--transport docker-daemon support

So we can do things like:

sudo bootc switch --transport docker-daemon localhost/bootc:latest

Signed-off-by: Eric Curtin <eric.curtin@docker.com>

crates/lib/src/bootc_composefs/repo.rs

@@ -56,12 +56,15 @@ pub(crate) async fn initialize_composefs_repository(
 /// Ex
 /// docker://quay.io/some-image
 /// containers-storage:some-image
+/// docker-daemon:some-image-id
 pub(crate) fn get_imgref(transport: &str, image: &str) -> String {
     let img = image.strip_prefix(":").unwrap_or(&image);
     let transport = transport.strip_suffix(":").unwrap_or(&transport);
 
     if transport == "registry" {
         format!("docker://{img}")
+    } else if transport == "docker-daemon" {
+        format!("docker-daemon:{img}")
     } else {
         format!("{transport}:{img}")
     }
@@ -138,4 +141,12 @@ mod tests {
             format!("docker://{IMAGE_NAME}")
         );
     }
+
+    #[test]
+    fn test_get_imgref_docker_daemon_transport() {
+        assert_eq!(
+            get_imgref("docker-daemon", IMAGE_NAME),
+            format!("docker-daemon:{IMAGE_NAME}")
+        );
+    }
 }

crates/lib/src/cli.rs

@@ -123,7 +123,7 @@ pub(crate) struct SwitchOpts {
     #[clap(long = "soft-reboot")]
     pub(crate) soft_reboot: Option<SoftRebootMode>,
 
-    /// The transport; e.g. oci, oci-archive, containers-storage.  Defaults to `registry`.
+    /// The transport; e.g. registry, oci, oci-archive, docker-daemon, containers-storage.  Defaults to `registry`.
     #[clap(long, default_value = "registry")]
     pub(crate) transport: String,
 

crates/ostree-ext/src/container/mod.rs

@@ -66,6 +66,8 @@ pub enum Transport {
     ContainerStorage,
     /// Local directory (`dir:`)
     Dir,
+    /// Local Docker daemon (`docker-daemon:`)
+    DockerDaemon,
 }
 
 /// Combination of a remote image reference and transport.
@@ -114,6 +116,7 @@ impl TryFrom<&str> for Transport {
             Self::DOCKER_ARCHIVE_STR => Self::DockerArchive,
             Self::CONTAINERS_STORAGE_STR => Self::ContainerStorage,
             Self::LOCAL_DIRECTORY_STR => Self::Dir,
+            Self::DOCKER_DAEMON_STR => Self::DockerDaemon,
             o => return Err(anyhow!("Unknown transport '{}'", o)),
         })
     }
@@ -126,6 +129,7 @@ impl Transport {
     const CONTAINERS_STORAGE_STR: &'static str = "containers-storage";
     const LOCAL_DIRECTORY_STR: &'static str = "dir";
     const REGISTRY_STR: &'static str = "registry";
+    const DOCKER_DAEMON_STR: &'static str = "docker-daemon";
 
     /// Retrieve an identifier that can then be re-parsed from [`Transport::try_from::<&str>`].
     pub fn serializable_name(&self) -> &'static str {
@@ -136,6 +140,7 @@ impl Transport {
             Transport::DockerArchive => Self::DOCKER_ARCHIVE_STR,
             Transport::ContainerStorage => Self::CONTAINERS_STORAGE_STR,
             Transport::Dir => Self::LOCAL_DIRECTORY_STR,
+            Transport::DockerDaemon => Self::DOCKER_DAEMON_STR,
         }
     }
 }
@@ -258,6 +263,7 @@ impl std::fmt::Display for Transport {
             Self::OciDir => "oci:",
             Self::ContainerStorage => "containers-storage:",
             Self::Dir => "dir:",
+            Self::DockerDaemon => "docker-daemon:",
         };
         f.write_str(s)
     }

crates/ostree-ext/src/container/unencapsulate.rs

@@ -205,9 +205,13 @@ pub(crate) async fn fetch_layer<'a>(
     let (blob, driver, size);
     let media_type: oci_image::MediaType;
     match transport_src {
-        Transport::ContainerStorage => {
-            let layer_info = layer_info
-                .ok_or_else(|| anyhow!("skopeo too old to pull from containers-storage"))?;
+        // Both containers-storage and docker-daemon store layers uncompressed in their
+        // local storage, even though the manifest may indicate they are compressed.
+        // We need to use the actual media type from layer_info to avoid decompression errors.
+        Transport::ContainerStorage | Transport::DockerDaemon => {
+            let layer_info = layer_info.ok_or_else(|| {
+                anyhow!("skopeo too old to pull from containers-storage or docker-daemon")
+            })?;
             let n_layers = layer_info.len();
             let layer_blob = layer_info.get(layer_index).ok_or_else(|| {
                 anyhow!("blobid position {layer_index} exceeds diffid count {n_layers}")

crates/ostree-ext/src/generic_decompress.rs

@@ -22,6 +22,11 @@ use crate::oci_spec::image as oci_image;
 /// TODO: change the skopeo code to shield us from this correctly
 const DOCKER_TYPE_LAYER_TAR: &str = "application/vnd.docker.image.rootfs.diff.tar";
 
+/// The Docker MIME type for gzipped layers when stored in docker-daemon.
+/// Even though this indicates gzip compression, docker-daemon actually stores
+/// the layers uncompressed, so we need to treat this as uncompressed.
+const DOCKER_TYPE_LAYER_TAR_GZIP: &str = "application/vnd.docker.image.rootfs.diff.tar.gzip";
+
 /// Extends the `Read` trait with another method to get mutable access to the inner reader
 trait ReadWithGetInnerMut: Read + Send + 'static {
     fn get_inner_mut(&mut self) -> &mut dyn Read;
@@ -125,6 +130,9 @@ impl Decompressor {
             oci_image::MediaType::Other(t) if t.as_str() == DOCKER_TYPE_LAYER_TAR => {
                 Box::new(TransparentDecompressor(src))
             }
+            oci_image::MediaType::Other(t) if t.as_str() == DOCKER_TYPE_LAYER_TAR_GZIP => {
+                Box::new(TransparentDecompressor(src))
+            }
             o => anyhow::bail!("Unhandled layer type: {}", o),
         };
         Ok(Self {
@@ -228,4 +236,17 @@ mod tests {
         assert_eq!(e.to_string(), "Unknown frame descriptor".to_string());
         drop(d)
     }
+
+    #[test]
+    fn test_docker_tar_gzip_media_type_uses_transparent_decompressor() {
+        // Test that the docker-daemon gzip media type is treated as uncompressed
+        let data = b"test data";
+        let media_type = oci_image::MediaType::Other(DOCKER_TYPE_LAYER_TAR_GZIP.to_string());
+        let mut d = Decompressor::new(&media_type, &data[..]).unwrap();
+        let mut buf = [0u8; 32];
+        let n = d.read(&mut buf).unwrap();
+        assert_eq!(n, data.len());
+        assert_eq!(&buf[..n], data);
+        drop(d)
+    }
 }