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

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Message-ID: <5AB17953.5000609@ORACLE.COM>
Date:   Tue, 20 Mar 2018 23:12:51 +0200
From:   Liran Alon <LIRAN.ALON@...CLE.COM>
To:     valdis.kletnieks@...edu
CC:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, idan.brown@...CLE.COM,
        yuval.shaia@...CLE.COM
Subject: Re: [PATCH] net: dev_forward_skb(): Scrub packet's per-netns info
 only when crossing netns

On 20/03/18 20:51, valdis.kletnieks@...edu wrote:
> On Tue, 20 Mar 2018 18:39:47 +0200, Liran Alon said:
>> What is your opinion in regards if it's OK to put the flag enabling this
>> "fix" in /proc/sys/net/core? Do you think it's sufficient?
>
> Umm.. *which* /proc/sys/net/core?  These could differ for things that
> are in different namespaces.  Or are you proposing one systemwide
> global value (which also gets "interesting" if it's writable inside a
> container and changes the behavior a different container sees...)
>

I'm indeed proposing an opt-in system-wide global value.
I think it is the simplest approach to fix the issue at
hand here while maintaining backwards-compatibility.

I'm open to suggestions to where that system-wide
global value should be.

It must be a system-wide global value if we are not going
with the per-netdev flag approach as this system-wide global flag
should control how a skb is travelled between different netns.
So it doesn't belong to any one single netns.