Add --guestfwd arg to boco boot

init/src/main.rs

@@ -353,6 +353,9 @@ fn exec_command(argv: &[String], user: Option<UserSpec>) -> ! {
     let c_prog = cstrings[0].clone();
     let c_refs: Vec<&CString> = cstrings.iter().collect();
 
+    // If UserSpec is 0:0, don't fork.
+    let user = user.filter(|u| !u.uid.is_root() || u.gid != Gid::from_raw(0));
+
     match user {
         None => {
             // No privilege drop: exec directly, PID 1 becomes the command.
@@ -362,6 +365,7 @@ fn exec_command(argv: &[String], user: Option<UserSpec>) -> ! {
             std::process::exit(1);
         }
         Some(user) => {
+            warn(&format!("dropping privileges to {}:{}", user.uid, user.gid));
             // Drop privileges in a child so PID 1 (root) can poweroff afterwards.
             match unsafe { fork() } {
                 Ok(ForkResult::Child) => {

scripts/setup.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -ex
+
+cd "$(dirname "$0")/.."
+
+mkdir -p "$HOME/.local/share/boco"
+cargo build --release --target x86_64-unknown-linux-musl -p boco-init
+
+target_dir="${CARGO_TARGET_DIR:-target}"
+cp "$target_dir/x86_64-unknown-linux-musl/release/boco-init" "$HOME/.local/share/boco/"
+

src/qemu.rs

@@ -24,6 +24,10 @@ pub struct BootCmd {
     #[clap(long)]
     forward: Vec<PortForward>,
 
+    /// Pass a `guestfwd=...` argument to qemu `-nic` argument.
+    #[clap(long)]
+    guestfwd: Vec<String>,
+
     /// Override the command to exec in the VM (base64-encoded on the kernel
     /// cmdline as `boco.cmd=<b64>`). Overrides the CMD inferred at build time.
     #[clap(long)]
@@ -35,6 +39,9 @@ pub struct BootCmd {
     /// relative to the image's WORKINGDIR. Can be repeated.
     #[clap(long)]
     mount: Vec<String>,
+
+    /// Extra arguments to qemu
+    extra: Vec<String>,
 }
 
 /// Invoke `qemu` to boot a boco image. See [`BootCmd`] for options
@@ -46,8 +53,10 @@ pub(crate) fn boot(
         name,
         memory,
         forward,
+        guestfwd,
         cmd,
         mount,
+        extra,
     }: BootCmd,
 ) -> Result<()> {
     let reg_dir = registry_dir(&name)?;
@@ -149,6 +158,9 @@ pub(crate) fn boot(
     for forward in &forward {
         _ = write!(&mut network, ",hostfwd={forward}");
     }
+    for guestfwd in &guestfwd {
+        _ = write!(&mut network, ",guestfwd={guestfwd}");
+    }
 
     let mut command = Command::new("qemu-system-x86_64");
 
@@ -165,7 +177,8 @@ pub(crate) fn boot(
         .args(["-no-reboot"])
         .args(["-append", &cmdline])
         .args(["-nographic"])
-        .args(["-nic", &network]);
+        .args(["-nic", &network])
+        .args(&extra);
 
     println!("{command:?}");