netdev - Re: [PATCH bpf-next v7 05/11] bpf: implement BPF_PROG_QUERY for BPF_LSM

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Date:   Wed, 25 May 2022 19:50:41 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH bpf-next v7 05/11] bpf: implement BPF_PROG_QUERY for BPF_LSM_CGROUP

On Wed, May 25, 2022 at 6:23 PM Martin KaFai Lau <kafai@...com> wrote:
>
> On Wed, May 25, 2022 at 05:03:40PM -0700, Martin KaFai Lau wrote:
> > > But the problem with going link-only is that I'd have to teach bpftool
> > > to use links for BPF_LSM_CGROUP and it brings a bunch of problems:
> > > * I'd have to pin those links somewhere to make them stick around
> > > * Those pin paths essentially become an API now because "detach" now
> > >   depends on them?
> > > * (right now it automatically works with the legacy apis without any
> > > changes)
> > It is already the current API for all links (tracing, cgroup...).  It goes
> > away (detach) with the process unless it is pinned.  but yeah, it will
> > be a new exception in the "bpftool cgroup" subcommand only for
> > BPF_LSM_CGROUP.
> >
> > If it is an issue with your use case, may be going back to v6 that extends
> > the query bpf_attr with attach_btf_id and support both attach API ?
> [ hit sent too early... ]
> or extending the bpf_prog_info as you also mentioned in the earlier reply.
> It seems all have their ups and downs.

I'm thinking on putting everything I need into bpf_prog_info and
exporting a list of attach_flags in prog_query (as it's done here in
v7 + add attach_btf_obj_id).
I'm a bit concerned with special casing bpf_lsm_cgroup even more if we
go with a link-only api :-(
I can definitely also put this info into bpf_link_info, but I'm not
sure what's Andrii's preference? I'm assuming he was suggesting to do
either bpf_prog_info or bpf_link_info, but not both?