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From: Luca Boccassi <bluca@debian.org>
To: Dan Gora <dg@adax.com>, Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	David Marchand <david.marchand@redhat.com>,
	 Jerin Jacob <jerinjacobk@gmail.com>
Subject: Re: [dpdk-dev] [PATCH 2/2] eal: resolve getentropy at run time for random seed
Date: Thu, 23 Apr 2020 11:04:16 +0100
Message-ID: <db596f278ed58965d90b5a94da9b5226bcef1ec5.camel@debian.org> (raw)
In-Reply-To: <CAGyogRb=uGbBsVgMycgLy93EzLafP78xjOX910Yct_1AoxZORg@mail.gmail.com>

On Wed, 2020-04-22 at 17:35 -0300, Dan Gora wrote:
> On Wed, Apr 22, 2020 at 5:14 PM Mattias Rönnblom
> <mattias.ronnblom@ericsson.com> wrote:
> > On 2020-04-22 19:44, Dan Gora wrote:
> > > On Wed, Apr 22, 2020 at 5:28 AM Mattias Rönnblom
> > > <mattias.ronnblom@ericsson.com> wrote:
> > > > On 2020-04-21 21:54, Dan Gora wrote:
> > > > > The getentropy() function was introduced into glibc v2.25 and so is
> > > > > not available on all supported platforms.  Previously, if DPDK was
> > > > > compiled (using meson) on a system which has getentropy(), it would
> > > > > introduce a dependency on glibc v2.25 which would prevent that binary
> > > > > from running on a system with an older glibc.  Similarly if DPDK was
> > > > > compiled on a system which did not have getentropy(), getentropy()
> > > > > could not be used even if the execution system supported it.
> > > > > 
> > > > > Introduce a new static function, __rte_getentropy() which will try to
> > > > > resolve the getentropy() function dynamically using dlopen()/dlsym(),
> > > > > returning failure if the getentropy() function cannot be resolved or
> > > > > if it fails.
> > > > 
> > > > Two other options: providing a DPDK-native syscall wrapper for
> > > > getrandom(), or falling back to reading /dev/urandom. Have you
> > > > considered any of those two options? If so, why do you prefer
> > > > dlopen()/dlsym()?
> > > I didn't give any thought at all to using /dev/urandom.  The goal was
> > > not really to change how the thing worked, just to remove the
> > > dependency on glibc 2.25.
> > 
> > /dev/urandom is basically only a different interface to the same
> > underlying mechanism.

This is not the whole story though - while the end result when all
works is the same, there are important differences in getting there.
There's a reason a programmatic interface was added - it's just better
in general.
Just to name one - opening files has implications for LSMs like
SELinux. You now need a specific policy to allow it, which means
applications that upgrade from one version of DPDK to the next will
break.

In general, I do not think we should go backwards. The programmatic
interface to the random pools are good and we should use them by
default - of course by all means add fallbacks to urandom if they are
not available.

But as Stephen said glibc generally does not support compiling on new +
running on old - so if it's not this that breaks, it will be something
else.

-- 
Kind regards,
Luca Boccassi

  reply	other threads:[~2020-04-23 10:04 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-21 19:54 [dpdk-dev] [PATCH 0/2] eal: choose initial PRNG seed source at runtime Dan Gora
2020-04-21 19:54 ` [dpdk-dev] [PATCH 1/2] eal: check for rdseed at run time for random seed Dan Gora
2020-04-22  8:22   ` Mattias Rönnblom
2020-04-21 19:54 ` [dpdk-dev] [PATCH 2/2] eal: resolve getentropy " Dan Gora
2020-04-21 21:03   ` Stephen Hemminger
2020-04-21 21:08     ` Dan Gora
2020-04-22  8:28   ` Mattias Rönnblom
2020-04-22 17:44     ` Dan Gora
2020-04-22 20:14       ` Mattias Rönnblom
2020-04-22 20:35         ` Dan Gora
2020-04-23 10:04           ` Luca Boccassi [this message]
2020-04-23 17:38             ` Dan Gora
2020-04-27 12:44               ` Luca Boccassi
2020-04-27 16:57                 ` Dan Gora
2020-04-30  8:41                   ` Luca Boccassi
2020-04-30 20:43                     ` Dan Gora
2020-05-01 10:33                       ` Luca Boccassi
2020-05-01 21:05                         ` Dan Gora
2020-05-04  8:04                           ` Mattias Rönnblom
2020-05-04 14:13                             ` Dan Gora
2020-05-04 14:19                               ` Dan Gora
2020-06-02  5:10                                 ` Dan Gora
2020-06-09 15:37                                   ` Dan Gora
2020-06-10  8:15                                     ` Thomas Monjalon
2020-06-10  8:33                                       ` Luca Boccassi
2020-06-10  8:07                               ` Thomas Monjalon
2020-04-23 12:36           ` Mattias Rönnblom
2020-04-23 17:27             ` Dan Gora
2020-04-21 20:41 ` [dpdk-dev] [PATCH v2 0/2] eal: choose initial PRNG seed source at runtime Dan Gora
2020-04-21 20:41   ` [dpdk-dev] [PATCH v2 1/2] eal: check for rdseed at run time for random seed Dan Gora
2020-04-21 20:41   ` [dpdk-dev] [PATCH v2 2/2] eal: resolve getentropy " Dan Gora
2020-04-22 18:15 ` [dpdk-dev] [PATCH v3 0/2] eal: choose initial PRNG seed source at runtime Dan Gora
2020-04-22 18:15   ` [dpdk-dev] [PATCH v3 1/2] eal: check for rdseed at run time for random seed Dan Gora
2020-04-22 18:15   ` [dpdk-dev] [PATCH v3 2/2] eal: resolve getentropy " Dan Gora
2020-04-22 23:42 ` [dpdk-dev] [PATCH v4 0/2] eal: choose initial PRNG seed source at runtime Dan Gora
2020-04-22 23:42   ` [dpdk-dev] [PATCH v4 1/2] eal: check for rdseed at run time for random seed Dan Gora
2020-04-22 23:42   ` [dpdk-dev] [PATCH v4 2/2] eal: emulate glibc getentropy for initial " Dan Gora
2020-04-23  2:39     ` Stephen Hemminger
2020-04-23 17:42       ` Dan Gora
2020-06-29  9:30     ` Mattias Rönnblom
2020-06-29 17:57       ` Dan Gora
2020-06-29 20:57         ` Mattias Rönnblom
2020-06-29  9:32   ` [dpdk-dev] [PATCH v4 0/2] eal: choose initial PRNG seed source at runtime Mattias Rönnblom
2020-06-29 18:01     ` Dan Gora
2020-06-29 18:04       ` Dan Gora
2020-06-29 21:05       ` Mattias Rönnblom
2020-06-29 21:14         ` Dan Gora

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