[!] add cross-platform support for ARP gratuitous requests, fixes #288

Author: pashagolub

README.md

@@ -3,8 +3,8 @@ module github.com/cybertec-postgresql/vip-manager
 go 1.23.0
 
 require (
+	github.com/google/gopacket v1.1.19
 	github.com/hashicorp/consul/api v1.31.0
-	github.com/mdlayher/arp v0.0.0-20220512170110-6706a2966875
 	github.com/spf13/pflag v1.0.6
 	github.com/spf13/viper v1.19.0
 	go.etcd.io/etcd/client/v3 v3.5.18
@@ -13,11 +13,11 @@ require (
 )
 
 require (
-	github.com/armon/go-metrics v0.5.3 // indirect
+	github.com/armon/go-metrics v0.5.4 // indirect
 	github.com/coreos/go-semver v0.3.1 // indirect
 	github.com/coreos/go-systemd/v22 v22.5.0 // indirect
-	github.com/fatih/color v1.17.0 // indirect
-	github.com/fsnotify/fsnotify v1.7.0 // indirect
+	github.com/fatih/color v1.18.0 // indirect
+	github.com/fsnotify/fsnotify v1.8.0 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang/protobuf v1.5.4 // indirect
 	github.com/hashicorp/errwrap v1.1.0 // indirect
@@ -29,34 +29,29 @@ require (
 	github.com/hashicorp/golang-lru v1.0.2 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/hashicorp/serf v0.10.1 // indirect
-	github.com/josharian/native v1.1.0 // indirect
-	github.com/magiconair/properties v1.8.7 // indirect
-	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/magiconair/properties v1.8.9 // indirect
+	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/mdlayher/ethernet v0.0.0-20220221185849-529eae5b6118 // indirect
-	github.com/mdlayher/packet v1.1.2 // indirect
-	github.com/mdlayher/socket v0.5.1 // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/pelletier/go-toml/v2 v2.2.3 // indirect
-	github.com/sagikazarmark/locafero v0.6.0 // indirect
+	github.com/sagikazarmark/locafero v0.7.0 // indirect
 	github.com/sagikazarmark/slog-shim v0.1.0 // indirect
 	github.com/sourcegraph/conc v0.3.0 // indirect
-	github.com/spf13/afero v1.11.0 // indirect
-	github.com/spf13/cast v1.7.0 // indirect
+	github.com/spf13/afero v1.12.0 // indirect
+	github.com/spf13/cast v1.7.1 // indirect
 	github.com/subosito/gotenv v1.6.0 // indirect
 	go.etcd.io/etcd/api/v3 v3.5.18 // indirect
 	go.etcd.io/etcd/client/pkg/v3 v3.5.18 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
-	golang.org/x/exp v0.0.0-20240823005443-9b4947da3948 // indirect
+	golang.org/x/exp v0.0.0-20250106191152-7588d65b2ba8 // indirect
 	golang.org/x/net v0.34.0 // indirect
-	golang.org/x/sync v0.10.0 // indirect
 	golang.org/x/text v0.21.0 // indirect
-	google.golang.org/genproto/googleapis/api v0.0.0-20240823204242-4ba0660f739c // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20240823204242-4ba0660f739c // indirect
-	google.golang.org/grpc v1.65.0 // indirect
-	google.golang.org/protobuf v1.34.2 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20250106144421-5f5ef82da422 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250106144421-5f5ef82da422 // indirect
+	google.golang.org/grpc v1.69.4 // indirect
+	google.golang.org/protobuf v1.36.2 // indirect
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect

go.mod

@@ -5,7 +5,9 @@ import (
 	"net"
 	"strings"
 
-	arp "github.com/mdlayher/arp"
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+	"github.com/google/gopacket/pcap"
 )
 
 // BasicConfigurer can be used to enable vip-management on nodes
@@ -16,7 +18,6 @@ import (
 // nearby routers and other devices.
 type BasicConfigurer struct {
 	*IPConfiguration
-	arpClient  *arp.Client
 	ntecontext uint32 //used by Windows to delete IP address
 }
 
@@ -48,8 +49,51 @@ func (c *BasicConfigurer) queryAddress() bool {
 	return false
 }
 
