with closesocket or CloseHandle).  However,
bind seems to be extra-fussy and unless the reused handle
was closed with a closesocket it fails with WSAEINVAL.

I added some code so that set_inheritance can call
closesocket if a handle is a socket and my problem
goes away.  Similarly, if I don't use close-on-exec
the problem goes away.

Does this make any sense?

Thanks.

Eric Fifer