Implement sending commands via Unix sockets with optional systemd socket activation.

burrow/Cargo.toml

@@ -7,14 +7,17 @@ edition = "2021"
 crate-type = ["lib", "staticlib"]
 
 [dependencies]
-tokio = { version = "1.21", features = ["rt", "macros"] }
-tun = { version = "0.1", path = "../tun" }
+tokio = { version = "1.21", features = ["rt", "sync", "io-util", "macros"] }
+tun = { version = "0.1", path = "../tun", features = ["serde"] }
 clap = { version = "4.3.2", features = ["derive"] }
 env_logger = "0.10"
 log = "0.4"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 caps = "0.5.5"
+libsystemd = "0.6"
 
 [target.'cfg(target_vendor = "apple")'.dependencies]
 nix = { version = "0.26.2" }

burrow/src/daemon/command.rs

@@ -0,0 +1,13 @@
+use serde::{Deserialize, Serialize};
+use tun::TunOptions;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum DaemonCommand {
+    Start(DaemonStartOptions),
+    Stop,
+}
+
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct DaemonStartOptions {
+    pub(super) tun: TunOptions,
+}

burrow/src/daemon/instance.rs

@@ -0,0 +1,40 @@
+use super::*;
+
+pub struct DaemonInstance {
+    rx: mpsc::Receiver<DaemonCommand>,
+    tun_interface: Option<TunInterface>,
+}
+
+impl DaemonInstance {
+    pub fn new(rx: mpsc::Receiver<DaemonCommand>) -> Self {
+        Self {
+            rx,
+            tun_interface: None,
+        }
+    }
+
+    pub async fn run(&mut self) -> Result<()> {
+        while let Some(command) = self.rx.recv().await {
+            match command {
+                DaemonCommand::Start(options) => {
+                    if self.tun_interface.is_none() {
+                        self.tun_interface = Some(options.tun.open()?);
+                        eprintln!("Daemon starting tun interface.");
+                    } else {
+                        eprintln!("Got start, but tun interface already up.");
+                    }
+                }
+                DaemonCommand::Stop => {
+                    if self.tun_interface.is_some() {
+                        self.tun_interface = None;
+                        eprintln!("Daemon stopping tun interface.");
+                    } else {
+                        eprintln!("Got stop, but tun interface is not up.")
+                    }
+                }
+            }
+        }
+
+        Ok(())
+    }
+}

burrow/src/daemon/mod.rs

@@ -0,0 +1,19 @@
+use super::*;
+use tokio::sync::mpsc;
+
+mod command;
+mod instance;
+mod net;
+
+use instance::DaemonInstance;
+use net::listen;
+
+pub use command::{DaemonCommand, DaemonStartOptions};
+pub use net::DaemonClient;
+
+pub async fn daemon_main() -> Result<()> {
+    let (tx, rx) = mpsc::channel(2);
+    let mut inst = DaemonInstance::new(rx);
+
+    tokio::try_join!(inst.run(), listen(tx)).map(|_| ())
+}

burrow/src/daemon/net/mod.rs

@@ -0,0 +1,29 @@
+use super::*;
+use serde::{Deserialize, Serialize};
+
+#[cfg(target_family = "unix")]
+mod unix;
+#[cfg(all(target_family = "unix", not(target_os = "linux")))]
+pub use unix::{listen, DaemonClient};
+
+#[cfg(target_os = "linux")]
+mod systemd;
+#[cfg(target_os = "linux")]
+pub use systemd::{listen, DaemonClient};
+
+#[cfg(target_os = "windows")]
+mod windows;
+#[cfg(target_os = "windows")]
+pub use windows::{listen, DaemonClient};
+
+#[derive(Clone, Serialize, Deserialize)]
+pub struct DaemonRequest {
+    pub id: u32,
+    pub command: DaemonCommand,
+}
+
+#[derive(Clone, Serialize, Deserialize)]
+pub struct DaemonResponse {
+    //  Error types can't be serialized, so this is the second best option.
+    result: std::result::Result<(), String>,
+}

burrow/src/daemon/net/systemd.rs

@@ -0,0 +1,16 @@
+use super::*;
+use std::os::fd::IntoRawFd;
+
+pub async fn listen(cmd_tx: mpsc::Sender<DaemonCommand>) -> Result<()> {
+    if !libsystemd::daemon::booted() || listen_with_systemd(cmd_tx.clone()).await.is_err() {
+        unix::listen(cmd_tx).await?;
+    }
+    Ok(())
+}
+
+async fn listen_with_systemd(cmd_tx: mpsc::Sender<DaemonCommand>) -> Result<()> {
+    let fds = libsystemd::activation::receive_descriptors(false).unwrap();
+    super::unix::listen_with_optional_fd(cmd_tx, Some(fds[0].clone().into_raw_fd())).await
+}
+
+pub type DaemonClient = unix::DaemonClient;

