Hi Gregg,

On Thursday, December 05, 2013 at 8:03 PM, Gregg Levine wrote:
> Okay so I've managed to install the VDE components and the PCAP
> development components on my Raspberry Pi. Invoking make caused the
> build system to "choose" the VDE components. Why? When both are
> present I figured it would chose both rather then the one I'm not familiar
> with.
> 
> In any case I know I can work with what the methods chose and eventually
> accomplish what I am planning on doing with the appropriate simulators.

The build It is not an either or process.   It will build using whatever 
Ethernet transports methods are available on the local environment when the 
build is done and each of those may be available when running with the 
simulator you built.

As I recall, when I did this on the Raspberry Pi, I didn't have to look for 
libpcap-dev for that platform, I believe it was packaged with the OS.  If 
/usr/include/pcap.h exists AND libpcap's shared object is available on the 
system (i.e. if tcpdump works) that is sufficient to build (and later use at 
runtime) with libpcap support.

You don't explain how you think it chose just VDE rather than both.  If you 
provide the output that make produced while building the simulator it will be 
more clear what capabilities are being built in.

Meanwhile, to use one Ethernet transport method over another at run time will 
depend on several different goals.  You need to be running as root on any Linux 
platform in order to inject packets into the network using libpcap.  On the 
other hand, using VDE you can run as a normal unprivileged user as long as the 
VDE environment is already setup by some components running as root (maybe 
startup scripts, etc...).  The simulator's "show xq ether" command will list 
the Ethernet transports which can be used by the process issuing that command.  
You would see different output if you were running as root.  Additionally, you 
may or may not desire to have the simulated system actually be able to speak 
(exchange IP packets) with the host it is running on.  If that is a goal, then 
on Linux you can't do that directly with libpcap.  If that is a goal, then VDE 
can help you or you can build your own internal bridge with kernel bridging and 
tun/tap network interfaces.

- Mark

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