bzero cmsgbuf before using it, silences valgrind warnings.

henning@ "sure"

return ERANGE instead of ENOMEM, so callers can differentiate real oom
from this case where we have a static buffer and cant realloc.

ok phessler, claudio, reyk

limits.h rather than sys/param.h

original bug diagnosed by sthen: automatic retry in msgbuf_write on
EAGAIN causes spinning.

fix from claudio:
"Let msgbuf_write return -1 with errno EAGAIN. The users then must
check if this was the

original bug diagnosed by sthen: automatic retry in msgbuf_write on
EAGAIN causes spinning.

fix from claudio:
"Let msgbuf_write return -1 with errno EAGAIN. The users then must
check if this was the case and readd the event or poll again. The
current handling in the imsg code is wrong for sure."

ok gilles

show more ...

in imsg_read() avoid calling recvmsg() if we detect that we will be short
on descriptors, this can be achieved thanks to the new getdtablecount()
system call. application may provide a reserve count

in imsg_read() avoid calling recvmsg() if we detect that we will be short
on descriptors, this can be achieved thanks to the new getdtablecount()
system call. application may provide a reserve count to ensure that the
recvmsg() call is not called when they don't have enough descriptors to
work properly.

change the API so that transient errors that can be retried immediately
are retried within the function right away, whereas transient errors for
which the application may want to take action will set errno to EAGAIN.

ok deraadt@ and henning@

show more ...

Move imsg into libutil and add a man page.

Minor bump for libutil.

Previous versions of this diff and man page looked at by various people.

"you should just commit" deraadt