burrow/src/daemon/net/unix.rs

@@ -0,0 +1,102 @@
+use super::*;
+use std::{
+    os::fd::{FromRawFd, RawFd},
+    os::unix::net::UnixListener as StdUnixListener,
+    path::Path,
+};
+use tokio::{
+    io::{AsyncBufReadExt, AsyncWriteExt, BufReader},
+    net::{UnixListener, UnixStream},
+};
+
+const UNIX_SOCKET_PATH: &str = "/run/burrow.sock";
+
+pub async fn listen(cmd_tx: mpsc::Sender<DaemonCommand>) -> Result<()> {
+    listen_with_optional_fd(cmd_tx, None).await
+}
+
+pub(crate) async fn listen_with_optional_fd(
+    cmd_tx: mpsc::Sender<DaemonCommand>,
+    raw_fd: Option<RawFd>,
+) -> Result<()> {
+    let path = Path::new(UNIX_SOCKET_PATH);
+
+    let listener = if let Some(raw_fd) = raw_fd {
+        let listener = unsafe { StdUnixListener::from_raw_fd(raw_fd) };
+        listener.set_nonblocking(true)?;
+        UnixListener::from_std(listener)
+    } else {
+        UnixListener::bind(path)
+    };
+    let listener = if let Ok(listener) = listener {
+        listener
+    } else {
+        //  Won't help all that much, if we use the async version of fs.
+        std::fs::remove_file(path)?;
+        UnixListener::bind(path)?
+    };
+    loop {
+        let (stream, _) = listener.accept().await?;
+        let cmd_tx = cmd_tx.clone();
+
+        //  I'm pretty sure we won't need to manually join / shut this down,
+        //  `lines` will return Err during dropping, and this task should exit gracefully.
+        tokio::task::spawn(async {
+            let cmd_tx = cmd_tx;
+            let mut stream = stream;
+            let (mut read_stream, mut write_stream) = stream.split();
+            let buf_reader = BufReader::new(&mut read_stream);
+            let mut lines = buf_reader.lines();
+            while let Ok(Some(line)) = lines.next_line().await {
+                let mut res = DaemonResponse { result: Ok(()) };
+                let command = match serde_json::from_str::<DaemonRequest>(&line) {
+                    Ok(req) => Some(req.command),
+                    Err(e) => {
+                        res.result = Err(format!("{}", e));
+                        None
+                    }
+                };
+                let mut res = serde_json::to_string(&res).unwrap();
+                res.push('\n');
+
+                write_stream.write_all(res.as_bytes()).await.unwrap();
+
+                //  I want this to come at the very end so that we always send a reponse back.
+                if let Some(command) = command {
+                    cmd_tx.send(command).await.unwrap();
+                }
+            }
+        });
+    }
+}
+
+pub struct DaemonClient {
+    connection: UnixStream,
+}
+
+impl DaemonClient {
+    pub async fn new() -> Result<Self> {
+        Self::new_with_path(UNIX_SOCKET_PATH).await
+    }
+
+    pub async fn new_with_path(path: &str) -> Result<Self> {
+        let path = Path::new(path);
+        let connection = UnixStream::connect(path).await?;
+
+        Ok(Self { connection })
+    }
+
+    pub async fn send_command(&mut self, command: DaemonCommand) -> Result<()> {
+        let mut command = serde_json::to_string(&DaemonRequest { id: 0, command })?;
+        command.push('\n');
+
+        self.connection.write_all(command.as_bytes()).await?;
+        let buf_reader = BufReader::new(&mut self.connection);
+        let mut lines = buf_reader.lines();
+        //  This unwrap *should* never cause issues.
+        let response = lines.next_line().await?.unwrap();
+        let res: DaemonResponse = serde_json::from_str(&response)?;
+        res.result.unwrap();
+        Ok(())
+    }
+}

burrow/src/daemon/net/windows.rs

@@ -0,0 +1,17 @@
+use super::*;
+
+pub async fn listen(_: mpsc::Sender<DaemonCommand>) -> Result<()> {
+    unimplemented!("This platform does not currently support daemon mode.")
+}
+
+pub struct DaemonClient;
+
+impl DaemonClient {
+    pub async fn new() -> Result<Self> {
+        unimplemented!("This platform does not currently support daemon mode.")
+    }
+
+    pub async fn send_command(&mut self, _: DaemonCommand) -> Result<()> {
+        unimplemented!("This platform does not currently support daemon mode.")
+    }
+}

burrow/src/main.rs

@@ -8,6 +8,10 @@ use tokio::io::Result;
 use burrow::retrieve;
 use tun::TunInterface;
 
