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// Copyright 2018 The gVisor 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 cmd
import (
"context"
"encoding/json"
"os"
"github.com/google/subcommands"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/runsc/cmd/util"
"gvisor.dev/gvisor/runsc/config"
"gvisor.dev/gvisor/runsc/container"
"gvisor.dev/gvisor/runsc/flag"
)
const (
unsetPID = -1
)
// Wait implements subcommands.Command for the "wait" command.
type Wait struct {
rootPID int
pid int
checkpoint uint
}
// Name implements subcommands.Command.Name.
func (*Wait) Name() string {
return "wait"
}
// Synopsis implements subcommands.Command.Synopsis.
func (*Wait) Synopsis() string {
return "wait on a process inside a container"
}
// Usage implements subcommands.Command.Usage.
func (*Wait) Usage() string {
return `wait [flags] <container id>`
}
// SetFlags implements subcommands.Command.SetFlags.
func (wt *Wait) SetFlags(f *flag.FlagSet) {
f.IntVar(&wt.rootPID, "rootpid", unsetPID, "select a PID in the sandbox root PID namespace to wait on instead of the container's root process")
f.IntVar(&wt.pid, "pid", unsetPID, "select a PID in the container's PID namespace to wait on instead of the container's root process")
f.UintVar(&wt.checkpoint, "checkpoint", 0, "wait for (n-1)th checkpoint to complete successfully, then waits for the next checkpoint attempt and returns its status. When set to 0, it disables checkpoint waiting.")
}
// Execute implements subcommands.Command.Execute. It waits for a process in a
// container to exit before returning.
func (wt *Wait) Execute(_ context.Context, f *flag.FlagSet, args ...any) subcommands.ExitStatus {
if f.NArg() != 1 {
f.Usage()
return subcommands.ExitUsageError
}
// You can't specify both -pid and -rootpid.
if wt.rootPID != unsetPID && wt.pid != unsetPID {
util.Fatalf("only one of -pid and -rootPid can be set")
}
id := f.Arg(0)
conf := args[0].(*config.Config)
c, err := container.Load(conf.RootDir, container.FullID{ContainerID: id}, container.LoadOpts{})
if err != nil {
util.Fatalf("loading container: %v", err)
}
if wt.checkpoint > 0 {
if wt.rootPID != unsetPID || wt.pid != unsetPID {
log.Warningf("waiting for checkpoint to complete, ignoring -pid and -rootpid")
}
if err := c.WaitCheckpoint(uint32(wt.checkpoint)); err != nil {
util.Fatalf("waiting for %d-th checkpoint to complete: %v", wt.checkpoint, err)
}
return subcommands.ExitSuccess
}
var waitStatus unix.WaitStatus
switch {
// Wait on the whole container.
case wt.rootPID == unsetPID && wt.pid == unsetPID:
ws, err := c.Wait()
if err != nil {
util.Fatalf("waiting on container %q: %v", c.ID, err)
}
waitStatus = ws
// Wait on a PID in the root PID namespace.
case wt.rootPID != unsetPID:
ws, err := c.WaitRootPID(int32(wt.rootPID))
if err != nil {
util.Fatalf("waiting on PID in root PID namespace %d in container %q: %v", wt.rootPID, c.ID, err)
}
waitStatus = ws
// Wait on a PID in the container's PID namespace.
case wt.pid != unsetPID:
ws, err := c.WaitPID(int32(wt.pid))
if err != nil {
util.Fatalf("waiting on PID %d in container %q: %v", wt.pid, c.ID, err)
}
waitStatus = ws
}
result := waitResult{
ID: id,
ExitStatus: exitStatus(waitStatus),
}
// Write json-encoded wait result directly to stdout.
if err := json.NewEncoder(os.Stdout).Encode(result); err != nil {
util.Fatalf("marshaling wait result: %v", err)
}
return subcommands.ExitSuccess
}
type waitResult struct {
ID string `json:"id"`
ExitStatus int `json:"exitStatus"`
}
// exitStatus returns the correct exit status for a process based on if it
// was signaled or exited cleanly.
func exitStatus(status unix.WaitStatus) int {
if status.Signaled() {
return 128 + int(status.Signal())
}
return status.ExitStatus()
}
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