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|
package portmapper
import (
"fmt"
"io"
"net"
"os"
"os/exec"
"runtime"
"strconv"
"syscall"
"time"
)
const userlandProxyCommandName = "docker-proxy"
func newProxyCommand(proto string, hostIP net.IP, hostPort int, containerIP net.IP, containerPort int, proxyPath string) (userlandProxy, error) {
path := proxyPath
if proxyPath == "" {
cmd, err := exec.LookPath(userlandProxyCommandName)
if err != nil {
return nil, err
}
path = cmd
}
args := []string{
path,
"-proto", proto,
"-host-ip", hostIP.String(),
"-host-port", strconv.Itoa(hostPort),
"-container-ip", containerIP.String(),
"-container-port", strconv.Itoa(containerPort),
}
return &proxyCommand{
cmd: &exec.Cmd{
Path: path,
Args: args,
SysProcAttr: &syscall.SysProcAttr{
Pdeathsig: syscall.SIGTERM, // send a sigterm to the proxy if the creating thread in the daemon process dies (https://go.dev/issue/27505)
},
},
wait: make(chan error, 1),
}, nil
}
// proxyCommand wraps an exec.Cmd to run the userland TCP and UDP
// proxies as separate processes.
type proxyCommand struct {
cmd *exec.Cmd
wait chan error
}
func (p *proxyCommand) Start() error {
r, w, err := os.Pipe()
if err != nil {
return fmt.Errorf("proxy unable to open os.Pipe %s", err)
}
defer r.Close()
p.cmd.ExtraFiles = []*os.File{w}
// As p.cmd.SysProcAttr.Pdeathsig is set, the signal will be sent to the
// process when the OS thread on which p.cmd.Start() was executed dies.
// If the thread is allowed to be released back into the goroutine
// thread pool, the thread could get terminated at any time if a
// goroutine gets scheduled onto it which calls runtime.LockOSThread()
// and exits without a matching number of runtime.UnlockOSThread()
// calls. Ensure that the thread from which Start() is called stays
// alive until the proxy or the daemon process exits to prevent the
// proxy from getting terminated early. See https://go.dev/issue/27505
// for more details.
started := make(chan error)
go func() {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
err := p.cmd.Start()
started <- err
if err != nil {
return
}
p.wait <- p.cmd.Wait()
}()
if err := <-started; err != nil {
return err
}
w.Close()
errchan := make(chan error, 1)
go func() {
buf := make([]byte, 2)
r.Read(buf)
if string(buf) != "0\n" {
errStr, err := io.ReadAll(r)
if err != nil {
errchan <- fmt.Errorf("Error reading exit status from userland proxy: %v", err)
return
}
errchan <- fmt.Errorf("Error starting userland proxy: %s", errStr)
return
}
errchan <- nil
}()
select {
case err := <-errchan:
return err
case <-time.After(16 * time.Second):
return fmt.Errorf("Timed out proxy starting the userland proxy")
}
}
func (p *proxyCommand) Stop() error {
if p.cmd.Process != nil {
if err := p.cmd.Process.Signal(os.Interrupt); err != nil {
return err
}
return <-p.wait
}
return nil
}
|