-func (c *BasicConfigurer) cleanupArp() {
-	if c.arpClient != nil {
-		c.arpClient.Close()
+const (
+	MACAddressSize  = 6
+	IPv4AddressSize = 4
+)
+
+// arpSendGratuitous is a function that sends gratuitous ARP requests
+func (c *BasicConfigurer) arpSendGratuitous() error {
+	// Open the network interface for sending
+	handle, err := pcap.OpenLive(c.Iface.Name, 65536, false, pcap.BlockForever)
+	if err != nil {
+		return err
+	}
+	defer handle.Close()
+
+	// Create the Ethernet layer
+	ethLayer := &layers.Ethernet{
+		SrcMAC:       c.Iface.HardwareAddr,
+		DstMAC:       net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, // Broadcast
+		EthernetType: layers.EthernetTypeARP,
+	}
+
+	// Create the ARP layer
+	arpLayer := &layers.ARP{
+		AddrType:          layers.LinkTypeEthernet,
+		Protocol:          layers.EthernetTypeIPv4,
+		HwAddressSize:     MACAddressSize,
+		ProtAddressSize:   IPv4AddressSize,
+		Operation:         layers.ARPReply, // Gratuitous ARP is sent as a reply
+		SourceHwAddress:   c.Iface.HardwareAddr,
+		SourceProtAddress: c.IPConfiguration.VIP.AsSlice(),
+		DstHwAddress:      c.Iface.HardwareAddr, // Gratuitous ARP targets itself
+		DstProtAddress:    c.IPConfiguration.VIP.AsSlice(),
+	}
+
+	// Create a packet with the layers
+	buffer := gopacket.NewSerializeBuffer()
+	opts := gopacket.SerializeOptions{
+		FixLengths:       true,
+		ComputeChecksums: true,
 	}
+	err = gopacket.SerializeLayers(buffer, opts, ethLayer, arpLayer)
+	if err != nil {
+		return err
+	}
+
+	// Send the packet
+	return handle.WritePacketData(buffer.Bytes())
 }

go.sum

@@ -1,39 +1,22 @@
 package ipmanager
 
 import (
-	"net"
 	"os/exec"
-	"time"
-
-	arp "github.com/mdlayher/arp"
 )
 
 const (
 	arpRequestOp = 1
 	arpReplyOp   = 2
 )
 
-var (
-	ethernetBroadcast = net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
-)
-
 // configureAddress assigns virtual IP address
 func (c *BasicConfigurer) configureAddress() bool {
-	if c.arpClient == nil {
-		if err := c.createArpClient(); err != nil {
-			log.Error("Couldn't create an Arp client:", err)
-		}
-	}
-
 	log.Infof("Configuring address %s on %s", c.getCIDR(), c.Iface.Name)
-
 	result := c.runAddressConfiguration("add")
-
 	if result {
-		// For now it is save to say that also working even if a
-		// gratuitous arp message could not be send but logging an
-		// errror should be enough.
-		_ = c.arpSendGratuitous()
+		if err := c.arpSendGratuitous(); err != nil {
+			log.Error("Failed to send gratuitous ARP: ", err)
+		}
 	}
 
