netdev - Re: bond procfs hw addr prints

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Date:   Mon, 13 Mar 2017 22:06:06 -0400
From:   Jarod Wilson <jarod@...hat.com>
To:     Jay Vosburgh <jay.vosburgh@...onical.com>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: bond procfs hw addr prints

On 2017-03-13 8:28 PM, Jay Vosburgh wrote:
> Jarod Wilson <jarod@...hat.com> wrote:
>
>> I've got a bug report for someone using a Intel OPA devices in a bond, and
>> it appears these devices have a hardware address length of 20, opposed to
>> the typical 6 on ethernet. When they dump /proc/net/bonding/bondX, it only
>> prints the first 6 of the address, per %pM and mac_address_string(), while
>> sysfs for the interface does print the right thing, since it uses
>> sysfs_print_mac(), which takes a length argument.
>
> 	This (20 octet MAC length) is true for any Infiniband device.
>
>> So the question is... What's the best route to take here? Expand %pM to
>> support variable length hardware addresses? Use sysfs_* in procfs?
>> Reinvent the wheel? Nothing I've tinkered with just yet feels very clean,
>> on top of not actually working yet. :)
>
> 	sysfs_format_mac (not _print_mac) uses "%*phC", len, addr in its
> format string.  Perhaps that format would be a better choice than %pM
> for this case?

Ah, I'd failed to fully grasp how %phC worked, had actually tried it w/o 
the * in there, and only the first char of the addr was printing. 
Working on an updated version that uses %*phC properly, which does look 
like the way to go here. (Didn't help that I was also looking at an 
older codebase that didn't have the sysfs_format_mac de-duplication). 
I'll try to have a tested patch in flight tomorrow.

-- 
Jarod Wilson
jarod@...hat.com