apple/containerization currently runs containers in per-container VMs on
macOS hosts via Virtualization.framework. This adds a second VMM backend
so the same Swift orchestration layer (LinuxContainer / LinuxPod /
Vminitd gRPC contract) runs on Linux hosts via cloud-hypervisor + KVM.
**CloudHypervisor Swift package** (`Sources/CloudHypervisor/`) — a thin
client for cloud-hypervisor's REST-over-UDS API, layered on
AsyncHTTPClient. Endpoints cover VMM / VM lifecycle / hotplug (disk, fs,
net, vsock, remove-device). Cross-platform (compiles on macOS for unit
tests; consumed at runtime only by the Linux side of Containerization).
**CH backend in Containerization** — one cloud-hypervisor subprocess per
VM, gated behind `#if os(Linux)`. CHVirtualMachineManager /
CHVirtualMachineInstance mirror the VZ shape behind the existing
VirtualMachineManager / VirtualMachineInstance protocol. CHProcess and
VirtiofsdProcess manage the binaries; CHHotplugProvider handles
virtio-blk and virtio-fs runtime hotplug (with one virtiofsd per unique
source-hash tag, refcounted across containers).
**Linux host networking** — BridgeManager brings up a Linux bridge with
an IPv4 subnet and (opt-in via `--enable-nat`) iptables MASQUERADE +
scoped FORWARD rules. LinuxBridgedNetwork enslaves a fresh TAP per
container to the bridge. State is recorded under `/run/containerization`
so `cctl bridge delete` reverses exactly what create did. Bridge
teardown verifies the link kind via sysfs to refuse deleting non-bridge
interfaces.
**cctl run / bridge** — end-to-end Linux container run path (image pull,
ext4 rootfs assembly, VM boot, container exec) plus `cctl bridge
create|delete` for the host network plumbing.
**Build & dist** — `make linux-build` / `make linux-integration` build
and exercise the host side inside an apple/container `--virtualization`
dev container. `make dist-x86_64` produces a deployment tarball (cctl +
cloud-hypervisor + virtiofsd + initfs + kernel) cross-compiled from the
aarch64 dev container; pipeline documented in `docs/x86_64-build.md`.
Static-musl C deps and the Zig cross compiler are pinned by SHA256.
The host orchestrator runs as root. Per-VM runtime state lives under
`/run/containerization/ch/<UUID>` with mode 0700; UDS sockets inside are
bound with mode 0600. Vminitd's gRPC channel inherits that trust
boundary — socket-file perms are the auth.
Sandbox flags are upstream-secure by default. Two per-component opt-outs
exist for the apple/container dev-container case (where the host seccomp
profile SIGSYS-kills CH and virtiofsd):
- `CONTAINERIZATION_NO_CH_SECCOMP=1` — `cloud-hypervisor --seccomp
false`.
- `CONTAINERIZATION_NO_VIRTIOFSD_SANDBOX=1` — `virtiofsd --sandbox
none`. Each emits a one-shot `logger.warning` at process start. Legacy
alias `CONTAINERIZATION_RELAXED_SANDBOX=1` flips both. cctl spawns both
binaries with `setsid` and a minimal env allowlist (PATH / HOME /
RUST_LOG / RUST_BACKTRACE) so the parent's secrets don't leak to
children.
`make linux-integration` runs the cross-platform integration suite
against a real cloud-hypervisor VM inside the dev container. Linux runs
the cross-platform subset (`process true`/`false`/`echo hi`, virtiofs
round-trip, hotplug); the macOS suite is unchanged.
Signed-off-by: michael_crosby <michael_crosby@apple.com>
Related to https://github.com/apple/container/issues/1251
Change to sharing in the parent directory, and then bind mounting in the
file into the container. This has the unfortunate reality of being less
secure, but the current approach is burdended by a couple things,
namely:
1. You can't share in files that are on a different volume
2. There is a Virtualization bug that causes spurious errors when trying
to open the file.
I've added a doc to go over the approach we've taken, and some
workarounds if the approach is not satisfactory.
Michael Crosby