vcontainer: add multi-arch OCI support

Add functions to detect and handle multi-architecture OCI Image Index
format with automatic platform selection during import. Also add
oci-multiarch.bbclass for build-time multi-arch OCI creation.

Runtime support (vcontainer-common.sh):
- is_oci_image_index() - detect multi-arch OCI images
- get_oci_platforms() - list available platforms
- select_platform_manifest() - select manifest for target architecture
- extract_platform_oci() - extract single platform to new OCI dir
- normalize_arch_to_oci/from_oci() - architecture name mapping
- Update vimport to auto-select platform from multi-arch images

Build-time support (oci-multiarch.bbclass):
- Create OCI Image Index from multiconfig builds
- Collect images from vruntime-aarch64, vruntime-x86-64
- Combine blobs and create unified manifest list

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1 files changed, 243 insertions, 0 deletions

diff --git a/classes/oci-multiarch.bbclass b/classes/oci-multiarch.bbclass
new file mode 100644
index 00000000..9960b7cc
--- /dev/null
+++ b/classes/oci-multiarch.bbclass
@@ -0,0 +1,243 @@
+# SPDX-FileCopyrightText: Copyright (C) 2025 Bruce Ashfield
+#
+# SPDX-License-Identifier: MIT
+#
+# oci-multiarch.bbclass
+# ===========================================================================
+# Build multi-architecture OCI container images locally
+# ===========================================================================
+#
+# This class creates OCI Image Index (manifest list) from multiple
+# single-architecture OCI images built via multiconfig.
+#
+# USAGE:
+#   # In your recipe (e.g., myapp-container-multiarch.bb):
+#   inherit oci-multiarch
+#
+#   OCI_MULTIARCH_RECIPE = "myapp-container"
+#   OCI_MULTIARCH_PLATFORMS = "aarch64 x86_64"
+#
+#   # Optional: custom multiconfig mapping
+#   OCI_MULTIARCH_MC[aarch64] = "vruntime-aarch64"
+#   OCI_MULTIARCH_MC[x86_64] = "vruntime-x86-64"
+#
+# OUTPUT:
+#   ${DEPLOY_DIR_IMAGE}/${PN}-multiarch-oci/
+#     index.json        - OCI Image Index with platform entries
+#     oci-layout        - OCI layout marker
+#     blobs/sha256/     - Combined blobs from all architectures
+#
+# REQUIREMENTS:
+#   - Multiconfig must be enabled in local.conf:
+#       BBMULTICONFIG = "vruntime-aarch64 vruntime-x86-64"
+#   - OCI_MULTIARCH_RECIPE must inherit image-oci or produce OCI output
+#
+# ===========================================================================
+
+inherit nopackages
+
+INHIBIT_DEFAULT_DEPS = "1"
+
+# Required variables
+OCI_MULTIARCH_RECIPE ?= ""
+OCI_MULTIARCH_PLATFORMS ?= ""
+
+# Default multiconfig mapping (uses existing vruntime-* configs)
+OCI_MULTIARCH_MC[aarch64] ?= "vruntime-aarch64"
+OCI_MULTIARCH_MC[x86_64] ?= "vruntime-x86-64"
+
+# Machine mapping for deploy directory paths
+OCI_MULTIARCH_MACHINE[aarch64] ?= "qemuarm64"
+OCI_MULTIARCH_MACHINE[x86_64] ?= "qemux86-64"
+
+# Architecture to OCI platform name mapping
+OCI_ARCH_TO_PLATFORM[aarch64] = "arm64"
+OCI_ARCH_TO_PLATFORM[x86_64] = "amd64"
+
+# Output directory
+OCI_MULTIARCH_OUTPUT = "${DEPLOY_DIR_IMAGE}/${PN}-multiarch-oci"
+
+# Delete standard tasks we don't need
+deltask do_fetch
+deltask do_unpack
+deltask do_patch
+deltask do_configure
+deltask do_compile
+deltask do_install
+deltask do_populate_lic
+deltask do_populate_sysroot
+deltask do_package
+deltask do_package_qa
+deltask do_packagedata
+
+# Generate mcdepends at parse time
+python __anonymous() {
+    recipe = d.getVar('OCI_MULTIARCH_RECIPE')
+    platforms = d.getVar('OCI_MULTIARCH_PLATFORMS')
+
+    if not recipe:
+        bb.fatal("OCI_MULTIARCH_RECIPE must be set")
+
+    if not platforms:
+        bb.fatal("OCI_MULTIARCH_PLATFORMS must be set (e.g., 'aarch64 x86_64')")
+
+    # Build mcdepends string for each platform
+    mcdepends = []
+    for platform in platforms.split():
+        mc = d.getVarFlag('OCI_MULTIARCH_MC', platform)
+        if not mc:
+            bb.fatal(f"No multiconfig defined for platform '{platform}'. Set OCI_MULTIARCH_MC[{platform}]")
+        mcdepends.append(f"mc::{mc}:{recipe}:do_image_oci")
+
+    # Set the mcdepends for our main task
+    d.setVarFlag('do_create_multiarch_index', 'mcdepends', ' '.join(mcdepends))
+
+    bb.note(f"OCI multi-arch: building {recipe} for platforms: {platforms}")
+}
+
+python do_create_multiarch_index() {
+    import os
+    import json
+    import shutil
+    import hashlib
+
+    recipe = d.getVar('OCI_MULTIARCH_RECIPE')
+    platforms = d.getVar('OCI_MULTIARCH_PLATFORMS').split()
+    topdir = d.getVar('TOPDIR')
+    output_dir = d.getVar('OCI_MULTIARCH_OUTPUT')
+
+    bb.plain(f"Creating multi-arch OCI Image Index for {recipe}")
+    bb.plain(f"Platforms: {' '.join(platforms)}")
+
+    # Clean output directory
+    if os.path.exists(output_dir):