 	return result
@@ -64,96 +47,3 @@ func (c *BasicConfigurer) runAddressConfiguration(action string) bool {
 	}
 	return true
 }
-
-func (c *BasicConfigurer) createArpClient() (err error) {
-	for i := 0; i < c.RetryNum; i++ {
-		if c.arpClient, err = arp.Dial(&c.Iface); err == nil {
-			return
-		}
-		log.Infof("Problems with producing the arp client: %s", err)
-		time.Sleep(time.Duration(c.RetryAfter) * time.Millisecond)
-	}
-	return
-}
-
-// sends a gratuitous ARP request and reply
-func (c *BasicConfigurer) arpSendGratuitous() error {
-	/* While RFC 2002 does not say whether a gratuitous ARP request or reply is preferred
-	 * to update ones neighbours' MAC tables, the Wireshark Wiki recommends sending both.
-	 *		https://wiki.wireshark.org/Gratuitous_ARP
-	 * This site also recommends sending a reply, as requests might be ignored by some hardware:
-	 *		https://support.citrix.com/article/CTX112701
-	 */
-	if c.arpClient == nil {
-		log.Info("No arp client available, skip send gratuitous ARP")
-		return nil
-	}
-	gratuitousReplyPackage, err := arp.NewPacket(
-		arpReplyOp,
-		c.Iface.HardwareAddr,
-		c.VIP,
-		c.Iface.HardwareAddr,
-		c.VIP,
-	)
-	if err != nil {
-		log.Infof("Gratuitous arp reply package is malformed: %s", err)
-		return err
-	}
-
-	/* RFC 2002 specifies (in section 4.6) that a gratuitous ARP request
-	 * should "not set" the target Hardware Address (THA).
-	 * Since the arp package offers no option to leave the THA out, we specify the Zero-MAC.
-	 * If parsing that fails for some reason, we'll just use the local interface's address.
-	 * The field is probably ignored by the receivers' implementation anyway.
-	 */
-	arpRequestDestMac, err := net.ParseMAC("00:00:00:00:00:00")
-	if err != nil {
-		// not entirely RFC-2002 conform but better then nothing.
-		arpRequestDestMac = c.Iface.HardwareAddr
-	}
-
-	gratuitousRequestPackage, err := arp.NewPacket(
-		arpRequestOp,
-		c.Iface.HardwareAddr,
-		c.VIP,
-		arpRequestDestMac,
-		c.VIP,
-	)
-	if err != nil {
-		log.Infof("Gratuitous arp request package is malformed: %s", err)
-		return err
-	}
-
-	for i := 0; i < c.RetryNum; i++ {
-		errReply := c.arpClient.WriteTo(gratuitousReplyPackage, ethernetBroadcast)
-		if err != nil {
-			log.Error("Couldn't write to the arpClient:", errReply)
-		} else {
-			log.Info("Sent gratuitous ARP reply")
-		}
-
-		errRequest := c.arpClient.WriteTo(gratuitousRequestPackage, ethernetBroadcast)
-		if err != nil {
-			log.Error("Couldn't write to the arpClient:", errRequest)
-		} else {
-			log.Info("Sent gratuitous ARP request")
-		}
-
-		if errReply != nil || errRequest != nil {
-			/* If something went wrong while sending the packages, we'll recreate the ARP client for the next try,
-			 * to avoid having a stale client that gives "network is down" error.
-			 */
-			err = c.createArpClient()
-		} else {
-			//TODO: think about whether to leave this out to achieve simple repeat sending of GARP packages
-			break
-		}
-		time.Sleep(time.Duration(c.RetryAfter) * time.Millisecond)
-	}
-	if err != nil {
-		log.Error("Too many retries", err)
-		return err
-	}
-
-	return nil
-}

ipmanager/basicConfigurer.go

@@ -25,10 +25,10 @@ func (c *BasicConfigurer) configureAddress() bool {
 		log.Error("Failed to add address: ", err)
 		return false
 	}
-	// For now it is save to say that also working even if a
-	// gratuitous arp message could not be send but logging an
-	// errror should be enough.
-	//_ = c.ARPSendGratuitous()
+
+	if err := c.arpSendGratuitous(); err != nil {
+		log.Error("Failed to send gratuitous ARP: ", err)
+	}
 	return true
 }
 

ipmanager/basicConfigurer_linux.go

@@ -275,8 +275,3 @@ func (c *HetznerConfigurer) runAddressConfiguration() bool {
 	c.cachedState = unknown
 	return false
 }
-
-func (c *HetznerConfigurer) cleanupArp() {
-	// dummy function as the usage of interfaces requires us to have this function.
-	// It is sufficient for the leader to tell Hetzner to switch the IP, no cleanup needed.
-}

ipmanager/basicConfigurer_windows.go

@@ -16,7 +16,6 @@ type ipConfigurer interface {
 	configureAddress() bool
 	deconfigureAddress() bool
 	getCIDR() string
-	cleanupArp()
 }
 
 var log *zap.SugaredLogger = zap.L().Sugar()
@@ -124,7 +123,6 @@ func (m *IPManager) SyncStates(ctx context.Context, states <-chan bool) {
 			}
 		case <-ctx.Done():
 			m.configurer.deconfigureAddress()
-			m.configurer.cleanupArp()
 			return
 		}
 	}