filter multicast macs

arp.go

@@ -0,0 +1,114 @@
+package tendrils
+
+import (
+	"bufio"
+	"context"
+	"log"
+	"net"
+	"os/exec"
+	"runtime"
+	"strings"
+	"time"
+)
+
+func (t *Tendrils) pollARP(ctx context.Context) {
+	ticker := time.NewTicker(30 * time.Second)
+	defer ticker.Stop()
+
+	t.readARPTable()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			t.readARPTable()
+		}
+	}
+}
+
+type arpEntry struct {
+	ip    net.IP
+	mac   net.HardwareAddr
+	iface string
+}
+
+func (t *Tendrils) readARPTable() {
+	entries := t.parseARPTable()
+
+	for _, entry := range entries {
+		if isBroadcastOrZero(entry.mac) {
+			continue
+		}
+
+		t.nodes.Update([]net.IP{entry.ip}, []net.HardwareAddr{entry.mac}, entry.iface, "", "arp")
+	}
+}
+
+func (t *Tendrils) parseARPTable() []arpEntry {
+	if runtime.GOOS == "darwin" {
+		return t.parseARPDarwin()
+	}
+	return t.parseARPLinux()
+}
+
+func (t *Tendrils) parseARPDarwin() []arpEntry {
+	cmd := exec.Command("arp", "-a")
+	output, err := cmd.Output()
+	if err != nil {
+		return nil
+	}
+
+	var entries []arpEntry
+	scanner := bufio.NewScanner(strings.NewReader(string(output)))
+	for scanner.Scan() {
+		line := scanner.Text()
+		fields := strings.Fields(line)
+		if len(fields) < 6 {
+			continue
+		}
+
+		ipStr := strings.Trim(fields[1], "()")
+		ip := net.ParseIP(ipStr)
+		if ip == nil {
+			continue
+		}
+
+		macStr := fields[3]
+		if macStr == "(incomplete)" {
+			continue
+		}
+
+		macStr = normalizeMACAddress(macStr)
+		mac, err := net.ParseMAC(macStr)
+		if err != nil {
+			log.Printf("[arp] failed to parse MAC %q for IP %s: %v", macStr, ipStr, err)
+			continue
+		}
+
+		ifaceName := fields[5]
+
+		entries = append(entries, arpEntry{
+			ip:    ip,
+			mac:   mac,
+			iface: ifaceName,
+		})
+	}
+
+	return entries
+}
+
+func (t *Tendrils) parseARPLinux() []arpEntry {
+	var entries []arpEntry
+	return entries
+}
+
+func normalizeMACAddress(mac string) string {
+	parts := strings.Split(mac, ":")
+	for i, part := range parts {
+		if len(part) == 1 {
+			parts[i] = "0" + part
+		}
+	}
+	return strings.Join(parts, ":")
+}