netdev - Re: [PATCH net v2 7/9] bridge: Properly check if local fdb entry can be deleted in br_fdb_delete_by

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Date:	Wed, 18 Dec 2013 11:27:18 +0900
From:	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:	vyasevic@...hat.com
Cc:	"David S . Miller" <davem@...emloft.net>,
	Stephen Hemminger <stephen@...workplumber.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net v2 7/9] bridge: Properly check if local fdb entry
 can be deleted in br_fdb_delete_by_port

On Tue, 2013-12-17 at 14:12 -0500, Vlad Yasevich wrote:
> On 12/17/2013 07:03 AM, Toshiaki Makita wrote:
> > br_fdb_delete_by_port() doesn't care about vlan and mac address of the
> > bridge device.
> > 
> > As the check is almost the same as mac address changing, slightly modify
> > fdb_delete_local() and use it.
> > 
> > Note:
> > - We change the dst of a local entry when the same address is found.
> >   This occurs in the case kernel has inserted the same address for another
> >   port but has failed due to dup. We can regard changing dst as deleting
> >   old one and inserting new one that should have been added by the dup
> >   port, so we can always set its added_by_user to 0 in fdb_delete_local().
> 
> I disagree.  What happens if the user tries add a duplicate fdb with
> the local bit set?  

If the user add a dup local entry, the existent entry will be
overwritten and its add_by_user is set to 1 (if !NLM_F_EXCL).
The user never fails to add an entry due to dup in !NLM_F_EXCL case.

> That is permitted and in fact a default because in
> iproute right now.  That fdb should persist until the port is removed or
> user removes the fdb.
> 
> added_by_user flag should only be changed in the netlink code since the
> user has full control of it.

Maybe my changelog is misleading.

br_fdb_delete_by_port() calls fdb_delete_local() for local entries
regardless of its added_by_user. In this case, we have to check if
another port has the same address and vlan, and if found, we have to
create the entry (by changing dst). This is kernel-added entry, not
user-added.

br_fdb_changeaddr()/nbp_vlan_delete() doesn't call fdb_delete_local()
for user-added entry.

So it is safe to set added_by_user to 0 in fdb_delete_local().

will reword the changelog.

Thanks,
Toshiaki Makita


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