netdev - Re: [net-next PATCH] net: netlink messages for HW addr programming

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Message-ID: <57E0C9AF.4090406@cumulusnetworks.com>
Date:   Mon, 19 Sep 2016 22:31:27 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Patrick Ruddy <pruddy@...cade.com>
CC:     "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Luca Boccassi <lboccass@...cade.com>,
        "alexander.h.duyck@...el.com" <alexander.h.duyck@...el.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        Sven-Thorsten Dietrich <sven@...cade.com>
Subject: Re: [net-next PATCH] net: netlink messages for HW addr programming

On 9/19/16, 7:46 AM, Patrick Ruddy wrote:
> On Sun, 2016-09-18 at 07:51 -0700, Roopa Prabhu wrote:
>> On 9/15/16, 9:48 AM, Patrick Ruddy wrote:
>>> Add RTM_NEWADDR and RTM_DELADDR netlink messages with family
>>> AF_UNSPEC to indicate interest in specific unicast and multicast
>>> hardware addresses. These messages are sent when addresses are
>>> added or deleted from the appropriate interface driver.
>>> Added AF_UNSPEC GETADDR function to allow the netlink notifications
>>> to be replayed to avoid loss of state due to application start
>>> ordering or restart.
>>>
>>> Signed-off-by: Patrick Ruddy <pruddy@...cade.com>
>>> ---
>> RTM_NEWADDR and RTM_DELADDR are not used to add these entries to the kernel.
>> so, it seems a bit wrong to use RTM_NEWADDR and RTM_DELADDR to notify them to
>> userspace and also to request a special dump of these addresses.
>>
>> This could just be a new nested netlink attribute in the existing link dump ?
> Hi Roopa
>
> Thanks for the review. I did initially code this using NEW/DEL/GET_LINK
> messages but was asked to change to to ADDR messages by Stephen
> Hemminger (cc'd). 
>
> However I agree that these addresses fall between the LINK and ADDR
> areas so I'm happy to change this if we can reach some consensus on the
> format.
>
ok, thanks for the history. yes, they do lie in a weird spot.
the general convention for other rtnl registrations seems to be
AF_UNSPEC family means include all supported families. thats where this seems a bit odd.

On the other hand, one reason I see where using RTM_*ADDR will be useful for this is if we wanted
to provide a way to add these uc and mc address via ip addr add in the future.
ip addr add <lladdr> dev eth0

Does this patch allow that in the future ?

also, will these l2 addresses now show up in 'ip addr show' output ?.

thanks,
Roopa