So I’ve been running a highly modified version of OpenVPN and speed and performance have been pretty good overall, however, I noticed that some very few apps would use a custom UDP based API call for data transfer (Ring live video app) and the video would appear very choppy and blurry. I suspected this is because the multi-threaded version of OpenVPN does not preserve UDP packet ordering (whereas UDP protocols like QUIC seem to be more advanced and capable).

I am now experimenting with a solution to this issue by running two VPN tunnels at the same time, one is bulk-mode-multi-threaded for the majority of smart protocols and data and the second is bulk-mode-single-threaded for some of the simpler UDP protocols that assume a specific order of packets arriving from a server or service. This technique requires use of iptables mangle packet marking as well as ip rule mark setting with additional routing table rules.