+        shutil.rmtree(output_dir)
+    os.makedirs(os.path.join(output_dir, 'blobs', 'sha256'))
+
+    # Collect manifests from each platform
+    index_manifests = []
+
+    for platform in platforms:
+        mc = d.getVarFlag('OCI_MULTIARCH_MC', platform)
+        machine = d.getVarFlag('OCI_MULTIARCH_MACHINE', platform)
+        oci_platform = d.getVarFlag('OCI_ARCH_TO_PLATFORM', platform) or platform
+
+        if not mc or not machine:
+            bb.fatal(f"Missing configuration for platform {platform}")
+
+        # Find the OCI image in the multiconfig's deploy directory
+        # Pattern: tmp-<mc>/deploy/images/<machine>/<recipe>-latest-oci/
+        mc_deploy_base = os.path.join(topdir, f'tmp-{mc}', 'deploy', 'images', machine)
+
+        # Try different naming patterns
+        oci_patterns = [
+            f"{recipe}-latest-oci",
+            f"{recipe}-{machine}-latest-oci",
+            f"{recipe}-oci",
+        ]
+
+        oci_dir = None
+        for pattern in oci_patterns:
+            candidate = os.path.join(mc_deploy_base, pattern)
+            if os.path.isdir(candidate) and os.path.exists(os.path.join(candidate, 'index.json')):
+                oci_dir = candidate
+                break
+
+        if not oci_dir:
+            bb.fatal(f"OCI image not found for {platform} ({mc}:{recipe})")
+            bb.fatal(f"Looked in: {mc_deploy_base}")
+            continue
+
+        bb.plain(f"  Found {platform} OCI: {oci_dir}")
+
+        # Read the source index.json
+        with open(os.path.join(oci_dir, 'index.json'), 'r') as f:
+            src_index = json.load(f)
+
+        # Get the manifest entry (should be first/only one for single-arch)
+        if not src_index.get('manifests'):
+            bb.warn(f"No manifests found in {oci_dir}/index.json")
+            continue
+
+        src_manifest_entry = src_index['manifests'][0]
+        manifest_digest = src_manifest_entry['digest']
+        manifest_size = src_manifest_entry['size']
+
+        # Copy all blobs from source to output
+        src_blobs = os.path.join(oci_dir, 'blobs', 'sha256')
+        dst_blobs = os.path.join(output_dir, 'blobs', 'sha256')
+
+        if os.path.isdir(src_blobs):
+            for blob in os.listdir(src_blobs):
+                src_blob = os.path.join(src_blobs, blob)
+                dst_blob = os.path.join(dst_blobs, blob)
+                if not os.path.exists(dst_blob):
+                    shutil.copy2(src_blob, dst_blob)
+                    bb.note(f"    Copied blob: {blob[:12]}...")
+
+        # Create manifest entry with platform info
+        manifest_entry = {
+            'mediaType': 'application/vnd.oci.image.manifest.v1+json',
+            'digest': manifest_digest,
+            'size': manifest_size,
+            'platform': {
+                'architecture': oci_platform,
+                'os': 'linux'
+            }
+        }
+        index_manifests.append(manifest_entry)
+        bb.plain(f"    Added {oci_platform}/linux manifest: {manifest_digest[:19]}...")
+
+    if not index_manifests:
+        bb.fatal("No manifests collected - cannot create multi-arch index")
+
+    # Create the OCI Image Index
+    image_index = {
+        'schemaVersion': 2,
+        'mediaType': 'application/vnd.oci.image.index.v1+json',
+        'manifests': index_manifests
+    }
+
+    # Write index.json
+    index_path = os.path.join(output_dir, 'index.json')
+    with open(index_path, 'w') as f:
+        json.dump(image_index, f, indent=2)
+
+    # Write oci-layout
+    layout_path = os.path.join(output_dir, 'oci-layout')
+    with open(layout_path, 'w') as f:
+        json.dump({'imageLayoutVersion': '1.0.0'}, f)
+
+    bb.plain("")
+    bb.plain(f"Created multi-arch OCI Image Index:")
+    bb.plain(f"  {output_dir}")
+    bb.plain(f"  Platforms: {', '.join(d.getVarFlag('OCI_ARCH_TO_PLATFORM', p) or p for p in platforms)}")
+    bb.plain("")
+    bb.plain("To import into vdkr (will auto-select platform):")
+    bb.plain(f"  vdkr vimport {output_dir} {recipe}:latest")
+}
+
+addtask do_create_multiarch_index before do_build
+
+# Stamp includes platforms to rebuild when platforms change
+do_create_multiarch_index[stamp-extra-info] = "${OCI_MULTIARCH_PLATFORMS}"
+
+# Deploy the multi-arch OCI
+python do_deploy() {
+    import os
+    import shutil
+
+    output_dir = d.getVar('OCI_MULTIARCH_OUTPUT')
+    deploy_dir = d.getVar('DEPLOY_DIR_IMAGE')
+
+    # Already deployed in place (output_dir is in deploy_dir)
+    # Just verify it exists
+    if not os.path.exists(os.path.join(output_dir, 'index.json')):
+        bb.fatal(f"Multi-arch OCI not found: {output_dir}")
+
+    bb.plain(f"Multi-arch OCI available at: {output_dir}")
+}
+
+addtask do_deploy after do_create_multiarch_index before do_build
+
+EXCLUDE_FROM_WORLD = "1"