linux-kernel - Re: [RFC PATCH v2 1/7] bpf: Introduce BPF_PROG_TYPE_VNET

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 17 Oct 2023 12:03:48 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Akihiko Odaki <akihiko.odaki@...nix.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        bpf <bpf@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Yuri Benditovich <yuri.benditovich@...nix.com>,
        Andrew Melnychenko <andrew@...nix.com>
Subject: Re: [RFC PATCH v2 1/7] bpf: Introduce BPF_PROG_TYPE_VNET_HASH

On Mon, Oct 16, 2023 at 7:38 PM Jason Wang <jasowang@...hat.com> wrote:
>
> On Tue, Oct 17, 2023 at 7:53 AM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Sun, Oct 15, 2023 at 10:10 AM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
> > >
> > > On 2023/10/16 1:07, Alexei Starovoitov wrote:
> > > > On Sun, Oct 15, 2023 at 7:17 AM Akihiko Odaki <akihiko.odaki@...nix.com> wrote:
> > > >>
> > > >> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > >> index 0448700890f7..298634556fab 100644
> > > >> --- a/include/uapi/linux/bpf.h
> > > >> +++ b/include/uapi/linux/bpf.h
> > > >> @@ -988,6 +988,7 @@ enum bpf_prog_type {
> > > >>          BPF_PROG_TYPE_SK_LOOKUP,
> > > >>          BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> > > >>          BPF_PROG_TYPE_NETFILTER,
> > > >> +       BPF_PROG_TYPE_VNET_HASH,
> > > >
> > > > Sorry, we do not add new stable program types anymore.
> > > >
> > > >> @@ -6111,6 +6112,10 @@ struct __sk_buff {
> > > >>          __u8  tstamp_type;
> > > >>          __u32 :24;              /* Padding, future use. */
> > > >>          __u64 hwtstamp;
> > > >> +
> > > >> +       __u32 vnet_hash_value;
> > > >> +       __u16 vnet_hash_report;
> > > >> +       __u16 vnet_rss_queue;
> > > >>   };
> > > >
> > > > we also do not add anything to uapi __sk_buff.
> > > >
> > > >> +const struct bpf_verifier_ops vnet_hash_verifier_ops = {
> > > >> +       .get_func_proto         = sk_filter_func_proto,
> > > >> +       .is_valid_access        = sk_filter_is_valid_access,
> > > >> +       .convert_ctx_access     = bpf_convert_ctx_access,
> > > >> +       .gen_ld_abs             = bpf_gen_ld_abs,
> > > >> +};
> > > >
> > > > and we don't do ctx rewrites like this either.
> > > >
> > > > Please see how hid-bpf and cgroup rstat are hooking up bpf
> > > > in _unstable_ way.
> > >
> > > Can you describe what "stable" and "unstable" mean here? I'm new to BPF
> > > and I'm worried if it may mean the interface stability.
> > >
> > > Let me describe the context. QEMU bundles an eBPF program that is used
> > > for the "eBPF steering program" feature of tun. Now I'm proposing to
> > > extend the feature to allow to return some values to the userspace and
> > > vhost_net. As such, the extension needs to be done in a way that ensures
> > > interface stability.
> >
> > bpf is not an option then.
> > we do not add stable bpf program types or hooks any more.
>
> Does this mean eBPF could not be used for any new use cases other than
> the existing ones?

It means that any new use of bpf has to be unstable for the time being.

> > If a kernel subsystem wants to use bpf it needs to accept the fact
> > that such bpf extensibility will be unstable and subsystem maintainers
> > can decide to remove such bpf support in the future.
>
> I don't see how it is different from the existing ones.

Can we remove BPF_CGROUP_RUN_PROG_INET_INGRESS hook along
with BPF_PROG_TYPE_CGROUP_SKB program type?
Obviously not.
We can refactor it. We can move it around, but not remove.
That's the difference in stable vs unstable.