[Bridge] Hardware requirements for bridging wired+wireless together

[Bridge] Hardware requirements for bridging wired+wireless together

[Umar Qureshey]

Hi,

I have been trolling the 'net as well as the archives of this list for
quite a while now.

I am still unclear on the requirements for getting an Ethernet and
Wireless interface to bridge together.

Currently, I am working with an esoteric radio that only supports Ad-Hoc
and Managed modes.  There seemingly is not support for WDS (Wireless
Distribution System) on this radio.

I have been trying to bridge my eth0 and wlan0 but it doesn't seem to
work.  Currently, my commands to get the bridge up are:

ifconfig eth0 0.0.0.0
ifconfig wlan0 0.0.0.0
brctl addbr br0
brctl addif br0 eth0
brctl setfd br0 1           #BusyBox version of brctl doesn't take 0 as
a time parameter so I change it to 1 (sec)
ifconfig br0 up
wpa_supplicant -Dwext -iwlan0 -bbr0 -c/root/wpa_supplicant.conf

Then I try to run udhcpc (DHCP client) on the bridge hoping to get DHCP
from the AP/router:

# udhcpc -ibr0 -b
udhcpc (v1.15.2) started
Sending discover...
Sending discover...
Sending discover...
No lease, forking to background

What I'd like to inquire is that is WDS support in the firmware/hardware
of the radio required to bridge eth0 and wlan0?
Any other tips to get the above interfaces to successfully bridge
together would be great.

Thanks,
Umar
 
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Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Nicolas de Pesloüan]

Umar Qureshey wrote:
> Hi,
>
> I have been trolling the 'net as well as the archives of this list for
> quite a while now.
>
> I am still unclear on the requirements for getting an Ethernet and
> Wireless interface to bridge together.
>
> Currently, I am working with an esoteric radio that only supports Ad-Hoc
> and Managed modes.  There seemingly is not support for WDS (Wireless
> Distribution System) on this radio.
>
> I have been trying to bridge my eth0 and wlan0 but it doesn't seem to
> work.  Currently, my commands to get the bridge up are:
>
> ifconfig eth0 0.0.0.0
> ifconfig wlan0 0.0.0.0
> brctl addbr br0
> brctl addif br0 eth0
> brctl setfd br0 1           #BusyBox version of brctl doesn't take 0 as
> a time parameter so I change it to 1 (sec)
> ifconfig br0 up
> wpa_supplicant -Dwext -iwlan0 -bbr0 -c/root/wpa_supplicant.conf

I think you forgot to add wlan0 to the bridge:

brctl addif br0 wlan0

	Nicolas.

> Then I try to run udhcpc (DHCP client) on the bridge hoping to get DHCP
> from the AP/router:
>
> # udhcpc -ibr0 -b
> udhcpc (v1.15.2) started
> Sending discover...
> Sending discover...
> Sending discover...
> No lease, forking to background
>
> What I'd like to inquire is that is WDS support in the firmware/hardware
> of the radio required to bridge eth0 and wlan0?
> Any other tips to get the above interfaces to successfully bridge
> together would be great.
>
> Thanks,
> Umar
>
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>

Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Umar Qureshey]

-----Original Message-----
From: Nicolas de Pesloüan [mailto:nicolas.2p.debian@free.fr] 
Sent: Tuesday, May 18, 2010 12:32 PM
To: Umar Qureshey
Cc: bridge@lists.linux-foundation.org
Subject: Re: [Bridge] Hardware requirements for bridging wired+wireless together

Umar Qureshey wrote:
> Hi,
>
> I have been trolling the 'net as well as the archives of this list for
> quite a while now.
>
> I am still unclear on the requirements for getting an Ethernet and
> Wireless interface to bridge together.
>
> Currently, I am working with an esoteric radio that only supports Ad-Hoc
> and Managed modes.  There seemingly is not support for WDS (Wireless
> Distribution System) on this radio.
>
> I have been trying to bridge my eth0 and wlan0 but it doesn't seem to
> work.  Currently, my commands to get the bridge up are:
>
> ifconfig eth0 0.0.0.0
> ifconfig wlan0 0.0.0.0
> brctl addbr br0
> brctl addif br0 eth0
> brctl setfd br0 1           #BusyBox version of brctl doesn't take 0 as
> a time parameter so I change it to 1 (sec)
> ifconfig br0 up
> wpa_supplicant -Dwext -iwlan0 -bbr0 -c/root/wpa_supplicant.conf

I think you forgot to add wlan0 to the bridge:

brctl addif br0 wlan0

	Nicolas.

