Add --userland-proxy daemon flag

The `--userland-proxy` daemon flag makes it possible to rely on hairpin
NAT and additional iptables routes instead of userland proxy for port
publishing and inter-container communication.

Usage of the userland proxy remains the default as hairpin NAT is
unsupported by older kernels.

Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>
Upstream-commit: f42348e18f73d1d775d77ac75bc96466aae56d7c
Component: engine

components/engine/integration-cli/docker_cli_nat_test.go

@@ -4,14 +4,26 @@ import (
 	"fmt"
 	"net"
 	"os/exec"
+	"strconv"
 	"strings"
 
 	"github.com/go-check/check"
 )
 
-func (s *DockerSuite) TestNetworkNat(c *check.C) {
-	testRequires(c, SameHostDaemon, NativeExecDriver)
+func startServerContainer(c *check.C, proto string, port int) string {
+	cmd := []string{"-d", "-p", fmt.Sprintf("%d:%d", port, port), "busybox", "nc", "-lp", strconv.Itoa(port)}
+	if proto == "udp" {
+		cmd = append(cmd, "-u")
+	}
 
+	name := "server"
+	if err := waitForContainer(name, cmd...); err != nil {
+		c.Fatalf("Failed to launch server container: %v", err)
+	}
+	return name
+}
+
+func getExternalAddress(c *check.C) net.IP {
 	iface, err := net.InterfaceByName("eth0")
 	if err != nil {
 		c.Skip(fmt.Sprintf("Test not running with `make test`. Interface eth0 not found: %v", err))
@@ -27,35 +39,65 @@ func (s *DockerSuite) TestNetworkNat(c *check.C) {
 		c.Fatalf("Error retrieving the up for eth0: %s", err)
 	}
 
-	runCmd := exec.Command(dockerBinary, "run", "-dt", "-p", "8080:8080", "busybox", "nc", "-lp", "8080")
+	return ifaceIP
+}
+
+func getContainerLogs(c *check.C, containerID string) string {
+	runCmd := exec.Command(dockerBinary, "logs", containerID)
 	out, _, err := runCommandWithOutput(runCmd)
 	if err != nil {
 		c.Fatal(out, err)
 	}
+	return strings.Trim(out, "\r\n")
+}
 
-	cleanedContainerID := strings.TrimSpace(out)
-
-	runCmd = exec.Command(dockerBinary, "run", "busybox", "sh", "-c", fmt.Sprintf("echo hello world | nc -w 30 %s 8080", ifaceIP))
-	out, _, err = runCommandWithOutput(runCmd)
+func getContainerStatus(c *check.C, containerID string) string {
+	runCmd := exec.Command(dockerBinary, "inspect", "-f", "{{.State.Running}}", containerID)
+	out, _, err := runCommandWithOutput(runCmd)
 	if err != nil {
 		c.Fatal(out, err)
 	}
-
-	runCmd = exec.Command(dockerBinary, "logs", cleanedContainerID)
-	out, _, err = runCommandWithOutput(runCmd)
-	if err != nil {
-		c.Fatalf("failed to retrieve logs for container: %s, %v", out, err)
-	}
-
-	out = strings.Trim(out, "\r\n")
-
-	if expected := "hello world"; out != expected {
-		c.Fatalf("Unexpected output. Expected: %q, received: %q for iface %s", expected, out, ifaceIP)
-	}
-
-	killCmd := exec.Command(dockerBinary, "kill", cleanedContainerID)
-	if out, _, err = runCommandWithOutput(killCmd); err != nil {
-		c.Fatalf("failed to kill container: %s, %v", out, err)
-	}
-
+	return strings.Trim(out, "\r\n")
+}
+
+func (s *DockerSuite) TestNetworkNat(c *check.C) {
+	testRequires(c, SameHostDaemon, NativeExecDriver)
+	defer deleteAllContainers()
+
+	srv := startServerContainer(c, "tcp", 8080)
+
+	// Spawn a new container which connects to the server through the
+	// interface address.
+	endpoint := getExternalAddress(c)
+	runCmd := exec.Command(dockerBinary, "run", "busybox", "sh", "-c", fmt.Sprintf("echo hello world | nc -w 30 %s 8080", endpoint))
+	if out, _, err := runCommandWithOutput(runCmd); err != nil {
+		c.Fatalf("Failed to connect to server: %v (output: %q)", err, string(out))
+	}
+
+	result := getContainerLogs(c, srv)
+	if expected := "hello world"; result != expected {
+		c.Fatalf("Unexpected output. Expected: %q, received: %q", expected, result)
+	}
+}
+
+func (s *DockerSuite) TestNetworkLocalhostTCPNat(c *check.C) {
+	testRequires(c, SameHostDaemon, NativeExecDriver)
+	defer deleteAllContainers()
+
+	srv := startServerContainer(c, "tcp", 8081)
+
+	// Attempt to connect from the host to the listening container.
+	conn, err := net.Dial("tcp", "localhost:8081")
+	if err != nil {
+		c.Fatalf("Failed to connect to container (%v)", err)
+	}
+	if _, err := conn.Write([]byte("hello world\n")); err != nil {
+		c.Fatal(err)
+	}
+	conn.Close()
+
+	result := getContainerLogs(c, srv)
+	if expected := "hello world"; result != expected {
+		c.Fatalf("Unexpected output. Expected: %q, received: %q", expected, result)
+	}
 }