netdev - Re: [PATCH bpf-next 1/2] bpf: add get_netns

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Message-ID: <96dbd7df-1fa7-4caa-a52c-372d696e0f38@linux.dev>
Date: Thu, 27 Feb 2025 12:32:43 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Mahe Tardy <mahe.tardy@...il.com>
Cc: daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
 andrii@...nel.org, jolsa@...nel.org, bpf@...r.kernel.org,
 Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/2] bpf: add get_netns_cookie helper to tracing
 programs

On 2/27/25 10:28 AM, Mahe Tardy wrote:
> This is needed in the context of Cilium and Tetragon to retrieve netns
> cookie from hostns when traffic leaves Pod, so that we can correlate
> skb->sk's netns cookie.
> 
> Signed-off-by: Mahe Tardy <mahe.tardy@...il.com>
> ---
> This is a follow-up of c221d3744ad3 ("bpf: add get_netns_cookie helper
> to cgroup_skb programs") and eb62f49de7ec ("bpf: add get_netns_cookie
> helper to tc programs"), adding this helper respectively to cgroup_skb
> and tcx programs.
> 
> I looked up a patch doing a similar thing c5dbb89fc2ac ("bpf: Expose
> bpf_get_socket_cookie to tracing programs") and there was an item about
> "sleepable context". It seems it indeed concerns tracing and LSM progs
> from reading 1e6c62a88215 ("bpf: Introduce sleepable BPF programs"). Is
> this needed here?

Regarding sleepable, I think the bpf_get_netns_cookie_sock is only reading, 
should be fine.

The immediate question is whether sock_net(sk) must be non-NULL for tracing.