netdev - Re: [PATCH RFC net-next 07/20] net/ipv6: Move nexthop data to fib6

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Message-ID: <2d706063-6ffd-5c71-59de-d8f8cf3c5a20@gmail.com>
Date:   Mon, 26 Feb 2018 15:47:55 -0700
From:   David Ahern <dsahern@...il.com>
To:     Wei Wang <weiwan@...gle.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Ido Schimmel <idosch@...sch.org>, roopa@...ulusnetworks.com,
        Eric Dumazet <eric.dumazet@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH RFC net-next 07/20] net/ipv6: Move nexthop data to fib6_nh

On 2/26/18 3:28 PM, Wei Wang wrote:
> On Sun, Feb 25, 2018 at 11:47 AM, David Ahern <dsahern@...il.com> wrote:
>> Introduce fib6_nh structure and move nexthop related data from
>> rt6_info and rt6_info.dst to fib6_nh. References to dev, gateway or
>> lwtstate from a FIB lookup perspective are converted to use fib6_nh;
>> datapath references to dst version are left as is.
>>
> 
> My understanding is that after your whole patch series, sibling routes
> will still have their own fib6_info. Does it make sense to make this
> fib6_nh as an array in fib6_info so that sibling routes will share
> fib6_info but will have their own fib6_nh as a future improvement? It
> matches ipv4 behavior. And I think it will make the sibling route
> handling code easier?

I was not planning to. IPv6 allowing individual nexthops to be added and
deleted is very convenient. I do agree the existing sibling route
linkage makes the code much more complicated than it needs to be.

After this set, I plan to send patches for nexthops as separate objects
- which will have an impact on how multipath routes are done. With
nexthop objects there will be 1 prefix route pointing to a nexthop
object that is multipath (meaning it points in turn to a series of
nexthop objects). This provides the simplification (no sibling linkage)
without losing the individual nexhtop add / delete option.