netdev - Re: [BUG] moving fq back to clock monotonic breaks my setup

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Message-ID: <351f5da149072c8c1165f8f205ac5c852a92dff8.camel@redhat.com>
Date:   Thu, 10 Jan 2019 09:55:24 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Ian Kumlien <ian.kumlien@...il.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] moving fq back to clock monotonic breaks my setup

On Thu, 2019-01-10 at 09:25 +0100, Ian Kumlien wrote:
> On Thu, Jan 10, 2019 at 6:53 AM Eric Dumazet <edumazet@...gle.com> wrote:
> > On Wed, Jan 9, 2019 at 4:48 PM Ian Kumlien <ian.kumlien@...il.com> wrote:
> > > Hi,
> > > 
> > > Just been trough ~5+ hours of bisecting and eventually actually found
> > > the culprit =)
> > > 
> > > commit fb420d5d91c1274d5966917725e71f27ed092a85 (refs/bisect/bad)
> > > Author: Eric Dumazet <edumazet@...gle.com>
> > > Date:   Fri Sep 28 10:28:44 2018 -0700
> > > 
> > >     tcp/fq: move back to CLOCK_MONOTONIC
> > > 
> > > [--8<--]
> > > 
> > > So this might be because my setup might be "odd".
> > > 
> > > Basically I have a firewall with four nics that uses two of those nics
> > > to handle my normal
> > > internet connection (firewall/MASQ/NAT) and the other two are assigned
> > > to one bridge each.
> > > 
> > > The firewall is also my local caching DNS server and DHCP server,
> > > which is also used by the VM:s...
> > > But with 4.20 DHCP replies disappeared before entering the bridge - i
> > > couldn't even see them in
> > > tcpdump! (all nics are ixgbe on a atom soc)
> > > 
> > > I'm currently running a kernel with that patch reversed but I'm also
> > > wondering about possible ways
> > > forward since I'm reverting a fix from someone else...
> > 
> > I suggest you use netdev@ mailing list instead of lkml
> > 
> > Then, we probably need to clear skb->tstamp in more paths (you are
> > mentioning bridge ...)
> > 
> > See commit 8203e2d844d34af247a151d8ebd68553a6e91785 for reference.
> > 
> > Can you try :
> > 
> > diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
> > index 5372e2042adfe20d3cd039c29057535b2413be61..bd4fa141420c92a44716bd93fcd8aa3d3310203a
> > 100644
> > --- a/net/bridge/br_forward.c
> > +++ b/net/bridge/br_forward.c
> > @@ -53,6 +53,7 @@ int br_dev_queue_push_xmit(struct net *net, struct
> > sock *sk, struct sk_buff *skb
> >                 skb_set_network_header(skb, depth);
> >         }
> > 
> > +       skb->tstamp = 0;
> >         dev_queue_xmit(skb);
> > 
> >         return 0;
> 
> This works, and so does: https://marc.info/?l=linux-netdev&m=154696956604748&w=2
> 
> Pointed out by Paolo (tested both separately)

Note: I cleared the tstamp in br_forward_finish() instead of
br_dev_queue_push_xmit() because I think the latter could be called
also in the local xmit path, via br_nf_post_routing.

We must preserve the tstamp in output path, right?

Thanks,

Paolo