netdev - Re: [patch net-next RFC 04/12] rtnl: expose physical switch id for particular device

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Message-ID: <20140826083223.GQ1878@nanopsycho.lan>
Date:	Tue, 26 Aug 2014 10:32:23 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, nhorman@...driver.com,
	andy@...yhouse.net, tgraf@...g.ch, dborkman@...hat.com,
	ogerlitz@...lanox.com, jesse@...ira.com, pshelar@...ira.com,
	azhou@...ira.com, ben@...adent.org.uk, stephen@...workplumber.org,
	jeffrey.t.kirsher@...el.com, vyasevic@...hat.com,
	xiyou.wangcong@...il.com, john.r.fastabend@...el.com,
	edumazet@...gle.com, jhs@...atatu.com, sfeldma@...ulusnetworks.com,
	f.fainelli@...il.com, roopa@...ulusnetworks.com,
	linville@...driver.com, dev@...nvswitch.org, jasowang@...hat.com,
	ebiederm@...ssion.com, nicolas.dichtel@...nd.com,
	ryazanov.s.a@...il.com, buytenh@...tstofly.org,
	aviadr@...lanox.com, nbd@...nwrt.org, alexei.starovoitov@...il.com,
	Neil.Jerram@...aswitch.com, ronye@...lanox.com
Subject: Re: [patch net-next RFC 04/12] rtnl: expose physical switch id for
 particular device

Fri, Aug 22, 2014 at 09:08:39PM CEST, john.fastabend@...il.com wrote:
>On 08/21/2014 09:18 AM, Jiri Pirko wrote:
>>The netdevice represents a port in a switch, it will expose
>>IFLA_PHYS_SWITCH_ID value via rtnl. Two netdevices with the same value
>>belong to one physical switch.
>>
>>Signed-off-by: Jiri Pirko <jiri@...nulli.us>
>
>What is the relation between phys_port_id and phys_switch_id?
>
>phys_port_id was intended to identify a set of ports that belong
>to a single uplink port,
>
>
>	eth0     eth1    eth2   eth3      (host facing)
>          |       |       |      |
>          |       |       |      |
>      +---+-------+-------+------+---+
>      |      embedded switch         |
>      +------------------------------+
>                     |
>                    MAC                   (network)
>
>In the NIC case there is a simply switch with a port to the
>network which we currently don't represent with a netdev. Any
>netdev where the phys_switch_id's are behind the same embedded
>switch.

I think that MAC in your picture should be represented as netdev (switch
port). Also, the other ports connected to eth0-3 should be represented
as netdevs. All of these + the MAC should have the same switch id.

>
>In the switch id case we are indicating the port is attached to
>the same embedded switch as well.
>
>         eth0 eth1 eth2 eth3
>          |    |    |    |
>     +----+----+----+----+----+
>     |         switch         |
>     +----+----+----+----+----+
>
>but they do not share an uplink port? So in this case each ethx
>has a unique phys_port_id but the same phys_switch_id?

Yes.

>
>In the first case both phys_port_id and phys_switch_id should
>be equal for all interfaces correct?

See above. In case of embedded switch on nic I believe that eth0-eth3
shoud have the same port_id and no switch_id as they are not ports of
switch (the counterparts in switch (marked as "+" on your picture are
the switch ports)

>
>Is that clear/useful at all? We need to document this somewhere
>if/when the patches are submitted otherwise I doubt we will get it
>consistently right across drivers. There could for example be
>somewhat strange devices with virtual functions hanging off of the
>switch.

I will extend the documentation to my "net: introduce generic switch
devices support" patch.

>
>Thanks,
>John
>
>-- 
>John Fastabend         Intel Corporation
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