Improving Mac discovery

internal/clientinfo/arp_windows.go

@@ -0,0 +1,38 @@
+package clientinfo
+
+import (
+	"os/exec"
+	"strings"
+)
+
+func (a *arpDiscover) scan() {
+	data, err := exec.Command("arp", "-a").Output()
+	if err != nil {
+		return
+	}
+
+	header := false
+	for _, line := range strings.Split(string(data), "\n") {
+		if len(line) == 0 {
+			continue // empty lines
+		}
+		if line[0] != ' ' {
+			header = true // "Interface:" lines, next is header line.
+			continue
+		}
+		if header {
+			header = false // header lines
+			continue
+		}
+
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+
+		ip := fields[0]
+		mac := strings.ReplaceAll(fields[1], "-", ":")
+		a.mac.Store(ip, mac)
+		a.ip.Store(mac, ip)
+	}
+}