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

[Jason Wang]

On 2018å08æ16æ 12:05, Alexei Starovoitov wrote:
> 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.

David said the port can have arbitrary layers stacked on it. So if we 
try to enumerate them before making forwarding decisions purely by BPF 
program, it looks to me a loop is needed here.

Thanks