netdev - Re: [RFC PATCH net-next V2 0/6] XDP rx handler

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Message-ID: <ae0e09a1-a20a-a2fc-36a0-82e109216bf4@gmail.com>
Date:   Fri, 17 Aug 2018 15:15:01 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jason Wang <jasowang@...hat.com>,
        Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ast@...nel.org, daniel@...earbox.net, mst@...hat.com
Subject: Re: [RFC PATCH net-next V2 0/6] XDP rx handler

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.