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From: Stanislav Fomichev <sdf@fomichev.me>
To: Song Liu <liu.song.a23@gmail.com>
Cc: Stanislav Fomichev <sdf@google.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Petar Penkov <ppenkov@google.com>
Subject: Re: [PATCH bpf-next 1/2] bpf/flow_dissector: add mode to enforce global BPF flow dissector
Date: Wed, 2 Oct 2019 14:31:21 -0700	[thread overview]
Message-ID: <20191002213121.GB3223377@mini-arch> (raw)
In-Reply-To: <CAPhsuW6ywq5yySKjtdna8rXGBWdUyFgxQuy0+=2-gReXSTQ=ow@mail.gmail.com>

On 10/02, Song Liu wrote:
> On Wed, Oct 2, 2019 at 10:36 AM Stanislav Fomichev <sdf@google.com> wrote:
> >
> > Always use init_net flow dissector BPF program if it's attached and fall
> > back to the per-net namespace one. Also, deny installing new programs if
> > there is already one attached to the root namespace.
> > Users can still detach their BPF programs, but can't attach any
> > new ones (-EPERM).
> >
> > Cc: Petar Penkov <ppenkov@google.com>
> > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > ---
> >  Documentation/bpf/prog_flow_dissector.rst |  3 +++
> >  net/core/flow_dissector.c                 | 11 ++++++++++-
> >  2 files changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/bpf/prog_flow_dissector.rst b/Documentation/bpf/prog_flow_dissector.rst
> > index a78bf036cadd..4d86780ab0f1 100644
> > --- a/Documentation/bpf/prog_flow_dissector.rst
> > +++ b/Documentation/bpf/prog_flow_dissector.rst
> > @@ -142,3 +142,6 @@ BPF flow dissector doesn't support exporting all the metadata that in-kernel
> >  C-based implementation can export. Notable example is single VLAN (802.1Q)
> >  and double VLAN (802.1AD) tags. Please refer to the ``struct bpf_flow_keys``
> >  for a set of information that's currently can be exported from the BPF context.
> > +
> > +When BPF flow dissector is attached to the root network namespace (machine-wide
> > +policy), users can't override it in their child network namespaces.
> > diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> > index 7c09d87d3269..494e2016fe84 100644
> > --- a/net/core/flow_dissector.c
> > +++ b/net/core/flow_dissector.c
> > @@ -115,6 +115,11 @@ int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
> >         struct bpf_prog *attached;
> >         struct net *net;
> >
> > +       if (rcu_access_pointer(init_net.flow_dissector_prog)) {
> > +               /* Can't override root flow dissector program */
> > +               return -EPERM;
> 
> Maybe -EBUSY is more accurate?
I'm not sure, -EBUSY to me means that I can retry and (maybe) eventually
will succeed. Maybe return -EEXIST? At least it gives a hint that BPF
flow dissector is already there and retrying won't help. Thoughts?

> Thanks,
> Song

  reply	other threads:[~2019-10-02 21:31 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 17:33 [PATCH bpf-next 0/2] " Stanislav Fomichev
2019-10-02 17:33 ` [PATCH bpf-next 1/2] " Stanislav Fomichev
2019-10-02 20:57   ` Song Liu
2019-10-02 21:31     ` Stanislav Fomichev [this message]
2019-10-02 23:29   ` Andrii Nakryiko
2019-10-03  1:43     ` Stanislav Fomichev
2019-10-03  2:47       ` Andrii Nakryiko
2019-10-03 16:01         ` Stanislav Fomichev
2019-10-03 16:26           ` Andrii Nakryiko
2019-10-03 17:45             ` John Fastabend
2019-10-03 17:58               ` Stanislav Fomichev
2019-10-02 17:33 ` [PATCH bpf-next 2/2] selftests/bpf: add test for BPF flow dissector in the root namespace Stanislav Fomichev

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