netdev - Re: Regression: net/ipv6/mld running system out of memory (not a leak)

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Date:   Wed, 12 Feb 2020 18:08:13 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Jo-Philipp Wich <jo@...n.io>
Subject: Re: Regression: net/ipv6/mld running system out of memory (not a
 leak)

On Wed, Feb 12, 2020 at 09:49:02AM +0100, Rafał Miłecki wrote:
> On 12.02.2020 09:24, Hangbin Liu wrote:
> > On Wed, Feb 12, 2020 at 08:37:31AM +0100, Rafał Miłecki wrote:
> > > Hi, I need some help with my devices running out of memory. I've
> > > debugging skills but I don't know net subsystem.
> > > 
> > > I run Linux based OpenWrt distribution on home wireless devices (ARM
> > > routers and access points with brcmfmac wireless driver). I noticed
> > > that using wireless monitor mode interface results in my devices (128
> > > MiB RAM) running out of memory in about 2 days. This is NOT a memory
> > > leak as putting wireless down brings back all the memory.
> > > 
> > > Interestingly this memory drain requires at least one of:
> > > net.ipv6.conf.default.forwarding=1
> > > net.ipv6.conf.all.forwarding=1
> > > to be set. OpenWrt happens to use both by default.
> > > 
> > > This regression was introduced by the commit 1666d49e1d41 ("mld: do
> > > not remove mld souce list info when set link down") - first appeared
> > > in 4.10 and then backported. This bug exists in 4.9.14 and 4.14.169.
> > > Reverting that commit from 4.9.14 and 4.14.169 /fixes/ the problem.
> > > 
> > > Can you look at possible cause/fix of this problem, please? Is there
> > > anything I can test or is there more info I can provide?
> > 
> > Hi Rafał,
> > 
> > Thanks for the report. Although you said this is not a memory leak. Maybe
> > you can try a84d01647989 ("mld: fix memory leak in mld_del_delrec()").
> 
> Thanks, that commit was also pointed by Eric and I verified it was
> backported as:
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.9.y&id=df9c0f8a15c283b3339ef636642d3769f8fbc434
> 
> So it must be some other bug affecting me.

Hmm, I'm surprised that IGMP works for you, as it requires enable IPv6
forwarding. Do you have a lot IPv6 multicast groups on your device?
What dose `ip maddr list` show?

Thanks
Hangbin