[Bridge] Bridging between user processes

[Derek Smalls]

Hi, 

What is the easiest way to bridge between two
user-space processes that talk directly to Ethernet
interfaces? 

I have two applications that write/read Ethernet
frames to/from Linux Ethernet ports (e.g. eth0). The
applications can successfully talk to each other when
they run on two machines connected over Ethernet. I
would like to be able to test them on a single machine
without employing the physical network. Would TAP +
bridging do the job? 

If so, what am I doing wrong?  Linux 2.4.20, root
user. I set up tap interfaces like this: 

>tunctl tap4 
>ifconfig tap4 4.4.4.4 promisc up 
>tunctl tap5 
>ifconfig tap5 5.5.5.5 promisc up 

I then set up the bridge and add the tap interfaces to
it: 

>brctl addbr tapbr 
>brctl setfd tapbr 0 
>brctl sethello tapbr 0 
>brctl stp tapbr off 
>ifconfig tapbr 7.7.7.7 netmask 255.255.255.0 up
>brctl addif tapbr tap4 
>brctl addif tapbr tap5 

I then do a ping over tap4: 
>ping -I tap4 8.8.8.8 

and tcpdump on tap5: 
>tcpdump -i tap5 

and see nothing. Shouldn't I see the ping requests on
tap5 now? 

BTW, if I enable STP on the bridge I start seeing the
STP frames on tap5. 

Thanks! 

Derek 




		
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