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From: Antonio Quartulli <a@unstable.cc>
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Date: Tue, 19 Jan 2016 08:39:07 +0800
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Subject: Re: [B.A.T.M.A.N.] [RFC] batman-adv: Remove recursive bat-on-bat
 netdevice check
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To: Sven Eckelmann <sven@narfation.org>
Cc: Jetmir Gigollai <jetmir_gigollaj@web.de>, The list for a Better Approach To Mobile Ad-hoc Networking <b.a.t.m.a.n@lists.open-mesh.org>

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Hi Sven and thanks for this RFC. Sorry for taking soo long to comment.



On 14/11/15 03:46, Sven Eckelmann wrote:
> batman-adv checks in different situation if a new device is already on =
top
> of a different batman-adv device. This is done by getting the iflink of=
 a
> device and all its parent. It assumes that this iflink is always a pare=
nt
> device in an acyclic graph. But this assumption is broken by devices li=
ke
> veth which are actually a pair of two devices linked to each other. The=

> recursive check would therefore get veth0 when calling dev_get_iflink o=
n
> veth1. And it gets veth0 when calling dev_get_iflink with veth1.
>=20

I agree that this check implemented this way represents a problem.
However I also believe that we should still have some kind of prevention
against this particular scenario (chain of batman interfaces), because
if ignored it could lead to troubles.

Unfortunately I don't know how to implement this check in an elegant and
extendible manner.

First of all we should add a check that follows the master interface,
but at the same time we should still follow the iflink, otherwise we
can't check relationships like VLAN_DEV->REAL_DEV. But how to implement
the latter without hitting the cyclic case is not clear to me ..

An option is to add a specific check for veth and break the recursion,
but this is not really nice, because the next time a cyclic interface
type will be introduced our check will become troublesome again.

Suggestions?


Cheers,

--=20
Antonio Quartulli


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