[Simh] Networking and SIMH

[Mark Pizzolato - Info Comm]

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