LinuxContainer: Allow reuse after being stopped (#240)

After the container is stopped it's a bit odd how we don't allow the
object to be restarted. If someone wanted to continuously rerun the same
container they'd need to make a new object every time even though all
guest state is blown away on stop() so it's a clean slate.

This change makes it so that you can create+start again after stop
(although create stands out like a sore thumb now as stop -> create is
just strange).

Sources/Containerization/LinuxContainer.swift

@@ -194,7 +194,7 @@ public final class LinuxContainer: Container, Sendable {
 
         mutating func setCreating() throws {
             switch self {
-            case .initialized:
+            case .initialized, .stopped:
                 self = .creating(.init())
             default:
                 throw ContainerizationError(

Sources/Integration/Suite.swift

@@ -211,6 +211,7 @@ struct IntegrationSuite: AsyncParsableCommand {
             "container mount": testMounts,
             "nested virt": testNestedVirtualizationEnabled,
             "container manager": testContainerManagerCreate,
+            "container reuse": testContainerReuse,
         ]
 
         var passed = 0

Sources/Integration/VMTests.swift

@@ -121,6 +121,57 @@ extension IntegrationSuite {
         }
     }
 
+    func testContainerReuse() async throws {
+        let id = "test-container-reuse"
+
+        // Get the kernel from bootstrap
+        let bs = try await bootstrap()
+
+        // Create ContainerManager with kernel and initfs reference
+        let manager = try ContainerManager(vmm: bs.vmm)
+        defer {
+            try? manager.delete(id)
+        }
+
+        let buffer = BufferWriter()
+        let container = try await manager.create(
+            id,
+            image: bs.image,
+            rootfs: bs.rootfs
+        ) { config in
+            config.process.arguments = ["/bin/echo", "ContainerManager test"]
+            config.process.stdout = buffer
+        }
+
+        // Start the container
+        try await container.create()
+        try await container.start()
+
+        // Wait for completion
+        var status = try await container.wait()
+        guard status == 0 else {
+            throw IntegrationError.assert(msg: "process status \(status) != 0")
+        }
+        try await container.stop()
+
+        // Recreate things.
+        try await container.create()
+        try await container.start()
+
+        // Wait for completion.. again.
+        status = try await container.wait()
+        guard status == 0 else {
+            throw IntegrationError.assert(msg: "process status \(status) != 0")
+        }
+
+        let output = String(data: buffer.data, encoding: .utf8)
+        let expected = "ContainerManager test\nContainerManager test\n"
+        guard output == expected else {
+            throw IntegrationError.assert(
+                msg: "process should have returned '\(expected)' != '\(output ?? "nil")'")
+        }
+    }
+
     private func createMountDirectory() throws -> URL {
         let dir = FileManager.default.uniqueTemporaryDirectory(create: true)
         try "hello".write(to: dir.appendingPathComponent("hi.txt"), atomically: true, encoding: .utf8)