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22.1 Legacy Series / Re: 22.1rc1 slow in Hyper-V
« on: February 04, 2022, 11:43:07 am »
Hi, I've run into the same issue on a new server and also could reproduced it locally. My input regarding this:
It only seems to happen if the data sender is on the same Hyper-V host (or the host it self) as the Opnsense VM. For the same connection in the opposite direction, it is not a problem. Also I tested without NAT, just routing packets.
Some more information about the RSC feature which seems to cause this problem. When RSC is turned on, Hyper-V vSwitch tries to coalesce small TCP packets into a larger one and send it the receiving guest. From my experience, it happens only when the sender and receiver are on same Hyper-V host. When Opnsense is acting as a packet forwarder, vSwitch on Hyper-V is not supposed to perform RSC. But in this case it seems the RSC is happening on the Opnsense guest for forwarding traffic. So there might be some config setting which confuses vSwitch.
It only seems to happen if the data sender is on the same Hyper-V host (or the host it self) as the Opnsense VM. For the same connection in the opposite direction, it is not a problem. Also I tested without NAT, just routing packets.