140 lines
2.9 KiB
Go
140 lines
2.9 KiB
Go
package tendrils
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import (
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"context"
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"fmt"
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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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type Tendrils struct {
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goroutines map[string]context.CancelFunc
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}
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func New() *Tendrils {
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return &Tendrils{
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goroutines: map[string]context.CancelFunc{},
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}
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}
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func (t *Tendrils) Run() {
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ticker := time.NewTicker(1 * time.Second)
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defer ticker.Stop()
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for {
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interfaces := t.listInterfaces()
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t.updateGoroutines(interfaces)
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<-ticker.C
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}
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}
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func (t *Tendrils) listInterfaces() []net.Interface {
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interfaces, err := net.Interfaces()
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if err != nil {
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log.Printf("[ERROR] error getting interfaces: %v", err)
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return nil
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}
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var validInterfaces []net.Interface
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for _, iface := range interfaces {
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if iface.Flags&net.FlagUp == 0 {
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continue
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}
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if iface.Flags&net.FlagLoopback != 0 {
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continue
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}
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if iface.Flags&net.FlagPointToPoint != 0 {
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continue
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}
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if iface.Flags&net.FlagBroadcast == 0 {
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continue
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}
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if len(iface.HardwareAddr) == 0 {
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continue
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}
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addrs, err := iface.Addrs()
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if err != nil || len(addrs) == 0 {
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continue
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}
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validInterfaces = append(validInterfaces, iface)
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}
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return validInterfaces
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}
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func (t *Tendrils) updateGoroutines(interfaces []net.Interface) {
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current := map[string]bool{}
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for _, iface := range interfaces {
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current[iface.Name] = true
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}
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for name, cancel := range t.goroutines {
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if !current[name] {
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log.Printf("interface removed: %s", name)
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cancel()
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delete(t.goroutines, name)
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}
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}
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for _, iface := range interfaces {
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if _, exists := t.goroutines[iface.Name]; !exists {
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log.Printf("interface added: %s", iface.Name)
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ctx, cancel := context.WithCancel(context.Background())
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t.goroutines[iface.Name] = cancel
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go t.handleInterface(ctx, iface)
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}
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}
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}
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func (t *Tendrils) handleInterface(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: %v", iface.Name, err)
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return
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}
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defer handle.Close()
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bpfFilter := fmt.Sprintf("ether proto 0x88cc")
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if err := handle.SetBPFFilter(bpfFilter); err != nil {
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log.Printf("[ERROR] failed to set BPF filter on %s: %v", iface.Name, err)
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return
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}
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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.handleLLDPPacket(iface.Name, packet)
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}
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}
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}
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func (t *Tendrils) handleLLDPPacket(ifaceName string, packet gopacket.Packet) {
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lldpLayer := packet.Layer(layers.LayerTypeLinkLayerDiscovery)
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if lldpLayer == nil {
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return
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}
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lldp, ok := lldpLayer.(*layers.LinkLayerDiscovery)
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if !ok {
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return
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}
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log.Printf("[%s] lldp packet received: ChassisID=%x PortID=%s TTL=%d",
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ifaceName, lldp.ChassisID.ID, lldp.PortID.ID, lldp.TTL)
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}
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