netdev - Re: [PATCH] rtnetlink: expose value from SET_NETDEV_DEVTYPE via IFLA

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Message-ID: <20180830051445.GF2181@nanopsycho>
Date:   Thu, 30 Aug 2018 07:14:45 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>, netdev@...r.kernel.org,
        davem@...emloft.net
Subject: Re: [PATCH] rtnetlink: expose value from SET_NETDEV_DEVTYPE via
 IFLA_DEVTYPE attribute

Wed, Aug 29, 2018 at 05:24:28PM CEST, stephen@...workplumber.org wrote:
>On Wed, 29 Aug 2018 09:18:55 +0200
>Jiri Pirko <jiri@...nulli.us> wrote:
>
>> Tue, Aug 28, 2018 at 10:58:11PM CEST, marcel@...tmann.org wrote:
>> >The name value from SET_NETDEV_DEVTYPE only ended up in the uevent sysfs
>> >file as DEVTYPE= information. To avoid any kind of race conditions
>> >between netlink messages and reading from sysfs, it is useful to add the
>> >same string as new IFLA_DEVTYPE attribute included in the RTM_NEWLINK
>> >messages.
>> >
>> >For network managing daemons that have to classify ARPHRD_ETHER network
>> >devices into different types (like Wireless LAN, Bluetooth etc.), this
>> >avoids the extra round trip to sysfs and parsing of the uevent file.
>> >
>> >Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
>> >---
>> > include/uapi/linux/if_link.h |  2 ++
>> > net/core/rtnetlink.c         | 12 ++++++++++++
>> > 2 files changed, 14 insertions(+)
>> >
>> >diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
>> >index 43391e2d1153..781294972bb4 100644
>> >--- a/include/uapi/linux/if_link.h
>> >+++ b/include/uapi/linux/if_link.h
>> >@@ -166,6 +166,8 @@ enum {
>> > 	IFLA_NEW_IFINDEX,
>> > 	IFLA_MIN_MTU,
>> > 	IFLA_MAX_MTU,
>> >+	IFLA_DEVTYPE,		/* Name value from SET_NETDEV_DEVTYPE */  
>> 
>> This is not something netdev-related. dev->dev.type is struct device_type.
>> This is a generic "device" thing. Incorrect to expose over
>> netdev-specific API. Please use "device" API for this.
>
>There is no device API in netlink. The whole point of this patch is to
>do it in one message. It might be a performance optimization, but I can't
>see how it could be a race condition. Devices set type before registering.

I understand. My point is to avoid exposing generic "struct device"
values over rtnetlink. It mixes apples and oranges.