AF_XDP kind of is a complete bypass, right? RX get scooped right off the DMA buffer for the card, and TX get shoved right back in.

Yeah fair point. I should have been more precise. AF_XDP with ZC bypasses the kernel networking stack and the NIC DMA's directly into UMEM and so in that sense it absolutely is a kernel bypass.

The difference I was getting at vs DPDK is that the kernel NIC driver/NAPI/XDP path is still involvd. With DPDK the userspace PMD is effectively driving the NIC and accessing the queues directly.

either way, it's great and everyone should use it :) that is assuming they have a use case for it. The use-cases are perhaps somewhat limited as it also bypasses the kernel tcp-ip stack, so you gotta do a lot yourself.