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

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
Date: Wed, 15 Aug 2018 21:05:18 -0700	[thread overview]
Message-ID: <20180816040517.7vjm4bwxosyzvapu@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <2792239a-ed3b-d66e-0c1c-e99455311eff@redhat.com>

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.