81 lines
1.5 KiB
Go
81 lines
1.5 KiB
Go
package utils
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import (
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"fmt"
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"net"
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"packets/internal/consts"
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"strconv"
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"strings"
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"time"
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"golang.org/x/net/ipv4"
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)
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type Peer struct {
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IP net.IP
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Port int
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}
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func BroadcastAddr(ip net.IP, mask net.IPMask) net.IP {
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b := make(net.IP, len(ip))
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for i := range ip {
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b[i] = ip[i] | ^mask[i]
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}
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return b
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}
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func AskLAN(filename string) ([]Peer, error) {
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var peers []Peer
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query := []byte("Q:" + filename)
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pc, err := net.ListenPacket("udp", ":0")
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if err != nil {
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return []Peer{}, err
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}
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defer pc.Close()
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if pconn := ipv4.NewPacketConn(pc); pconn != nil {
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_ = pconn.SetTTL(1)
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}
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ifaces, _ := net.Interfaces()
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for _, ifc := range ifaces {
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if ifc.Flags&net.FlagUp == 0 || ifc.Flags&net.FlagLoopback != 0 {
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continue
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}
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addrs, _ := ifc.Addrs()
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for _, a := range addrs {
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ipnet, ok := a.(*net.IPNet)
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if !ok || ipnet.IP.To4() == nil {
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continue
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}
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bcast := BroadcastAddr(ipnet.IP.To4(), ipnet.Mask)
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dst := &net.UDPAddr{IP: bcast, Port: 1333}
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_, err = pc.WriteTo(query, dst)
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if err != nil {
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fmt.Printf(":: (%s) can't send to %s: %s\n", ifc.Name, bcast, err.Error())
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}
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}
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}
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_ = pc.SetDeadline(time.Now().Add(consts.LANDeadline))
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buf := make([]byte, 1500)
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for {
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n, addr, err := pc.ReadFrom(buf)
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if err != nil {
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break
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}
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msg := string(buf[:n])
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if strings.HasPrefix(msg, "H:"+filename) {
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parts := strings.Split(msg, ":")
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port, _ := strconv.Atoi(parts[2])
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peers = append(peers, Peer{IP: addr.(*net.UDPAddr).IP, Port: port})
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}
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}
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return peers, nil
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}
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