netdev - Re: [PATCH net-next v5 09/22] ethtool: implement EVENT notifications

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Message-ID: <20190328091639.GK14297@nanopsycho>
Date:   Thu, 28 Mar 2019 10:16:39 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Andrew Lunn <andrew@...n.ch>,
        John Linville <linville@...driver.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 09/22] ethtool: implement EVENT notifications

Thu, Mar 28, 2019 at 07:41:43AM CET, mkubecek@...e.cz wrote:
>On Wed, Mar 27, 2019 at 07:14:43PM -0700, Florian Fainelli wrote:
>> 
>> 
>> On 3/27/2019 7:14 AM, Michal Kubecek wrote:
>> > On Wed, Mar 27, 2019 at 02:04:28PM +0100, Jiri Pirko wrote:
>> >> Mon, Mar 25, 2019 at 06:08:21PM CET, mkubecek@...e.cz wrote:
>> >>> Three types of netlink notifications are introduced:
>> >>>
>> >>>  - ETHA_EVENT_NEWDEV to notify about newly registered network devices
>> >>>  - ETHA_EVENT_DELDEV to notify about unregistered network devices
>> >>>  - ETHA_EVENT_RENAMEDEV to notify about renamed network device
>> >>>
>> >>> The notifications are triggered by NETDEV_REGISTER, NETDEV_UNREGISTER and
>> >>> NETDEV_CHANGENAME notifiers.
>> >>>
>> >>> These notifications are intended for applications and daemons monitoring
>> >>> ethtool events to allow updating the list of existing devices without
>> >>> having to open another socket for rtnetlink.
>> >>
>> >> Wait. You duplicate events that are already going out through RTNETLINK.
>> >> App should open RTNETLINK in order to get those. Other apps are doing
>> >> that too. I don't think that duplications like this are desirable :/
>> > 
>> > Is there a way to filter or at least recognize these events when using
>> > rtnetlink? I couldn't find any. The only way seems to be getting every
>> > RTM_NEWLINK message (there can be quite a lot of those), always perform
>> > the lookup in my device list and recognize what happened - only to
>> > almost always find that nothing interesting. It is possible, sure, but
>> > I would really like to avoid it.
>> 
>> I am afraid you are right about this, would adding a filtering
>> capability specifically for this in rtnetlink be a better route?
>
>Maybe we could add new IFLA_EVENT_* values and use IFLA_EVENT to mark
>RTM_NEWLINK messages announcing "new device" and "device rename". That
>way, monitoring application would still need to parse all RTM_NEWLINK
>messages but it would be able to recognize which announce a change in
>device list without a lookup in its structures.

Hmm, that sounds good.

>
>Michal