netdev - Re: [PATCH net] ipvlan: call dev_change

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Date:   Wed, 20 Jun 2018 10:45:39 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Hangbin Liu <liuhangbin@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Stefano Brivio <sbrivio@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Mahesh Bandewar <maheshb@...gle.com>
Subject: Re: [PATCH net] ipvlan: call dev_change_flags when reset ipvlan mode

On Tue, Jun 19, 2018 at 10:31 PM, David Miller <davem@...emloft.net> wrote:
> From: Hangbin Liu <liuhangbin@...il.com>
> Date: Wed, 20 Jun 2018 11:22:54 +0800
>
>> The only case dev_change_flags() return an err is when we change IFF_UP flag.
>> Since we only set/reset IFF_NOARP, do you think we still need to check the
>> return value?
>
> It is bad to try and take shortcuts on error handling using assumptions
> like that.
>
> If dev_change_flags() is adjusted to return error codes in more
> situations, nobody is going to remember to undo your "optimziation"
> here.
>
> Please check for errors, thank you.

Yeah. Also since the notifier is triggered in this case:

        if (dev->flags & IFF_UP &&
            (changes & ~(IFF_UP | IFF_PROMISC | IFF_ALLMULTI | IFF_VOLATILE))) {
                struct netdev_notifier_change_info change_info = {
                        .info = {
                                .dev = dev,
                        },
                        .flags_changed = changes,
                };

                call_netdevice_notifiers_info(NETDEV_CHANGE, &change_info.info);
        }

the return value of call_netdevice_notifiers_info() isn't captured
either, but it should be.