linux-kernel - Re: [PATCH net-next v2 4/4] bonding: balance ICMP echoes in layer3+4 mode

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Message-ID: <a7ef0f1b-e7f5-229c-3087-6eaed9652185@cumulusnetworks.com>
Date:   Tue, 29 Oct 2019 20:41:49 +0200
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Matteo Croce <mcroce@...hat.com>, netdev@...r.kernel.org
Cc:     Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S . Miller" <davem@...emloft.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Paul Blakey <paulb@...lanox.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 4/4] bonding: balance ICMP echoes in layer3+4
 mode

On 29/10/2019 20:35, Nikolay Aleksandrov wrote:
> On 29/10/2019 15:50, Matteo Croce wrote:
>> The bonding uses the L4 ports to balance flows between slaves. As the ICMP
>> protocol has no ports, those packets are sent all to the same device:
>>
>>     # tcpdump -qltnni veth0 ip |sed 's/^/0: /' &
>>     # tcpdump -qltnni veth1 ip |sed 's/^/1: /' &
>>     # ping -qc1 192.168.0.2
>>     1: IP 192.168.0.1 > 192.168.0.2: ICMP echo request, id 315, seq 1, length 64
>>     1: IP 192.168.0.2 > 192.168.0.1: ICMP echo reply, id 315, seq 1, length 64
>>     # ping -qc1 192.168.0.2
>>     1: IP 192.168.0.1 > 192.168.0.2: ICMP echo request, id 316, seq 1, length 64
>>     1: IP 192.168.0.2 > 192.168.0.1: ICMP echo reply, id 316, seq 1, length 64
>>     # ping -qc1 192.168.0.2
>>     1: IP 192.168.0.1 > 192.168.0.2: ICMP echo request, id 317, seq 1, length 64
>>     1: IP 192.168.0.2 > 192.168.0.1: ICMP echo reply, id 317, seq 1, length 64
>>
>> But some ICMP packets have an Identifier field which is
>> used to match packets within sessions, let's use this value in the hash
>> function to balance these packets between bond slaves:
>>
>>     # ping -qc1 192.168.0.2
>>     0: IP 192.168.0.1 > 192.168.0.2: ICMP echo request, id 303, seq 1, length 64
>>     0: IP 192.168.0.2 > 192.168.0.1: ICMP echo reply, id 303, seq 1, length 64
>>     # ping -qc1 192.168.0.2
>>     1: IP 192.168.0.1 > 192.168.0.2: ICMP echo request, id 304, seq 1, length 64
>>     1: IP 192.168.0.2 > 192.168.0.1: ICMP echo reply, id 304, seq 1, length 64
>>
>> Aso, let's use a flow_dissector_key which defines FLOW_DISSECTOR_KEY_ICMP,
> 
> Also ?
> 
>> so we can balance pings encapsulated in a tunnel when using mode encap3+4:
>>
>>     # ping -q 192.168.1.2 -c1
>>     0: IP 192.168.0.1 > 192.168.0.2: GREv0, length 102: IP 192.168.1.1 > 192.168.1.2: ICMP echo request, id 585, seq 1, length 64
>>     0: IP 192.168.0.2 > 192.168.0.1: GREv0, length 102: IP 192.168.1.2 > 192.168.1.1: ICMP echo reply, id 585, seq 1, length 64
>>     # ping -q 192.168.1.2 -c1
>>     1: IP 192.168.0.1 > 192.168.0.2: GREv0, length 102: IP 192.168.1.1 > 192.168.1.2: ICMP echo request, id 586, seq 1, length 64
>>     1: IP 192.168.0.2 > 192.168.0.1: GREv0, length 102: IP 192.168.1.2 > 192.168.1.1: ICMP echo reply, id 586, seq 1, length 64
>>
>> Signed-off-by: Matteo Croce <mcroce@...hat.com>
>> ---
>>  drivers/net/bonding/bond_main.c | 77 ++++++++++++++++++++++++++++++---
>>  1 file changed, 70 insertions(+), 7 deletions(-)
>>
> 
> 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.
> 

Ooh I just noticed you'd like to balance replies as well. Nevermind

> Or maybe I've misunderstood why this change is needed. :)
> It would actually be nice to include the use-case which brought this on
> in the commit message.
> 
> Cheers,
>  Nik
>