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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jakub Kicinski <kuba@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	ast@kernel.org, john.fastabend@gmail.com, netdev@vger.kernel.org,
	bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next 2/6] bpf, net: rework cookie generator as per-cpu one
Date: Fri, 25 Sep 2020 17:15:17 +0200	[thread overview]
Message-ID: <c9fee768-4f35-e596-001b-2e2a0e4f48a1@gmail.com> (raw)
In-Reply-To: <20200925080020.013165a0@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>



On 9/25/20 5:00 PM, Jakub Kicinski wrote:
                    unlikely((val & (COOKIE_LOCAL_BATCH - 1)) == 0)) {
> 
> Can we reasonably assume we won't have more than 4k CPUs and just
> statically divide this space by encoding CPU id in top bits?

This might give some food to side channel attacks, since this would
give an indication of cpu that allocated the id.

Also, I hear that some distros enabled 8K cpus.


  reply	other threads:[~2020-09-25 15:15 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-24 18:21 [PATCH bpf-next 0/6] Various BPF helper improvements Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 1/6] bpf: add classid helper only based on skb->sk Daniel Borkmann
2020-09-25 14:46   ` Jakub Kicinski
2020-09-25 15:35     ` Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 2/6] bpf, net: rework cookie generator as per-cpu one Daniel Borkmann
2020-09-24 18:58   ` Eric Dumazet
2020-09-24 22:03     ` Daniel Borkmann
2020-09-25  7:49       ` Eric Dumazet
2020-09-25  9:26         ` Daniel Borkmann
2020-09-25 15:00       ` Jakub Kicinski
2020-09-25 15:15         ` Eric Dumazet [this message]
2020-09-25 15:31           ` Jakub Kicinski
2020-09-25 15:45             ` Eric Dumazet
2020-09-24 18:21 ` [PATCH bpf-next 3/6] bpf: add redirect_neigh helper as redirect drop-in Daniel Borkmann
2020-09-24 22:12   ` David Ahern
2020-09-24 22:19     ` Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 4/6] bpf, libbpf: add bpf_tail_call_static helper for bpf programs Daniel Borkmann
2020-09-24 20:53   ` Andrii Nakryiko
2020-09-24 22:17     ` Daniel Borkmann
2020-09-25 15:42       ` Daniel Borkmann
2020-09-25 15:52         ` Daniel Borkmann
2020-09-25 16:50           ` Andrii Nakryiko
2020-09-25 19:52             ` Daniel Borkmann
2020-09-25  6:13   ` Yonghong Song
2020-09-24 18:21 ` [PATCH bpf-next 5/6] bpf, selftests: use bpf_tail_call_static where appropriate Daniel Borkmann
2020-09-24 19:25   ` Maciej Fijalkowski
2020-09-24 22:03     ` Daniel Borkmann
2020-09-24 18:21 ` [PATCH bpf-next 6/6] bpf, selftests: add redirect_neigh selftest Daniel Borkmann

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