netdev - Re: [PATCHv2 bpf-next] samples/bpf: add xdp program on egress for xdp_redirect

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Message-ID: <20201130131020.GC277949@localhost.localdomain>
Date:   Mon, 30 Nov 2020 21:10:20 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Yonghong Song <yhs@...com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: Re: [PATCHv2 bpf-next] samples/bpf: add xdp program on egress for
 xdp_redirect_map

On Mon, Nov 30, 2020 at 10:32:08AM +0100, Jesper Dangaard Brouer wrote:
> > I plan to write a example about vlan header modification based on egress
> > index. I will post the patch later.
> 
> I did notice the internal thread you had with Toke.  I still think it
> will be more simple to modify the Ethernet mac addresses.  Adding a
> VLAN id tag is more work, and will confuse benchmarks.  You are

I plan to only modify the vlan id if there has. If you prefer to modify the
mac address, which way you'd like? Set src mac to egress interface's MAC?

> As Alexei already pointed out, you assignment is to modify the packet
> in the 2nd devmap XDP-prog.  Why: because you need to realize that this
> will break your approach to multicast in your previous patchset.
> (Yes, the offlist patch I gave you, that move running 2nd devmap
> XDP-prog to a later stage, solved this packet-modify issue).

BTW, it looks with your patch, the counter on egress would make more sense.
Should I add the counter after your patch posted?

Thanks
Hangbin