chore: import upstream snapshot with attribution

Sources/Containerization/CHInterface.swift

@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the Containerization 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.
+//===----------------------------------------------------------------------===//
+
+#if os(Linux)
+import CloudHypervisor
+import ContainerizationExtras
+
+/// An `Interface` specialization that can produce a `CloudHypervisor.NetConfig`
+/// describing how the cloud-hypervisor VMM should attach the device.
+public protocol CHInterface {
+    func chNetConfig() throws -> CloudHypervisor.NetConfig
+}
+
+/// A TAP-backed network interface for the cloud-hypervisor backend.
+///
+/// IP configuration on the guest side is delegated to `vminitd` (matching the
+/// macOS path). `chNetConfig()` therefore leaves CH's `ip`/`mask` fields nil —
+/// those would assign an address to the host end of the TAP, which we do not
+/// use. Bringing up the TAP and any bridge/NAT plumbing is the caller's
+/// responsibility.
+public struct TAPInterface: CHInterface, Interface, Sendable {
+    public let tapName: String
+    public let ipv4Address: CIDRv4
+    public let ipv4Gateway: IPv4Address?
+    public let macAddress: MACAddress?
+    public let mtu: UInt32
+
+    public init(
+        tapName: String,
+        ipv4Address: CIDRv4,
+        ipv4Gateway: IPv4Address? = nil,
+        macAddress: MACAddress? = nil,
+        mtu: UInt32 = 1500
+    ) {
+        self.tapName = tapName
+        self.ipv4Address = ipv4Address
+        self.ipv4Gateway = ipv4Gateway
+        self.macAddress = macAddress
+        self.mtu = mtu
+    }
+
+    public func chNetConfig() throws -> CloudHypervisor.NetConfig {
+        CloudHypervisor.NetConfig(
+            tap: tapName,
+            ip: nil,
+            mask: nil,
+            mac: macAddress?.description,
+            mtu: Int(mtu),
+            numQueues: nil,
+            queueSize: nil,
+            id: nil
+        )
+    }
+}
+#endif