Add vmnet support to linuxkit run hyperkit

Allows routed networking, so long as you runhyperkit as root.

This has quite a few downsides, including the requirement to
run as root in order to set up the networking, but some people
really want VMs that are routable from the host.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

vendor/github.com/moby/hyperkit/go/hyperkit.go

@@ -98,6 +98,9 @@ type HyperKit struct {
 	// VSock guest CID
 	VSockGuestCID int `json:"vsock_guest_cid"`
 
+	// VMNet whether to create vmnet network
+	VMNet bool `json:"vmnet"`
+
 	// 9P sockets
 	Sockets9P []Socket9P `json:"9p_sockets"`
 
@@ -415,6 +418,11 @@ func (h *HyperKit) buildArgs(cmdline string) {
 		nextSlot++
 	}
 
+	if h.VMNet {
+		a = append(a, "-s", fmt.Sprintf("%d:0,virtio-net", nextSlot))
+		nextSlot++
+	}
+
 	if h.UUID != "" {
 		a = append(a, "-U", h.UUID)
 	}