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Date:   Sun, 3 Feb 2019 13:34:01 +0800
From:   戈润栋 <>
To:     Andrew Lunn <>
Cc:     Florian Fainelli <>,,,
Subject: Re: [PATCH] net: dsa: slave: Don't propagate flag changes on down
 slave interfaces

Hi Andrew

Sorry for the previous mails due to my error mail format setting on browser.

I have reproduced the tcpdump issue in my env, but not sure if it is the
same issue as you mentioned.
Ifdown a slave interface which is under tcpdump capturing will also decrease
the master's promiscuous twice.

So when I do:
a) tcpdump -i ethx
b) ifdown ethx
c) ifup ethx
d) goto a
for several times the promiscuous count of master will go negative.


Andrew Lunn <> 于2019年2月3日周日 上午1:16写道:
> On Sat, Feb 02, 2019 at 09:05:11AM -0800, Florian Fainelli wrote:
> > Le 2/2/19 à 6:29 AM, Rundong Ge a écrit :
> > > The unbalance of master's promiscuity or allmulti will happen after ifdown
> > > and ifup a slave interface which is in a bridge.
> > >
> > > When we ifdown a slave interface , both the 'dsa_slave_close' and
> > > 'dsa_slave_change_rx_flags' will clear the master's flags. The flags
> > > of master will be decrease twice.
> > > In the other hand, if we ifup the slave interface again, since the
> > > slave's flags were cleared the 'dsa_slave_open' won't set the master's
> > > flag, only 'dsa_slave_change_rx_flags' that triggered by 'br_add_if'
> > > will set the master's flags. The flags of master is increase once.
> > >
> > > Only propagating flag changes when a slave interface is up makes
> > > sure this does not happen. The 'vlan_dev_change_rx_flags' had the
> > > same problem and was fixed, and changes here follows that fix.
> >
> > VLAN code under net/8021q/vlan_dev.c::vlan_dev_change_rx_flags() appears
> > to do the same thing that you are proposing, so this looks fine to me.
> > Since that is a bugfix, we should probably add:
> Hi Rundong, Florian
> I've seen issues with tcpdump causing the promiscuous count to go
> negative. I wounder if this will fix that at well?
>           Andrew

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