netdev - Re: [net-next PATCH] hsr: Simplify code for announcing HSR nodes timer setup

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Message-ID: <20240430145243.34b82105@wsk>
Date: Tue, 30 Apr 2024 14:52:43 +0200
From: Lukasz Majewski <lukma@...x.de>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>, Casper
 Andersson <casper.casan@...il.com>, Andrew Lunn <andrew@...n.ch>, Eric
 Dumazet <edumazet@...gle.com>, Vladimir Oltean <olteanv@...il.com>, "David
 S. Miller" <davem@...emloft.net>, Oleksij Rempel <o.rempel@...gutronix.de>,
 Tristram.Ha@...rochip.com, Sebastian Andrzej Siewior
 <bigeasy@...utronix.de>, Ravi Gunasekaran <r-gunasekaran@...com>, Simon
 Horman <horms@...nel.org>, Nikita Zhandarovich <n.zhandarovich@...tech.ru>,
 Murali Karicheri <m-karicheri2@...com>, Jiri Pirko <jiri@...nulli.us>, Dan
 Carpenter <dan.carpenter@...aro.org>, Ziyang Xuan
 <william.xuanziyang@...wei.com>, Shigeru Yoshida <syoshida@...hat.com>,
 "Ricardo B. Marliere" <ricardo@...liere.net>, linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH] hsr: Simplify code for announcing HSR nodes
 timer setup

Hi Jakub,

> On Mon, 29 Apr 2024 12:09:04 +0200 Lukasz Majewski wrote:
> > > if the
> > > timer is already running we'll mess with the spacing of the
> > > frames, no?    
> > 
> > When NETDEV_CHANGE is trigger for reason different than carrier (or
> > port state) change and the netif_oper_up() returns true, the period
> > for HSR supervisory frames (i.e. HSR_ANNOUNCE_INTEVAL) would be
> > violated.
> > 
> > What are here the potential threads?  
> 
> Practically speaking I'm not sure if anyone uses any of the weird
> IFF_* flags, but they are defined in uAPI (enum net_device_flags) and
> I don't see much validation so presumably it's possible to flip them.

Ok, I see.

Then - what would you recommend instead? The approach with manual
checking the previous state has described drawbacks.

I've poked around kernel sources and it looks like the netif_oper_up()
is used in conjunction with netif_running():

netif_running(dev) && netif_oper_up(dev)

so, IMHO the netif_running(dev) shall be added to the condition.

In the uapi/include/linux/if.h there are serveral IF_OPER_* flags
defined. It looks to me that only for the IF_OPER_UP the HSR interface
shall send announcement supervisory frames. With other conditions it
shall be turned off.

Best regards,

Lukasz Majewski

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