> Then I try to run udhcpc (DHCP client) on the bridge hoping to get DHCP
> from the AP/router:
>
> # udhcpc -ibr0 -b
> udhcpc (v1.15.2) started
> Sending discover...
> Sending discover...
> Sending discover...
> No lease, forking to background
>
> What I'd like to inquire is that is WDS support in the firmware/hardware
> of the radio required to bridge eth0 and wlan0?
> Any other tips to get the above interfaces to successfully bridge
> together would be great.
>
> Thanks,
> Umar
>

Hi,

I just wrote it wrong in a rush.  My board has two interfaces: eth0 and wlan0.  My sequence is as follows now:

ifconfig eth0 0.0.0.0
ifconfig wlan0 0.0.0.0
brctl addbr br0
brctl addif br0 eth0
brctl setfd br0 1
ifconfig br0 hw ether [MAC address of wlan0]
wpa_supplicant -Dwext -iwlan0 -bbr0 -c/root/wpa_supplicant.conf -B
brctl addif br0 wlan0
ifconfig br0 192.168.1.100 up

With the above sequence, I can ping the AP at 192.168.1.1 from the board ok.
However, when I try to ping the wireless AP from a computer connected via an Ethernet crosswire cable to eth0, I get the following in my kernel buffer log for *each* incoming ping:

[   88.510000] wlan0: received packet with  own address as source address
[   94.010000] wlan0: received packet with  own address as source address
[   97.360000] wlan0: received packet with  own address as source address
[  109.190000] wlan0: received packet with  own address as source address


I tried two permutations on the above scenario:

#1) Using the same exact above sequence but omitting the "ifconfig br0 hw ether [MAC address of wlan0]" command, I notice the br0 takes the MAC address of eth0.  In this case when I ping 192.168.1.1 from the board, I get the same warning in my kernel log:

[  124.800000] wlan0: received packet with  own address as source address
[  292.900000] wlan0: received packet with  own address as source address

I am also unable to ping from the computer connected via an Ethernet crosswire cable to eth0.


#2) Now if I use the same exact sequence above but spoof the MAC address to a fake one with the "ifconfig br0 hw ether [spoofed MAC address]" command, I cannot ping the AP at 192.168.1.1 anymore from the board.  For each ping that goes out from the board, in the kernel log buffer I get:

[  355.160000] wlan0: received packet with  own address as source address
[  359.660000] wlan0: received packet with  own address as source address

I am still unable to ping from the computer connected via an Ethernet crosswire cable to eth0.


So, in conclusion, I tried assigning to the bridge (br0) the wlan0's MAC address in which case I could ping the AP from the board.  In case of assigning the bridge the MAC address of eth0, I could not ping the AP from the board anymore.  Finally, assigning br0 a totally spoofed MAC address, I was still unable to ping the AP from the board.
In all cases above, I am unable to ping the AP via a machine that is connected to eth0 with a Ethernet crosswire cable.  This is what would really prove the bridge is working because the Linux board would be receiving the ICMP request on its eth0 interface which it would bridge to wlan0 interface which would then send that ICMP ping to the AP.  The AP would respond to the ping and send response to wlan0 which would bridge it to eth0 which would pass it back to the destination machine (the reverse route of outgoing).

I am wondering where and how WDS would come in to get the bridge to work.

