[Simh] VAX: tap/tun.

[Andrew Back]

Hello,

So I'm having some trouble working out how to get host-vax networking up 
and running with simh via tap/tun.

I'm running an Ubuntu 6.06 Linux host, with current simh & pcap built from
source. I have xq attached to vlan100, which is in turn trunked across 
eth0 to a DECnet only vlan. This works fine, and also works fine if I 
attached xq to br0 and put vlan100 in it. What I would now like to do is 
add another device to this bridge, say tap0, which I can run IP over to 
the host (172.16.x.x) to facilitate mounting an NFS export.

I've tried creating a tap0 with 'tunctl', setting it to 172.16.1.1, and 
then configuring xq to 172.16.1.2. I can't ping from host or vax 
regardless of whether I attach xq to tap0 directly, or br0 with tap0 as a 
member. Either way all I see is an increasing count of dropped TX packets 
on tap0. Does this mean simh is not opening tap0 properly? When it starts 
it says it's opened tap0/br0 - don't see any problems. Have tried setting 
the route via the tap0, and enabling IP forwarding.

I have tried using 'taptap.c' and this works if I configure say IP on tun0 
on the host, and attach xq to tun1. But if I then try attaching xq to br0 
and putting tun1 in the bridge it stops working. I'm guessing this is 
something to do with tun working at the IP layer.

Would be very grateful of any advice as to how I can attach the vax xq to 
a pseudo/virtual interface that can then be put into a bridge such that I 
the vax can see both vlan100 and communicate via IP on a tap or similar to 
the host.

Lastly is there any way to create and attach a second xq in the simulator?

Regards,

Andrew

----------------
Andrew Back
a at smokebelch.org