Post #700354

A while back I noticed that my hosted-at-home services (media library etc.) sometimes felt very slow from outside. But never thought much of it. Needed to do a large file transfer from home and seeing 200KB/s, finally had enough. Only affects IPv6. Only affects traffic to the OpnSense router itself (not routed traffic), which proxies most of my services. I was ready to blame the ISP for doing weird stuff with the IA_NA address, when I confirmed it happens for the LAN PD address too. Turns out that when I switched from VirtIO/linux-bridge to PCIe passthrough, in a quest for performance, I inadvertently and implicitly enabled TSO offload. Which is badly broken for igc devices for IPv6 traffic. And capped egress goodput to around 2mbps. That one took me rather a bit of poking to find. #ipv6