netdev - Re: [Patch net 3/3] team: use a larger struct for mac address

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Message-ID: <CAM_iQpUGSy7My+hLXhsreq-8wPEdAKzNkQRzu-aiP5nkk+wSdw@mail.gmail.com>
Date:   Wed, 26 Apr 2017 10:28:12 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jarod Wilson <jarod@...hat.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [Patch net 3/3] team: use a larger struct for mac address

On Wed, Apr 26, 2017 at 9:46 AM, Jarod Wilson <jarod@...hat.com> wrote:
> On 2017-04-26 12:11 PM, Cong Wang wrote:
>>
>> On Wed, Apr 26, 2017 at 8:55 AM, Jarod Wilson <jarod@...hat.com> wrote:
>>>
>>>
>>> We already have struct sockaddr_storage that could be used throughout
>>> this
>>> set as well. We just converted a few pieces of the bonding driver over to
>>> using it for better support of ipoib bonds, via commit
>>> faeeb317a5615076dff1ff44b51e862e6064dbd0. Might be better to just use
>>> that
>>> in both bonding and team, rather than having different per-driver
>>> structs,
>>> or Yet Another Address Storage implementation.
>>
>>
>> Technically, struct sockaddr_storage is not enough either, given the
>> max is MAX_ADDR_LEN. This is why I gave up on sockaddr_storage.
>
>
> Wait, what? Am I missing something? MAX_ADDR_LEN is 32, and sockaddr_storage
> is a #define for __kernel_sockaddr_storage, which has it's __data member
> defined as being of size 128 - sizeof(unsigned short).

My bad, I thought it is same with sizeof(in6addr) without looking into it.
The question is, why do we waste 126 - 32 = 94 bytes on stack to just
use struct sockaddr_storage?

I totally understand we want a unified struct, but we already redefine
it in multiple places in tree...