Configure eth0 down before running systemd from the system image

oak_containers_stage1/Cargo.toml

@@ -14,6 +14,7 @@ clap = { version = "*", features = ["derive"] }
 futures-util = "*"
 nix = "*"
 prost = { workspace = true }
+rtnetlink = "*"
 tar = "*"
 tokio = { version = "*", features = [
  "rt-multi-thread",

oak_containers_stage1/src/main.rs

@@ -22,6 +22,7 @@ mod image;
 use anyhow::Context;
 use clap::Parser;
 use client::LauncherClient;
+use futures_util::TryStreamExt;
 use nix::{
  mount::{mount, umount2, MntFlags, MsFlags},
  unistd::chroot,
@@ -101,5 +102,29 @@ async fn main() -> Result<(), Box<dyn Error>> {
  if !Path::new("/etc/machine-id").exists() {
  fs::write("/etc/machine-id", []).context("error writing placeholder /etc/machine-id")?;
  }
+
+ // Configure eth0 down, as systemd will want to manage it itself and gets confused if it already
+ // has an IP address.
+ {
+ let (connection, handle, _) =
+ rtnetlink::new_connection().context("error opening netlink connection")?;
+ tokio::spawn(connection);
+
+ // `ip link show eth0`
+ let mut links = handle.link().get().match_name("eth0".to_string()).execute();
+
+ if let Some(link) = links.try_next().await? {
+ // `ip link set dev $INDEX down`
+ handle
+ .link()
+ .set(link.header.index)
+ .down()
+ .execute()
+ .await?;
+ } else {
+ println!("warning: eth0 not found");
+ }
+ }
+
  image::switch(&args.init).context("error switching to the system image")?
 }