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 18:11:49 +0200 Message-ID: <5AB132C5.5010806@ORACLE.COM> References: <1520953642-8145-1-git-send-email-liran.alon@oracle.com> <20180320.104759.796804827689233281.davem@davemloft.net> <5AB12A0E.2060704@ORACLE.COM> <20180320.120036.1999626754164343704.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: <20180320.120036.1999626754164343704.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 20/03/18 18:00, David Miller wrote: > From: Liran Alon > Date: Tue, 20 Mar 2018 17:34:38 +0200 > >> I personally don't understand why we should maintain >> backwards-comparability to this behaviour. > > The reason is because not breaking things is a cornerstone of Linux > kernel development. > >> This feature is not documented to user-mode and I don't see why it >> is legit for the user to rely on it. > > Whether it is documented or not is irrelevant. A lot of our > interfaces and behaviors are not documented or poorly documented > at best. > >> 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. > > Making it opt-in makes it more palatable, that's for sure. > 1. Do we want to make a flag for every bug that is user-space visible? I think there is place for consideration on a per-case basis. I still don't see how a user can utilize this behaviour. He is basically loosing information (skb->mark) without this patch. 2. Having said that, I don't mind changing patch to maintain backwards compatibility here. However, there was also a discussion here on where the flag should sit. I think that a global /proc/sys/net/core/ flag should be enough. Do you agree it's sufficient for now? Thanks, -Liran