netdev - Re: [PATCH net-next 1/3] net/sched: Introduce action ct

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Date:   Thu, 13 Jun 2019 11:00:37 +0000
From:   Kevin Darbyshire-Bryant <kevin@...byshire-bryant.me.uk>
To:     Paul Blakey <paulb@...lanox.com>
CC:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>, Roi Dayan <roid@...lanox.com>,
        Yossi Kuperman <yossiku@...lanox.com>,
        Oz Shlomo <ozsh@...lanox.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Aaron Conole <aconole@...hat.com>,
        Zhike Wang <wangzhike@...com>,
        Rony Efraim <ronye@...lanox.com>,
        "nst-kernel@...hat.com" <nst-kernel@...hat.com>,
        John Hurley <john.hurley@...ronome.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Justin Pettit <jpettit@....org>
Subject: Re: [PATCH net-next 1/3] net/sched: Introduce action ct



> On 11 Jun 2019, at 16:15, Paul Blakey <paulb@...lanox.com> wrote:
> 
> 
> On 6/11/2019 4:59 PM, Toke Høiland-Jørgensen wrote:
>> Paul Blakey <paulb@...lanox.com> writes:
>> 
>>> Allow sending a packet to conntrack and set conntrack zone, mark,
>>> labels and nat parameters.
>> How is this different from the newly merged ctinfo action?
>> 
>> -Toke
> 
> Hi,
> 
> ctinfo does one of two very specific things,
> 
> 1) copies DSCP values that have been placed in the firewall conntrack
> mark back into the IPv4/v6 diffserv field
> 
> 2) copies the firewall conntrack mark to the skb's mark field (like
> act_connmark)

It can do both at the same time if required, taking advantage of the single
conntrack entry lookup for both packet/skb mangling operations, but this isn’t
relevant to the discussion really.

> 
> Originally ctinfo action was named conndscp (then conntrack, which is
> what our ct shorthand stands for).
> 
> We also talked about merging both at some point, but they seem only
> coincidentally related.
> 
> don't know how it was then be agreed to be named ctinfo suggesting it
> does something else but the above.

I’m a newbie around here so trying to fit in.  conndscp did one thing, then it
suggested that as it was doing a similar lookup to act_connmark that the connmark
functionality could also be integrated.  There was a brief flirtation with a
new ‘act ct’ it sort of ‘fell out’ that they were only semi-related in function
by name only.

conndscp was clearly the wrong name for what act_ctinfo had become, amalgamating
two functions, so I thought it’s a “conntrack information lookup/user/extractor/mangler’
and thought ‘ctinfo’ was as good as anything - and nobody screamed and AFAIK no
kittens died :-)

But as a newbie around here I’m happy to fit in with whatever consensus is reached
as long as it is reached.

> 
> This action sends packets to conntrack, configures nat, and doesn't get
> "info" from conntrack, while the ctinfo already expects packets to be
> passed conntrack
> 
> by some other kernel mechanism.
> 

Yeah, one is pulling, the other is pushing :-)

Kevin


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