add dynlay

src/bin/dkl.rs

@@ -40,10 +40,31 @@ enum Command {
         /// Path where the logs are stored
         #[arg(long, short = 'p', default_value = "/var/log", env = "DKL_LOG_PATH")]
         log_path: String,
+        /// Name of the log set to operate on.
         log_name: String,
         #[command(subcommand)]
         op: LogOp,
     },
+    Dynlay {
+        layer: String,
+        version: String,
+        #[arg(
+            long,
+            short = 'u',
+            default_value = "https://dkl.novit.io/dist/layers",
+            env = "DKL_DYNLAY_URL"
+        )]
+        url_prefix: String,
+        #[arg(
+            long,
+            short = 'd',
+            default_value = "/opt/dynlay",
+            env = "DKL_DYNLAY_DIR"
+        )]
+        layers_dir: String,
+        #[arg(long, default_value = "/")]
+        chroot: std::path::PathBuf,
+    },
 }
 
 #[tokio::main(flavor = "current_thread")]
@@ -90,6 +111,21 @@ async fn main() -> Result<()> {
             log_name,
             op,
         } => op.run(&log_path, &log_name).await,
+        C::Dynlay {
+            ref layer,
+            ref version,
+            ref url_prefix,
+            ref layers_dir,
+            chroot,
+        } => {
+            dkl::dynlay::Dynlay {
+                url_prefix,
+                layers_dir,
+                chroot,
+            }
+            .install(layer, version)
+            .await
+        }
     }
 }
 

src/dynlay.rs

@@ -0,0 +1,165 @@
+use eyre::{format_err, Result};
+use log::{debug, error, info, warn};
+use std::path::PathBuf;
+use tokio::{fs, io::AsyncWriteExt, process::Command};
+
+use crate::fs::spawn_walk_dir;
+
+pub struct Dynlay<'t> {
+    pub url_prefix: &'t str,
+    pub layers_dir: &'t str,
+    pub chroot: PathBuf,
+}
+
+impl<'t> Dynlay<'t> {
+    pub async fn install(&self, layer: &str, version: &str) -> Result<()> {
+        let lay_dir = &format!("{base}/{layer}", base = self.layers_dir);
+
+        debug!("mkdir -p {lay_dir}");
+        fs::create_dir_all(lay_dir).await?;
+
+        let lay_path = &format!("{lay_dir}/{version}");
+
+        if !fs::try_exists(lay_path).await? {
+            let part_file = &format!("{lay_dir}/{version}.tmp");
+
+            self.fetch(layer, version, part_file).await?;
+
+            (fs::rename(part_file, lay_path).await)
+                .map_err(|e| format_err!("failed mv {part_file} {lay_path}: {e}"))?;
+        }
+
+        let mount_path = PathBuf::from(lay_dir).join("mounts").join(layer);
+        let mount_path_str = mount_path.to_string_lossy().into_owned();
+
+        (fs::create_dir_all(&mount_path).await)
+            .map_err(|e| format_err!("mkdir -p {mount_path:?} failed: {e}"))?;
+
+        let mount_path = &fs::canonicalize(mount_path).await?;
+
+        let mut mount_info = rsmount::tables::MountInfo::new()?;
+        mount_info.import_mountinfo()?;
+
+        if mount_info.find_target(mount_path).is_some() {
+            info!("clearing previous mount");
+
+            let mut paths = spawn_walk_dir(mount_path.clone());
+            while let Some(result) = paths.recv().await {
+                let Ok((path, md)) = result else {
+                    continue;
+                };
+                if !md.is_dir() {
+                    let path = self.chroot.join(&path);
+
+                    debug!("rm {path:?}");
+                    if let Err(e) = fs::remove_file(&path).await {
+                        warn!("rm {path:?} failed: {e}");
+                    }
+                }
+            }
+
+            sudo("umount", &[mount_path]).await?;
+        }
+
+        // mount layer
+        info!("mounting layer");
+        sudo("mount", &["-t", "squashfs", lay_path, &mount_path_str]).await?;
+
+        let mut paths = spawn_walk_dir(mount_path.clone());
+        while let Some(result) = paths.recv().await {
+            let Ok((path, md)) = result else {
+                continue;
+            };
+
+            let target = self.chroot.join(&path);
+
+            if md.is_dir() {
+                debug!("mkdir -p {target:?}");
+                if let Err(e) = fs::create_dir_all(&target).await {
+                    error!("mkdir -p {target:?} failed: {e}");
+                }
+            } else {
+                let _ = fs::remove_file(&target).await;
+
+                let source = mount_path.join(&path);
+
+                debug!("ln -s {source:?} {target:?}");
+                if let Err(e) = fs::symlink(&source, &target).await {
+                    error!("ln -s {source:?} {target:?} failed: {e}");
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    async fn fetch(&self, layer: &str, version: &str, part_file: &str) -> Result<()> {
+        let url = &format!("{}/{layer}/{version}", self.url_prefix);
+        info!("fetching {url}");
+
+        let mut out = (fs::File::create(part_file).await)
+            .map_err(|e| format_err!("failed to open {part_file}: {e}"))?;
+
+        let resp = reqwest::get(url).await?;
+        if !resp.status().is_success() {
+            return Err(format_err!("fetch failed: {}", resp.status()));
+        }
+
+        let sha1 = (resp.headers().get("x-content-sha1"))
+            .ok_or(format_err!("no content hash in response"))?;
+        let sha1 = (sha1.to_str()).map_err(|e| format_err!("invalid sha1: {e}"))?;
+
+        debug!("content sha1: {sha1}");
+        let mut exp_sha1 = [0; 20];
+        hex::decode_to_slice(sha1, &mut exp_sha1).map_err(|e| format_err!("invalid sha1: {e}"))?;
+
+        let mut hash = openssl::sha::Sha1::new();
+
+        use futures::StreamExt;
+        let mut stream = resp.bytes_stream();
+        while let Some(bytes) = stream.next().await {
+            let bytes = bytes.map_err(|e| format_err!("remote read error: {e}"))?;
+            hash.update(&bytes);
+            (out.write_all(&bytes).await).map_err(|e| format_err!("local write error: {e}"))?;
+        }
+
+        (out.flush().await).map_err(|e| format_err!("local write error: {e}"))?;
+        drop(out);
+
+        let dl_sha1 = hash.finish();
+        if dl_sha1 != exp_sha1 {
+            if let Err(e) = fs::remove_file(part_file).await {
+                error!("failed to remove {part_file}: {e}");
+            }
+            return Err(format_err!(
+                "invalid content hash: expected {exp}, got {got}",
+                exp = hex::encode(exp_sha1),
+                got = hex::encode(dl_sha1)
+            ));
+        }
+
+        Ok(())
+    }
+}
+
+async fn sudo<I, S>(program: &str, args: I) -> Result<()>
+where
+    I: IntoIterator<Item = S>,
+    S: AsRef<std::ffi::OsStr>,
+{
+    let mut cmd = if nix::unistd::geteuid().is_root() {
+        let mut cmd = Command::new(program);
+        cmd.args(args);
+        cmd
+    } else {
+        let mut cmd = Command::new("sudo");
+        cmd.arg(program).args(args);
+        cmd
+    };
+    let status = cmd.status().await?;
+    if status.success() {
+        Ok(())
+    } else {
+        Err(format_err!("{program} failed: {status}"))
+    }
+}

