[Bridge] connecting PDA (wlan) to Linux laptop with bridged connections (eth + wlan) ...

[Sandeep Khanna]

On Tue, 2005-03-29 at 14:21 -0800, Stephen Hemminger wrote:
> On Tue, 29 Mar 2005 16:43:11 -0500
> "Sandeep Khanna" <sandeep.khanna at villanova.edu> wrote:
> 
> > Hi All,
> > 
> > After hours of reading and trials, I got the following setup working...
> > 
> > 1. Dell Axim X30 PocketPC with 802.11b wireless using DHCP with Open WEP
> > 
> > -- successfully connected to -->
> > 
> > 2. Laptop with DLink Airplus DWL-650+ PCMCIA wireless with ndiswrapper
> > v1.1 driver with network bridge (wired + wireless) and running a DHCP
> > server listening on interface br0 (eth0 + wlan0)
> > 
> > Here is the situation:
> > - The Dell Axim X30 PDA shows connected to the laptop in Ad-Hoc wireless
> > mode.
> > - It successfully gets an MAC address based IP address from the DHCP
> > server running on the laptop.
> > - I can successfully ping the PDA (10.3.2.209) from the
> > laptop(10.3.2.175).
> > - I can successfully ping the laptop(10.3.2.175) from the
> > PDA(10.3.2.209).
> > - When I open a browser on the PDA and try to open www.dell.com, tcpdump
> > shows the following: 
> > 
> > 16:26:09.XXXXXX arp who-has 10.47.12.29 tell 10.3.2.209
> > 16:26:10.XXXXXX arp who-has 10.47.12.27 tell 10.3.2.209
> > 
> > The above shows:
> > time | protocol | who-has | Nameserver | tell | source IP address (PDA)
> > 
> > - Internet browsing using the above Nameservers(10.47.12.29,
> > 10.47.12.27) works on the laptop but apparently the PDA doesn't seem to
> > even know about the Nameservers(10.47.12.29, 10.47.12.27)!!
> > 
> > Going forward, if the above the setup works then, I would be able to
> > browse Internet, use ActiveSync and more on my PDA not only in office
> > (laptop eth0 active) but also at home (laptop wlan0 active).
> 
> 
> Since you only really want to handle one device and a limited range of protocols
> you probably would have better success with routing and/or socks. The problem
> is that most wireless interfaces don't allow source address spoofing.

Not that I am fully aware of what "soruce address spoofing" is and how
is plays a role in what I would like to get done... But, according to
what I have so far, it looks like I have it more or less working, accept
that the PDA doesn't seem to be able to resolve desired destination
hostnames (www.dell.com, www.microsoft.com, etc) Would having a local
DNS server on the laptop help? What
is /proc/sys/net/ipv4/conf/br0/proxy_arp ? Does that have anything to do
with this?

Also, Once I reach home and there is no more connectivity (IP address)
on the eth0 (wired connection), would the bridge (eth0 + wlan0) still
work? I just tried ifupping br0 but, it just tries to use the eth0 for
DHCP and not wlan0. Essentially I have eth0 (wired) up when in office
and wlan0 (wireless) when at home. But, I would just like to use the
bridge both places (office + home) if the above setup works which would
let me use my PDA seamlessly at both locations!

-Sandeep Khanna