proxy: request a vsock connection rather than a TCP/IP one

Note this means we don't need to figure out our local IP address.

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

alpine/packages/proxy/main.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"libproxy"
 	"strings"
+	"vsock"
 )
 
 func main() {
@@ -42,12 +43,7 @@ func exposePort(host net.Addr, port int) error {
 		log.Printf("Failed to open /port/%s/ctl: %#v\n", name, err)
 		return err
 	}
-	me, err := getMyAddress()
+	_, err = ctl.WriteString(fmt.Sprintf("%s:%d:%d", name, vsock.VSOCK_CID_SELF, vSockPortOffset + port))
-	if err != nil {
-		log.Printf("Failed to determine my local address: %#v\n", err)
-		return err
-	}
-	_, err = ctl.WriteString(fmt.Sprintf("%s:%s:%d", name, me, port))
 	if err != nil {
 		log.Printf("Failed to open /port/%s/ctl: %#v\n", name, err)
 		return err
@@ -84,28 +80,3 @@ func unexposePort(host net.Addr) {
 		log.Printf("Failed to remove /port/%s: %#v\n", name, err)
 	}
 }
-
-var myAddress string
-
-// getMyAddress returns a string representing my address from the host's
-// point of view. For now this is an IP address but it soon should be a vsock
-// port.
-func getMyAddress() (string, error) {
-	if myAddress != "" {
-		return myAddress, nil
-	}
-	d, err := os.Open("/port/docker")
-	if err != nil {
-		return "", err
-	}
-	defer d.Close()
-	bytes := make([]byte, 100)
-	count, err := d.Read(bytes)
-	if err != nil {
-		return "", err
-	}
-	s := string(bytes)[0:count]
-	bits := strings.Split(s, ":")
-	myAddress = bits[2]
-	return myAddress, nil
-}

alpine/packages/proxy/proxy.go

@@ -10,6 +10,7 @@ import (
 	"syscall"
 
 	"libproxy"
+	"vsock"
 )
 
 // sendError signals the error to the parent and quits the process.
@@ -28,6 +29,9 @@ func sendOK() {
 	f.Close()
 }
 
+// Map dynamic ports onto vsock ports over this offset
+var vSockPortOffset = 0x10000
+
 // From docker/libnetwork/portmapper/proxy.go:
 
 // parseHostContainerAddrs parses the flags passed on reexec to create the TCP or UDP
@@ -45,7 +49,8 @@ func parseHostContainerAddrs() (host net.Addr, port int, container net.Addr) {
 
 	switch *proto {
 	case "tcp":
-		host = &net.TCPAddr{IP: net.ParseIP(*hostIP), Port: *hostPort}
+		port = vSockPortOffset + *hostPort
+		host = &vsock.VsockAddr{Port: uint(port)}
 		port = *hostPort
 		container = &net.TCPAddr{IP: net.ParseIP(*containerIP), Port: *containerPort}
 	case "udp":

alpine/packages/proxy/vendor/vsock/vsock.go

@@ -26,8 +26,9 @@ int accept_vm(int fd, struct sockaddr_vm *sa_vm, socklen_t *sa_vm_len) {
 import "C"
 
 const (
-	AF_VSOCK      = 40
+	AF_VSOCK       = 40
-	VSOCK_CID_ANY = 4294967295 /* 2^32-1 */
+	VSOCK_CID_ANY  = 4294967295 /* 2^32-1 */
+	VSOCK_CID_SELF = 3
 )
 
 // Listen returns a net.Listener which can accept connections on the given