On 2017-03-13 10:06 PM, Jarod Wilson wrote:

On 2017-03-13 8:28 PM, Jay Vosburgh wrote:

quoted

Jarod Wilson [off-list ref] wrote:

quoted

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.

quoted

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@redhat.com