127 lines
2.3 KiB
Go
127 lines
2.3 KiB
Go
package main
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import (
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"encoding/binary"
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"encoding/hex"
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"fmt"
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"log"
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"net"
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"os"
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"os/exec"
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"sync"
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"baalvpn/shared"
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"github.com/songgao/water"
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)
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const IFACE_NAME = "baalvpn"
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type Peer struct {
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RealIP string
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InternalIP string
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}
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var (
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peers = map[string]*Peer{}
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peersMutex sync.Mutex
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nextIP = 3
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iface *water.Interface
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)
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func main() {
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if os.Geteuid() != 0 {
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panic("root permissions needed")
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}
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config := water.Config{DeviceType: water.TAP}
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config.Name = IFACE_NAME
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var err error
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iface, err = water.New(config)
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if err != nil {
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panic(err)
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}
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if err := exec.Command("ip", "addr", "add", "10.1.0.2/24", "dev", IFACE_NAME).Run(); err != nil {
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panic(err)
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}
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if err := exec.Command("ip", "link", "set", "dev", IFACE_NAME, "up").Run(); err != nil {
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panic(err)
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}
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receivePackets()
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}
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func receivePackets() {
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log.Println("Listening for packets...")
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listenAddr, err := net.ResolveUDPAddr("udp", ":38000")
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if err != nil {
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panic(err)
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}
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listener, err := net.ListenUDP("udp", listenAddr)
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if err != nil {
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panic(err)
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}
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defer listener.Close()
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for {
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buffer := make([]byte, 50000)
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n, addr, err := listener.ReadFromUDP(buffer)
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if err != nil {
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log.Println(err)
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continue
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}
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if n == 0 {
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continue
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}
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go receivePacket(listener, buffer[:n], addr)
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}
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}
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func receivePacket(conn *net.UDPConn, pkt []byte, addr *net.UDPAddr) {
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if len(pkt) < 4 {
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log.Println("packet too short")
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return
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}
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version := binary.LittleEndian.Uint16(pkt[0:])
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if version != shared.PROTO_VERSION {
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log.Println("mismatched packet version")
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return
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}
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pktType := binary.LittleEndian.Uint16(pkt[2:])
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peerIP := addr.IP.String()
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switch pktType {
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case shared.REQ_REGISTER:
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peersMutex.Lock()
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defer peersMutex.Unlock()
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internalIP := fmt.Sprintf("10.1.0.%d", nextIP)
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if peer, ok := peers[addr.IP.String()]; ok {
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internalIP = peer.InternalIP
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} else {
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peers[addr.IP.String()] = &Peer{
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RealIP: peerIP,
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InternalIP: internalIP,
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}
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nextIP++
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}
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resp := shared.BuildPkt(shared.RESP_REGISTER, net.ParseIP(internalIP).To4())
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if _, err := conn.WriteToUDP(resp, addr); err != nil {
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log.Println(err)
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}
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case shared.REQ_DATA:
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fmt.Println("received packet from " + peerIP + ":")
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fmt.Println(hex.EncodeToString(pkt[4:]))
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default:
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log.Println("unknown packet type")
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}
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}
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