netdev - Re: [PATCHv3 net-next] bonding: 3ad: send ifinfo notify when mux state changed

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Date: Fri, 28 Jun 2024 11:10:27 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Jay Vosburgh <jay.vosburgh@...onical.com>
Cc: Nikolay Aleksandrov <razor@...ckwall.org>,
	Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
	Andy Gospodarek <andy@...yhouse.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Ido Schimmel <idosch@...dia.com>, Jiri Pirko <jiri@...nulli.us>,
	Amit Cohen <amcohen@...dia.com>
Subject: Re: [PATCHv3 net-next] bonding: 3ad: send ifinfo notify when mux
 state changed

On Thu, Jun 27, 2024 at 07:24:10AM -0700, Jay Vosburgh wrote:
> Hangbin Liu <liuhangbin@...il.com> wrote:
> >Ah.. Yes, that's a sad fact :(
> 
> 	There are basically two paths that will change the LACP state
> that's passed up via netlink (the aggregator ID, and actor and partner
> oper port states): bond_3ad_state_machine_handler(), or incoming
> LACPDUs, which call into ad_rx_machine().  Administrative changes to the

Ah, thanks, I didn't notice this. I will also enable lacp notify
in ad_rx_machine().

> bond will do it too, like adding or removing interfaces, but those
> originate in user space and aren't happening asynchronously.
> 
> 	If you want (almost) absolute reliability in communicating every
> state change for the state machine and LACPDU processing, I think you'd
> have to (a) create an object with the changed state, (b) queue it
> somewhere, then (c) call a workqueue event to process that queue out of
> line.

Hmm... This looks too complex. If we store all the states. A frequent flashing
may consume the memory. If we made a limit for the queue, we may still loosing
some state changes.

I'm not sure which way is better.

> 
> >> It all depends on what are the requirements.
> >> 
> >> An uglier but lockless alternative would be to poll the slave's sysfs oper state,
> >> that doesn't require any locks and would be up-to-date.
> >
> >Hmm, that's a workaround, but the admin need to poll the state frequently as
> >they don't know when the state will change.
> >
> >Hi Jay, are you OK to add this sysfs in bonding?
> 
> 	I think what Nik is proposing is for your userspace to poll the
> /sys/class/net/${DEV}/operstate.

OK. There are 2 scenarios I got.

1) the local user want to get the local/partner state and make sure not
send pkts before they are in DISTRIBUTING state to avoid pkts drop, Or vice
versa. Only checking link operstate or up/down status is not enough.

2) the admin want to get the switch/partner status via LACP status incase
the switch is crashed.

Do you have any suggestion for the implementation?

Thanks
Hangbin