add igmp querier for multicast group membership tracking
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Ian Gulliver
@@ -11,11 +11,13 @@ func main() {
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noARP := flag.Bool("no-arp", false, "disable ARP discovery")
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noLLDP := flag.Bool("no-lldp", false, "disable LLDP discovery")
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noSNMP := flag.Bool("no-snmp", false, "disable SNMP discovery")
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noIGMP := flag.Bool("no-igmp", false, "disable IGMP querier")
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logEvents := flag.Bool("log-events", false, "log node events")
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logNodes := flag.Bool("log-nodes", false, "log full node details on changes")
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debugARP := flag.Bool("debug-arp", false, "debug ARP discovery")
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debugLLDP := flag.Bool("debug-lldp", false, "debug LLDP discovery")
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debugSNMP := flag.Bool("debug-snmp", false, "debug SNMP discovery")
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debugIGMP := flag.Bool("debug-igmp", false, "debug IGMP querier")
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flag.Parse()
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t := tendrils.New()
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@@ -23,10 +25,12 @@ func main() {
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t.DisableARP = *noARP
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t.DisableLLDP = *noLLDP
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t.DisableSNMP = *noSNMP
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t.DisableIGMP = *noIGMP
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t.LogEvents = *logEvents
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t.LogNodes = *logNodes
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t.DebugARP = *debugARP
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t.DebugLLDP = *debugLLDP
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t.DebugSNMP = *debugSNMP
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t.DebugIGMP = *debugIGMP
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t.Run()
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}
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228
igmp.go
Normal file
228
igmp.go
Normal file
@@ -0,0 +1,228 @@
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package tendrils
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import (
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"context"
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"log"
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"net"
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"time"
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"github.com/google/gopacket"
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"github.com/google/gopacket/layers"
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"github.com/google/gopacket/pcap"
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)
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func (t *Tendrils) listenIGMP(ctx context.Context, iface net.Interface) {
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handle, err := pcap.OpenLive(iface.Name, 65536, true, 5*time.Second)
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if err != nil {
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log.Printf("[ERROR] failed to open interface %s for igmp: %v", iface.Name, err)
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return
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}
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defer handle.Close()
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if err := handle.SetBPFFilter("igmp"); err != nil {
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log.Printf("[ERROR] failed to set igmp filter on %s: %v", iface.Name, err)
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return
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}
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go t.runIGMPQuerier(ctx, iface)
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packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
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packets := packetSource.Packets()
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for {
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select {
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case <-ctx.Done():
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return
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case packet, ok := <-packets:
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if !ok {
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return
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}
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t.handleIGMPPacket(iface.Name, packet)
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}
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}
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}
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func (t *Tendrils) handleIGMPPacket(ifaceName string, packet gopacket.Packet) {
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ipLayer := packet.Layer(layers.LayerTypeIPv4)
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if ipLayer == nil {
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return
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}
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ip := ipLayer.(*layers.IPv4)
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sourceIP := ip.SrcIP
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igmpLayer := packet.Layer(layers.LayerTypeIGMP)
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if igmpLayer == nil {
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return
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}
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switch igmp := igmpLayer.(type) {
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case *layers.IGMPv1or2:
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t.handleIGMPv1or2(ifaceName, sourceIP, igmp)
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case *layers.IGMP:
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t.handleIGMPv3(ifaceName, sourceIP, igmp)
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}
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}
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func (t *Tendrils) handleIGMPv1or2(ifaceName string, sourceIP net.IP, igmp *layers.IGMPv1or2) {
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switch igmp.Type {
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case layers.IGMPMembershipReportV1, layers.IGMPMembershipReportV2:
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groupIP := igmp.GroupAddress
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if !groupIP.IsMulticast() || groupIP.IsLinkLocalMulticast() {
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return
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}
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if t.DebugIGMP {
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log.Printf("[igmp] %s: join %s -> %s", ifaceName, sourceIP, groupIP)
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}
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t.nodes.UpdateMulticastMembership(sourceIP, groupIP)
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case layers.IGMPLeaveGroup:
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groupIP := igmp.GroupAddress
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if t.DebugIGMP {
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log.Printf("[igmp] %s: leave %s -> %s", ifaceName, sourceIP, groupIP)
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}
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t.nodes.RemoveMulticastMembership(sourceIP, groupIP)
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}
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}
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func (t *Tendrils) handleIGMPv3(ifaceName string, sourceIP net.IP, igmp *layers.IGMP) {
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if igmp.Type != layers.IGMPMembershipReportV3 {
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return
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}
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for _, record := range igmp.GroupRecords {
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groupIP := record.MulticastAddress
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if !groupIP.IsMulticast() || groupIP.IsLinkLocalMulticast() {
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continue
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}
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switch record.Type {
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case layers.IGMPIsEx, layers.IGMPToEx, layers.IGMPIsIn, layers.IGMPToIn:
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if t.DebugIGMP {
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log.Printf("[igmp] %s: v3 join %s -> %s", ifaceName, sourceIP, groupIP)
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}
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t.nodes.UpdateMulticastMembership(sourceIP, groupIP)
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case layers.IGMPBlock:
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if t.DebugIGMP {
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log.Printf("[igmp] %s: v3 leave %s -> %s", ifaceName, sourceIP, groupIP)
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}
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t.nodes.RemoveMulticastMembership(sourceIP, groupIP)
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}
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}
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}
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func (t *Tendrils) runIGMPQuerier(ctx context.Context, iface net.Interface) {
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addrs, err := iface.Addrs()
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if err != nil {
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return
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}
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var srcIP net.IP
