Add initial XDP skeleton

[Jake-Shadle]

This adds the initial XDP integration skeleton to make future PRs easier to review (hopefully). This PR doesn't "do" anything, but is meant to be small and easier to digest, future PRs will be more substantial.

There are two new crates:

crates/ebpf

This is the actual eBPF program that is loaded into the kernel and attached to a NIC so that it can determine if packets received need to be routed to quilkin or not. This is in a separate workspace because its build requirements are different from the rest of this repo, namely that it requires a different target, bpfel-unknown-none, and nightly due to needing build the core crate. For now, there is a bash script that can be used to build it, but this first pass just puts the final binary artifact in the repo since it is quite small and means CI has to do less work, but can be built from source later if we really want that.

crates/xdp

This is a shim crate that basically wraps the two main crates involved with XDP, aya, which is the external rust crate used to load and manage eBPF programs, and xdp the crate I've been working on that is used to create and handle AF_XDP sockets in userspace. The idea with having this separate crate is that quilkin itself will have a smaller surface area for interacting with XDP itself so that it's easier to make changes/remove it in the future and just generally reduce churn in quilkin itself.

[quilkin-bot]

Build Succeeded 🥳

Build Id: 3471c90a-5f7e-4ac5-a7ed-861afec7411e

The following development images have been built, and will exist for the next 30 days:

• us-docker.pkg.dev/quilkin/ci/quilkin:0.10.0-dev-a313a7c

To build this version:

git fetch [email protected]:googleforgames/quilkin.git pull/1052/head:pr_1052 && git checkout pr_1052
cargo build