- /control/dhcp/find_active_dhcp: fix DHCP server detection

Before this patch we couldn't receive incoming DHCP packets.
Now we bind() to 0.0.0.0 and set the required network interface
 using SO_BINDTODEVICE option.

As an improvement, we now wait until a reply to our request is
 received and skip all unknown packets.

dhcpd/os_windows.go

@@ -0,0 +1,12 @@
+package dhcpd
+
+import (
+	"net"
+
+	"golang.org/x/net/ipv4"
+)
+
+// Create a socket for receiving broadcast packets
+func newBroadcastPacketConn(bindAddr net.IP, port int, ifname string) (*ipv4.PacketConn, error) {
+	return nil, nil
+}