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for _, addr := range addrs {
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if ipnet, ok := addr.(*net.IPNet); ok && ipnet.IP.To4() != nil {
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srcIP = ipnet.IP.To4()
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break
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}
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}
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if srcIP == nil {
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return
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}
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ticker := time.NewTicker(60 * time.Second)
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defer ticker.Stop()
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t.sendIGMPQuery(iface.Name, srcIP)
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for {
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select {
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case <-ctx.Done():
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return
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case <-ticker.C:
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t.sendIGMPQuery(iface.Name, srcIP)
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}
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}
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}
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func (t *Tendrils) sendIGMPQuery(ifaceName string, srcIP net.IP) {
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handle, err := pcap.OpenLive(ifaceName, 65536, true, pcap.BlockForever)
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if err != nil {
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return
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}
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defer handle.Close()
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eth := &layers.Ethernet{
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SrcMAC: t.getInterfaceMAC(ifaceName),
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DstMAC: net.HardwareAddr{0x01, 0x00, 0x5e, 0x00, 0x00, 0x01},
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EthernetType: layers.EthernetTypeIPv4,
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}
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ip := &layers.IPv4{
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Version: 4,
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IHL: 6,
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TTL: 1,
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Protocol: layers.IPProtocolIGMP,
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SrcIP: srcIP,
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DstIP: net.IPv4(224, 0, 0, 1),
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Options: []layers.IPv4Option{{OptionType: 148, OptionLength: 4, OptionData: []byte{0, 0}}},
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}
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igmpPayload := buildIGMPQuery()
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buf := gopacket.NewSerializeBuffer()
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opts := gopacket.SerializeOptions{ComputeChecksums: true, FixLengths: true}
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if err := gopacket.SerializeLayers(buf, opts, eth, ip, gopacket.Payload(igmpPayload)); err != nil {
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if t.DebugIGMP {
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log.Printf("[igmp] %s: failed to serialize query: %v", ifaceName, err)
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}
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return
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}
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if err := handle.WritePacketData(buf.Bytes()); err != nil {
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if t.DebugIGMP {
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log.Printf("[igmp] %s: failed to send query: %v", ifaceName, err)
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}
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return
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}
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if t.DebugIGMP {
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log.Printf("[igmp] %s: sent general query", ifaceName)
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}
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}
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func buildIGMPQuery() []byte {
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data := make([]byte, 8)
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data[0] = 0x11
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data[1] = 100
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data[4] = 0
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data[5] = 0
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data[6] = 0
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data[7] = 0
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checksum := igmpChecksum(data)
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data[2] = byte(checksum >> 8)
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data[3] = byte(checksum)
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return data
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}
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func igmpChecksum(data []byte) uint16 {
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var sum uint32
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for i := 0; i < len(data)-1; i += 2 {
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sum += uint32(data[i])<<8 | uint32(data[i+1])
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}
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if len(data)%2 == 1 {
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sum += uint32(data[len(data)-1]) << 8
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}
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for sum > 0xffff {
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sum = (sum & 0xffff) + (sum >> 16)
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}
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return ^uint16(sum)
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}
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func (t *Tendrils) getInterfaceMAC(ifaceName string) net.HardwareAddr {
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iface, err := net.InterfaceByName(ifaceName)
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if err != nil {
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return net.HardwareAddr{0, 0, 0, 0, 0, 0}
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}
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return iface.HardwareAddr
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}
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157
nodes.go
157
nodes.go
@@ -133,29 +133,59 @@ func (n *Node) String() string {
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return joinParts(parts)
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}
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type MulticastGroup struct {
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IP net.IP
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}
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func (g *MulticastGroup) Name() string {
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ip := g.IP.To4()
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if ip == nil {
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return g.IP.String()
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}
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if ip[0] == 239 && ip[1] == 255 {
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universe := int(ip[2])*256 + int(ip[3])
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return fmt.Sprintf("sacn:%d", universe)
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}
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return g.IP.String()
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}
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type MulticastMembership struct {
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Node *Node
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LastSeen time.Time
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}
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type MulticastGroupMembers struct {
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Group *MulticastGroup
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Members map[string]*MulticastMembership // source IP -> membership
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}
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type Nodes struct {
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mu sync.RWMutex
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nodes map[int]*Node
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ipIndex map[string]int
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macIndex map[string]int
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nodeCancel map[int]context.CancelFunc
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nextID int
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t *Tendrils
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ctx context.Context
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cancelAll context.CancelFunc
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mu sync.RWMutex
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nodes map[int]*Node
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ipIndex map[string]int
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macIndex map[string]int
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nodeCancel map[int]context.CancelFunc
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multicastGroups map[string]*MulticastGroupMembers // group IP string -> group with members
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nextID int
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t *Tendrils
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ctx context.Context
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cancelAll context.CancelFunc
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}
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func NewNodes(t *Tendrils) *Nodes {
