From: "Theodore Ts'o" <tytso@MIT.EDU>
Date: Tue, 31 Oct 1995 11:52:56 +0800
To: "Josh M. Osborne" <stripes@va.pubnix.com>
Subject: Re: /dev/random for FreeBSD [was: Re: /dev/random for Linux]
In-Reply-To: <VAA13893.199510310259@garotte.va.pubnix.com>
Message-ID: <9510310316.AA26268@dcl.MIT.EDU>
MIME-Version: 1.0
Content-Type: text/plain


   Date: Mon, 30 Oct 1995 21:59:14 -0500
   From: "Josh M. Osborne" <stripes@va.pubnix.com>

   When /dev/random doesn't have "enough" enthropy left does reading
   from it return an error, or block?  I would strongly suggest
   blocking, as the non-blocking behavur is not really all that useful.

It acts like many character devices and named pipes in that if there is
no entropy available at all, it blocks.  If there is some entropy
available, but not enough, it returns what is available.  (A subsequent
read will then block, since no entropy will then be available.)

Actually, what's currently in Linux doesn't work precisely like this,
but it will soon.  After talking a number of people on both sides of the
block vs. non-blocking camp, this seemed to be a suitable compromise.
At least one Major Workstation Vendor is planning on using this behavior
for their /dev/random, to appear in a future OS release.  If we all can
standardize on this behavior, it'll make application writer's jobs that
much easier.

						- Ted