+mod daemon;
+
+use daemon::{DaemonClient, DaemonCommand, DaemonStartOptions};
+
 #[derive(Parser)]
 #[command(name = "Burrow")]
 #[command(author = "Hack Club <[email protected]>")]
@@ -30,6 +34,10 @@ enum Commands {
     Start(StartArgs),
     /// Retrieve the file descriptor of the tun interface
     Retrieve(RetrieveArgs),
+    /// Stop Burrow daemon
+    Stop,
+    /// Start Burrow daemon
+    Daemon(DaemonArgs),
 }
 
 #[derive(Args)]
@@ -38,14 +46,15 @@ struct StartArgs {}
 #[derive(Args)]
 struct RetrieveArgs {}
 
+#[derive(Args)]
+struct DaemonArgs {}
+
 #[cfg(any(target_os = "linux", target_vendor = "apple"))]
 async fn try_start() -> Result<()> {
-    burrow::ensureroot::ensure_root();
-    let iface = TunInterface::new()?;
-    println!("{:?}", iface.name());
-    let iface2 = retrieve();
-    println!("{}", iface2);
-    Ok(())
+    let mut client = DaemonClient::new().await?;
+    client
+        .send_command(DaemonCommand::Start(DaemonStartOptions::default()))
+        .await
 }
 
 #[cfg(any(target_os = "linux", target_vendor = "apple"))]
@@ -56,6 +65,13 @@ async fn try_retrieve() -> Result<()> {
     Ok(())
 }
 
+#[cfg(any(target_os = "linux", target_vendor = "apple"))]
+async fn try_stop() -> Result<()> {
+    let mut client = DaemonClient::new().await?;
+    client.send_command(DaemonCommand::Stop).await?;
+    Ok(())
+}
+
 #[cfg(not(any(target_os = "linux", target_vendor = "apple")))]
 async fn try_start() -> Result<()> {
     Ok(())
@@ -66,8 +82,13 @@ async fn try_retrieve() -> Result<()> {
     Ok(())
 }
 
+#[cfg(not(any(target_os = "linux", target_vendor = "apple")))]
+async fn try_stop() -> Result<()> {
+    Ok(())
+}
+
 #[tokio::main(flavor = "current_thread")]
-async fn main() {
+async fn main() -> Result<()> {
     println!("Platform: {}", std::env::consts::OS);
 
     let cli = Cli::parse();
@@ -80,5 +101,11 @@ async fn main() {
             try_retrieve().await.unwrap();
             println!("FINISHED");
         }
+        Commands::Stop => {
+            try_stop().await.unwrap();
+        }
+        Commands::Daemon(_) => daemon::daemon_main().await?,
     }
+
+    Ok(())
 }

systemd/burrow.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=Burrow
+After=burrow.socket
+
+[Service]
+ExecStart=/usr/local/bin/burrow daemon
+
+[Install]
+WantedBy=multi-user.target

systemd/burrow.socket

@@ -0,0 +1,8 @@
+[Unit]
+Description=Burrow Socket
+
+[Socket]
+ListenStream=/run/burrow.sock
+
+[Install]
+WantedBy=sockets.target

tun/Cargo.toml

@@ -11,10 +11,12 @@ socket2 = "0.4"
 tokio = { version = "1.28", features = [] }
 byteorder = "1.4"
 log = "0.4"
+serde = { version = "1", features = ["derive"], optional = true }
 
 futures = { version = "0.3.28", optional = true }
 
 [features]
+serde = ["dep:serde"]
 tokio = ["tokio/net", "dep:futures"]
 
 [target.'cfg(feature = "tokio")'.dev-dependencies]

tun/src/options.rs

@@ -3,7 +3,8 @@ use std::io::Error;
 
 use super::TunInterface;
 
-#[derive(Default)]
+#[derive(Debug, Clone, Default)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct TunOptions {
     /// (Windows + Linux) Name the tun interface.
     pub(crate) name: Option<String>,