RE: [PATCH bpf-next 0/8] Add support for transmitting packets using XDP in bpf_prog_run()

John Fastabend [off-list ref] writes:

Toke Høiland-Jørgensen wrote:

quoted

This series adds support for transmitting packets using XDP in
bpf_prog_run(), by enabling the xdp_do_redirect() callback so XDP programs
can perform "real" redirects to devices or maps, using an opt-in flag when
executing the program.

The primary use case for this is testing the redirect map types and the
ndo_xdp_xmit driver operation without generating external traffic. But it
turns out to also be useful for creating a programmable traffic generator.
The last patch adds a sample traffic generator to bpf/samples, which
can transmit up to 11.5 Mpps/core on my test machine.

To transmit the frames, the new mode instantiates a page_pool structure in
bpf_prog_run() and initialises the pages with the data passed in by
userspace. These pages can then be redirected using the normal redirection
mechanism, and the existing page_pool code takes care of returning and
recycling them. The setup is optimised for high performance with a high
number of repetitions to support stress testing and the traffic generator
use case; see patch 6 for details.

The series is structured as follows: Patches 1-2 adds a few features to
page_pool that are needed for the usage in bpf_prog_run(). Similarly,
patches 3-5 performs a couple of preparatory refactorings of the XDP
redirect and memory management code. Patch 6 adds the support to
bpf_prog_run() itself, patch 7 adds a selftest, and patch 8 adds the
traffic generator example to samples/bpf.

Overall looks pretty good. Couple questions in the series though.

Yay! Thank you for the review! Will reply to each of those...

-Toke