netdev - Re: [PATCH v2 bpf-next/net 2/8] bpf: Add a bpf hook in __inet

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Message-ID: <CAAVpQUBzWzVgvohLKOTS0U4ay9D29otB619T6O786m9W0YSWtg@mail.gmail.com>
Date: Mon, 25 Aug 2025 14:07:39 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Stanislav Fomichev <stfomichev@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, Stanislav Fomichev <sdf@...ichev.me>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Shakeel Butt <shakeel.butt@...ux.dev>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Neal Cardwell <ncardwell@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Mina Almasry <almasrymina@...gle.com>, Kuniyuki Iwashima <kuni1840@...il.com>, bpf@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v2 bpf-next/net 2/8] bpf: Add a bpf hook in __inet_accept().

On Mon, Aug 25, 2025 at 1:51 PM Stanislav Fomichev <stfomichev@...il.com> wrote:
>
> On 08/25, Kuniyuki Iwashima wrote:
> > We will store a flag in sk->sk_memcg by bpf_setsockopt().
> >
> > For a new child socket, memcg is not allocated until accept(),
> > and the child's sk_memcg is not always the parent's one.
> >
> > For details, see commit e876ecc67db8 ("cgroup: memcg: net: do not
> > associate sock with unrelated cgroup") and commit d752a4986532
> > ("net: memcg: late association of sock to memcg").
> >
> > Let's add a new hook for BPF_PROG_TYPE_CGROUP_SOCK in
> > __inet_accept().
> >
> > This hook does not fail by not supporting bpf_set_retval().
> >
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
>
> And similarly to [0], doing it in sock_ops's BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB
> is not an option because you want to run in the process context instead
> of softirq?

Yes, I considered the hook but ended up adding a new one
in accept(), only when we know sk_memcg is the intended one.


>
> 0: https://lore.kernel.org/netdev/daa73a77-3366-45b4-a770-fde87d4f50d8@linux.dev/