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Date:   Tue, 13 Apr 2021 02:27:30 +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,
        "David S. Miller" <davem@davemloft.net>,
        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>,
        zhang kai <zhangkaiheb@126.com>,
        Weilong Chen <chenweilong@huawei.com>,
        Roopa Prabhu <roopa@cumulusnetworks.com>,
        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 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).

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?

Marek