89 lines
1.7 KiB
Go
89 lines
1.7 KiB
Go
package main
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"net"
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"time"
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"github.com/google/gopacket"
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"github.com/google/gopacket/pcap"
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)
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func errCheck(err error) {
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if err != nil {
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panic(err)
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}
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return
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}
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func listenDiscoverResponse() {
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handle, err := pcap.OpenLive("any", int32(1600), true, pcap.BlockForever)
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errCheck(err)
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handle.SetBPFFilter("udp and port 8850")
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packets := gopacket.NewPacketSource(handle, handle.LinkType()).Packets()
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for pkt := range packets {
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fmt.Printf("%s\n", pkt.NetworkLayer().NetworkFlow().Src())
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}
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return
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}
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func toMaxHost(n *net.IPNet) (net.IP, error) {
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if n.IP.To4() == nil {
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return net.IP{}, errors.New("IP address is not IPv4")
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}
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ip := make(net.IP, len(n.IP.To4()))
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binary.BigEndian.PutUint32(ip,
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binary.BigEndian.Uint32(n.IP.To4())|^binary.BigEndian.Uint32(net.IP(n.Mask).To4()))
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return ip, nil
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}
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func bcastAddresses() ([]string) {
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var addrs []string = nil
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interfaceInfo, _ := net.Interfaces()
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for i := 0; i < len(interfaceInfo); i++ {
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addr, err := interfaceInfo[i].Addrs()
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errCheck(err)
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for j := 0; j < len(addr); j++ {
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_, ipNet, _ := net.ParseCIDR(addr[j].String())
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bcast, err := toMaxHost(ipNet)
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if err != nil {
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} else {
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addrs = append(addrs, bcast.String())
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}
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}
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}
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return addrs
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}
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func main() {
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sendAddrs := bcastAddresses()
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go listenDiscoverResponse()
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time.Sleep(1 * time.Second)
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for i := 0; i < len(sendAddrs); i++ {
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remoteAddr := sendAddrs[i] + ":8888"
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remote, err := net.ResolveUDPAddr("udp4", remoteAddr)
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errCheck(err)
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conn, err := net.DialUDP("udp4", nil, remote)
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errCheck(err)
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defer conn.Close()
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_, err = conn.Write([]byte(conn.LocalAddr().String()))
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errCheck(err)
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}
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time.Sleep(30 * time.Second)
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}
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