linux-kernel - Re: [PATCH] bpf: call get_random

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Message-ID: <730fd355-ad86-a8fa-6583-df23d39e0c23@iogearbox.net>
Date:   Mon, 5 Dec 2022 23:21:51 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>
Subject: Re: [PATCH] bpf: call get_random_u32() for random integers

On 12/5/22 7:15 PM, Jason A. Donenfeld wrote:
> Since BPF's bpf_user_rnd_u32() was introduced, there have been three
> significant developments in the RNG: 1) get_random_u32() returns the
> same types of bytes as /dev/urandom, eliminating the distinction between
> "kernel random bytes" and "userspace random bytes", 2) get_random_u32()
> operates mostly locklessly over percpu state, 3) get_random_u32() has
> become quite fast.

Wrt "quite fast", do you have a comparison between the two? Asking as its
often used in networking worst case on per packet basis (e.g. via XDP), would
be useful to state concrete numbers for the two on a given machine.

> So rather than using the old clunky Tausworthe prandom code, just call
> get_random_u32(), which should fit BPF uses perfectly.