[Bridge] bridge is not forwarding the packet

rahul bhardwaj rahul_bhardwaj36in at yahoo.co.in
Tue Sep 23 06:31:41 PDT 2008

Hi Stephen,

Thanks for your very prompt response!

Actually my
problem is not related to MAC address restrictions from wireless
interface/driver. The problem lies mainly in multiple bridges for different vlans.
Since bridging happens first, the packet ends up on wrong bridge and gets
discarded form that bridge.  If Vlan
handling is done prior to bridge handling, my setup will work fine. 


There is
also another thing which I did not understand. When we add an interface to
vlan, the newly created interface’s hard_header is set to vlan_dev_hard_header
function. This vlan_dev_hard_header adds the vlan tag for outing packet.

this happens after bridging code hand over the packet to interface. Conversely when
the packet is received, interface should remove the vlan tag and hand over the
packet to bridge. But we are seeing that bridge code is executing prior to vlan




Rahul Bhardwaj



--- On Mon, 22/9/08, Stephen Hemminger <shemminger at vyatta.com> wrote:
From: Stephen Hemminger <shemminger at vyatta.com>
Subject: Re: [Bridge] bridge is not forwarding the packet <Urgent, Please reply ASAP>
To: "rahul bhardwaj" <rahul_bhardwaj36in at yahoo.co.in>
Cc: bridge at lists.linux-foundation.org
Date: Monday, 22 September, 2008, 8:33 AM

On Mon, 22 Sep 2008 16:24:00 +0530 (IST)
rahul bhardwaj <rahul_bhardwaj36in at yahoo.co.in> wrote:

> Hello to all,
> I am stating my problem below in detail so that you all can understand it
> I am having setup of Linux box. In that box I am having one Ethernet
interface eth0 and one wireless interface ath0. I have also configured one vlan
port as eth0.100 with the help of vconfig (vconfig add eth 100).  Now I have
created two bridges br1 and br100. I have added eth0 into br1 so br1 is having
only one interface. I have added ath0 and eth0.100 into br100. Physically eth0
is connected to a switch which is configured to handle vlan 100. DHCP server is
also running into that switch to provide IP address to wireless stations. This
is all about my setup.
> After this I am associating one wireless station with the ath0. After
successful association station issues a dhclient to get ip address, which
reaches to ath0 interface of my Linux box. ath0 bridges that request to
eth0.100. Now eth0.100 adds it's vlan tags and forward that request to the
switch. Because switch is configured to support vlan 100, so it process the dhcp
request and send back the dhcp response with vlan tag 100. 
> Now I don't know but this response is not reaching to ath0. I have
putted wireshark and figured out that those dhcp responses are reaching on eth0
and as eth0 is part of br1 so this packet is reaching to br1 which is just
discarding them all. So the wireless station is not getting the ip address.
According to me eth0 should give these packets to eth0.100 port instead of br1.
Or what I mean to say first vlan handling should be done priror then  bridge
handling. Do I need to change something into Linux kernel for that or there is
some other problem with my setup?
> Can anybody help me in this? If anybody want more detail I will provide. I
am using Linux 2.6.15 kernel. Any kind of help will be much appreciated. 
> With Regards 
> Rahul Bhardwaj 

Full bridging to wireless requires WDS which Linux wireless does not support

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