From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liran Alon Subject: Re: [PATCH] net: dev_forward_skb(): Scrub packet's per-netns info only when crossing netns Date: Tue, 20 Mar 2018 17:34:38 +0200 Message-ID: <5AB12A0E.2060704@ORACLE.COM> References: <1520953642-8145-1-git-send-email-liran.alon@oracle.com> <20180320.104759.796804827689233281.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, idan.brown@ORACLE.COM, yuval.shaia@ORACLE.COM To: David Miller Return-path: In-Reply-To: <20180320.104759.796804827689233281.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 20/03/18 16:47, David Miller wrote: > From: Liran Alon > Date: Tue, 13 Mar 2018 17:07:22 +0200 > >> Before this commit, dev_forward_skb() always cleared packet's >> per-network-namespace info. Even if the packet doesn't cross >> network namespaces. > > There was a lot of discussion about this patch. > > Particularly whether it could potentially break current > users or not. > > If this is resolved and the patch should still be applied, > please repost and the folks involved in this dicussion should > add their ACKs. > > Thanks. > The problem is that I don't think we have reached an agreement. I would be happy to here your opinion on the issue at hand here. I personally don't understand why we should maintain backwards-comparability to this behaviour. How would a user rely on the fact that skb->mark is scrubbed when it is passed between 2 netdevs on the same netns but only when it is passed between very specific netdev type (one of them being veth-peers). This behaviour seems to have been created by mistake. This feature is not documented to user-mode and I don't see why it is legit for the user to rely on it. In addition, even if we do want to maintain backwards-comparability to this behaviour, I think it is enough to have an opt-in flag in /proc/sys/net/core/ that when set to 1 will activate the fix in dev_forward_skb() provided by this patch. That would also be a very simple change to the patch provided here. Do you agree? Or do you think we should have a flag per netdev like suggested in other replies to this thread? Thanks, -Liran