Allow to specify more than one networking adapter for vbox

Note: this patch introduces an incompatibility in the
`linuxkit run vbox` arguments.

It wasn't impossible to specify more than one network adapter
to the `linuxkit run vbox` command.

This patch allows to specify more than one `-networking` argument to specify
different network adapters.

For instance:
~~~sh
linuxkit run vbox -networking type=nat -networking type=hostonly,adapter=vboxnet0
~~~
will setup the VM with 2 NICs.

It is also possible to get rid of the `type` argument.

Signed-off-by: Brice Figureau <brice@daysofwonder.com>

docs/platform-vbox.md

@@ -22,9 +22,18 @@ stdio, providing interactive access to the VM.
 The Virtualbox backend support configuring a persistent disk using the
 standard `linuxkit` `-disk` syntax. Multiple disks are
 supported and can be created in `raw` format; other formats that VirtualBox
-supports can be attached
+supports can be attached. Note that additional drives are attached to the
+SATA Controller, unlike the VM disk which is on the IDE Controller.
 
 ## Networking
 
-You can select the networking mode, which defaults to the standard `nat`, but
-some networking modes may require additional configuration.
+You can select the networking mode, which defaults to the standard `nat`, by using the
+`-networking` command-line option. Some networking modes (`hostonly`, `bridge`) will require 
+the additional `adapter` parameter to the `-networking` option:
+
+~~~
+-networking hostonly,adapter=vboxnet0
+~~~
+
+You can specify more than one `-networking` option to setup multiple adapters. It is
+recommended to setup the first adapter as `nat`.

src/cmd/linuxkit/run_vbox.go

@@ -17,6 +17,43 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
+// VBNetwork is the config for a Virtual Box network
+type VBNetwork struct {
+	Type    string
+	Adapter string
+}
+
+// VBNetworks is the type for a list of VBNetwork
+type VBNetworks []VBNetwork
+
+func (l *VBNetworks) String() string {
+	return fmt.Sprint(*l)
+}
+
+// Set is used by flag to configure value from CLI
+func (l *VBNetworks) Set(value string) error {
+	d := VBNetwork{}
+	s := strings.Split(value, ",")
+	for _, p := range s {
+		c := strings.SplitN(p, "=", 2)
+		switch len(c) {
+		case 1:
+			d.Type = c[0]
+		case 2:
+			switch c[0] {
+			case "type":
+				d.Type = c[1]
+			case "adapter", "bridgeadapter", "hostadapter":
+				d.Adapter = c[1]
+			default:
+				return fmt.Errorf("Unknown network config: %s", c[0])
+			}
+		}
+	}
+	*l = append(*l, d)
+	return nil
+}
+
 func runVbox(args []string) {
 	invoked := filepath.Base(os.Args[0])
 	flags := flag.NewFlagSet("vbox", flag.ExitOnError)
@@ -51,8 +88,8 @@ func runVbox(args []string) {
 	uefiBoot := flags.Bool("uefi", false, "Use UEFI boot")
 
 	// networking
-	networking := flags.String("networking", "nat", "Networking mode. null|nat|bridged|intnet|hostonly|generic|natnetwork[<devicename>]")
-	bridgeadapter := flags.String("bridgeadapter", "", "Bridge adapter interface to use if networking mode is bridged")
+	var networks VBNetworks
+	flags.Var(&networks, "networking", "Network config, may be repeated. [type=](null|nat|bridged|intnet|hostonly|generic|natnetwork[<devicename>])[,[bridge|host]adapter=<interface>]")
 
 	if err := flags.Parse(args); err != nil {
 		log.Fatal("Unable to parse args")
@@ -201,26 +238,34 @@ func runVbox(args []string) {
 		}
 	}
 
-	_, out, err = manage(vboxmanage, "modifyvm", name, "--nictype1", "virtio")
+	for i, d := range networks {
+		nic := i + 1
+		_, out, err = manage(vboxmanage, "modifyvm", name, fmt.Sprintf("--nictype%d", nic), "virtio")
 		if err != nil {
 			log.Fatalf("modifyvm --nictype error: %v\n%s", err, out)
 		}
 
-	_, out, err = manage(vboxmanage, "modifyvm", name, "--nic1", *networking)
+		_, out, err = manage(vboxmanage, "modifyvm", name, fmt.Sprintf("--nic%d", nic), d.Type)
 		if err != nil {
 			log.Fatalf("modifyvm --nic error: %v\n%s", err, out)
 		}
-	if *networking == "bridged" {
-		_, out, err = manage(vboxmanage, "modifyvm", name, "--bridgeadapter1", *bridgeadapter)
+		if d.Type == "hostonly" {
+			_, out, err = manage(vboxmanage, "modifyvm", name, fmt.Sprintf("--hostonlyadapter%d", nic), d.Adapter)
+			if err != nil {
+				log.Fatalf("modifyvm --hostonlyadapter error: %v\n%s", err, out)
+			}
+		} else if d.Type == "bridged" {
+			_, out, err = manage(vboxmanage, "modifyvm", name, fmt.Sprintf("--bridgeadapter%d", nic), d.Adapter)
 			if err != nil {
 				log.Fatalf("modifyvm --bridgeadapter error: %v\n%s", err, out)
 			}
 		}
 
-	_, out, err = manage(vboxmanage, "modifyvm", name, "--cableconnected1", "on")
+		_, out, err = manage(vboxmanage, "modifyvm", name, fmt.Sprintf("--cableconnected%d", nic), "on")
 		if err != nil {
 			log.Fatalf("modifyvm --cableconnected error: %v\n%s", err, out)
 		}
+	}
 
 	// create socket
 	_ = os.Remove(consolePath)