Amazon Dash Button Server

dash_button_server.go

package main

import (
	"log"
	"net"

	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
)

func handleDashButton(macAddr string) error {
	switch macAddr {
	case "b4:7c:9c:xx:xx:xx":
		log.Printf("dash!")
	default:
	}
	return nil
}

// sudo -E go run dash_button_server.go
func main() {
	addr, err := net.ResolveUDPAddr("udp", ":67")
	if err != nil {
		log.Fatal(err)
	}

	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		log.Fatal(err)
	}

	defer conn.Close()

	buf := make([]byte, 1024)

	for {
		n, addr, err := conn.ReadFromUDP(buf)
		if err != nil {
			log.Println("ERROR: ", err)
			continue
		}
		dhcp := decodeDHCPPacket(buf[0:n])
		if dhcp == nil {
			log.Println("ERROR: decode failed")
			continue
		}
		log.Printf("received %s %s %s", addr, dhcp.Operation, dhcp.ClientHWAddr)
		for _, option := range dhcp.Options {
			if option.Type == layers.DHCPOptHostname {
				log.Printf("%s", option.String())
			}
		}
		err = handleDashButton(dhcp.ClientHWAddr.String())
		if err != nil {
			log.Println("ERROR: ", err)
			continue
		}
	}
}

func decodeDHCPPacket(buf []byte) *layers.DHCPv4 {
	p := gopacket.NewPacket(buf, layers.LayerTypeDHCPv4, gopacket.DecodeOptions{
		SkipDecodeRecovery: true,
	})
	dhcp, ok := p.Layer(layers.LayerTypeDHCPv4).(*layers.DHCPv4)
	if !ok {
		return nil
	}
	return dhcp
}