On 2012-06-07 08:39, Dave McGuire wrote: On 06/07/2012 02:26 AM, Mark Benson wrote: Now, you have due permission to beat me with a dried haddock if I'm being naive (I'm not a programmer, just a user observing a conversation that's 50% over my head) but... Wouldn't a kernel-agnostic DECnet implementation be a better shot? I mean if you can skim DECnet packets using libpcap (which is kernel agnostic as far as I can tell, hell it even works on Windows :)) and use that to handle DECnet for the bridge or SimH what's stopping it being used for a full DECnet comms package? It might not be very *fast* and it's sure as hell not secure but it'd work, right? With the fast pace of kernel change and the dropping of kernel support (and OSs like Ubuntu update the kernel regularly which will break things) for DECnet in the 3.x kernel it may be that kernel-based support is no longer practicable on modern Linux. Just a thought... It's a good idea, but I'm not sure it can be done. We need to change the MAC address on the interface...can that be done outside the kernel? No need. See below. SIMH uses libpcap and implements networking for emulated machines by kicking the interface into promiscuous mode. That's a bit dangerous from a traffic perspective; I'm not certain that'd be a good idea for anything other than the most casual use on a quiet network. Dangerous in which way? It will create a larger load on the system, but that's about it. And todays machines are fast enough that you really need a lot of traffic before it will become a serious problem from that point of view. Remember that most of the filtering out of unwanted packets are done in the kernel anyway, and not in user space. That's what the bpf interface and filter programs do for you. The main reason in the past for changing the MAC address has been that you want to control the source MAC address. However, most systems now allows you to spoof the source MAC when outputting packets on the ethernet, so that problem is solved. Load is the one remaining reason to even worry, and that is a rather small worry for most people. With todays network gear, you will not get most packets to your machine anyway, the switches are already doing the filtering for you, so promiscuous mode don't hurt much from that point either. Johnny