aa-proxy Wasmtime component sample

This is a minimal guest component project for the aa:packet/packet-hook WIT world.

What it does

This project is a minimal Wasmtime guest component for aa-proxy-rs.

It demonstrates how to:

• implement the aa:packet/packet-hook WIT world
• receive packet data from the host as typed WIT records
• inspect packet metadata such as proxy type, channel, flags, message id, and payload
• read selected host-side context/config values passed into the guest
• return a decision such as forward or drop
• call host functions to:
  • replace the current packet
  • send a new packet
  • write host-side log messages

The component is meant to be compiled into a .wasm WebAssembly component and then loaded by aa-proxy-rs from the hook directory.

In short, this repo is a starting point for writing packet-processing hooks for aa-proxy-rs in Rust, compiled to Wasmtime components.

Build

1) Install cargo-component

cargo install cargo-component --locked

2) Build the component

cargo component build --release

3) Copy the built artifact into aa-proxy

The output file name is typically:

target/wasm32-wasip1/release/aa_proxy_test_hook.wasm

Copy it to your hook folder, for example:

cp target/wasm32-wasip1/release/aa_proxy_test_hook.wasm /data/wasm-hooks/10_test_hook.wasm

Why the same .wasm works on ARM and RISC-V

The guest artifact is WebAssembly component bytecode, which is architecture-independent. Wasmtime compiles that same .wasm for the current host CPU at runtime. So you normally build the hook once and reuse the same .wasm on x86_64, ARM64, or riscv64 hosts, as long as the host Wasmtime build supports that architecture.

Notes

• Do not put .rs files into /data/wasm-hooks/.
• /data/wasm-hooks/ should contain compiled .wasm component files only.
• Edit source here, then rebuild and copy the .wasm output.