github.com/opencontainers/runc@v1.2.0-rc.1.0.20240520010911-492dc558cdd6/contrib/cmd/pidfd-kill/pidfd-kill.go (about)

     1  package main
     2  
     3  import (
     4  	"errors"
     5  	"fmt"
     6  	"net"
     7  	"os"
     8  	"os/signal"
     9  
    10  	"github.com/urfave/cli"
    11  	"golang.org/x/sys/unix"
    12  
    13  	"github.com/opencontainers/runc/libcontainer/utils"
    14  )
    15  
    16  const (
    17  	usage = `Open Container Initiative contrib/cmd/pidfd-kill
    18  
    19  pidfd-kill is an implementation of a consumer of runC's --pidfd-socket API.
    20  After received SIGTERM, pidfd-kill sends the given signal to init process by
    21  pidfd received from --pidfd-socket.
    22  
    23  To use pidfd-kill, just specify a socket path at which you want to receive
    24  pidfd:
    25  
    26      $ pidfd-kill [--signal KILL] socket.sock
    27  `
    28  )
    29  
    30  func main() {
    31  	app := cli.NewApp()
    32  	app.Name = "pidfd-kill"
    33  	app.Usage = usage
    34  
    35  	app.Flags = []cli.Flag{
    36  		cli.StringFlag{
    37  			Name:  "signal",
    38  			Value: "SIGKILL",
    39  			Usage: "Signal to send to the init process",
    40  		},
    41  		cli.StringFlag{
    42  			Name:  "pid-file",
    43  			Value: "",
    44  			Usage: "Path to write the pidfd-kill process ID to",
    45  		},
    46  	}
    47  
    48  	app.Action = func(ctx *cli.Context) error {
    49  		args := ctx.Args()
    50  		if len(args) != 1 {
    51  			return errors.New("required a single socket path")
    52  		}
    53  
    54  		socketFile := ctx.Args()[0]
    55  
    56  		pidFile := ctx.String("pid-file")
    57  		if pidFile != "" {
    58  			pid := fmt.Sprintf("%d\n", os.Getpid())
    59  			if err := os.WriteFile(pidFile, []byte(pid), 0o644); err != nil {
    60  				return err
    61  			}
    62  			defer os.Remove(pidFile)
    63  		}
    64  
    65  		sigStr := ctx.String("signal")
    66  		if sigStr == "" {
    67  			sigStr = "SIGKILL"
    68  		}
    69  		sig := unix.SignalNum(sigStr)
    70  
    71  		pidfdFile, err := recvPidfd(socketFile)
    72  		if err != nil {
    73  			return err
    74  		}
    75  		defer pidfdFile.Close()
    76  
    77  		signalCh := make(chan os.Signal, 16)
    78  		signal.Notify(signalCh, unix.SIGTERM)
    79  		<-signalCh
    80  
    81  		return unix.PidfdSendSignal(int(pidfdFile.Fd()), sig, nil, 0)
    82  	}
    83  	if err := app.Run(os.Args); err != nil {
    84  		fmt.Fprintln(os.Stderr, "fatal error:", err)
    85  		os.Exit(1)
    86  	}
    87  }
    88  
    89  func recvPidfd(socketFile string) (*os.File, error) {
    90  	ln, err := net.Listen("unix", socketFile)
    91  	if err != nil {
    92  		return nil, err
    93  	}
    94  	defer ln.Close()
    95  
    96  	conn, err := ln.Accept()
    97  	if err != nil {
    98  		return nil, err
    99  	}
   100  	defer conn.Close()
   101  
   102  	unixconn, ok := conn.(*net.UnixConn)
   103  	if !ok {
   104  		return nil, errors.New("failed to cast to unixconn")
   105  	}
   106  
   107  	socket, err := unixconn.File()
   108  	if err != nil {
   109  		return nil, err
   110  	}
   111  	defer socket.Close()
   112  
   113  	return utils.RecvFile(socket)
   114  }