|
| 1 | +package main |
| 2 | + |
| 3 | +import ( |
| 4 | + "net" |
| 5 | + "os" |
| 6 | + "strings" |
| 7 | + |
| 8 | + "github.com/rs/zerolog" |
| 9 | + "github.com/rs/zerolog/log" |
| 10 | + "github.com/spf13/pflag" |
| 11 | +) |
| 12 | + |
| 13 | +func main() { |
| 14 | + zerolog.TimeFieldFormat = zerolog.TimeFormatUnix |
| 15 | + log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr}).Level(zerolog.TraceLevel) |
| 16 | + |
| 17 | + config := parseOptions() |
| 18 | + |
| 19 | + listener, err := net.ListenUDP("udp", &net.UDPAddr{Port: config.Port}) |
| 20 | + if err != nil { |
| 21 | + log.Fatal().Err(err).Msg("Failed to listen") |
| 22 | + } |
| 23 | + |
| 24 | + log.Info().Int("port", config.Port).Msg("Listening on UDP port") |
| 25 | + log.Info().Msg("Forward targets:") |
| 26 | + for k, v := range config.Forwards { |
| 27 | + log.Info().Msgf(" %s -> %s", net.IP(k), v) |
| 28 | + } |
| 29 | + |
| 30 | + for { |
| 31 | + buf := make([]byte, 1024) |
| 32 | + n, addr, err := listener.ReadFromUDP(buf) |
| 33 | + if err != nil { |
| 34 | + log.Error().Err(err).Msg("Failed to read from UDP") |
| 35 | + continue |
| 36 | + } |
| 37 | + |
| 38 | + forward(config, addr, buf[:n]) |
| 39 | + } |
| 40 | +} |
| 41 | + |
| 42 | +type Config struct { |
| 43 | + Port int |
| 44 | + Forwards map[string]*net.UDPAddr |
| 45 | +} |
| 46 | + |
| 47 | +func parseOptions() *Config { |
| 48 | + port := pflag.Int("port", 5000, "Port to listen on") |
| 49 | + forwards := pflag.StringArray("forward", []string{}, "Forwards (can be specified multiple times, format: sourceIP:targetIP:targetPort)") |
| 50 | + |
| 51 | + pflag.Parse() |
| 52 | + |
| 53 | + return &Config{ |
| 54 | + Port: *port, |
| 55 | + Forwards: parseForwards(*forwards), |
| 56 | + } |
| 57 | +} |
| 58 | + |
| 59 | +func forward(config *Config, addr *net.UDPAddr, buf []byte) { |
| 60 | + remoteIP := addr.IP.String() |
| 61 | + |
| 62 | + l := log.With().Str("remote", remoteIP).Logger() |
| 63 | + |
| 64 | + target, ok := config.Forwards[string(addr.IP.To16())] |
| 65 | + if !ok { |
| 66 | + l.Warn().Msg("No forward for remote IP") |
| 67 | + return |
| 68 | + } |
| 69 | + targetAddr := target.String() |
| 70 | + |
| 71 | + l = l.With().Str("target", targetAddr).Logger() |
| 72 | + |
| 73 | + conn, err := net.DialUDP("udp", nil, target) |
| 74 | + if err != nil { |
| 75 | + l.Error().Err(err).Msg("Failed to connect to target") |
| 76 | + return |
| 77 | + } |
| 78 | + defer conn.Close() |
| 79 | + |
| 80 | + if _, err = conn.Write(buf); err != nil { |
| 81 | + l.Error().Err(err).Msg("Failed to write to target") |
| 82 | + return |
| 83 | + } |
| 84 | + |
| 85 | + l.Info().Int("bytes", len(buf)).Msg("Forwarded") |
| 86 | +} |
| 87 | + |
| 88 | +func parseForwards(raw []string) map[string]*net.UDPAddr { |
| 89 | + forwards := make(map[string]*net.UDPAddr) |
| 90 | + |
| 91 | + for _, rawForward := range raw { |
| 92 | + l := log.With().Str("forward", rawForward).Logger() |
| 93 | + |
| 94 | + parts := strings.SplitN(rawForward, ":", 2) |
| 95 | + if len(parts) != 2 { |
| 96 | + l.Error().Msg("Failed to parse forward, expected 2 parts separated by :") |
| 97 | + continue |
| 98 | + } |
| 99 | + |
| 100 | + rawSourceIP := parts[0] |
| 101 | + sourceIP := net.ParseIP(rawSourceIP) |
| 102 | + if sourceIP == nil { |
| 103 | + l.Error().Msg("Failed to parse source IP") |
| 104 | + continue |
| 105 | + } |
| 106 | + |
| 107 | + rawTarget := parts[1] |
| 108 | + target, err := net.ResolveUDPAddr("udp", rawTarget) |
| 109 | + if err != nil { |
| 110 | + l.Error().Err(err).Msg("Failed to resolve target") |
| 111 | + continue |
| 112 | + } |
| 113 | + |
| 114 | + forwards[string(sourceIP.To16())] = target |
| 115 | + } |
| 116 | + |
| 117 | + return forwards |
| 118 | +} |
0 commit comments