netdev - Allow bpf_perf_event_output to access packet data

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Message-ID: <CACAyw98SbTciw9n5=ANSQNgFc9hD41=Az2qxLnGBE3YdDMMvUQ@mail.gmail.com>
Date:   Fri, 7 Sep 2018 15:56:15 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     netdev@...r.kernel.org
Subject: Allow bpf_perf_event_output to access packet data

Re-sent due to HTML e-mail mess up, apologies.

---------- Forwarded message ----------
From: Lorenz Bauer <lmb@...udflare.com>
Date: 7 September 2018 at 15:53
Subject: Allow bpf_perf_event_output to access packet data
To: netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>

Hello list,

I'm attempting to use bpf_perf_event_output to do packet sampling from XDP.

The code basically runs before our other XDP code, does a
perf_event_output with the full packet (for now) and then tail calls
into DDoS mitigation, etc.

I've just discovered that perf_event_output isn't allowed to access
packet data by the verifier. Is this something that could be allowed?

Best
Lorenz

-- 
Lorenz Bauer  |  Systems Engineer
25 Lavington St., London SE1 0NZ

www.cloudflare.com