proxy: add a multiplexing server frontend

On a Hyper-V system we can only register one listening endpoint (with
a GUID), so we need to accept connections, read a header and then
start the proxy.

If the binary has argv[0] == "proxy-vsockd" then run this new frontend.

Signed-off-by: David Scott <dave.scott@docker.com>

alpine/packages/proxy/main.go

@@ -1,80 +1,14 @@
 package main
 
 import (
-	"errors"
-	"fmt"
-	"log"
-	"net"
 	"os"
-	"proxy/libproxy"
-	"strings"
-	"github.com/rneugeba/virtsock/go/vsock"
+	"path"
 )
 
 func main() {
-	host, port, container := parseHostContainerAddrs()
-
-	vsockP, err := libproxy.NewVsockProxy(&vsock.VsockAddr{Port: uint(port)}, container)
-	if err != nil {
-		sendError(err)
+	if path.Base(os.Args[0]) == "proxy-vsockd" {
+		manyPorts()
+		return
 	}
-	ipP, err := libproxy.NewIPProxy(host, container)
-	if err != nil {
-		sendError(err)
-	}
-
-	ctl, err := exposePort(host, port)
-	if err != nil {
-		sendError(err)
-	}
-
-	go handleStopSignals(ipP)
-	// TODO: avoid this line if we are running in a TTY
-	sendOK()
-	go ipP.Run()
-	vsockP.Run()
-	ctl.Close() // ensure ctl remains alive and un-GCed until here
-	os.Exit(0)
-}
-
-func exposePort(host net.Addr, port int) (*os.File, error) {
-	name := host.Network() + ":" + host.String()
-	log.Printf("exposePort %s\n", name)
-	err := os.Mkdir("/port/"+name, 0)
-	if err != nil {
-		log.Printf("Failed to mkdir /port/%s: %#v\n", name, err)
-		return nil, err
-	}
-	ctl, err := os.OpenFile("/port/"+name+"/ctl", os.O_RDWR, 0)
-	if err != nil {
-		log.Printf("Failed to open /port/%s/ctl: %#v\n", name, err)
-		return nil, err
-	}
-	_, err = ctl.WriteString(fmt.Sprintf("%s:%08x", name, port))
-	if err != nil {
-		log.Printf("Failed to open /port/%s/ctl: %#v\n", name, err)
-		return nil, err
-	}
-	_, err = ctl.Seek(0, 0)
-	if err != nil {
-		log.Printf("Failed to seek on /port/%s/ctl: %#v\n", name, err)
-		return nil, err
-	}
-	results := make([]byte, 100)
-	count, err := ctl.Read(results)
-	if err != nil {
-		log.Printf("Failed to read from /port/%s/ctl: %#v\n", name, err)
-		return nil, err
-	}
-	// We deliberately keep the control file open since 9P clunk
-	// will trigger a shutdown on the host side.
-
-	response := string(results[0:count])
-	if strings.HasPrefix(response, "ERROR ") {
-		os.Remove("/port/" + name + "/ctl")
-		response = strings.Trim(response[6:], " \t\r\n")
-		return nil, errors.New(response)
-	}
-	// Hold on to a reference to prevent premature GC and close
-	return ctl, nil
+	onePort()
 }