|
| 1 | +package main |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "errors" |
| 6 | + "flag" |
| 7 | + "fmt" |
| 8 | + "io" |
| 9 | + "log/slog" |
| 10 | + "net" |
| 11 | + "net/http" |
| 12 | + "net/http/httputil" |
| 13 | + "net/url" |
| 14 | + "os" |
| 15 | + "os/signal" |
| 16 | + "sync" |
| 17 | + "time" |
| 18 | +) |
| 19 | + |
| 20 | +var ( |
| 21 | + flagMac = flag.String("mac", "", "mac address to send WoL packet to") |
| 22 | + flagUpstream = flag.String("upstream", "", "upstream proxy address to send requests to") |
| 23 | + flagListen = flag.String("listen", ":8080", "listen address to listen on") |
| 24 | + flagLog = flag.String("log", "info", "log level (debug, info, warn, error)") |
| 25 | + flagTimeout = flag.Int("timeout", 60, "seconds requests wait for upstream response before failing") |
| 26 | +) |
| 27 | + |
| 28 | +func main() { |
| 29 | + flag.Parse() |
| 30 | + |
| 31 | + switch *flagLog { |
| 32 | + case "debug": |
| 33 | + slog.SetLogLoggerLevel(slog.LevelDebug) |
| 34 | + case "info": |
| 35 | + slog.SetLogLoggerLevel(slog.LevelInfo) |
| 36 | + case "warn": |
| 37 | + slog.SetLogLoggerLevel(slog.LevelWarn) |
| 38 | + case "error": |
| 39 | + slog.SetLogLoggerLevel(slog.LevelError) |
| 40 | + default: |
| 41 | + slog.Error("invalid log level", "logLevel", *flagLog) |
| 42 | + return |
| 43 | + } |
| 44 | + |
| 45 | + // Validate flags |
| 46 | + if *flagListen == "" { |
| 47 | + slog.Error("listen address is required") |
| 48 | + return |
| 49 | + } |
| 50 | + |
| 51 | + if *flagMac == "" { |
| 52 | + slog.Error("mac address is required") |
| 53 | + return |
| 54 | + } |
| 55 | + |
| 56 | + if *flagTimeout < 1 { |
| 57 | + slog.Error("timeout must be greater than 0") |
| 58 | + return |
| 59 | + } |
| 60 | + |
| 61 | + var upstreamURL *url.URL |
| 62 | + var err error |
| 63 | + // validate mac address |
| 64 | + if _, err = net.ParseMAC(*flagMac); err != nil { |
| 65 | + slog.Error("invalid mac address", "error", err) |
| 66 | + return |
| 67 | + } |
| 68 | + |
| 69 | + if *flagUpstream == "" { |
| 70 | + slog.Error("upstream proxy address is required") |
| 71 | + return |
| 72 | + } else { |
| 73 | + upstreamURL, err = url.ParseRequestURI(*flagUpstream) |
| 74 | + if err != nil { |
| 75 | + slog.Error("error parsing upstream url", "error", err) |
| 76 | + return |
| 77 | + } |
| 78 | + } |
| 79 | + |
| 80 | + proxy := newProxy(upstreamURL) |
| 81 | + server := &http.Server{ |
| 82 | + Addr: *flagListen, |
| 83 | + Handler: proxy, |
| 84 | + } |
| 85 | + |
| 86 | + // start the server |
| 87 | + go func() { |
| 88 | + slog.Info("server starting on", "address", *flagListen) |
| 89 | + if err := server.ListenAndServe(); err != nil { |
| 90 | + slog.Error("error starting server", "error", err) |
| 91 | + } |
| 92 | + }() |
| 93 | + |
| 94 | + // graceful shutdown |
| 95 | + ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt) |
| 96 | + defer stop() |
| 97 | + <-ctx.Done() |
| 98 | + shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second) |
| 99 | + defer cancel() |
| 100 | + if err := server.Shutdown(shutdownCtx); err != nil { |
| 101 | + slog.Error("server shutdown error", "error", err) |
| 102 | + } |
| 103 | +} |
| 104 | + |
| 105 | +type upstreamStatus string |
| 106 | + |
| 107 | +const ( |
| 108 | + notready upstreamStatus = "not ready" |
| 109 | + ready upstreamStatus = "ready" |
| 110 | +) |
| 111 | + |
| 112 | +type proxyServer struct { |
| 113 | + upstreamProxy *httputil.ReverseProxy |
| 114 | + failCount int |
| 115 | + statusMutex sync.RWMutex |
| 116 | + status upstreamStatus |
| 117 | +} |
| 118 | + |
| 119 | +func newProxy(url *url.URL) *proxyServer { |
| 120 | + p := httputil.NewSingleHostReverseProxy(url) |
| 121 | + proxy := &proxyServer{ |
| 122 | + upstreamProxy: p, |
| 123 | + status: notready, |
| 124 | + failCount: 0, |
| 125 | + } |
| 126 | + |
| 127 | + // start a goroutien to check upstream status |
| 128 | + go func() { |
| 129 | + checkUrl := url.Scheme + "://" + url.Host + "/wol-health" |
