tstest/tailmac: add support for mounting host directories in the guest (#13957)

updates tailscale/corp#24197

tailmac run now supports the --share option which will allow you
to specify a directory on the host which can be mounted in the guest
using  mount_virtiofs vmshare <path>.

Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>

tstest/tailmac/Swift/Common/Config.swift

@@ -14,6 +14,7 @@ class Config: Codable {
     var mac = "52:cc:cc:cc:cc:01"
     var ethermac = "52:cc:cc:cc:ce:01"
     var port: UInt32 = 51009
+    var sharedDir: String?
 
     // The virtual machines ID.  Also double as the directory name under which
     // we will store configuration, block device, etc.

tstest/tailmac/Swift/Common/TailMacConfigHelper.swift

@@ -141,5 +141,18 @@ struct TailMacConfigHelper {
     func createKeyboardConfiguration() -> VZKeyboardConfiguration {
         return VZMacKeyboardConfiguration()
     }
+
+    func createDirectoryShareConfiguration(tag: String) -> VZDirectorySharingDeviceConfiguration? {
+        guard let dir = config.sharedDir else { return nil }
+
+        let sharedDir = VZSharedDirectory(url: URL(fileURLWithPath: dir), readOnly: false)
+        let share = VZSingleDirectoryShare(directory: sharedDir)
+
+        // Create the VZVirtioFileSystemDeviceConfiguration and assign it a unique tag.
+        let sharingConfiguration = VZVirtioFileSystemDeviceConfiguration(tag: tag)
+        sharingConfiguration.share = share
+
+        return sharingConfiguration
+    }
 }
 

tstest/tailmac/Swift/Host/HostCli.swift

@@ -19,10 +19,12 @@ var config: Config = Config()
 extension HostCli {
     struct Run: ParsableCommand {
         @Option var id: String
+        @Option var share: String?
 
         mutating func run() {
-            print("Running vm with identifier \(id)")
             config = Config(id)
+            config.sharedDir = share
+            print("Running vm with identifier \(id) and sharedDir \(share ?? "<none>")")
             _ = NSApplicationMain(CommandLine.argc, CommandLine.unsafeArgv)
         }
     }

tstest/tailmac/Swift/Host/VMController.swift

@@ -95,6 +95,13 @@ class VMController: NSObject, VZVirtualMachineDelegate {
         virtualMachineConfiguration.keyboards = [helper.createKeyboardConfiguration()]
         virtualMachineConfiguration.socketDevices = [helper.createSocketDeviceConfiguration()]
 
+        if let dir = config.sharedDir, let shareConfig = helper.createDirectoryShareConfiguration(tag: "vmshare") {
+            print("Sharing \(dir) as vmshare.  Use: mount_virtiofs vmshare <path> in the guest to mount.")
+            virtualMachineConfiguration.directorySharingDevices = [shareConfig]
+        } else {
+            print("No shared directory created.  \(config.sharedDir ?? "none") was requested.")
+        }
+
         try! virtualMachineConfiguration.validate()
         try! virtualMachineConfiguration.validateSaveRestoreSupport()
 

tstest/tailmac/Swift/TailMac/TailMac.swift

@@ -95,6 +95,7 @@ extension Tailmac {
 extension Tailmac {
     struct Run: ParsableCommand {
         @Option(help: "The vm identifier") var id: String
+        @Option(help: "Optional share directory") var share: String?
         @Flag(help: "Tail the TailMac log output instead of returning immediatly") var tail
 
         mutating func run() {
@@ -115,7 +116,12 @@ extension Tailmac {
                 fatalError("Could not find Host.app at \(appPath).  This must be co-located with the tailmac utility")
             }
 
-            process.arguments = ["run", "--id", id]
+            var args = ["run", "--id", id]
+            if let share {
+                args.append("--share")
+                args.append(share)
+            }
+            process.arguments = args
 
             do {
                 process.standardOutput = stdOutPipe
@@ -124,26 +130,18 @@ extension Tailmac {
                 fatalError("Unable to launch the vm process")
             }
 
-            // This doesn't print until we exit which is not ideal, but at least we
-            // get the output
             if tail != 0 {
+                // (jonathan)TODO: How do we get the process output in real time?
+                //                  The child process only seems to flush to stdout on completion
                 let outHandle = stdOutPipe.fileHandleForReading
-
-                let queue =  OperationQueue()
-                NotificationCenter.default.addObserver(
-                    forName: NSNotification.Name.NSFileHandleDataAvailable,
-                    object: outHandle, queue: queue)
-                {
-                    notification -> Void in
-                    let data = outHandle.availableData
+                outHandle.readabilityHandler = { handle in
+                    let data = handle.availableData
                     if data.count > 0 {
                         if let str = String(data: data, encoding: String.Encoding.utf8) {
                             print(str)
                         }
                     }
-                    outHandle.waitForDataInBackgroundAndNotify()
                 }
-                outHandle.waitForDataInBackgroundAndNotify()
                 process.waitUntilExit()
             }
         }