netdev - Re: [PATCH RFC net-next 1/4] ipv4: fib_rules: support match on sport, dport and ip proto

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Date:   Tue, 13 Feb 2018 08:36:43 -0800
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     David Miller <davem@...emloft.net>
Cc:     Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
        David Ahern <dsa@...ulusnetworks.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Subject: Re: [PATCH RFC net-next 1/4] ipv4: fib_rules: support match on sport,
 dport and ip proto

On Tue, Feb 13, 2018 at 8:34 AM, David Miller <davem@...emloft.net> wrote:
> From: Roopa Prabhu <roopa@...ulusnetworks.com>
> Date: Tue, 13 Feb 2018 08:19:35 -0800
>
>> - Regardless of this series, I think we should optimize ip rules or
>> have a new implementation of policy based routing. happy to hear about
>> possible options here:
>>          - optimize the existing implementation (have there been
>> previous discussions on possible options ?)
>>          - @netdev2.2, I did outline a possible option for tc to
>> provide an l3 hook for policy based routing (people were ok with this
>> and I was told more tc hooks were in the works).
>>             tc was a choice mainly because of all its existing match
>> options (flower for example). Will that help ?
>>          - We should have an ebpf accelerated implementation
>> regardless for people to use it if they want to scale rules
>
> The problem is that arbitrary prefixing in the rules.  That prevents
> O(1) algorithms from being used to maintain the table.
>
> If they were all just non-prefixed keys we could do a hash table or
> similar.

ah, got it.

>
> I guess we could do a trie (on saddr) to a (on daddr) trie (like the
> ipv6 subtrees do), but that's a lot of complexity just for fib rules.
>

agreed.