| 130 | + client := &http.Client{Timeout: time.Second} |
| 131 | + ticker := time.NewTicker(2 * time.Second) |
| 132 | + defer ticker.Stop() |
| 133 | + for range ticker.C { |
| 134 | + |
| 135 | + slog.Debug("checking upstream status at", "url", checkUrl) |
| 136 | + resp, err := client.Get(checkUrl) |
| 137 | + |
| 138 | + // drain the body |
| 139 | + if err == nil && resp != nil { |
| 140 | + _, _ = io.Copy(io.Discard, resp.Body) |
| 141 | + _ = resp.Body.Close() |
| 142 | + } |
| 143 | + |
| 144 | + if err == nil && resp != nil && resp.StatusCode == http.StatusOK { |
| 145 | + slog.Debug("upstream status: ready") |
| 146 | + proxy.setStatus(ready) |
| 147 | + proxy.statusMutex.Lock() |
| 148 | + proxy.failCount = 0 |
| 149 | + proxy.statusMutex.Unlock() |
| 150 | + } else { |
| 151 | + slog.Debug("upstream status: notready", "error", err) |
| 152 | + proxy.setStatus(notready) |
| 153 | + proxy.statusMutex.Lock() |
| 154 | + proxy.failCount++ |
| 155 | + proxy.statusMutex.Unlock() |
| 156 | + } |
| 157 | + |
| 158 | + } |
| 159 | + }() |
| 160 | + |
| 161 | + return proxy |
| 162 | +} |
| 163 | + |
| 164 | +func (p *proxyServer) ServeHTTP(w http.ResponseWriter, r *http.Request) { |
| 165 | + if r.Method == "GET" && r.URL.Path == "/status" { |
| 166 | + p.statusMutex.RLock() |
| 167 | + status := string(p.status) |
| 168 | + failCount := p.failCount |
| 169 | + p.statusMutex.RUnlock() |
| 170 | + w.Header().Set("Content-Type", "text/plain") |
| 171 | + w.WriteHeader(200) |
| 172 | + fmt.Fprintf(w, "status: %s\n", status) |
| 173 | + fmt.Fprintf(w, "failures: %d\n", failCount) |
| 174 | + return |
| 175 | + } |
| 176 | + |
| 177 | + if p.getStatus() == notready { |
| 178 | + slog.Info("upstream not ready, sending magic packet", "mac", *flagMac) |
| 179 | + if err := sendMagicPacket(*flagMac); err != nil { |
| 180 | + slog.Warn("failed to send magic WoL packet", "error", err) |
| 181 | + } |
| 182 | + ticker := time.NewTicker(250 * time.Millisecond) |
| 183 | + timeout, cancel := context.WithTimeout(context.Background(), time.Duration(*flagTimeout)*time.Second) |
| 184 | + defer cancel() |
| 185 | + loop: |
| 186 | + for { |
| 187 | + select { |
| 188 | + case <-timeout.Done(): |
| 189 | + slog.Info("timeout waiting for upstream to be ready") |
| 190 | + http.Error(w, "timeout", http.StatusRequestTimeout) |
| 191 | + return |
| 192 | + case <-ticker.C: |
| 193 | + if p.getStatus() == ready { |
| 194 | + ticker.Stop() |
| 195 | + break loop |
| 196 | + } |
| 197 | + } |
| 198 | + } |
| 199 | + } |
| 200 | + |
| 201 | + p.upstreamProxy.ServeHTTP(w, r) |
| 202 | +} |
| 203 | + |
| 204 | +func (p *proxyServer) getStatus() upstreamStatus { |
| 205 | + p.statusMutex.RLock() |
| 206 | + defer p.statusMutex.RUnlock() |
| 207 | + return p.status |
| 208 | +} |
| 209 | + |
| 210 | +func (p *proxyServer) setStatus(status upstreamStatus) { |
| 211 | + p.statusMutex.Lock() |
| 212 | + defer p.statusMutex.Unlock() |
| 213 | + p.status = status |
| 214 | +} |
| 215 | + |
| 216 | +func sendMagicPacket(macAddr string) error { |
| 217 | + hwAddr, err := net.ParseMAC(macAddr) |
| 218 | + if err != nil { |
| 219 | + return err |
| 220 | + } |
| 221 | + |
| 222 | + if len(hwAddr) != 6 { |
| 223 | + return errors.New("invalid MAC address") |
| 224 | + } |
| 225 | + |
| 226 | + // Create the magic packet. |
| 227 | + packet := make([]byte, 102) |
| 228 | + // Add 6 bytes of 0xFF. |
| 229 | + for i := 0; i < 6; i++ { |
| 230 | + packet[i] = 0xFF |
| 231 | + } |
| 232 | + // Repeat the MAC address 16 times. |
| 233 | + for i := 1; i <= 16; i++ { |
| 234 | + copy(packet[i*6:], hwAddr) |
| 235 | + } |
| 236 | + |
| 237 | + // Send the packet using UDP. |
| 238 | + addr := net.UDPAddr{ |
| 239 | + IP: net.IPv4bcast, |
| 240 | + Port: 9, |
| 241 | + } |
| 242 | + conn, err := net.DialUDP("udp", nil, &addr) |
| 243 | + if err != nil { |
| 244 | + return err |
| 245 | + } |
| 246 | + defer conn.Close() |
| 247 | + |
| 248 | + _, err = conn.Write(packet) |
| 249 | + return err |
| 250 | +} |
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