netdev - Re: [PATCH] net: dev_forward_skb(): Scrub packet's per-netns info only when crossing netns

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Message-ID: <e653a52e-6a7d-49c9-aec6-6bc6437819c6@default>
Date:   Thu, 15 Mar 2018 09:35:51 -0700 (PDT)
From:   Liran Alon <liran.alon@...cle.com>
To:     <shmulik.ladkani@...il.com>
Cc:     <netdev@...r.kernel.org>, <daniel@...earbox.net>,
        <mrv@...atatu.com>, <davem@...emloft.net>,
        <linux-kernel@...r.kernel.org>, <yuval.shaia@...cle.com>,
        <idan.brown@...cle.com>
Subject: Re: [PATCH] net: dev_forward_skb(): Scrub packet's per-netns info
 only when crossing netns


----- shmulik.ladkani@...il.com wrote:

> On Thu, 15 Mar 2018 08:01:03 -0700 (PDT) Liran Alon
> <liran.alon@...cle.com> wrote:
> > 
> > I still think that default behavior should be to zero skb->mark only
> when skb
> > cross netdevs in different netns.
> 
> But the previous default was scrub the mark in *both* xnet and
> non-xnet
> situations.
> 
> Therefore, there might be users which RELY on this (strange) default
> behavior in their same-netns-veth-pair setups.
> Meaning, changing the default behavior might break their apps relying
> on
> the former default behavior.
> 
> This is why the "disable mark scrubbing in non-xnet case" should be
> opt-in.

We think the same.
The only difference is that I think this for now should be controllable
by a global /proc/sys/net/core file instead of giving a flexible per-netdev control.
Because that is a larger change that could be done later.

> 
> Regards,
> Shmulik