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Date:   Tue, 13 Apr 2021 17:14:43 +0200
From:   Marek Behun <marek.behun@nic.cz>
To:     Tobias Waldekranz <tobias@waldekranz.com>
Cc:     Vladimir Oltean <olteanv@gmail.com>,
        Ansuel Smith <ansuelsmth@gmail.com>, netdev@vger.kernel.org,
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        Jakub Kicinski <kuba@kernel.org>, Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andriin@fb.com>,
        Eric Dumazet <edumazet@google.com>,
        Wei Wang <weiwan@google.com>,
        Cong Wang <cong.wang@bytedance.com>,
        Taehee Yoo <ap420073@gmail.com>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>,
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        Weilong Chen <chenweilong@huawei.com>,
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        Di Zhu <zhudi21@huawei.com>,
        Francis Laniel <laniel_francis@privacyrequired.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC net-next 0/3] Multi-CPU DSA support
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On Tue, 13 Apr 2021 16:46:32 +0200
Tobias Waldekranz <tobias@waldekranz.com> wrote:

> On Tue, Apr 13, 2021 at 02:27, Marek Behun <marek.behun@nic.cz> wrote:
> > On Tue, 13 Apr 2021 01:54:50 +0200
> > Marek Behun <marek.behun@nic.cz> wrote:
> >  
> >> I will look into this, maybe ask some follow-up questions.  
> >
> > Tobias,
> >
> > it seems that currently the LAGs in mv88e6xxx driver do not use the
> > HashTrunk feature (which can be enabled via bit 11 of the
> > MV88E6XXX_G2_TRUNK_MAPPING register).  
> 
> This should be set at the bottom of mv88e6xxx_lag_sync_masks.
> 
> > If we used this feature and if we knew what hash function it uses, we
> > could write a userspace tool that could recompute new MAC
> > addresses for the CPU ports in order to avoid the problem I explained
> > previously...
> >
> > Or the tool can simply inject frames into the switch and try different
> > MAC addresses for the CPU ports until desired load-balancing is reached.
> >
> > What do you think?  
> 
> As you concluded in your followup, not being able to have a fixed MAC
> for the CPU seems weird.
> 
> Maybe you could do the inverse? Allow userspace to set the masks for an
> individual bond/team port in a hash-based LAG, then you can offload that
> to DSA. 

What masks?