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From: Nikolay Aleksandrov <nikolay@nvidia.com>
To: Vladimir Oltean <vladimir.oltean@nxp.com>,
	Ido Schimmel <idosch@idosch.org>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Jakub Kicinski <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jiri Pirko <jiri@resnulli.us>, Roopa Prabhu <roopa@nvidia.com>,
	"bridge@lists.linux-foundation.org" 
	<bridge@lists.linux-foundation.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	"syzbot+9ba1174359adba5a5b7c@syzkaller.appspotmail.com" 
	<syzbot+9ba1174359adba5a5b7c@syzkaller.appspotmail.com>
Subject: Re: [PATCH net] net: bridge: validate the NUD_PERMANENT bit when adding an extern_learn FDB entry
Date: Tue, 10 Aug 2021 13:15:32 +0300	[thread overview]
Message-ID: <c6d91ec7-6081-85d0-9bc8-569838d8f9a4@nvidia.com> (raw)
In-Reply-To: <20210810100928.uk7dfstrnts2may4@skbuf>

On 10/08/2021 13:09, Vladimir Oltean wrote:
> On Tue, Aug 10, 2021 at 09:46:34AM +0300, Ido Schimmel wrote:
>> 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"
> 
> Since NTF_EXT_LEARNED is part of ndm->ndm_flags and NUD_REACHABLE/NUD_NOARP
> are part of ndm->ndm_state, it is not at all clear to me that 'extern_learn'
> belongs to the same class of bridge neighbor attributes as 'static'/'dynamic',
> and that it is invalid to have the full degree of freedom. If it isn't,
> shouldn't the kernel validate that, instead of just ignoring the ndm->ndm_state?
> If it's too late to validate, shouldn't we at least document somewhere
> that the ndm_state is ignored in the presence of ndm_flags & NTF_EXT_LEARNED?
> It is user API after all, easter eggs like this aren't very enjoyable.
> 

It's too late unfortunately, ignoring other flags in that case has been the standard
behaviour for a long time (it has never made sense to specify flags for extern_learn
entries). I'll send a separate patch that adds a comment to document it or if you have
another thing in mind feel free to send a patch.

Thanks,
 Nik


  reply	other threads:[~2021-08-10 10:16 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-01 23:17 Vladimir Oltean
2021-08-02  7:42 ` Nikolay Aleksandrov
2021-08-02  9:20   ` Vladimir Oltean
2021-08-02  9:42     ` Nikolay Aleksandrov
2021-08-02 10:52       ` Vladimir Oltean
2021-08-02 11:02         ` Nikolay Aleksandrov
2021-08-02 11:20           ` Vladimir Oltean
2021-08-02 11:25 ` Nikolay Aleksandrov
2021-08-02 22:10 ` patchwork-bot+netdevbpf
2021-08-09 12:16 ` Ido Schimmel
2021-08-09 12:32   ` Vladimir Oltean
2021-08-09 15:33   ` Nikolay Aleksandrov
2021-08-10  6:40     ` Ido Schimmel
2021-08-10  7:21       ` [PATCH net] net: bridge: fix flags interpretation for extern learn fdb entries Nikolay Aleksandrov
2021-08-10 11:00         ` [PATCH net v2] " Nikolay Aleksandrov
2021-08-10 13:50           ` Vladimir Oltean
2021-08-10 20:20           ` patchwork-bot+netdevbpf
2021-08-09 16:05   ` [PATCH net] net: bridge: validate the NUD_PERMANENT bit when adding an extern_learn FDB entry Vladimir Oltean
2021-08-10  6:46     ` Ido Schimmel
2021-08-10 10:09       ` Vladimir Oltean
2021-08-10 10:15         ` Nikolay Aleksandrov [this message]
2021-08-10 10:38           ` Vladimir Oltean
2021-08-10 10:43             ` Nikolay Aleksandrov

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