I've started looking a little deeper, and the first thing I found is
this from linux-source/Documentation/networking/tuntap.txt:
4. What is the difference between TUN driver and TAP driver?
TUN works with IP frames. TAP works with Ethernet frames.
So it would seem that to get the desired multi-protocol generality, one
would want to use the TAP ioctls not the TUN ioctls that tunctl.c uses.
Meaning to support non IP protocols, the example in 0readme_ethernet.txt
would need to change to use a "tapctl" program rather than the tunctl
program it currently uses (or tunctl could be made into a more generic
tuntapctl program). Or perhaps it somehow works as desired right now,
in spite of the available documentation.
I downloaded the uml_utilities source, and unfortunately, the code
contains precious little commenting other than "Licensed under the GPL"
and no documentation. So figuring it out may take a little time.
There is a "uml_switch" program. If we're lucky, this may be a network
switch in software. Unfortunately, it uses the TUN ioctls, so if it is
a switch it would need reworking to use TAP ioctls for it to be an
ethernet switch rather than an IP switch. If only it were commented, I
could say more at this time.
- Michael
On 03/05/2012 05:55 AM, Mark Pizzolato - Info Comm wrote:
That is completely true for IP traffic.
However, the key goal for the simulator level networking is to have
these simulated systems be able to talk to other real or simulated systems
in all the ways that they did when they were natively networking. When
these systems were in their prime, IP was not the dominant networking
protocol.
These systems spoke DECnet, LAT, SCS(Vax Cluster Communications), etc.
All of these protocols were designed around communications on a LAN.
The 0readme_ethernet.txt document's goal is to try and get a simulator
to BOTH be able to participate with these protocols on the local LAN
AND to have the host system be able to also communicate with the host
System with whatever protocols they may actually share (usually only
IP these days).
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