linux-kernel - Re: [PATCH net-next v5 04/10] net: psample: allow using rate as probability

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <BB7EF7B1-1237-4EA9-AD05-C36563A3BCA3@redhat.com>
Date: Wed, 26 Jun 2024 16:28:12 +0200
From: Eelco Chaudron <echaudro@...hat.com>
To: Adrian Moreno <amorenoz@...hat.com>
Cc: netdev@...r.kernel.org, aconole@...hat.com, horms@...nel.org,
 i.maximets@....org, dev@...nvswitch.org, Yotam Gigi <yotam.gi@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 04/10] net: psample: allow using rate as
 probability

On 25 Jun 2024, at 22:51, Adrian Moreno wrote:

> Although not explicitly documented in the psample module itself, the
> definition of PSAMPLE_ATTR_SAMPLE_RATE seems inherited from act_sample.
>
> Quoting tc-sample(8):
> "RATE of 100 will lead to an average of one sampled packet out of every
> 100 observed."
>
> With this semantics, the rates that we can express with an unsigned
> 32-bits number are very unevenly distributed and concentrated towards
> "sampling few packets".
> For example, we can express a probability of 2.32E-8% but we
> cannot express anything between 100% and 50%.
>
> For sampling applications that are capable of sampling a decent
> amount of packets, this sampling rate semantics is not very useful.
>
> Add a new flag to the uAPI that indicates that the sampling rate is
> expressed in scaled probability, this is:
> - 0 is 0% probability, no packets get sampled.
> - U32_MAX is 100% probability, all packets get sampled.
>
> Signed-off-by: Adrian Moreno <amorenoz@...hat.com>

Acked-by: Eelco Chaudron <echaudro@...hat.com>