netdev - Re: bond procfs hw addr prints

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Message-ID: <88a9205f-363c-a6da-8db7-ee301bc080a1@redhat.com>
Date:   Mon, 13 Mar 2017 23:26:55 -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 10:06 PM, Jarod Wilson wrote:
> 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.

Hm... One problem I'm seeing: perm_hwaddr[ETH_ALEN], 
partner_system[ETH_ALEN], mac_addr_value[ETH_ALEN]. Looks like just 
about all places where storage for only ETH_ALEN is available needs to 
be adjusted to maybe MAX_ADDR_LEN?

So I have something tested that uses %*phC, but only on ethernet 
hardware so far, and I forsee bad juju for infiniband, because of that 
ETH_ALEN issue...

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