runtime-rs: add binary to exercise shim proper w/o containerd dependencies

After building the binary as usual with `cargo build` run it as follows.

It needs a configuration.toml in which only qemu keys `path`, `kernel`
and `initrd` will initially need to be set.  Point them to respective
files e.g. from a kata distribution tarball.

It also needs to be launched from an exported container bundle
directory.  One can be created by running

mkdir rootfs
podman export $(podman create busybox) | tar -C ./rootfs -xvf -
runc spec -b .

in a suitable directory.

Then launch the program like this:

KATA_CONF_FILE=/path/to/configuration-qemu.toml /path/to/shim-ctl

Fixes: #5817

Signed-off-by: Pavel Mores <pmores@redhat.com>

src/runtime-rs/Cargo.lock

@@ -2526,6 +2526,16 @@ dependencies = [
  "unix_socket2",
 ]
 
+[[package]]
+name = "shim-ctl"
+version = "0.1.0"
+dependencies = [
+ "common",
+ "logging",
+ "runtimes",
+ "tokio",
+]
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.0"

src/runtime-rs/Cargo.toml

@@ -1,4 +1,5 @@
 [workspace]
 members = [
     "crates/shim",
+    "crates/shim-ctl",
 ]

src/runtime-rs/README.md

@@ -120,6 +120,8 @@ See the
 See the
 [debugging section of the developer guide](../../docs/Developer-Guide.md#troubleshoot-kata-containers).
 
+An [experimental alternative binary](crates/shim-ctl/README.md) is available that removes containerd dependencies and makes it easier to run the shim proper outside of the runtime's usual deployment environment (i.e. on a developer machine).
+
 ## Limitations
 
 For Kata Containers limitations, see the

src/runtime-rs/crates/shim-ctl/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "shim-ctl"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "^1.0"
+common = { path = "../runtimes/common" }
+logging = { path = "../../../libs/logging"}
+runtimes = { path = "../runtimes" }
+tokio = { version = "1.8.0", features = [ "rt", "rt-multi-thread" ] }
+

src/runtime-rs/crates/shim-ctl/README.md

@@ -0,0 +1,51 @@
+### Purpose
+`shim-ctl` is a binary to exercise the shim proper without containerd
+dependencies.
+
+The actual Kata shim is hard to execute outside of deployment environments due
+to its dependency on containerd's shim v2 protocol.  Among others, the
+dependency requires having a socket with a remote end that's capable of driving
+the shim using the shim v2 `ttrpc` protocol, and a binary for shim to publish
+events to.
+
+Since at least some of the shim v2 protocol dependencies are fairly hard to
+mock up, this presents a significant obstacle to development.
+
+`shim-ctl` takes advantage of the fact that due to the shim implementation
+architecture, only the outermost couple of shim layers are
+containerd-dependent and all of the inner layers that do the actual heavy
+lifting don't depend on containerd.  This allows `shim-ctl` to replace the
+containerd-dependent layers with something that's easier to use on a
+developer's machine.
+
+### Usage
+
+After building the binary as usual with `cargo build` run `shim-ctl` as follows.
+
+Even though `shim-ctl` does away with containerd dependencies it still has
+some requirements of its execution environment.  In particular, it needs a
+Kata `configuration.toml` file, some Kata distribution files to point a bunch
+of `configuration.toml` keys to (like hypervisor keys `path`, `kernel` or
+`initrd`) and a container bundle.  These are however much easier to fulfill
+than the original containerd dependencies, and doing so is a one-off task -
+once done they can be reused for an unlimited number of modify-build-run
+development cycles.
+
+`shim-ctl` also needs to be launched from an exported container bundle
+directory.  One can be created by running
+
+```
+mkdir rootfs
+podman export $(podman create busybox) | tar -C ./rootfs -xvf -
+runc spec -b .
+```
+
+in a suitable directory.
+
+The program can then be launched like this:
+
+```
+cd /the/bundle/directory
+KATA_CONF_FILE=/path/to/configuration-qemu.toml /path/to/shim-ctl
+```
+

src/runtime-rs/crates/shim-ctl/src/main.rs

@@ -0,0 +1,45 @@
+// Copyright (c) 2022 Red Hat
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use anyhow::{Context, Result};
+use common::{
+    message::Message,
+    types::{ContainerConfig, Request},
+};
+use runtimes::RuntimeHandlerManager;
+use tokio::sync::mpsc::channel;
+
+const MESSAGE_BUFFER_SIZE: usize = 8;
+const WORKER_THREADS: usize = 2;
+
+async fn real_main() {
+    let (sender, _receiver) = channel::<Message>(MESSAGE_BUFFER_SIZE);
+    let manager = RuntimeHandlerManager::new("xxx", sender).await.unwrap();
+
+    let req = Request::CreateContainer(ContainerConfig {
+        container_id: "xxx".to_owned(),
+        bundle: ".".to_owned(),
+        rootfs_mounts: Vec::new(),
+        terminal: false,
+        options: None,
+        stdin: None,
+        stdout: None,
+        stderr: None,
+    });
+
+    manager.handler_message(req).await.ok();
+}
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let runtime = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(WORKER_THREADS)
+        .enable_all()
+        .build()
+        .context("prepare tokio runtime")?;
+
+    runtime.block_on(real_main());
+
+    Ok(())
+}