netdev - Re: [PATCH 1/3] net: add a new NETDEV

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAGVrzcahRhYJM-1KcNDOoekKCetSZCN67hHQ0fgjndehZ=9EUw@mail.gmail.com>
Date:	Tue, 20 Aug 2013 16:30:48 +0100
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	netdev <netdev@...r.kernel.org>, amwang <amwang@...hat.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Stephen Hemminger <stephen@...workplumber.org>,
	kaber <kaber@...sh.net>, David Miller <davem@...emloft.net>,
	vyasevic <vyasevic@...hat.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH 1/3] net: add a new NETDEV_CHANGEROOM event type

2013/8/20 Johannes Berg <johannes@...solutions.net>:
> On Tue, 2013-08-20 at 13:45 +0100, Florian Fainelli wrote:
>
>>  /**
>> + *   dev_set_headroom - Change device needed headroom
>> + *   @dev: device
>> + *   @new_headroom: new headroom size
>> + *
>> + *   Change the network device headroom space.
>> + */
>> +int dev_set_headroom(struct net_device *dev, unsigned short new_headroom)
>
> It seems that you need to invoke these under RTNL, might be worth
> documenting that.

Good point, yes.

>
> Also, maybe it would be worth doing it in one call? If you need to
> change both, then you'd end up calling the notifier twice, which is less
> efficient?

I have mixed feelings about this. I do not expect changing the
headroom/tailroom to be in a hot-path, and we would need to have a
name such as dev_set_head_and_tailroom() or something that clearly
states that it operates on both quantities. Looking at the subsystems
and drivers, there are quite a lot of users which only set one or the
other, occasionaly both before registration.

> I suppose you could make them 'int' arguments and reserve -1
> for no changes, or just require both new values to be given (if doing
> this at all.)

What I like about keeping them separate is that we can use the
"native" storage type that is used in struct net_device, and have
compile-time checking of this.
-- 
Florian
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html