wip v1.0.0

internal/vrrp/arp.go

@@ -0,0 +1,72 @@
+package vrrp
+
+import (
+	"fmt"
+	"net"
+	"net/netip"
+
+	"github.com/mdlayher/arp"
+)
+
+type ARPSender struct {
+	client *arp.Client
+	iface  *net.Interface
+}
+
+func NewARPSender(ifaceName string) (*ARPSender, error) {
+	iface, err := net.InterfaceByName(ifaceName)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get interface %s: %w", ifaceName, err)
+	}
+
+	client, err := arp.Dial(iface)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create ARP client: %w", err)
+	}
+
+	return &ARPSender{
+		client: client,
+		iface:  iface,
+	}, nil
+}
+
+func (a *ARPSender) SendGratuitousARP(ip net.IP) error {
+	if ip4 := ip.To4(); ip4 == nil {
+		return fmt.Errorf("invalid IPv4 address: %s", ip)
+	}
+
+	addr, err := netip.ParseAddr(ip.String())
+	if err != nil {
+		return fmt.Errorf("failed to parse IP: %w", err)
+	}
+
+	pkt, err := arp.NewPacket(
+		arp.OperationRequest,
+		a.iface.HardwareAddr,
+		addr,
+		net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+		addr,
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create ARP packet: %w", err)
+	}
+
+	if err := a.client.WriteTo(pkt, net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}); err != nil {
+		return fmt.Errorf("failed to send gratuitous ARP: %w", err)
+	}
+
+	return nil
+}
+
+func (a *ARPSender) SendGratuitousARPForIPs(ips []net.IP) error {
+	for _, ip := range ips {
+		if err := a.SendGratuitousARP(ip); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (a *ARPSender) Close() error {
+	return a.client.Close()
+}