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Subject: Re: bpf_sk_cgroup_id is not available in tracepoints
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To: Ivan Babrou <ivan@cloudflare.com>
Cc: bpf <bpf@vger.kernel.org>, kernel-team <kernel-team@cloudflare.com>,
 Alexei Starovoitov <ast@kernel.org>, Andrii Nakryiko <andrii@kernel.org>,
 Daniel Borkmann <daniel@iogearbox.net>, Stanislav Fomichev <sdf@google.com>,
 Martin KaFai Lau <kafai@fb.com>
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	lindbergh.monkeyblade.net

On 8/1/23 2:59 PM, Ivan Babrou wrote:
> I noticed that bpf_sk_cgroup_id is not available in a tracepoint (it
> is only available in cgroup related skb filters), even though I can
> easily do what it does manually:
> 
> u64 cgroup_id = sk->sk_cgrp_data.cgroup->kn->id;
> 
> It seems to me that bpf_sk_cgroup_id and similar functions should be
> added to bpf_base_func_proto (unless there's a better place).

This will make it available to all tracing progs. How to ensure doing 
'sk->sk_cgrp_data.cgroup->kn->id' is safe in all traceable context? so please 
don't do that.

bpf will handle the exception when the bpf prog reads 'sk->...' (eg. in case sk 
is an invalid ptr), so please keep using it for tracing programs.