Date: Wed, 1 Apr 2015 13:52:04 +0200 From: Mateusz Guzik <mjguzik@gmail.com> To: Gleb Smirnoff <glebius@FreeBSD.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r280955 - in head/sys: modules/notrandom dev/notrandom Message-ID: <20150401115204.GB16649@dft-labs.eu> In-Reply-To: <20150401114313.GZ64665@FreeBSD.org> References: <20150401113628.GA16649@dft-labs.eu> <20150401114313.GZ64665@FreeBSD.org>
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On Wed, Apr 01, 2015 at 02:43:13PM +0300, Gleb Smirnoff wrote: > On Wed, Apr 01, 2015 at 01:36:28PM +0200, Mateusz Guzik wrote: > M> Author: mjg > M> Date: Wed Apr 1 13:37:00 2015 > M> New Revision: 280955 > M> URL: https://svnweb.freebsd.org/changeset/base/280955 > M> > M> Log: > M> Add /dev/notrandom > M> > M> notrandom provides fast and reliable not random numbers. > M> > M> This was added in an effort to increase feature-compatiblity with > M> Solaris 10. > M> > M> See http://www.brendangregg.com/Specials/notrandom.c for Solaris > M> implementation. > M> > M> Reviewed-by: Bruce Schneier (ok, not really) > M> MFC after: 1 week > > What is the difference of this implementation with /dev/zero? > /dev/zero returns 0s, while notrandom was implemented to return 7s. We could e.g. symlink /dev/notrandom to /dev/zero, but that would break compatiblity with Solaris apps depending on this functionality. It could also introduce hard-to-debug problems. After all, readers get a different value than they expect. Given that we have some parts of Solaris merged (zfs, dtrace) and work with open source forks on these technologies, I think we should diverge only when necessary. As a side note I'm surprised with the choice of 7. I would expect 3, no more, no less. 3 would be the number returned, and the number readers receive would be 3. -- Mateusz Guzik <mjguzik gmail.com>
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