Hi,

I’ve been running the Panda distribution of TOPS-20 on the KLH10 simulator on a Raspberry Pi 4 for some years now. It’s WALACH on HECnet. The version of the Pi’s OS had been the 32 bit implementation but as some of these were being replaced by 8Gb versions, I recently took the plunge and updated (by re-imaging) everything to the current 64 bit Raspberry Pi OS.

In rebuilding SIMH and KLH10, I sync’d with the latest sources. With SIMH, there were no issues but the KLH10 updates, seemingly post ~2021 have broken networking. The line in my klt20.ini file is:

devdef ni0 564 ni20 dedic=true ifc=tapX ifmeth=tap+bridge ipaddr=192.168.2.46 enaddr=aa:00:04:00:6c:74

With the dpni20 executable running as root, the ‘old’ behaviour causes it to use the default bridge name ‘bridge0’  and create a tap device ‘tap0’ (it disregards the ifc=tapX part of the line).

The new behaviour results in a whole load of IOCTL errors while attempting to create the tap device.

I avoided the problem by restoring the original version of the KLH10 simulator sources and compiling.

The whole thing has reminded me that I wanted to fix the code a while back so that it would make use of an existing tap device, created via /etc/network/interfaces, with full control granted to the non-privileged user the rest of KLH10 runs under, then dpni20 would not need to be privileged. Once I’ve finished with the upgrades I might have a go…. along with all of the other half-done/half-forgotten projects in this area.

Keith