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From: Liran Alon <LIRAN.ALON@ORACLE.COM>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: shmulik.ladkani@gmail.com, netdev@vger.kernel.org,
	mrv@mojatatu.com, daniel@iogearbox.net, davem@davemloft.net,
	linux-kernel@vger.kernel.org, yuval.shaia@ORACLE.COM,
	idan.brown@ORACLE.COM
Subject: Re: [PATCH] net: dev_forward_skb(): Scrub packet's per-netns info only when crossing netns
Date: Tue, 20 Mar 2018 18:44:54 +0200	[thread overview]
Message-ID: <5AB13A86.9010607@ORACLE.COM> (raw)
In-Reply-To: <87tvta67gl.fsf@xmission.com>



On 20/03/18 18:24, ebiederm@xmission.com wrote:
>
> I don't believe the current behavior is a bug.
>
> I looked through the history.  Basically skb_scrub_packet
> started out as the scrubbing needed for crossing network
> namespaces.
>
> Then tunnels which needed 90% of the functionality started
> calling it, with the xnet flag added.  Because the tunnels
> needed to preserve their historic behavior.
>
> Then dev_forward_skb started calling skb_scrub_packet.
>
> A veth pair is supposed to give the same behavior as a cross-over
> cable plugged into two local nics.  A cross over cable won't
> preserve things like the skb mark.  So I don't see why anyone would
> expect a veth pair to preserve the mark.

I disagree with this argument.

I think that a skb crossing netns is what simulates a real packet 
crossing physical computers. Following your argument, why would 
skb->mark should be preserved when crossing netdevs on same netns via 
routing? But this does today preserve skb->mark.

Therefore, I do think that skb->mark should conceptually only be 
scrubbed when crossing netns. Regardless of the netdev used to cross it.

>
> Right now I don't see the point of handling packets that don't cross
> network namespace boundaries specially, other than to preserve backwards
> compatibility.
>
> Eric
>

  reply	other threads:[~2018-03-20 16:45 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-15 17:14 [PATCH] net: dev_forward_skb(): Scrub packet's per-netns info only when crossing netns Liran Alon
2018-03-20 16:24 ` Eric W. Biederman
2018-03-20 16:44   ` Liran Alon [this message]
2018-03-20 17:07     ` Ben Greear
2018-03-20 18:35       ` Eric W. Biederman
  -- strict thread matches above, loose matches on Subject: below --
2018-03-15 16:35 Liran Alon
2018-03-15 16:50 ` Shmulik Ladkani
2018-03-15 15:05 Liran Alon
2018-03-15 15:01 Liran Alon
2018-03-15 16:11 ` Shmulik Ladkani
2018-03-15 12:23 Liran Alon
2018-03-15 14:35 ` Roman Mashak
2018-03-15 14:53   ` Daniel Borkmann
2018-03-15 12:14 Liran Alon
2018-03-13 15:07 Liran Alon
2018-03-13 16:13 ` Yuval Shaia
2018-03-14 12:03   ` Yuval Shaia
2018-03-15  9:21 ` Shmulik Ladkani
2018-03-15 11:56   ` Daniel Borkmann
2018-03-15 12:50     ` Shmulik Ladkani
2018-03-15 15:13       ` Daniel Borkmann
2018-03-15 15:54         ` Shmulik Ladkani
2018-03-15 17:48           ` Daniel Borkmann
2018-03-20 14:47 ` David Miller
2018-03-20 15:34   ` Liran Alon
2018-03-20 16:00     ` David Miller
2018-03-20 16:11       ` Liran Alon
2018-03-20 16:34         ` David Miller
2018-03-20 16:39           ` Liran Alon
2018-03-20 18:51             ` valdis.kletnieks
2018-03-20 21:12               ` Liran Alon

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