That’s very interesting, thank you for sharing. Looks like it could be a very useful tool for testing high performance networking.

I wonder if something similar could be done using TC BPF instead of AF_XDP? My only reservation about AF XDP is that it requires a special NIC to support it, so it may not be useful for a “regular Joe” user. I wonder if TC BPF would also work since it similarly bypasses the Kernel networking stack, I believe you can put packets directly into the NIC TX queue for transmission

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tptacek 3 days ago | parent | next [-]

You can, but the interesting thing about AF_XDP is that you've got a userland path to writing directly to the card's DMA buffers; TC BPF still allocates an skbuff for every packet you send.

	▲	adrian_b 2 days ago \| parent [-]
		Also with liburing you have zero-copy send and receive operations for normal protocols like UDP or TCP, but this requires a NIC that supports scatter/gather DMA (so that the packet headers go to/from kernel buffers, while the data goes to/from userland buffers). AF_XDP is also available in older kernels, but with recent enough kernels (zero-copy receive is a recent addition) and with a good NIC, liburing should provide a similar performance.

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Palomides 2 days ago | parent | prev | next [-]

it seems like every NIC on the market that can do 100Gb has support in its linux kernel driver, so probably not a big deal in practice

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bgpdude 3 days ago | parent | prev [-]

you can use generic af_xdp which sits at the TC layer. Just get a bit less performance.

	▲	bgpdude 3 days ago \| parent [-]
		That's what the veth examples are using