Regards,
Umar
 
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Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Stephen Hemminger]

On Tue, 18 May 2010 16:38:54 -0700
"Umar Qureshey" <umar.qureshey@lantronix.com> wrote:

> -----Original Message-----
> From: Nicolas de Pesloüan [mailto:nicolas.2p.debian@free.fr] 
> Sent: Tuesday, May 18, 2010 12:32 PM
> To: Umar Qureshey
> Cc: bridge@lists.linux-foundation.org
> Subject: Re: [Bridge] Hardware requirements for bridging wired+wireless together
> 
> Umar Qureshey wrote:
> > Hi,
> >
> > I have been trolling the 'net as well as the archives of this list for
> > quite a while now.
> >
> > I am still unclear on the requirements for getting an Ethernet and
> > Wireless interface to bridge together.
> >
> > Currently, I am working with an esoteric radio that only supports Ad-Hoc
> > and Managed modes.  There seemingly is not support for WDS (Wireless
> > Distribution System) on this radio.
> >
> > I have been trying to bridge my eth0 and wlan0 but it doesn't seem to
> > work.  Currently, my commands to get the bridge up are:
> >
> > ifconfig eth0 0.0.0.0
> > ifconfig wlan0 0.0.0.0
> > brctl addbr br0
> > brctl addif br0 eth0
> > brctl setfd br0 1           #BusyBox version of brctl doesn't take 0 as
> > a time parameter so I change it to 1 (sec)
> > ifconfig br0 up
> > wpa_supplicant -Dwext -iwlan0 -bbr0 -c/root/wpa_supplicant.conf
> 
> I think you forgot to add wlan0 to the bridge:
> 
> brctl addif br0 wlan0
> 

I believe bridging in station mode won't work (usually).
Recent kernels even reject the attempt.

There are exceptions with some devices and if the stack supports WDS
(which Linux wireless doesn't yet).

There are some cases like VMware that appear to do MAC level NAT
(ie replace Ethernet address), but the regular kernel doesn't support that.

Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Umar Qureshey]

-----Original Message-----
From: Stephen Hemminger [mailto:shemminger@linux-foundation.org] 
Sent: Tuesday, May 18, 2010 4:51 PM
To: Umar Qureshey
Cc: Nicolas de Pesloüan; bridge@lists.linux-foundation.org
Subject: Re: [Bridge] Hardware requirements for bridging wired+wireless together

On Tue, 18 May 2010 16:38:54 -0700
"Umar Qureshey" <umar.qureshey@lantronix.com> wrote:

> -----Original Message-----
> From: Nicolas de Pesloüan [mailto:nicolas.2p.debian@free.fr] 
> Sent: Tuesday, May 18, 2010 12:32 PM
> To: Umar Qureshey
> Cc: bridge@lists.linux-foundation.org
> Subject: Re: [Bridge] Hardware requirements for bridging wired+wireless together
> 
> Umar Qureshey wrote:
> > Hi,
> >
> > I have been trolling the 'net as well as the archives of this list for
> > quite a while now.
> >
> > I am still unclear on the requirements for getting an Ethernet and
> > Wireless interface to bridge together.
> >
> > Currently, I am working with an esoteric radio that only supports Ad-Hoc
> > and Managed modes.  There seemingly is not support for WDS (Wireless
> > Distribution System) on this radio.
> >
> > I have been trying to bridge my eth0 and wlan0 but it doesn't seem to
> > work.  Currently, my commands to get the bridge up are:
> >
> > ifconfig eth0 0.0.0.0
> > ifconfig wlan0 0.0.0.0
> > brctl addbr br0
> > brctl addif br0 eth0
> > brctl setfd br0 1           #BusyBox version of brctl doesn't take 0 as
> > a time parameter so I change it to 1 (sec)
> > ifconfig br0 up
> > wpa_supplicant -Dwext -iwlan0 -bbr0 -c/root/wpa_supplicant.conf
> 
> I think you forgot to add wlan0 to the bridge:
> 
> brctl addif br0 wlan0
> 

> > >I believe bridging in station mode won't work (usually).
> > >Recent kernels even reject the attempt.

> > >There are exceptions with some devices and if the stack supports WDS
> > > (which Linux wireless doesn't yet).

> > >There are some cases like VMware that appear to do MAC level NAT
> > > (ie replace Ethernet address), but the regular kernel doesn't support that.

