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

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Date:   Wed, 12 Feb 2020 16:24:34 +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 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
Hangbin

> 
> I'm not sure why this issue appears only when using monitor mode.
> Using wireless __ap mode interface (with hostapd) won't expose this
> issue. I guess it may be a matter of monitor interfaces not being
> bridged?
> 
> -- 
> Rafał