This setup is rather complex, so apologies for the length of this mail. I'm also not at all sure where my problem is, so again I apologise if this is the wrong place to ask. I have a raspberry pi sitting in a remote office (hostname 'pi' below), a VPS hosted on someone's cloud (hostname 'vps' below) and my local laptop (hostname 'laptop'). The remote office then has another piece of equipment which is discoverable by sending a UDP multicast packet to a specific multicast address and listening for a response. I have a python script that can discover this device and also some Windows software from the vendor that can discover it. What I'm trying to achieve is running the vendor's software locally and have it discover the remote piece of equipment. The raspberry pi connects to the VPS by SSH and opens a reverse channel, connecting vps:127.0.0.1:9001 to pi:22. I then ssh to the VPS and set up a local forward from laptop:9001 to vps:9001. I set up tap adapters on the laptop and the pi, both called tap0. On the pi, tap0 and eth0 are both connected to a bridge br0, which gets a LAN IP address by DHCP. I then connect to the pi from my laptop, using the two tunnels I've described above, like this: ssh -o Tunnel=ethernet -w 0:0 -p 9001 me@localhost dhclient tap0 route del default This works and tap0 gets an IP address on the remote LAN by DHCP (I haven't figured out the DHCP magic to ignore the default route it's sent, so I have to delete the new default route manually). I can then run my python script and discover the remote equipment - multicast UDP traffic is working across the tunnel. Now I kick off a VirtualBox VM running Windows 10. It has a virtual ethernet adapter which is bridged to tap0 on my laptop. This comes up and also receives an IP address on the remote LAN by DHCP and I can ping addresses on the remote network. At this stage, my python script running on the laptop still works and can discover the remote equipment. I then start the vendor's software and ask it to discover the remote equipment. This fails and, at the same time, my python script on the laptop stops working. I can still ping remote addresses from both the laptop and the VM, but multicast UDP across the link no longer works. Even if I shut down the VM, the tunnel is still working for 'normal' IP traffic is still working but the multicast UDP discovery doesn't work any more. Adding '-v' to the ssh commandline doesn't show anything happening when I run the vendor's software. Before running the vendor's software, I can also run the python script on the VM and it succeeds. After I run the vendor's software, it fails. If I exit ssh, kill dhclient, bring the local tap1 down and then start it all back up again, it works again, until I run the vendor's software again. Then it fails again. I don't even know where to start looking for the problem here. Can anyone give some advice or pointers in the right direction? Thanks for reading, Tom _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
