containerization/vminitd/Sources/VminitdCore/StandardIO.swift

//===----------------------------------------------------------------------===//
// 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 ContainerizationError
import ContainerizationOS
import Foundation
import Logging
import Synchronization

final class StandardIO: ManagedProcess.IO & Sendable {
    private struct State {
        var stdin: IOPair?
        var stdout: IOPair?
        var stderr: IOPair?

        var stdinPipe: Pipe?
        var stdoutPipe: Pipe?
        var stderrPipe: Pipe?
    }

    private let log: Logger?
    private let hostStdio: HostStdio
    private let state: Mutex<State>

    init(
        stdio: HostStdio,
        log: Logger?
    ) {
        self.hostStdio = stdio
        self.log = log
        self.state = Mutex(State())
    }

    // NOP
    func attach(pid: Int32, fd: Int32) throws {}

    func start(process: inout Command) throws {
        // [Nucleic vendored patch] All-or-nothing: a failure partway (a vsock connect or a
        // relay registration throwing) used to discard the IO object with earlier pairs
        // LIVE — the supervisor's handler map retains a registered IOPair forever, so a
        // dead exec left a relay pumping host stdin into a pipe no child would ever read,
        // plus its socket, pipe fds, and epoll slot. Dial each socket safely, and on any
        // failure close every pair created so far before rethrowing.
        try self.state.withLock {
            func dialHost(port: UInt32) throws -> Socket {
                let type = VsockType(port: port, cid: VsockType.hostCID)
                let socket = try Socket(type: type, closeOnDeinit: false)
                do {
                    try socket.connect()
                } catch {
                    try? socket.close()
                    throw error
                }
                return socket
            }
            do {
                if let stdinPort = self.hostStdio.stdin {
                    let inPipe = Pipe()
                    process.stdin = inPipe.fileHandleForReading
                    $0.stdinPipe = inPipe

                    let pair = IOPair(
                        readFrom: try dialHost(port: stdinPort),
                        writeTo: inPipe.fileHandleForWriting,
                        reason: "StandardIO stdin",
                        logger: log
                    )
                    $0.stdin = pair

                    try pair.relay()
                }

                if let stdoutPort = self.hostStdio.stdout {
                    let outPipe = Pipe()
                    process.stdout = outPipe.fileHandleForWriting
                    $0.stdoutPipe = outPipe

                    let pair = IOPair(
                        readFrom: outPipe.fileHandleForReading,
                        writeTo: try dialHost(port: stdoutPort),
                        reason: "StandardIO stdout",
                        logger: log
                    )
                    $0.stdout = pair

                    try pair.relay()
                }

                if let stderrPort = self.hostStdio.stderr {
                    let errPipe = Pipe()
                    process.stderr = errPipe.fileHandleForWriting
                    $0.stderrPipe = errPipe

                    let pair = IOPair(
                        readFrom: errPipe.fileHandleForReading,
                        writeTo: try dialHost(port: stderrPort),
                        reason: "StandardIO stderr",
                        logger: log
                    )
                    $0.stderr = pair

                    try pair.relay()
                }
            } catch {
                // IOPair.close is idempotent and closes both of a pair's fds; pairs whose
                // relay registration never happened are closed the same way.
                $0.stdin?.close()
                $0.stdin = nil
                $0.stdout?.close()
                $0.stdout = nil
                $0.stderr?.close()
                $0.stderr = nil
                throw error
            }
        }
    }

    func resize(size: Terminal.Size) throws {
        throw ContainerizationError(.unsupported, message: "resize not supported")
    }

    func close() throws {
        self.state.withLock {
            if let stdin = $0.stdin {
                stdin.close()
                $0.stdin = nil
            }

            if let stdout = $0.stdout {
                stdout.close()
                $0.stdout = nil
            }

            if let stderr = $0.stderr {
                stderr.close()
                $0.stderr = nil
            }
        }
    }

    func closeStdin() throws {
        self.state.withLock {
            if let stdin = $0.stdin {
                stdin.close()
                $0.stdin = nil
            }
        }
    }

    func closeAfterExec() throws {
        try self.state.withLock {
            if let stdin = $0.stdinPipe {
                try stdin.fileHandleForReading.close()
                $0.stdinPipe = nil
            }
            if let stdout = $0.stdoutPipe {
                try stdout.fileHandleForWriting.close()
                $0.stdoutPipe = nil
            }
            if let stderr = $0.stderrPipe {
                try stderr.fileHandleForWriting.close()
                $0.stderrPipe = nil
            }
        }
    }
}

#endif