netdev - Re: [PATCH net-next RESEND] net: Do not call ndo_dflt_fdb_dump if ndo_fdb

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Date:	Tue, 16 Dec 2014 14:35:38 -0000
From:	"Hubert Sokolowski" <h.sokolowski@....edu.pl>
To:	"Jamal Hadi Salim" <jhs@...atatu.com>
Cc:	"John Fastabend" <john.fastabend@...il.com>,
	"Roopa Prabhu" <roopa@...ulusnetworks.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Vlad Yasevich" <vyasevic@...hat.com>
Subject: Re: [PATCH net-next RESEND] net: Do not call ndo_dflt_fdb_dump if
 ndo_fdb_dump is defined.

>
> I am glad this happened ;-> Otherwise we wouldnt be having this
> discussion. When Vlad was asking me I was in a rush to get the patch
> out and didnt question because i thought this was something some crazy
> virtualization people needed.
> If Vlad's use case goes away, then Hubert's little restoration is fine.
>

I'm afraid there might be a little more to fix in here. I just tested
my patch after I moved the dflt_fdb_dump unconditional call inside br_fdb_dump,
so the "self" is returned again for the bridge and saw that br_fdb_dump is called
twice in some cases. As a result I saw duplicate "self" entries.
I think the problem is in rtnl_fdb_dump how it invokes ndo_fdb_dump.
In 3.16 the algorithm was very simple, now it is a little bit more complicated.

I tested on 3.18 without my changes only added pr_info inside br_fdb_dump:
pr_info("br fdb dump called dev %s filter dev %s.\n", dev->name,
			filter_dev->name);

I loaded dummy module, created bridge br0 with brctl and then attached dummy0
to that bridge:
    brctl  addif  br0 dummy0
Then when trying to filter by brport only:
./bridge fdb show brport dummy0
5e:e2:a0:21:0c:f5 vlan 1 master br0 permanent
5e:e2:a0:21:0c:f5 master br0 permanent
33:33:00:00:00:01 self permanent

Even though the output looks OK, I see in the journalctl logs the callback
was called twice with same attributes:
Dec 16 09:15:39 localhost.localdomain kernel: br fdb dump called dev br0 filter dev dummy0.
Dec 16 09:15:39 localhost.localdomain kernel: br fdb dump called dev br0 filter dev dummy0.

Do you have any idea why this is happening? I hope this test makes sense :).

Thanks,
Hubert

--
Hubert Sokolowski           Intel Corporation

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