[Simh] VAX XQ and wireless networking

[Johnny Billquist]

If that's how VirtualBox works, then it is rather broken.
How about when you talk DECnet? There are no IP addresses involved at all.

	Johnny

On 2012-11-18 00:07, TJ Merritt wrote:
> The TUN interface will get the packets injected into the system, but
> will not get them bridged across the wireless network which uses the MAC
> address for managing the wireless network.  Since your MAC address for
> the virtual interface is not the same as the mac address for the host,
> reply packets over wireless will get dropped.  The trick is to get the
> packets to go out with the host's MAC address and replies routed back to
> the virtual interface.
>
> VirtualBox does this by sending packets out with the original IP address
> but the MAC address of the host, they then record the virtual interface
> that the IP address came from, when the reply packet comes back, they
> use the IP address to look up the virtual interface associated with that
> IP address and route the packet to that interface.  There are special
> cases of course for things like broadcast, multicast, and IP addresses
> that are shared between multiple VM's.  VirtualBox does not currently
> support IPv6 addresses though. This would also not help for DECnet.
> This is effectively a layer 3 switching capability that works around the
> lack of layer 2 switching in the wireless network.
>
> Another approach would be to setup NAT so that the NAT layer can take
> care of the MAC address rewriting.  It will also rewrite the IP address
> though.  If this is satisfactory, you there should be plenty of NAT
> resources available to you on Mint such that no code writing is
> required.
>
> Adding virutal networking support for wireless networks would be a major
> undertaking for SimH, but if done, could eliminate most of the hiccups
> with virtual networking over wireless networks.
>
> Of course, not of these issues occur over wired netowrks.
>
> -- TJ
>
> On Sat, 2012-11-17 at 15:24 -0500, Dan Gahlinger wrote:
>> It works...
>> use the TUN interface and the bridging, works just fine.
>>
>>
>> Dan.
>>
>>
>>> Date: Sat, 17 Nov 2012 14:14:24 -0600
>>> From: tivo.overo at gmail.com
>>> To: simh at trailing-edge.com
>>> Subject: [Simh] VAX XQ and wireless networking
>>>
>>> Is this even possible? I have SIMH 3.9 on Linux Mint 12, running the
>>> VAX with OpenVMS 7.3. It works great, except for networking. The
>>> hardware is ASUS EeePC with Atheros AR5001 wireless network adapter
>>> and Atheros L2 Fast Ethernet adapter.
>>>
>>> I have libpcap version 1.1.1 (which is also callable as version 0.8)
>>> installed on Linux. The VAX module was compiled with networking
>>> enabled.
>>>
>>> The configuration file has an "attach xq0 wlan0" or "attach xq0
>> eth0"
>>> depending on which interface I'm trying to use. With the wired
>>> ethernet (eth0) I am able to use both TCP/IP and DECNET Plus. With
>> the
>>> wireless (wlan0) neither one works.
>>>
>>> I've tried disabling the DECNET IV compatibility mode, which was
>>> recommended in one source for wireless compatibility, and also tried
>>> adding "set xq xx-yy-zz-aa-bb-cc" (with the actual MAC address of
>> the
>>> wireless adapter) to the configuration. The first did nothing I
>> could
>>> discern, and the second generated an error message during startup of
>>> the SIMH module, saying that the MAC address was already in use and
>>> could not be assigned.
>>>
>>> Obviously the workaround is to use a cabled connection when the VAX
>>> emulator is needed, but this isn't very practical in most cases. Is
>>> there any other possibility I've overlooked?
>>>
>>> I notice that this is a frequently found question when using Google
>> to
>>> look for answers, but I found no responses other than the two
>>> solutions mentioned above. I suppose a different network card
>>> emulation for VAX could make the wi-fi adapter look like a normal
>>> ethernet interface, but apparently that hasn't been done yet and
>> it's
>>> probably beyond my very rudimentary C coding abilities.
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>>
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-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol