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moby--moby/daemon/networkdriver/portmapper/proxy.go

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package portmapper
import (
"flag"
"fmt"
"io/ioutil"
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"log"
"net"
"os"
"os/exec"
"os/signal"
"strconv"
"syscall"
"time"
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"github.com/docker/docker/pkg/proxy"
"github.com/docker/docker/pkg/reexec"
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)
const userlandProxyCommandName = "docker-proxy"
func init() {
reexec.Register(userlandProxyCommandName, execProxy)
}
type UserlandProxy interface {
Start() error
Stop() error
}
// proxyCommand wraps an exec.Cmd to run the userland TCP and UDP
// proxies as separate processes.
type proxyCommand struct {
cmd *exec.Cmd
}
// execProxy is the reexec function that is registered to start the userland proxies
func execProxy() {
f := os.NewFile(3, "signal-parent")
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host, container := parseHostContainerAddrs()
p, err := proxy.NewProxy(host, container)
if err != nil {
fmt.Fprintf(f, "1\n%s", err)
f.Close()
os.Exit(1)
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}
go handleStopSignals(p)
fmt.Fprint(f, "0\n")
f.Close()
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// Run will block until the proxy stops
p.Run()
}
// parseHostContainerAddrs parses the flags passed on reexec to create the TCP or UDP
// net.Addrs to map the host and container ports
func parseHostContainerAddrs() (host net.Addr, container net.Addr) {
var (
proto = flag.String("proto", "tcp", "proxy protocol")
hostIP = flag.String("host-ip", "", "host ip")
hostPort = flag.Int("host-port", -1, "host port")
containerIP = flag.String("container-ip", "", "container ip")
containerPort = flag.Int("container-port", -1, "container port")
)
flag.Parse()
switch *proto {
case "tcp":
host = &net.TCPAddr{IP: net.ParseIP(*hostIP), Port: *hostPort}
container = &net.TCPAddr{IP: net.ParseIP(*containerIP), Port: *containerPort}
case "udp":
host = &net.UDPAddr{IP: net.ParseIP(*hostIP), Port: *hostPort}
container = &net.UDPAddr{IP: net.ParseIP(*containerIP), Port: *containerPort}
default:
log.Fatalf("unsupported protocol %s", *proto)
}
return host, container
}
func handleStopSignals(p proxy.Proxy) {
s := make(chan os.Signal, 10)
signal.Notify(s, os.Interrupt, syscall.SIGTERM, syscall.SIGSTOP)
for _ = range s {
p.Close()
os.Exit(0)
}
}
func NewProxyCommand(proto string, hostIP net.IP, hostPort int, containerIP net.IP, containerPort int) UserlandProxy {
args := []string{
userlandProxyCommandName,
"-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: reexec.Self(),
Args: args,
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SysProcAttr: &syscall.SysProcAttr{
Pdeathsig: syscall.SIGTERM, // send a sigterm to the proxy if the daemon process dies
},
},
}
}
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}
if err := p.cmd.Start(); 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 := ioutil.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")
}
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}
func (p *proxyCommand) Stop() error {
if p.cmd.Process != nil {
if err := p.cmd.Process.Signal(os.Interrupt); err != nil {
return err
}
return p.cmd.Wait()
}
return nil
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}