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From: Dan Gora <dg@adax.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: dev@dpdk.org, Mattias Rönnblom <mattias.ronnblom@ericsson.com>,
	 David Marchand <david.marchand@redhat.com>,
	Jerin Jacob <jerinjacobk@gmail.com>
Subject: Re: [dpdk-dev] [PATCH v4 2/2] eal: emulate glibc getentropy for initial random seed
Date: Thu, 23 Apr 2020 14:42:51 -0300
Message-ID: <CAGyogRYOSdkovUkNUnTdvR_-n_7mW6RmWp20itx8nP0GpbxREA@mail.gmail.com> (raw)
In-Reply-To: <20200422193939.20841234@hermes.lan>

On Wed, Apr 22, 2020 at 11:39 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Wed, 22 Apr 2020 20:42:54 -0300
> Dan Gora <dg@adax.com> wrote:
>
> > +     fd = open("/dev/urandom", O_RDONLY);
> > +     if (fd < 0) {
> > +             errno = ENODEV;
> > +             return -1;
> > +     }
> > +
> > +     end = start + length;
> > +     while (start < end) {
> > +             bytes = read(fd, start, end - start);
> > +             if (bytes < 0) {
>
> You are overdoing the complexity here. More error handling is not better.

I've definitely never heard that expression before!

> 1. This should only be called once at startup EINTR is not an issue then
> 2. The amount requested is always returned when using urandom (see man page for random(4))
>
>        The  O_NONBLOCK  flag  has  no effect when opening /dev/urandom.  When calling
>        read(2) for the device /dev/urandom, reads of up to 256 bytes will  return  as
>        many  bytes  as are requested and will not be interrupted by a signal handler.
>        Reads with a buffer over this limit may return less than the requested  number
>        of bytes or fail with the error EINTR, if interrupted by a signal handler.

I didn't just make this up out of whole cloth... This code was lifted,
almost verbatim, from the glibc implementation of getentropy(), which
is the function that we are trying to emulate:

https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/getentropy.c;h=1778632ff1f1fd77019401c3fbaa164c167248b0;hb=92dcaa3e2f7bf0f7f1c04cd2fb6a317df1a4e225

I assumed that they added this error handling for a reason.

Yes, since this function is only called once at startup EINTR should
not be an issue, but if we need to add __rte_getentropy() as a
generic, exported interface later, that error case would already be
taken care of.

thanks
dan

  reply	other threads:[~2020-04-23 17:43 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
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 [this message]
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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