chore: import upstream snapshot with attribution

Sources/ContainerResource/Network/NetworkMode.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+/// Networking mode that applies to client containers.
+public enum NetworkMode: String, Codable, Sendable {
+    /// NAT networking mode.
+    /// Containers do not have routable IPs, and the host performs network
+    /// address translation to allow containers to reach external services.
+    case nat = "nat"
+
+    /// Host only networking mode
+    /// Containers can talk with each other in the same subnet only.
+    case hostOnly = "hostOnly"
+}
+
+extension NetworkMode {
+    public init() {
+        self = .nat
+    }
+
+    public init?(_ value: String) {
+        switch value.lowercased() {
+        case "nat": self = .nat
+        case "hostOnly": self = .hostOnly
+        default: return nil
+        }
+    }
+}