[Simh] simh and tap device under linux

[Andrew Warkentin]

Seth Morabito wrote:
> On Tue, Aug 25, 2009 at 10:45 AM, Tim Newsham<newsham at lava.net> wrote:
>   
>>> The other technique works as long as you have 'sudo' installed. You
>>> can add a line to your /etc/sudoers file to let a normal user (login
>>> 'foobar') run the executable as root:
>>>
>>> foobar           ALL=NOPASSWD: /path/to/pdp11
>>>       
>> You might as well just give root access to the person who will
>> run pdp11.  If its setuid you can just shell out and run
>> commands as root:
>>     
>
> Good point - I was totally unaware that the ! command existed in SIMH
> and allowed shell access. So both of those techniques are no good.
> I've never had any reason to allow anyone (but myself) to run SIMH, so
> I guess we're back at square one.
>
> FWIW, I've been toying with creating a small JEOS VMware virtual
> machine for SIMH, but it suffers a related problem: VMware will
> complain if you attempt to put a guest ethernet device in promiscuous
> mode. The host needs special permissions set on the /dev/vmnet*
> interfaces for it to work, so it's not a drop-in solution either.
>
> A purely user-space networking solution for SIMH is badly needed
> (well, for some definitions of 'badly'.  And 'needed'. But it would
> certainly be very welcome.)
>
> -Seth
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>   
There is a patch that replaces the libpcap-based network support with 
SLiRP. It is IP-only, and the only way to run servers on it is to 
redirect specific guest ports to host ports (these kinds of restrictions 
will affect just about any userspace network stack).
Maybe SIMH should have support for using /dev/tap* or /dev/net/tun like 
e.g. Hercules does. That would get around both the problem of having to 
run the simulator as root, and the inability of the guest to talk to the 
host, while still allowing the guest to be fully accessible from the 
outside and use non-IP protocols.