What about bridging in Ad-Hoc mode?  Would that technically work?

I guess what I am trying to figure out is why bridging would work in WDS mode?  What is it about that mode that allows bridging to work?

If one were to try to modify the kernel code to allow MAC-level NAT, which area of the kernel code would one look at?

 
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Re: [Bridge] Hardware requirements for bridging wired+wireless together

[John W. Linville]

On Wed, May 19, 2010 at 10:15:35AM -0700, Umar Qureshey wrote:

> What about bridging in Ad-Hoc mode?  Would that technically work?

No.
 
> I guess what I am trying to figure out is why bridging would work in WDS mode?  What is it about that mode that allows bridging to work?

It has to do with the MAC-layer addressing on wireless LANs.  Wireless
frames can use 2, 3, or 4 MAC addresses to identify the transmitter,
receiver, sender, and destination.  For most frames and most modes,
3 MAC addresses are used.  The FromDS and ToDS bits in the header
are used to allow one of the MAC address fields to specify either
the transmitter and sender or the destination and receiver.  This is
sufficient for non-bridged cases since the wireless station is either
an endpoint of the communication or possibly a router (and therefore
a Layer-2 endpoint).

WDS (or 4 address) mode removes this limitation by using 4 MAC
addresses to identify all 4 roles independently.  So, the wireless
station is able to forward frames received off the air to the
appropriate destination with the correct sender information intact.

mac80211-based devices can have interfaces created with support for
4 address mode using the iw command.  For this to work, your AP has
to be willing to accept and forward those frames appropriately --
some do, others don't.  This is only supported for "managed" mode
interfaces AFAIK.

> If one were to try to modify the kernel code to allow MAC-level NAT, which area of the kernel code would one look at?

netfilter -- I thought there was already some ebtables code to
do this...?

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.

Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Simon Barber]

I did write an ebtables module to work around this 802.11 3 address 
problem - it performed L2 NAT on DHCP, ARP and IP packets, so allowing 
an 802.11 client be added to a bridge. It was released under GPL about 5 
years ago (from my previous company Instant802/Devicescape), but I can't 
find the source anymore!!!

Simon


On 05/19/2010 12:20 PM, John W. Linville wrote:
> On Wed, May 19, 2010 at 10:15:35AM -0700, Umar Qureshey wrote:
>
>> What about bridging in Ad-Hoc mode?  Would that technically work?
>
> No.
>
>> I guess what I am trying to figure out is why bridging would work in WDS mode?  What is it about that mode that allows bridging to work?
>
> It has to do with the MAC-layer addressing on wireless LANs.  Wireless
> frames can use 2, 3, or 4 MAC addresses to identify the transmitter,
> receiver, sender, and destination.  For most frames and most modes,
> 3 MAC addresses are used.  The FromDS and ToDS bits in the header
> are used to allow one of the MAC address fields to specify either
> the transmitter and sender or the destination and receiver.  This is
> sufficient for non-bridged cases since the wireless station is either
> an endpoint of the communication or possibly a router (and therefore
> a Layer-2 endpoint).
>
> WDS (or 4 address) mode removes this limitation by using 4 MAC
> addresses to identify all 4 roles independently.  So, the wireless
> station is able to forward frames received off the air to the
> appropriate destination with the correct sender information intact.
>
> mac80211-based devices can have interfaces created with support for
> 4 address mode using the iw command.  For this to work, your AP has
> to be willing to accept and forward those frames appropriately --
> some do, others don't.  This is only supported for "managed" mode
> interfaces AFAIK.
>
>> If one were to try to modify the kernel code to allow MAC-level NAT, which area of the kernel code would one look at?
>
> netfilter -- I thought there was already some ebtables code to
> do this...?
>
> John

Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Umar Qureshey]

