Enable setting networking mode for docker

This patch enables setting networking mode for the docker
driver. This does not handle the `container` mode.
Closes #175

client/driver/docker.go

@@ -118,6 +118,23 @@ func createContainer(ctx *ExecContext, task *structs.Task, logger *log.Logger) d
 	logger.Printf("[DEBUG] driver.docker: using %d bytes memory for %s", hostConfig.Memory, task.Config["image"])
 	logger.Printf("[DEBUG] driver.docker: using %d cpu shares for %s", hostConfig.CPUShares, task.Config["image"])
 
+	mode, ok := task.Config["network_mode"]
+        if !ok || mode == "" {
+                // docker default
+                logger.Printf("[WARN] driver.docker: no mode specified for networking, defaulting to bridge")
+                mode = "bridge"
+        }
+
+        // Ignore the container mode for now
+        switch mode {
+        case "default", "bridge", "none", "host":
+                logger.Printf("[DEBUG] driver.docker: using %s as network mode", mode)
+        default:
+                logger.Printf("[WARN] invalid setting for network mode %s, defaulting to bridge mode on docker0", mode)
+                mode = "bridge"
+        }
+	hostConfig.NetworkMode = mode
+
 	// Setup port mapping (equivalent to -p on docker CLI). Ports must already be
 	// exposed in the container.
 	if len(task.Resources.Networks) == 0 {

client/driver/docker_test.go

@@ -287,3 +287,29 @@ func TestDocker_StartNVersions(t *testing.T) {
 
 	t.Log("==> Test complete!")
 }
+
+func TestDockerHostNet(t *testing.T) {
+        task := &structs.Task{
+                Config: map[string]string{
+                        "image": "redis",
+                        "network_mode": "host",
+                },
+                Resources: &structs.Resources{
+                        MemoryMB: 256,
+                        CPU:      512,
+                        },
+                }
+	driverCtx := testDriverContext(task.Name)
+	ctx := testDriverExecContext(task, driverCtx)
+	defer ctx.AllocDir.Destroy()
+	d := NewDockerDriver(driverCtx)
+
+	handle, err := d.Start(ctx, task)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if handle == nil {
+		t.Fatalf("missing handle")
+	}
+	defer handle.Kill()
+}

website/source/docs/drivers/docker.html.md

@@ -23,6 +23,11 @@ The `docker` driver supports the following configuration in the job specificatio
 
 * `command` - (Optional) The command to run when starting the container.
 
+* `network_mode` - (Optional) The network mode to be used for the container.
+   Valid options are `net`, `bridge`, `host` or `none`. If nothing is
+   specified, the container will start in `bridge` mode. The `container`
+   network mode is not supported right now.
+
 ### Port Mapping
 
 Nomad uses port binding to expose services running in containers using the port