netdev - Re: [PATCH net] net: bridge: validate the NUD_PERMANENT bit when adding an extern

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Date:   Tue, 10 Aug 2021 09:46:34 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "nikolay@...dia.com" <nikolay@...dia.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...nulli.us>, Roopa Prabhu <roopa@...dia.com>,
        "bridge@...ts.linux-foundation.org" 
        <bridge@...ts.linux-foundation.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        "syzbot+9ba1174359adba5a5b7c@...kaller.appspotmail.com" 
        <syzbot+9ba1174359adba5a5b7c@...kaller.appspotmail.com>
Subject: Re: [PATCH net] net: bridge: validate the NUD_PERMANENT bit when
 adding an extern_learn FDB entry

On Mon, Aug 09, 2021 at 04:05:22PM +0000, Vladimir Oltean wrote:
> On Mon, Aug 09, 2021 at 03:16:40PM +0300, Ido Schimmel wrote:
> > I have at least once selftest where I forgot the 'static' keyword:
> >
> > bridge fdb add de:ad:be:ef:13:37 dev $swp1 master extern_learn vlan 1
> >
> > This patch breaks the test when run against both the kernel and hardware
> > data paths. I don't mind patching these tests, but we might get more
> > reports in the future.
> 
> Is it the 'static' keyword that you forgot, or 'dynamic'? The
> tools/testing/selftests/net/forwarding/bridge_vlan_aware.sh selftest
> looks to me like it's testing the behavior of an FDB entry which should
> roam, and which without the extern_learn flag would be ageable.

static - no aging, no roaming
dynamic - aging, roaming
extern_learn - no aging, roaming

So these combinations do not make any sense and the kernel will ignore
static/dynamic when extern_learn is specified. It's needed to work
around iproute2 behavior of "assume permanent"