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bundle: add more comments with quotation from the image spec
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The OCI image spec has a section named `Conversion to OCI Runtime
Configuration`, which defines how to generate a default runtime
configuration from an image.

So add more comments to create_runtime_config() by quoting spec
definitions.

Signed-off-by: Jiang Liu <[email protected]>
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@jiangliu
jiangliu committed Apr 21, 2022
1 parent 17ade53 commit a98956e
Showing 1 changed file with 72 additions and 24 deletions.
96 changes: 72 additions & 24 deletions src/bundle.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,15 +20,25 @@ const ANNOTATION_CREATED: &str = "org.opencontainers.image.created";
const ANNOTATION_STOP_SIGNAL: &str = "org.opencontainers.image.stopSignal";
const ANNOTATION_EXPOSED_PORTS: &str = "org.opencontainers.image.exposedPorts";

/// create_runtime_config will create the config.json file under the bundle_path,
/// and return the final bundle config path.
/// Convert an `application/vnd.oci.image.config.v1+json` object into an OCI runtime configuration
/// blob and write to `config.json`.
///
/// [OCI Image Spec: Conversion to OCI Runtime Configuration](https://github.com/opencontainers/image-spec/blob/main/conversion.md)
/// states:
///
/// The "default generated runtime configuration" MAY be overridden or combined with externally
/// provided inputs from the caller. In addition, a converter MAY have its own
/// implementation-defined defaults and extensions which MAY be combined with the "default generated
/// runtime configuration".
pub fn create_runtime_config(
image_config: &ImageConfiguration,
bundle_path: &Path,
) -> Result<PathBuf> {
let mut spec = Spec::default();

// Update the default hostname of `youki`
spec.set_hostname(Some(BUNDLE_HOSTNAME.to_string()));

let mut annotations: HashMap<String, String> = HashMap::new();
annotations.insert(ANNOTATION_OS.to_string(), image_config.os().to_string());
annotations.insert(
Expand All @@ -41,39 +51,88 @@ pub fn create_runtime_config(
if let Some(created) = image_config.created() {
annotations.insert(ANNOTATION_CREATED.to_string(), created.to_string());
}
let mut process = Process::default();

if let Some(config) = image_config.config() {
let mut process = Process::default();

// Verbatim Fields:
//
// A compliant configuration converter MUST extract the following fields verbatim to the
// corresponding field in the generated runtime configuration:
// - WorkingDir
// - Env
// - EntryPoint
// - Cmd
if let Some(working_dir) = config.working_dir() {
process.set_cwd(PathBuf::from(working_dir));
}

// The converter MAY add additional entries to process.env but it SHOULD NOT add entries
// that have variable names present in Config.Env.
if let Some(env) = config.env() {
process.set_env(Some(env.to_vec()));
}

// If both Config.Entrypoint and Config.Cmd are specified, the converter MUST append the
// value of Config.Cmd to the value of Config.Entrypoint and set process.args to that
// combined value.
let mut args: Vec<String> = vec![];
if let Some(entrypoint) = config.entrypoint() {
args.extend(entrypoint.clone());
}

if let Some(cmd) = config.cmd() {
args.extend(cmd.clone());
}

if !args.is_empty() {
process.set_args(Some(args));
}

// Annotation Fields
if let Some(labels) = config.labels() {
annotations.extend(labels.clone());
}
if let Some(stop_signal) = config.stop_signal() {
annotations.insert(ANNOTATION_STOP_SIGNAL.to_string(), stop_signal.to_string());
}

// Parsed Fields:
//
// Certain image configuration fields have a counterpart that must first be translated.
// A compliant configuration converter SHOULD parse all of these fields and set the
// corresponding fields in the generated runtime configuration:
// - User
// TODO: parse image config user info and extract uid from rootfs passwd file
// github issue: https://github.com/confidential-containers/image-rs/issues/8

let mut mounts: Vec<Mount> = vec![];
// Optional Fields:
//
// Certain image configuration fields are not applicable to all conversion use cases, and
// thus are optional for configuration converters to implement. A compliant configuration
// converter SHOULD provide a way for users to extract these fields into the generated
// runtime configuration:
// - ExposedPorts
// - Volumes

// The runtime configuration does not have a corresponding field for this image field.
// However, converters SHOULD set the org.opencontainers.image.exposedPorts annotation.
if let Some(exposed_ports) = config.exposed_ports() {
annotations.insert(
ANNOTATION_EXPOSED_PORTS.to_string(),
exposed_ports.join(","),
);
}

// Implementations SHOULD provide mounts for these locations such that application data is
// not written to the container's root filesystem. If a converter implements conversion for
// this field using mountpoints, it SHOULD set the destination of the mountpoint to the
// value specified in Config.Volumes. An implementation MAY seed the contents of the mount
// with data in the image at the same location. If a new image is created from a container
// based on the image described by this configuration, data in these paths SHOULD NOT be
// included in the new image. The other mounts fields are platform and context dependent,
// and thus are implementation-defined.
//
// Note that the implementation of Config.Volumes need not use mountpoints, as it is
// effectively a mask of the filesystem.
if let Some(volumes) = config.volumes() {
let mut mounts: Vec<Mount> = vec![];
for v in volumes.iter() {
let mut m = Mount::default();
m.set_destination(PathBuf::from(v))
Expand All @@ -88,23 +147,12 @@ pub fn create_runtime_config(
]));
mounts.push(m.clone());
}
}

if !mounts.is_empty() {
if let Some(default_mounts) = spec.mounts() {
mounts.extend(default_mounts.clone());
if !mounts.is_empty() {
if let Some(default_mounts) = spec.mounts() {
mounts.extend(default_mounts.clone());
}
spec.set_mounts(Some(mounts));
}
spec.set_mounts(Some(mounts));
}

if let Some(stop_signal) = config.stop_signal() {
annotations.insert(ANNOTATION_STOP_SIGNAL.to_string(), stop_signal.to_string());
}
if let Some(exposed_ports) = config.exposed_ports() {
annotations.insert(
ANNOTATION_EXPOSED_PORTS.to_string(),
exposed_ports.join(","),
);
}
}

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