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Date:   Wed, 15 Aug 2018 21:05:18 -0700
From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     David Ahern <dsahern@gmail.com>,
        Jesper Dangaard Brouer <jbrouer@redhat.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        ast@kernel.org, daniel@iogearbox.net, mst@redhat.com
Subject: Re: [RFC PATCH net-next V2 0/6] XDP rx handler
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On Thu, Aug 16, 2018 at 11:34:20AM +0800, Jason Wang wrote:
> > Nothing about the topology is hard coded. The idea is to mimic a
> > hardware pipeline and acknowledging that a port device can have an
> > arbitrary layers stacked on it - multiple vlan devices, bonds, macvlans, etc
> 
> I may miss something but BPF forbids loop. Without a loop how can we make
> sure all stacked devices is enumerated correctly without knowing the
> topology in advance?

not following. why do you need a loop to implement macvlan as an xdp prog?
if loop is needed, such algorithm is not going to scale whether
it's implemented as bpf program or as in-kernel c code.