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

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Date:   Wed, 9 Jan 2019 21:53:26 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     ian.kumlien@...il.com, netdev <netdev@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] moving fq back to clock monotonic breaks my setup

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;

Thanks.