update

.gitignore

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+nwm
+runtime

go.mod

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+module nwm
+
+go 1.16

index.html

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+<div>
+  <canvas id="myChart"></canvas>
+</div>
+
+<script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
+
+<script src="https://cdn.jsdelivr.net/npm/chart.js@^3"></script>
+<script src="https://cdn.jsdelivr.net/npm/moment@^2"></script>
+<script src="https://cdn.jsdelivr.net/npm/chartjs-adapter-moment@^1"></script>
+
+<script>
+  const ctx = document.getElementById('myChart');
+
+  const fails = [
+    {{.Data}}
+  ]
+
+  new Chart(ctx, {
+    type: 'line',
+    data: {
+      datasets: [
+        {
+          label: 'Public Network',
+          data: fails.filter(el=>el.name=='Public'),
+          borderColor: 'rgb(255, 99, 132)',
+          backgroundColor: 'rgb(255, 99, 132)',
+        },
+        {
+          label: 'DSL',
+          data: fails.filter(el=>el.name=='DSL'),
+          borderColor: 'rgb(75, 192, 192)',
+          backgroundColor: 'rgb(75, 192, 192)'
+        },
+        {
+          label: 'Asus Router',
+          data: fails.filter(el=>el.name=='Asus'),
+          borderColor: 'rgb(255, 205, 86)',
+          backgroundColor: 'rgb(255, 205, 86)'
+        }
+      ]
+    },
+    options: {
+      scales: {
+        x: {
+          type: 'time',
+          time: {
+            unit: 'second'
+          },
+          position: 'bottom'
+        },
+        y: {
+          type: 'category',
+          labels: ['', 'ok','failed','']
+        }
+      },
+      decimation: {
+        enabled: true,
+        algorithm: 'lttb'
+      }
+    }
+  });
+</script>

main.go

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+package main
+
+import (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+	"text/template"
+	"time"
+)
+
+//go:embed index.html
+var tmpl string
+
+var report = template.Must(template.New("").Parse(tmpl))
+var write_report chan bool
+var interval = time.Second * 2
+
+type Network struct {
+	Name   string
+	IP     string
+	OnFail string
+}
+
+var Networks = []*Network{
+	{
+		Name:   "DSL",
+		IP:     "220.135.85.67",
+		OnFail: "nmcli connection up DSL",
+	},
+	{
+		Name: "Asus",
+		IP:   "192.168.50.48",
+	},
+}
+
+func main() {
+	write_report = make(chan bool, 1)
+
+	file, err := os.OpenFile("network.log", os.O_WRONLY|os.O_APPEND|os.O_CREATE, os.ModePerm)
+	if err != nil {
+		log.Panicln(err)
+	}
+	defer file.Close()
+
+	log.Println("starting network monitor")
+
+	go func() {
+
+		perr := false
+		derr := false
+
+		for reducer := 0; ; reducer++ {
+			now := time.Now().Format("2006-01-02 15:04:05")
+
+			// Public
+			go func(print bool) {
+				_, err = net.LookupIP("google.com")
+				if err != nil {
+					if !perr {
+						perr = true
+						log.Println(err)
+					}
+					fmt.Fprintf(file, `{"x": "%s", "y": "%s", "name": "%s"},`, now, "failed", "Public")
+					fmt.Fprintf(file, "\n")
+				} else {
+					perr = false
+					if print {
+						fmt.Fprintf(file, `{"x": "%s", "y": "%s", "name": "%s"},`, now, "ok", "Public")
+						fmt.Fprintf(file, "\n")
+					}
+				}
+			}(reducer == 0)
+
+			// devices
+			go func(print bool) {
+				for i := range Networks {
+					_, err = GetOutboundIP(Networks[i].IP + ":0")
+					if err != nil {
+						if !derr {
+							derr = true
+							log.Println(err)
+						}
+						fmt.Fprintf(file, `{"x": "%s", "y": "%s", "name": "%s"},`, now, "failed", Networks[i].Name)
+						fmt.Fprintf(file, "\n")
+						// fmt.Fprintf(file, "%s\t%s\t%s\n", now, Networks[i].Name, "failed")
+					} else {
+						derr = false
+						if print {
+							fmt.Fprintf(file, `{"x": "%s", "y": "%s", "name": "%s"},`, now, "ok", Networks[i].Name)
+							fmt.Fprintf(file, "\n")
+						}
+					}
+				}
+			}(reducer == 0)
+
+			<-time.After(interval)
+			if reducer >= 9 {
+				reducer = -1
+			}
+		}
+	}()
+
+	go func() {
+		for {
+			<-time.After(time.Minute * 10)
+			WriteReport()
+		}
+	}()
+
+	go func() {
+		http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+			http.ServeFile(w, r, strings.TrimPrefix(r.URL.Path, "/"))
+		})
+		if err := http.ListenAndServe("0.0.0.0:1080", nil); err != nil {
+			log.Fatalln(err)
+		}
+	}()
+
+	wait := make(chan os.Signal, 1)
+	signal.Notify(wait, syscall.SIGINT, syscall.SIGTERM)
+
+	<-wait
+	WriteReport()
+}
+
+func WriteReport() {
+
+	select {
+	case write_report <- true:
+
+	default:
+		return
+	}
+	defer func() { <-write_report }()
+
+	f, err := os.OpenFile("report.html", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.ModePerm)
+	if err != nil {
+		log.Println(err)
+		return
+	}
+	defer f.Close()
+
+	data, err := os.ReadFile("network.log")
+	if err != nil {
+		log.Println(err)
+		return
+	}
+
+	content := &bytes.Buffer{}
+	if err = report.Execute(content, map[string]string{"Data": string(data)}); err != nil {
+		log.Println(err)
+		return
+	}
+	content.WriteTo(f)
+
+}
+
+// Get preferred outbound ip of this machine
+func GetOutboundIP(addr string) (net.IP, error) {
+
+	iface, err := net.ResolveUDPAddr("udp", addr)
+	if err != nil {
+		return nil, err
+	}
+
+	dialer := &net.Dialer{LocalAddr: iface}
+
+	conn, err := dialer.Dial("udp", "8.8.8.8:80")
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+
+	localAddr := conn.LocalAddr().(*net.UDPAddr)
+
+	return localAddr.IP, nil
+}

nwm.service

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+[Unit]
+Description=Evan Network Monitor
+
+[Service]
+WorkingDirectory=/home/evan/Documents/network-monitor/runtime
+ExecStart=/home/evan/Documents/network-monitor/nwm
+Restart=always
+
+StandardOutput=append:/home/evan/Documents/network-monitor/runtime/service.log
+StandardError=append:/home/evan/Documents/network-monitor/runtime/service.log
+
+[Install]
+WantedBy=multi-user.target

restart.sh

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+
+
+sudo systemctl stop nwm
+
+go build -o nwm main.go
+
+sudo systemctl start nwm