> >-----Original Message-----
> >From: Simon Barber [mailto:simon@superduper.net] 
> >Sent: Wednesday, May 19, 2010 1:59 PM
> >To: John W. Linville
> >Cc: Umar Qureshey; bridge@lists.linux-foundation.org
> >Subject: Re: [Bridge] Hardware requirements for bridging
wired+wireless together
> >
> >I did write an ebtables module to work around this 802.11 3 address 
> >problem - it performed L2 NAT on DHCP, ARP and IP packets, so
allowing 
> >an 802.11 client be added to a bridge. It was released under GPL
about 5 
> >years ago (from my previous company Instant802/Devicescape), but I
can't 
> >find the source anymore!!!
> >
> >Simon

That would be very useful.  Probably even more useful now than 5 years
ago!  Apparently, Windows does MAC-level NAT allowing for the bridging
of Ethernet and WiFi interfaces irrespective of the underlying Wifi
chipset.
 
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Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Simon Barber]

The problem is not the WiFi chipset - it's the IEEE802.11 standard. The 
standard does not allow for 'promiscuous mode' (not to be confused with 
monitor mode), nor does it require clients and access points to support 
4 address format frames which the bridge needs to work.

Simon

On 05/19/2010 02:08 PM, Umar Qureshey wrote:
>>> -----Original Message-----
>>> From: Simon Barber [mailto:simon@superduper.net]
>>> Sent: Wednesday, May 19, 2010 1:59 PM
>>> To: John W. Linville
>>> Cc: Umar Qureshey; bridge@lists.linux-foundation.org
>>> Subject: Re: [Bridge] Hardware requirements for bridging
> wired+wireless together
>>>
>>> I did write an ebtables module to work around this 802.11 3 address
>>> problem - it performed L2 NAT on DHCP, ARP and IP packets, so
> allowing
>>> an 802.11 client be added to a bridge. It was released under GPL
> about 5
>>> years ago (from my previous company Instant802/Devicescape), but I
> can't
>>> find the source anymore!!!
>>>
>>> Simon
>
> That would be very useful.  Probably even more useful now than 5 years
> ago!  Apparently, Windows does MAC-level NAT allowing for the bridging
> of Ethernet and WiFi interfaces irrespective of the underlying Wifi
> chipset.
>
> **********************************************************************
> This e-mail is the property of Lantronix. It is intended only for the person or entity to which it is addressed and may contain information that is privileged, confidential, or otherwise protected from disclosure. Distribution or copying of this e-mail, or the information contained herein, to anyone other than the intended recipient is prohibited.

Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Umar Qureshey]

> >-----Original Message-----
> >From: John W. Linville [mailto:linville@tuxdriver.com] 
> >Sent: Wednesday, May 19, 2010 12:20 PM
> >To: Umar Qureshey
> >Cc: Stephen Hemminger; bridge@lists.linux-foundation.org
> >Subject: Re: [Bridge] Hardware requirements for bridging
wired+wireless together
> >
> >On Wed, May 19, 2010 at 10:15:35AM -0700, Umar Qureshey wrote:
> >
> > > What about bridging in Ad-Hoc mode?  Would that technically work?
> >
> >No.
> > 
> > > I guess what I am trying to figure out is why bridging would work
in WDS mode?  What is it about that mode that allows bridging to work?
> >
> >It has to do with the MAC-layer addressing on wireless LANs.
Wireless
> >frames can use 2, 3, or 4 MAC addresses to identify the transmitter,
> >receiver, sender, and destination.  For most frames and most modes,
> >3 MAC addresses are used.  The FromDS and ToDS bits in the header
> >are used to allow one of the MAC address fields to specify either
> >the transmitter and sender or the destination and receiver.  This is
> >sufficient for non-bridged cases since the wireless station is either
> >an endpoint of the communication or possibly a router (and therefore
> >a Layer-2 endpoint).
> >
> >WDS (or 4 address) mode removes this limitation by using 4 MAC
> >addresses to identify all 4 roles independently.  So, the wireless
> >station is able to forward frames received off the air to the
> >appropriate destination with the correct sender information intact.
> >
> >mac80211-based devices can have interfaces created with support for
> >4 address mode using the iw command.  For this to work, your AP has
> >to be willing to accept and forward those frames appropriately --
> >some do, others don't.  This is only supported for "managed" mode
> >interfaces AFAIK.
> >
> > > If one were to try to modify the kernel code to allow MAC-level
NAT, which area of the kernel code would one look at?
> >
> >netfilter -- I thought there was already some ebtables code to
> >do this...?
> >
> >John
> >-- 
> >John W. Linville		Someday the world will need a hero, and
you
> >linville@tuxdriver.com			might be all we have.
Be ready.

