tap and vlan

Oguzhan Kayhan oguzhank at bilkent.edu.tr
Fri Oct 24 08:12:33 UTC 2008


> The usetap option has always been highly experimental and largely
> useless. A while back there was a bug with certain features that was
> worked around using usetap, which has been fixed (the details I would
> have to lookup). Using a tap doesn't make much sense, at the end of the
> day. You want to use the tun interface so that the kernel has the
> ability to route the packet appropriately, out through the default
> gateway if not a local destination. However, with a tap, chilli would
> have to figure out if the destination is local or not before deciding on
> the destination MAC address.
>
> I'm interested to know what doesn't work when you use a tun interface
> (assuming you are using at least chilli 1.0.12, or even better, the svn
> version) and why the tap is required in your environment.
>
> David
>
Hi David and thank you for your fast reply.
Actually, in some parts of our network we were still using chillispot 1.1
not coova-chilli. And in that areas, we were observing some packets on
physical interface which chilli runs which suppose to belong to network
behind tun interface.We can see this packets both on arp table of this
physical interface and and also with tcpdump command.And this mac-ids that
we saw on the physical part mostly belongs to the users creating huge
amounts of packets or connections like torrent or emule users.
And we thought maybe tun is not able to deal with such high amount of
packets and , when we figure out we can use tap instead of tun, maybe
working on layer 2 might help our situation.
Actually i cant say i tested coova-chilli tun performance in such parts of
our network yet.And even not sure if it is about chilli or tun driver
itself on kernel. Just testing..




>
> On Fri, 2008-10-24 at 10:43 +0300, Oguzhan Kayhan wrote:
>> Hello,
>> In our campus, we wanted to test TAP instead of tun.
>> And we found out something.Maybe a bug, or a thing that should not
>> suppose to do.
>>
>>
>> Normally,
>> when we use usetap parameter in normal coova configurations, everything
>> works fine.
>>
>> But if we try to run chilli on a vlan interface with usetap parameter,
>> Clients can able to get their ip addresses via coova but, unable to go
>> anywhere beyond, seems like can not get tagged by vlan. But if we
>> tcpdump
>> on vlan interface we see the packets.So it should be ok till kernel
>> level.
>>
>> I am wondering what can cause this.. A bug in chilli-coova or in kernel
>> level..
>>
>>
>>
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>
>
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