netdev - Re: [PATCH net-next v3] net: ipv4: add support for ECMP hash policy choice

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Message-ID: <0c0473f7-beab-ea87-6dde-77aa345258ff@cumulusnetworks.com>
Date:   Tue, 14 Mar 2017 17:45:06 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Stephen Hemminger <stephen@...workplumber.org>,
        Roopa Prabhu <roopa@...ulusnetworks.com>
Cc:     David Miller <davem@...emloft.net>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>, jkbs@...hat.com,
        Eric Dumazet <edumazet@...gle.com>,
        Peter Christensen <pch@...bogen.com>
Subject: Re: [PATCH net-next v3] net: ipv4: add support for ECMP hash policy
 choice

On 3/14/17 5:27 PM, Stephen Hemminger wrote:
> On Tue, 14 Mar 2017 15:38:40 -0700
> Roopa Prabhu <roopa@...ulusnetworks.com> wrote:
> 
>>>>>>> That's what my initial version did, but this was discussed during NetConf in Seville
>>>>>>> and it was decided that it's best to make a global sysctl, thus the change.  
>>>>>>
>>>>>> Correct, we discussed this, and we all agreed to only have a sysctl for now.  
>>>>>
>>>>> Why? If you are going to have private discussions please post the rationale
>>>>> in public.  
>>>>
>>>> Stephen, is there any reason to have a per ecmp route multipath algo
>>>> selection ?.
>>>> All platforms have a global multipath selection algo. I also don't see
>>>> routing daemons ready or willing to specify a per ecmp route multipath
>>>> selection algo attribute.  
>>>
>>> There is no compelling reason to make the attribute per route. But the
>>> issue is more that configuration through sysctl's is problematic. It doesn't
>>> fit into the standard API paradigm. Sysctl's are like routing patches not
>>> part of the real CLI. Trying to trap sysctl's for things like switchedev
>>> offload is particularly problematic. I can see the case for either way,
>>> and don't have a fixed opinion.  
>>
>> ok. understand the switchdev offload part. It was that way in the past...but
>> today you can listen to sysctl updates on the netconf netlink channel.
>> it works pretty well.
> 
> Is there another patch to add the NETCONFA_ECMP support?
> 

does userspace care?

switchdev uses notifiers for in kernel notification of FIB changes
(routes and rules).