src/fs.rs

@@ -0,0 +1,60 @@
+use eyre::Result;
+use std::fs::Metadata;
+use std::path::PathBuf;
+use tokio::fs::read_dir;
+use tokio::sync::mpsc;
+
+pub fn spawn_walk_dir(
+    dir: impl Into<PathBuf> + Send + 'static,
+) -> mpsc::Receiver<Result<(PathBuf, Metadata)>> {
+    let (tx, rx) = mpsc::channel(1);
+    tokio::spawn(walk_dir(dir, tx));
+    rx
+}
+
+pub async fn walk_dir(dir: impl Into<PathBuf>, tx: mpsc::Sender<Result<(PathBuf, Metadata)>>) {
+    let dir: PathBuf = dir.into();
+
+    let mut todo = std::collections::LinkedList::new();
+    if let Ok(rd) = read_dir(&dir).await {
+        todo.push_front(rd);
+    }
+
+    while let Some(rd) = todo.front_mut() {
+        let entry = match rd.next_entry().await {
+            Ok(v) => v,
+            Err(e) => {
+                if tx.send(Err(e.into())).await.is_err() {
+                    return;
+                }
+                todo.pop_front(); // skip dir on error
+                continue;
+            }
+        };
+
+        let Some(entry) = entry else {
+            todo.pop_front();
+            continue;
+        };
+
+        let Ok(md) = entry.metadata().await else {
+            continue;
+        };
+        let is_dir = md.is_dir();
+
+        let Ok(path) = entry.path().strip_prefix(&dir).map(|p| p.to_path_buf()) else {
+            continue; // sub-entry not in dir, weird but semantically, we ignore
+        };
+
+        if tx.send(Ok((path, md))).await.is_err() {
+            return;
+        }
+
+        // recurse in sub directories
+        if is_dir {
+            if let Ok(rd) = read_dir(entry.path()).await {
+                todo.push_front(rd);
+            }
+        }
+    }
+}

src/lib.rs

@@ -2,6 +2,8 @@ pub mod apply;
 pub mod bootstrap;
 pub mod dls;
 pub mod logger;
+pub mod dynlay;
+pub mod fs;
 
 #[derive(Debug, serde::Deserialize, serde::Serialize)]
 pub struct Config {