containerd/internal/cri/server/streaming.go

/*
   Copyright The containerd 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

       http://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.
*/

package server

import (
	"context"
	"fmt"
	"io"
	"math"

	ctrdutil "github.com/containerd/containerd/v2/internal/cri/util"
	streaming "k8s.io/cri-streaming/pkg/streaming"
	remotecommand "k8s.io/cri-streaming/pkg/streaming/remotecommand"
	"k8s.io/streaming/pkg/runtime"
)

// exitError is an interface that presents an API similar to os.ProcessState, which is
// what exitError from os/exec is. This is designed to make testing a bit easier and
// probably loses some of the cross-platform properties of the underlying library.
//
// exitError matches [k8s.io/utils/exec.ExitError], which is used by
// [remotecommand.ServeExec] to distinguish a command exiting with a non-zero
// status from an error executing the command.
//
// FIXME(thaJeztah): define this contract in k8s.io/cri-streaming instead.
// ServeExec only requires Exited and ExitStatus, so the upstream interface
// could be reduced to those methods in addition to error.
//
// - https://github.com/kubernetes/cri-streaming/blob/v0.36.3/pkg/streaming/remotecommand/exec.go#L48-L64
// - https://github.com/kubernetes/utils/blob/28399d86e0b55e612b83ad94dc6bac8e5de2a5ac/exec/exec.go#L83-L91
type exitError interface {
	error
	fmt.Stringer
	Exited() bool
	ExitStatus() int
}

// codeExitError is an implementation of exitError consisting of an error object
// and an exit code (the upper bits of os.exec.ExitStatus).
type codeExitError struct {
	error
	code int
}

func (e codeExitError) String() string  { return e.Error() }
func (e codeExitError) Exited() bool    { return true }   // Exited is to check if the process has finished
func (e codeExitError) ExitStatus() int { return e.code } // ExitStatus is for checking the error code

// FIXME(thaJeztah): assert against remotecommand.ExitError once k8s.io/cri-streaming defines the exit-error contract.
var _ exitError = (*codeExitError)(nil)

type streamRuntime struct {
	c *criService
}

func newStreamRuntime(c *criService) streaming.Runtime {
	return &streamRuntime{c: c}
}

// Exec executes a command inside the container. An exitError is returned if
// the command exits with a non-zero status.
func (s *streamRuntime) Exec(ctx context.Context, containerID string, cmd []string, stdin io.Reader, stdout, stderr io.WriteCloser,
	tty bool, resize <-chan remotecommand.TerminalSize) error {
	exitCode, err := s.c.execInContainer(ctrdutil.WithNamespace(ctx), containerID, execOptions{
		cmd:    cmd,
		stdin:  stdin,
		stdout: stdout,
		stderr: stderr,
		tty:    tty,
		resize: resize,
	})
	if err != nil {
		return fmt.Errorf("failed to exec in container: %w", err)
	}
	if *exitCode == 0 {
		return nil
	}
	return &codeExitError{
		error: fmt.Errorf("error executing command %v, exit code %d", cmd, *exitCode),
		code:  int(*exitCode),
	}
}

func (s *streamRuntime) Attach(ctx context.Context, containerID string, in io.Reader, out, err io.WriteCloser, tty bool,
	resize <-chan remotecommand.TerminalSize) error {
	return s.c.attachContainer(ctrdutil.WithNamespace(ctx), containerID, in, out, err, tty, resize)
}

func (s *streamRuntime) PortForward(ctx context.Context, podSandboxID string, port int32, stream io.ReadWriteCloser) error {
	if port <= 0 || port > math.MaxUint16 {
		return fmt.Errorf("invalid port %d", port)
	}
	ctx = ctrdutil.WithNamespace(ctx)
	return s.c.portForward(ctx, podSandboxID, port, stream)
}

// handleResizing spawns a goroutine that processes the resize channel, calling resizeFunc for each
// remotecommand.TerminalSize received from the channel.
func handleResizing(ctx context.Context, resize <-chan remotecommand.TerminalSize, resizeFunc func(size remotecommand.TerminalSize)) {
	if resize == nil {
		return
	}

	go func() {
		defer runtime.HandleCrash()

		for {
			select {
			case <-ctx.Done():
				return
			case size, ok := <-resize:
				if !ok {
					return
				}
				if size.Height < 1 || size.Width < 1 {
					continue
				}
				resizeFunc(size)
			}
		}
	}()
}