netdev - Re: [PATCH net-next] tcp: Revert no longer abort SYN

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Message-ID: <20240102191304.GB5160@unreal>
Date: Tue, 2 Jan 2024 21:13:04 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Gal Pressman <gal@...dia.com>, David Ahern <dsahern@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Shachar Kagan <skagan@...dia.com>, netdev@...r.kernel.org,
	Bagas Sanjaya <bagasdotme@...il.com>,
	"Linux regression tracking (Thorsten Leemhuis)" <regressions@...mhuis.info>
Subject: Re: [PATCH net-next] tcp: Revert no longer abort SYN_SENT when
 receiving some ICMP

On Tue, Jan 02, 2024 at 07:33:23PM +0100, Eric Dumazet wrote:
> On Tue, Jan 2, 2024 at 7:01 PM Leon Romanovsky <leon@...nel.org> wrote:
> >
> > On Tue, Jan 02, 2024 at 04:31:15PM +0100, Eric Dumazet wrote:
> > > On Tue, Jan 2, 2024 at 12:41 PM Leon Romanovsky <leon@...nel.org> wrote:
> > > >
> > > > On Tue, Jan 02, 2024 at 11:03:55AM +0100, Eric Dumazet wrote:
> > > > > On Tue, Jan 2, 2024 at 10:58 AM Leon Romanovsky <leon@...nel.org> wrote:
> > > > > >
> > > > > > On Tue, Jan 02, 2024 at 10:46:13AM +0100, Eric Dumazet wrote:
> > > > > > > On Tue, Jan 2, 2024 at 10:01 AM Leon Romanovsky <leon@...nel.org> wrote:
> > > > > > > >
> > > > > > > > From: Shachar Kagan <skagan@...dia.com>
> > > > > > > >
> > > > > > > > This reverts commit 0a8de364ff7a14558e9676f424283148110384d6.
> > > > > > > >
> > > > > > > > Shachar reported that Vagrant (https://www.vagrantup.com/), which is
> > > > > > > > very popular tool to manage fleet of VMs stopped to work after commit
> > > > > > > > citied in Fixes line.
> > > > > > > >
> > > > > > > > The issue appears while using Vagrant to manage nested VMs.
> > > > > > > > The steps are:
> > > > > > > > * create vagrant file
> > > > > > > > * vagrant up
> > > > > > > > * vagrant halt (VM is created but shut down)
> > > > > > > > * vagrant up - fail
> > > > > > > >
> > > > > > >
> > > > > > > I would rather have an explanation, instead of reverting a valid patch.
> > > > > > >
> > > > > > > I have been on vacation for some time. I may have missed a detailed
> > > > > > > explanation, please repost if needed.
> > > > > >
> > > > > > Our detailed explanation that revert worked. You provided the patch that
> > > > > > broke, so please let's not require from users to debug it.
> > > > > >
> > > > > > If you need a help to reproduce and/or test some hypothesis, Shachar
> > > > > > will be happy to help you, just ask.
> > > > >
> > > > > I have asked already, and received files that showed no ICMP relevant
> > > > > interactions.
> > > > >
> > > > > Can someone from your team help Shachar to get  a packet capture of
> > > > > both TCP _and_ ICMP packets ?
> > > >
> > > > I or Gal will help her, but for now let's revert it, before we will see
> > > > this breakage in merge window and later in all other branches which will
> > > > be based on -rc1.
> > >
> > > Patch is in net-next, we have at least four weeks to find the root cause.
> >
> > I saw more than once claims that netdev is fast to take patches but also
> > fast in reverts. There is no need to keep patch with known regression,
> > while we are in -rc8.
> 
> This patch is not in rc8, unless I am mistaken ?

Patch is not, but the timeline is. Right now, we are in -rc8 and in next
week, the merge window will start.

> 
> >
> > >
> > > I am a TCP maintainer, I will ask you to respect my choice, we have
> > > tests and reverting the patch is breaking one of them.
> >
> > At least for ipv6, you changed code from 2016 and the patch which I'm asking
> > to revert is not even marked as a fix. So I don't understand the urgency to keep
> > the patch.
> 
> Do you have an issue with IPv4 code or IPv6 ?

I think that IPv4, I looked on IPv6 dates just because it was easy to
do. It looks like IPv4 code which you are changing existed in its
current form even before git era.

> 
> It would help to have details.

We prepared raw PCAP files and I'm uploading them. It takes time.

> >
> > There are two things to consider:
> > 1. Linux rule number one is "do not break userspace".
> 
> No released kernel contains the issue yet. Nothing broke yet.

After merge window, it will and I want to avoid it.

> 
> net-next is for developers.

It is encouraged to test net-next, so we did it and reported.

> 
> > 2. Linux is a community project and people can have different opinions,
> > which can be different from your/mine.
> >
> > Thanks
> 
> I think we have time, and getting this patch with potential users on
> it will help to debug the issue.

Like I said, Shachar can test any debug patches, just ask her.

Thanks