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/many.go

@@ -0,0 +1,114 @@
+package main
+
+import (
+	"encoding/binary"
+	"flag"
+	"github.com/rneugeba/virtsock/go/vsock"
+	"github.com/rneugeba/virtsock/go/hvsock"
+	"log"
+	"net"
+	"proxy/libproxy"
+)
+
+// Listen on virtio-vsock and AF_HYPERV for multiplexed connections
+func manyPorts() {
+	var (
+		vsockPort = flag.Int("vsockPort", 62373, "virtio-vsock port")
+		hvGuid    = flag.String("hvGuid", "0B95756A-9985-48AD-9470-78E060895BE7", "Hyper-V service GUID")
+	)
+	flag.Parse()
+
+	listeners := make([]net.Listener, 0)
+
+	vsock, err := vsock.Listen(uint(*vsockPort))
+	if err != nil {
+		log.Printf("Failed to bind to vsock port %d: %#v", vsockPort, err)
+	} else {
+		listeners = append(listeners, vsock)
+	}
+	svcid, _ := hvsock.GuidFromString(*hvGuid)
+	hvsock, err := hvsock.Listen(hvsock.HypervAddr{VmId: hvsock.GUID_WILDCARD, ServiceId: svcid})
+	if err != nil {
+		log.Printf("Failed to bind hvsock guid: %s: %#v", *hvGuid, err)
+	} else {
+		listeners = append(listeners, hvsock)
+	}
+
+	quit := make(chan bool)
+	defer close(quit)
+
+	for _, l := range listeners {
+		go func(l net.Listener) {
+			for {
+				conn, err := l.Accept()
+				if err != nil {
+					log.Printf("Error accepting connection: %#v", err)
+					return // no more listening
+				}
+				go func(conn net.Conn) {
+					// Read header which describes TCP/UDP and destination IP:port
+					d, err := unmarshalDestination(conn)
+					if err != nil {
+						log.Printf("Failed to unmarshal header: %#v", err)
+						conn.Close()
+						return
+					}
+					switch d.Proto {
+					case TCP:
+						backendAddr := net.TCPAddr{IP: d.IP, Port: int(d.Port), Zone: ""}
+						libproxy.HandleTCPConnection(conn.(libproxy.Conn), &backendAddr, quit)
+						break
+					case UDP:
+						backendAddr := &net.UDPAddr{IP: d.IP, Port: int(d.Port), Zone: ""}
+
+						proxy, err := libproxy.NewUDPProxy(backendAddr, libproxy.NewUDPConn(conn), backendAddr)
+						if err != nil {
+							log.Printf("Failed to setup UDP proxy for %s: %#v", backendAddr, err)
+							conn.Close()
+							return
+						}
+						proxy.Run()
+						break
+					default:
+						log.Printf("Unknown protocol: %d", d.Proto)
+						conn.Close()
+						return
+					}
+				}(conn)
+			}
+		}(l)
+	}
+	forever := make(chan int)
+	<-forever
+}
+
+const (
+	TCP = 1
+	UDP = 2
+)
+
+type destination struct {
+	Proto uint8
+	IP    net.IP
+	Port  uint16
+}
+
+func unmarshalDestination(conn net.Conn) (destination, error) {
+	d := destination{}
+	if err := binary.Read(conn, binary.LittleEndian, &d.Proto); err != nil {
+		return d, err
+	}
+	var length uint16
+	// IP length
+	if err := binary.Read(conn, binary.LittleEndian, &length); err != nil {
+		return d, err
+	}
+	d.IP = make([]byte, length)
+	if err := binary.Read(conn, binary.LittleEndian, &d.IP); err != nil {
+		return d, err
+	}
+	if err := binary.Read(conn, binary.LittleEndian, &d.Port); err != nil {
+		return d, err
+	}
+	return d, nil
+}