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Subject: Re: [PATCH net-next v2 4/4] bonding: balance ICMP echoes in layer3+4
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To:     Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
        Matteo Croce <mcroce@redhat.com>, netdev@vger.kernel.org
Cc:     Jay Vosburgh <j.vosburgh@gmail.com>,
        Veaceslav Falico <vfalico@gmail.com>,
        Andy Gospodarek <andy@greyhouse.net>,
        "David S . Miller" <davem@davemloft.net>,
        Stanislav Fomichev <sdf@google.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Song Liu <songliubraving@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Paul Blakey <paulb@mellanox.com>, linux-kernel@vger.kernel.org
References: <20191029135053.10055-1-mcroce@redhat.com>
 <20191029135053.10055-5-mcroce@redhat.com>
 <5be14e4e-807f-486d-d11a-3113901e72fe@cumulusnetworks.com>
From:   Eric Dumazet <eric.dumazet@gmail.com>
Message-ID: <576a4a96-861b-6a86-b059-6621a22d191c@gmail.com>
Date:   Tue, 29 Oct 2019 14:03:08 -0700
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On 10/29/19 11:35 AM, Nikolay Aleksandrov wrote:

> Hi Matteo,
> Wouldn't it be more useful and simpler to use some field to choose the slave (override the hash
> completely) in a deterministic way from user-space ?
> For example the mark can be interpreted as a slave id in the bonding (should be
> optional, to avoid breaking existing setups). ping already supports -m and
> anything else can set it, this way it can be used to do monitoring for a specific
> slave with any protocol and would be a much simpler change.
> User-space can then implement any logic for the monitoring case and as a minor bonus
> can monitor the slaves in parallel. And the opposite as well - if people don't want
> these balanced for some reason, they wouldn't enable it.
> 

I kind of agree giving user more control. But I do not believe we need to use the mark
(this might be already used by other layers)

TCP uses sk->sk_hash to feed skb->hash.

Anything using skb_set_owner_w() is also using sk->sk_hash if set.

So presumably we could add a generic SO_TXHASH socket option to let user space
read/set this field.