netdev - Re: [PATCH bpf-next 4/7] bpf: allow to retrieve cgroup v1 classid from v2 hooks

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Message-ID: <3e519e0e-aa52-67a5-98f6-0e259745e400@iogearbox.net>
Date:   Sat, 28 Mar 2020 02:56:37 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Martynas Pumputis <m@...bda.lt>,
        Joe Stringer <joe@...d.net.nz>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next 4/7] bpf: allow to retrieve cgroup v1 classid
 from v2 hooks

On 3/28/20 1:41 AM, Andrii Nakryiko wrote:
> On Fri, Mar 27, 2020 at 9:00 AM Daniel Borkmann <daniel@...earbox.net> wrote:
>>
>> Today, Kubernetes is still operating on cgroups v1, however, it is
>> possible to retrieve the task's classid based on 'current' out of
>> connect(), sendmsg(), recvmsg() and bind-related hooks for orchestrators
>> which attach to the root cgroup v2 hook in a mixed env like in case
>> of Cilium, for example, in order to then correlate certain pod traffic
>> and use it as part of the key for BPF map lookups.
> 
> Have you tried getting this classid directly from task_struct in your
> BPF program with vmlinux.h and CO-RE? Seems like it should be pretty
> straightforward and not requiring a special BPF handler just for that?

To answer both questions (5/7 and this one) in the same mail here: my
understanding is that this would require to install additional tracing
programs on these hooks instead of being able to integrate them into [0]
for usage out of sock_addr and sock progs (similar as they are available
as well from tc from skb)?

Thanks,
Daniel

   [0] https://github.com/cilium/cilium/blob/master/bpf/bpf_sock.c