Introduce new experimental LinuxPod type (#343)

Closes #319

Introduces a new type capable of running > 1 container in the guest. The
API mostly follows LinuxContainer, and each individual container can be
addressed via any of the methods that require you to pass the
containerID as the first param. Today there's no support for namespace
sharing, but that shouldn't be terrible to support.

Author: dcantah

Sources/Containerization/LinuxContainer.swift

@@ -39,7 +39,7 @@ public final class LinuxContainer: Container, Sendable {
     /// The configuration for the LinuxContainer.
     public struct Configuration: Sendable {
         /// Configuration for the init process of the container.
-        public var process = LinuxProcessConfiguration.init()
+        public var process = LinuxProcessConfiguration()
         /// The amount of cpus for the container.
         public var cpus: Int = 4
         /// The memory in bytes to give to the container.
@@ -380,7 +380,7 @@ extension LinuxContainer {
                 let containerMounts = createdState.vm.mounts[self.id] ?? []
                 spec.mounts = containerMounts.dropFirst().map { $0.to }
 
-                let stdio = Self.setupIO(
+                let stdio = IOUtil.setup(
                     portAllocator: self.hostVsockPorts,
                     stdin: self.config.process.stdin,
                     stdout: self.config.process.stdout,
@@ -577,7 +577,7 @@ extension LinuxContainer {
             try configuration(&config)
             spec.process = config.toOCI()
 
-            let stdio = Self.setupIO(
+            let stdio = IOUtil.setup(
                 portAllocator: self.hostVsockPorts,
                 stdin: config.stdin,
                 stdout: config.stdout,
@@ -606,7 +606,7 @@ extension LinuxContainer {
             var spec = self.generateRuntimeSpec()
             spec.process = configuration.toOCI()
 
-            let stdio = Self.setupIO(
+            let stdio = IOUtil.setup(
                 portAllocator: self.hostVsockPorts,
                 stdin: configuration.stdin,
                 stdout: configuration.stdout,
@@ -710,7 +710,7 @@ extension LinuxContainer {
 extension VirtualMachineInstance {
     /// Scoped access to an agent instance to ensure the resources are always freed (mostly close(2)'ing
     /// the vsock fd)
-    fileprivate func withAgent<T>(fn: @Sendable (VirtualMachineAgent) async throws -> T) async throws -> T {
+    func withAgent<T>(fn: @Sendable (VirtualMachineAgent) async throws -> T) async throws -> T {
         let agent = try await self.dialAgent()
         do {
             let result = try await fn(agent)
@@ -724,7 +724,7 @@ extension VirtualMachineInstance {
 }
 
 extension AttachedFilesystem {
-    fileprivate var to: ContainerizationOCI.Mount {
+    var to: ContainerizationOCI.Mount {
         .init(
             type: self.type,
             source: self.source,
@@ -734,4 +734,46 @@ extension AttachedFilesystem {
     }
 }
 
+struct IOUtil {
+    static func setup(
+        portAllocator: borrowing Atomic<UInt32>,
+        stdin: ReaderStream?,
+        stdout: Writer?,
+        stderr: Writer?
+    ) -> LinuxProcess.Stdio {
+        var stdinSetup: LinuxProcess.StdioReaderSetup? = nil
+        if let reader = stdin {
+            let ret = portAllocator.wrappingAdd(1, ordering: .relaxed)
+            stdinSetup = .init(
+                port: ret.oldValue,
+                reader: reader
+            )
+        }
+
+        var stdoutSetup: LinuxProcess.StdioSetup? = nil
+        if let writer = stdout {
+            let ret = portAllocator.wrappingAdd(1, ordering: .relaxed)
+            stdoutSetup = LinuxProcess.StdioSetup(
+                port: ret.oldValue,
+                writer: writer
+            )
+        }
+
+        var stderrSetup: LinuxProcess.StdioSetup? = nil
+        if let writer = stderr {
+            let ret = portAllocator.wrappingAdd(1, ordering: .relaxed)
+            stderrSetup = LinuxProcess.StdioSetup(
+                port: ret.oldValue,
+                writer: writer
+            )
+        }
+
+        return LinuxProcess.Stdio(
+            stdin: stdinSetup,
+            stdout: stdoutSetup,
+            stderr: stderrSetup
+        )
+    }
+}
+
 #endif