Checkpoint

internal/netutil/arp/arp_unix.go

@@ -0,0 +1,37 @@
+//go:build !linux
+// +build !linux
+
+// ^ Linux isn't Unix anyway :P
+
+package arp
+
+import (
+	"net"
+	"os/exec"
+	"strings"
+)
+
+func lookup() (map[string]net.HardwareAddr, error) {
+	data, err := exec.Command("arp", "-an").Output()
+	if err != nil {
+		return nil, err
+	}
+
+	t := make(map[string]net.HardwareAddr)
+	for _, line := range strings.Split(string(data), "\n") {
+		fields := strings.Fields(line)
+		if len(fields) < 3 {
+			continue
+		}
+
+		// strip brackets around IP
+		ip := strings.ReplaceAll(fields[1], "(", "")
+		ip = strings.ReplaceAll(ip, ")", "")
+
+		if mac, err := net.ParseMAC(fields[3]); err == nil {
+			t[ip] = mac
+		}
+	}
+
+	return t, nil
+}