netdev - Re: [PATCH net-next v3 0/4] net: ipv6: Improve user experience with multipath routes

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Message-ID: <b5948673-c30d-c4b3-1fcb-b5e984480b4a@6wind.com>
Date:   Mon, 30 Jan 2017 18:03:38 +0100
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     David Ahern <dsa@...ulusnetworks.com>,
        Roopa Prabhu <roopa@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next v3 0/4] net: ipv6: Improve user experience with
 multipath routes

Le 30/01/2017 à 16:23, David Ahern a écrit :
> On 1/30/17 4:07 AM, Nicolas Dichtel wrote:
>> Le 29/01/2017 à 19:02, David Ahern a écrit :
>> [snip]
>>> Data centers are moving to L3, and multipath is a big part of that. Anyone who looks at ip -6 route enough knows it gets painful mentally pulling the individual routes into a single one.
>> I agree, but it's only an iproute2 problem. iproute2 could group routes to have
>> a better output, there is no need to have a kernel patch for this ;-)
>>
> 
> iproute2 is not the only rtnetlink user. The comment above uses ip show as an example. libnl has a workaround for IPv6 to update route objects versus replacing them - unnecessary complexity that does not need to replicated to iproute2, Quagga/FRR or python libraries implementing rtnetlink. Really, RTA_MULTIPATH support in notifications should have been added when multipath support was added to the IPv6. Patch 3 is mostly a refactoring of rt6_fill_node to fill in nexthop information. This could have been done 4+ years ago when RTA_MULTIPATH route adds was added to the stack.
> 
Like I said, I fully agree that RTA_MULTIPATH is better for the dump. For the
notifications, I'm not convinced. I did not this 4 years ago on purpose ;-)

I don't think that ipv4 is the right reference because the implementation is
really different. ipv6 is more flexible and this implies differences in the
notifications.