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ctx, cancel := context.WithCancel(context.Background())
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return &Nodes{
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nodes: map[int]*Node{},
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ipIndex: map[string]int{},
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macIndex: map[string]int{},
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nodeCancel: map[int]context.CancelFunc{},
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nextID: 1,
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t: t,
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ctx: ctx,
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cancelAll: cancel,
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nodes: map[int]*Node{},
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ipIndex: map[string]int{},
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macIndex: map[string]int{},
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nodeCancel: map[int]context.CancelFunc{},
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multicastGroups: map[string]*MulticastGroupMembers{},
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nextID: 1,
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t: t,
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ctx: ctx,
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cancelAll: cancel,
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}
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}
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@@ -433,6 +463,52 @@ func (n *Nodes) UpdateMACTable(node *Node, peerMAC net.HardwareAddr, ifaceName s
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node.MACTable[peerMAC.String()] = ifaceName
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}
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func (n *Nodes) UpdateMulticastMembership(sourceIP, groupIP net.IP) {
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n.mu.Lock()
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defer n.mu.Unlock()
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node := n.getNodeByIPLocked(sourceIP)
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groupKey := groupIP.String()
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sourceKey := sourceIP.String()
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gm := n.multicastGroups[groupKey]
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if gm == nil {
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gm = &MulticastGroupMembers{
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Group: &MulticastGroup{IP: groupIP},
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Members: map[string]*MulticastMembership{},
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}
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n.multicastGroups[groupKey] = gm
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}
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gm.Members[sourceKey] = &MulticastMembership{
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Node: node,
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LastSeen: time.Now(),
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}
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}
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func (n *Nodes) RemoveMulticastMembership(sourceIP, groupIP net.IP) {
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n.mu.Lock()
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defer n.mu.Unlock()
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groupKey := groupIP.String()
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sourceKey := sourceIP.String()
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if gm := n.multicastGroups[groupKey]; gm != nil {
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delete(gm.Members, sourceKey)
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if len(gm.Members) == 0 {
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delete(n.multicastGroups, groupKey)
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}
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}
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}
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func (n *Nodes) getNodeByIPLocked(ip net.IP) *Node {
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if id, exists := n.ipIndex[ip.String()]; exists {
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return n.nodes[id]
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}
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return nil
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}
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func (n *Nodes) logNode(node *Node) {
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name := node.Name
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if name == "" {
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@@ -508,6 +584,53 @@ func (n *Nodes) LogAll() {
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log.Printf("[sigusr1] %s", link)
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}
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}
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n.expireMulticastMemberships()
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if len(n.multicastGroups) > 0 {
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var groups []*MulticastGroupMembers
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for _, gm := range n.multicastGroups {
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groups = append(groups, gm)
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}
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sort.Slice(groups, func(i, j int) bool {
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return sortorder.NaturalLess(groups[i].Group.Name(), groups[j].Group.Name())
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})
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log.Printf("[sigusr1] ================ %d multicast groups ================", len(groups))
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for _, gm := range groups {
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var memberNames []string
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for sourceIP, membership := range gm.Members {
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var name string
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if membership.Node != nil {
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name = membership.Node.Name
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if name == "" {
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name = sourceIP
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}
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} else {
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name = sourceIP
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}
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memberNames = append(memberNames, name)
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}
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sort.Slice(memberNames, func(i, j int) bool {
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return sortorder.NaturalLess(memberNames[i], memberNames[j])
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})
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log.Printf("[sigusr1] %s: %v", gm.Group.Name(), memberNames)
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}
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}
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}
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func (n *Nodes) expireMulticastMemberships() {
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expireTime := time.Now().Add(-5 * time.Minute)
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for groupKey, gm := range n.multicastGroups {
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for sourceKey, membership := range gm.Members {
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if membership.LastSeen.Before(expireTime) {
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delete(gm.Members, sourceKey)
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}
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}
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if len(gm.Members) == 0 {
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delete(n.multicastGroups, groupKey)
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}
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}
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}
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type Link struct {
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1
snmp.go
1
snmp.go
@@ -517,3 +517,4 @@ func (t *Tendrils) getInterfaceNames(snmp *gosnmp.GoSNMP) map[int]string {
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return names
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}
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@@ -18,11 +18,13 @@ type Tendrils struct {
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DisableARP bool
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DisableLLDP bool
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DisableSNMP bool
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DisableIGMP bool
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LogEvents bool
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LogNodes bool
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DebugARP bool
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DebugLLDP bool
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DebugSNMP bool
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DebugIGMP bool
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}
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func New() *Tendrils {
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@@ -178,4 +180,7 @@ func (t *Tendrils) startInterface(ctx context.Context, iface net.Interface) {
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if !t.DisableLLDP {
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go t.listenLLDP(ctx, iface)
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}
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if !t.DisableIGMP {
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go t.listenIGMP(ctx, iface)
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}
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}
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Reference in New Issue
Block a user