TCP/IP stack:
* mutt prepares to exec the smtp client: it forks and closes all
file descriptors
* when the next networking syscall is done, rumpclient detects that
the communication fd returned EBADF and does a reconnect,
gets descriptor 0 for the socket and descriptor 1 for kqueue
* mutt opens the mail file and implicitly assumes it'll get 0-2,
but in fact gets 2-4
* mutt execs the smtp agent which tries to read the mail from
stdin (rumpclient communication socket) and fails
Even if mutt correctly did dup2() things would go south when trying
to communicate with the kernel server the next time, since rumpclient
would actually be talking with some mail body instead (well, it
could work, but in that case you'd need to write *really* weird
mails ;).
Hence, prevent rumpclient from using the special fd's 0-2 for its
purposes.
Should fix mutt problem reported by Alexander Nasonov.
82aa883702