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Date: Wed, 2 Oct 2019 13:57:07 -0700 From: Song Liu <liu.song.a23@...il.com> To: Stanislav Fomichev <sdf@...gle.com> Cc: Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, "David S . Miller" <davem@...emloft.net>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Petar Penkov <ppenkov@...gle.com> Subject: Re: [PATCH bpf-next 1/2] bpf/flow_dissector: add mode to enforce global BPF flow dissector On Wed, Oct 2, 2019 at 10:36 AM Stanislav Fomichev <sdf@...gle.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@...gle.com> > Signed-off-by: Stanislav Fomichev <sdf@...gle.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? Thanks, Song
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