Allow reusing virtiofs mounts

Sources/Containerization/Hash.swift

@@ -18,10 +18,15 @@
 
 import Crypto
 import ContainerizationError
+import Foundation
 
 func hashMountSource(source: String) throws -> String {
-    guard let data = source.data(using: .utf8) else {
-        throw ContainerizationError(.invalidArgument, message: "\(source) could not be converted to Data")
+    let resolvedSource = URL(fileURLWithPath: source)
+        .resolvingSymlinksInPath()
+        .path
+
+    guard let data = resolvedSource.data(using: .utf8) else {
+        throw ContainerizationError(.invalidArgument, message: "\(resolvedSource) could not be converted to Data")
     }
     return String(SHA256.hash(data: data).encoded.prefix(36))
 }

Sources/Containerization/Mount.swift

@@ -132,7 +132,7 @@ public struct Mount: Sendable {
 #if os(macOS)
 
 extension Mount {
-    func configure(config: inout VZVirtualMachineConfiguration) throws {
+    func configure(config: inout VZVirtualMachineConfiguration, usedVirtioFSTags: inout Set<String>) throws {
         switch self.runtimeOptions {
         case .virtioblk(let options):
             let device = try VZDiskImageStorageDeviceAttachment.mountToVZAttachment(mount: self, options: options)
@@ -144,6 +144,13 @@ extension Mount {
             }
 
             let name = try hashMountSource(source: self.source)
+
+            // Skip creating VZVirtioFileSystemDeviceConfiguration if tag already exists.
+            if usedVirtioFSTags.contains(name) {
+                return
+            }
+
+            usedVirtioFSTags.insert(name)
             let urlSource = URL(fileURLWithPath: source)
 
             let device = VZVirtioFileSystemDeviceConfiguration(tag: name)

Sources/Containerization/VZVirtualMachineInstance.swift

@@ -57,6 +57,8 @@ struct VZVirtualMachineInstance: VirtualMachineInstance, Sendable {
         public var initialFilesystem: Mount?
         /// File path to store the sandbox boot logs.
         public var bootlog: URL?
+        /// Set of virtiofs tags that have already been configured to avoid duplicates.
+        var usedVirtioFSTags: Set<String> = []
 
         init() {
             self.cpus = 4
@@ -65,6 +67,7 @@ struct VZVirtualMachineInstance: VirtualMachineInstance, Sendable {
             self.nestedVirtualization = false
             self.mounts = []
             self.interfaces = []
+            self.usedVirtioFSTags = []
         }
     }
 
@@ -86,6 +89,7 @@ struct VZVirtualMachineInstance: VirtualMachineInstance, Sendable {
     }
 
     init(group: MultiThreadedEventLoopGroup, config: Configuration, logger: Logger?) throws {
+        var mutableConfig = config
         self.config = config
         self.group = group
         self.lock = .init()
@@ -95,7 +99,7 @@ struct VZVirtualMachineInstance: VirtualMachineInstance, Sendable {
         self.timeSyncer = .init(logger: logger)
 
         self.vm = VZVirtualMachine(
-            configuration: try config.toVZ(),
+            configuration: try mutableConfig.toVZ(),
             queue: self.queue
         )
     }
@@ -243,7 +247,7 @@ extension VZVirtualMachineInstance.Configuration {
         return [c]
     }
 
-    func toVZ() throws -> VZVirtualMachineConfiguration {
+    mutating func toVZ() throws -> VZVirtualMachineConfiguration {
         var config = VZVirtualMachineConfiguration()
 
         config.cpuCount = self.cpus
@@ -301,9 +305,9 @@ extension VZVirtualMachineInstance.Configuration {
         loader.commandLine = kernel.linuxCommandline(initialFilesystem: initialFilesystem)
         config.bootLoader = loader
 
-        try initialFilesystem.configure(config: &config)
+        try initialFilesystem.configure(config: &config, usedVirtioFSTags: &usedVirtioFSTags)
         for mount in self.mounts {
-            try mount.configure(config: &config)
+            try mount.configure(config: &config, usedVirtioFSTags: &usedVirtioFSTags)
         }
 
         let platform = VZGenericPlatformConfiguration()

Sources/Integration/Suite.swift

@@ -209,6 +209,7 @@ struct IntegrationSuite: AsyncParsableCommand {
             "container hostname": testHostname,
             "container hosts": testHostsFile,
             "container mount": testMounts,
+            "container mount duplicate": testDuplicateMount,
             "nested virt": testNestedVirtualizationEnabled,
             "container manager": testContainerManagerCreate,
         ]

Sources/Integration/VMTests.swift

@@ -27,8 +27,10 @@ extension IntegrationSuite {
 
         let bs = try await bootstrap()
         let buffer = BufferWriter()
+        let directory = try createMountDirectory()
+        defer { try? FileManager.default.removeItem(at: directory) }
+
         let container = try LinuxContainer(id, rootfs: bs.rootfs, vmm: bs.vmm) { config in
-            let directory = try createMountDirectory()
             config.process.arguments = ["/bin/cat", "/mnt/hi.txt"]
             config.mounts.append(.share(source: directory.path, destination: "/mnt"))
             config.process.stdout = buffer
@@ -121,6 +123,39 @@ extension IntegrationSuite {
         }
     }
 
+    func testDuplicateMount() async throws {
+        let id = "test-duplicate-mounts"
+
+        let bs = try await bootstrap()
+        let buffer = BufferWriter()
+        let directory = try createMountDirectory()
+        defer { try? FileManager.default.removeItem(at: directory) }
+
+        let container = try LinuxContainer(id, rootfs: bs.rootfs, vmm: bs.vmm) { config in
+            config.process.arguments = ["/bin/sh", "-c", "cat /mnt1/hi.txt && cat /mnt2/hi.txt"]
+            // Mount the same directory to two different destinations
+            config.mounts.append(.share(source: directory.path, destination: "/mnt1"))
+            config.mounts.append(.share(source: directory.path, destination: "/mnt2"))
+            config.process.stdout = buffer
+        }
+
+        try await container.create()
+        try await container.start()
+
+        let status = try await container.wait()
+        try await container.stop()
+
+        guard status == 0 else {
+            throw IntegrationError.assert(msg: "process status \(status) != 0")
+        }
+
+        let value = String(data: buffer.data, encoding: .utf8)
+        guard value == "hellohello" else {
+            throw IntegrationError.assert(
+                msg: "process should have returned 'hellohello' != '\(String(data: buffer.data, encoding: .utf8)!)'")
+        }
+    }
+
     private func createMountDirectory() throws -> URL {
         let dir = FileManager.default.uniqueTemporaryDirectory(create: true)
         try "hello".write(to: dir.appendingPathComponent("hi.txt"), atomically: true, encoding: .utf8)