From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Ahern <dsahern@gmail.com>
Subject: Re: [RFC PATCH net-next V2 0/6] XDP rx handler
Date: Fri, 17 Aug 2018 15:15:01 -0600
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Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        ast@kernel.org, daniel@iogearbox.net, mst@redhat.com
To: Jason Wang <jasowang@redhat.com>,
        Jesper Dangaard Brouer <jbrouer@redhat.com>
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On 8/15/18 9:34 PM, Jason Wang wrote:
> 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?

netdev_for_each_upper_dev_rcu

BPF helpers allow programs to do lookups in kernel tables, in this case
the ability to find an upper device that would receive the packet.