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

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Message-ID: <57E0D8FD.2040407@cumulusnetworks.com>
Date:   Mon, 19 Sep 2016 23:36:45 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Jiri Pirko <jiri@...nulli.us>
CC:     Patrick Ruddy <pruddy@...cade.com>,
        "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>,
        Sven-Thorsten Dietrich <sven@...cade.com>
Subject: Re: [net-next PATCH] net: netlink messages for HW addr programming

On 9/19/16, 10:49 PM, Jiri Pirko wrote:
> Tue, Sep 20, 2016 at 07:31:27AM CEST, roopa@...ulusnetworks.com wrote:
>> 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.
> They are l2 addresses, they should be threated accordingly. Am I missing
> something?
>
>
>> 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 ?
> This shoul go under ip link I believe. "ip addr" is for l3.
>
>
yes, ...my initial comment was the same (two new attributes to cover UC and MC addresses).
patrick had it in link first..and there were some suggestions on doing it in addr. he is ok with either.

My questions were to make sure we don't lose anything ...by adding it under link.
there is no external way to add addrs to uc and mc lists today. hence would be nice
to cover that case as well when we are exposing the dev uc and mc lists to userspace.
and ofcourse ..it does not have to be RTM_NEWADDR ...
RTM_NEWLINK can cover it both ways also.

so, if stephen has no major objections, we can still go with attributes in RTM_*LINK.