Ok thanks for the explanation about WDS.  

Stepping back into a Linux box with two interfaces, one Ethernet (eth0)
and one wireless 802.11 (wlan0), and one bridge (br0) that bridges these
two interfaces together:


                           br0
                            |
                 eth0-------+-------wlan0

Can one say that, in this case, the bridge is not working because br0 is
passing to wlan0 Ethernet 802.3 frames which (naturally) the wlan0
interface has no idea how to decode?

 
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Re: [Bridge] Hardware requirements for bridging wired+wireless together

[Simon Barber]

Unfortunately the concept of a native 802.11 interface got removed from 
the kernel a few months ago. This is a great shame, since it means that 
it's now impossible to write qdiscs that work correctly for WiFi when 
using 802.11's own priority mechanisms as well. The wlan0 interface is a 
virtual interface that works with 802.3 format frames.

Simon


On 05/19/2010 02:01 PM, Umar Qureshey wrote:
>>> -----Original Message-----
>>> From: John W. Linville [mailto:linville@tuxdriver.com]
>>> Sent: Wednesday, May 19, 2010 12:20 PM
>>> To: Umar Qureshey
>>> Cc: Stephen Hemminger; bridge@lists.linux-foundation.org
>>> Subject: Re: [Bridge] Hardware requirements for bridging
> wired+wireless together
>>>
>>> On Wed, May 19, 2010 at 10:15:35AM -0700, Umar Qureshey wrote:
>>>
>>>> What about bridging in Ad-Hoc mode?  Would that technically work?
>>>
>>> No.
>>>
>>>> I guess what I am trying to figure out is why bridging would work
> in WDS mode?  What is it about that mode that allows bridging to work?
>>>
>>> It has to do with the MAC-layer addressing on wireless LANs.
> Wireless
>>> frames can use 2, 3, or 4 MAC addresses to identify the transmitter,
>>> receiver, sender, and destination.  For most frames and most modes,
>>> 3 MAC addresses are used.  The FromDS and ToDS bits in the header
>>> are used to allow one of the MAC address fields to specify either
>>> the transmitter and sender or the destination and receiver.  This is
>>> sufficient for non-bridged cases since the wireless station is either
>>> an endpoint of the communication or possibly a router (and therefore
>>> a Layer-2 endpoint).
>>>
>>> WDS (or 4 address) mode removes this limitation by using 4 MAC
>>> addresses to identify all 4 roles independently.  So, the wireless
>>> station is able to forward frames received off the air to the
>>> appropriate destination with the correct sender information intact.
>>>
>>> mac80211-based devices can have interfaces created with support for
>>> 4 address mode using the iw command.  For this to work, your AP has
>>> to be willing to accept and forward those frames appropriately --
>>> some do, others don't.  This is only supported for "managed" mode
>>> interfaces AFAIK.
>>>
>>>> If one were to try to modify the kernel code to allow MAC-level
> NAT, which area of the kernel code would one look at?
>>>
>>> netfilter -- I thought there was already some ebtables code to
>>> do this...?
>>>
>>> John
>>> --
>>> John W. Linville		Someday the world will need a hero, and
> you
>>> linville@tuxdriver.com			might be all we have.
> Be ready.
>
> Ok thanks for the explanation about WDS.
>
> Stepping back into a Linux box with two interfaces, one Ethernet (eth0)
> and one wireless 802.11 (wlan0), and one bridge (br0) that bridges these
> two interfaces together:
>
>
>                             br0
>                              |
>                   eth0-------+-------wlan0
>
> Can one say that, in this case, the bridge is not working because br0 is
> passing to wlan0 Ethernet 802.3 frames which (naturally) the wlan0
> interface has no idea how to decode?
>
>
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