tendrils/tendrils.go

package tendrils

import (
	"context"
	"log"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"
)

type Tendrils struct {
	activeInterfaces map[string]context.CancelFunc
	nodes            *Nodes

	Interface   string
	DisableARP  bool
	DisableLLDP bool
	DisableSNMP bool
	LogEvents   bool
	LogNodes    bool
	DebugARP    bool
	DebugLLDP   bool
	DebugSNMP   bool
}

func New() *Tendrils {
	t := &Tendrils{
		activeInterfaces: map[string]context.CancelFunc{},
	}
	t.nodes = NewNodes(t)
	return t
}

func (t *Tendrils) Run() {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGUSR1)
	go func() {
		for range sigCh {
			t.nodes.LogAll()
		}
	}()

	t.populateLocalAddresses()

	if !t.DisableARP {
		t.readARPTable()
		go t.pollARP(ctx)
	}

	ticker := time.NewTicker(1 * time.Second)
	defer ticker.Stop()

	for {
		interfaces := t.listInterfaces()
		t.updateInterfaces(interfaces)
		<-ticker.C
	}
}

func (t *Tendrils) populateLocalAddresses() {
	interfaces, err := net.Interfaces()
	if err != nil {
		return
	}

	hostname, _ := os.Hostname()

	var target *Node
	for _, netIface := range interfaces {
		if len(netIface.HardwareAddr) == 0 {
			continue
		}

		var ips []net.IP
		addrs, err := netIface.Addrs()
		if err == nil {
			for _, addr := range addrs {
				if ipnet, ok := addr.(*net.IPNet); ok {
					if ipnet.IP.To4() != nil && !ipnet.IP.IsLoopback() {
						ips = append(ips, ipnet.IP)
					}
				}
			}
		}

		t.nodes.Update(target, netIface.HardwareAddr, ips, netIface.Name, hostname, "local")
		if target == nil {
			target = t.nodes.GetByMAC(netIface.HardwareAddr)
		}
	}
}

func (t *Tendrils) getLocalNode() *Node {
	interfaces, err := net.Interfaces()
	if err != nil {
		return nil
	}

	for _, iface := range interfaces {
		if len(iface.HardwareAddr) > 0 {
			if node := t.nodes.GetByMAC(iface.HardwareAddr); node != nil {
				return node
			}
		}
	}
	return nil
}

func (t *Tendrils) listInterfaces() []net.Interface {
	interfaces, err := net.Interfaces()
	if err != nil {
		log.Printf("[ERROR] error getting interfaces: %v", err)
		return nil
	}

	var validInterfaces []net.Interface
	for _, iface := range interfaces {
		if t.Interface != "" && iface.Name != t.Interface {
			continue
		}
		if iface.Flags&net.FlagUp == 0 {
			continue
		}
		if iface.Flags&net.FlagLoopback != 0 {
			continue
		}
		if iface.Flags&net.FlagPointToPoint != 0 {
			continue
		}
		if iface.Flags&net.FlagBroadcast == 0 {
			continue
		}
		if len(iface.HardwareAddr) == 0 {
			continue
		}

		addrs, err := iface.Addrs()
		if err != nil || len(addrs) == 0 {
			continue
		}

		validInterfaces = append(validInterfaces, iface)
	}

	return validInterfaces
}

func (t *Tendrils) updateInterfaces(interfaces []net.Interface) {
	current := map[string]bool{}
	for _, iface := range interfaces {
		current[iface.Name] = true
	}

	for name, cancel := range t.activeInterfaces {
		if !current[name] {
			log.Printf("[iface] remove: %s", name)
			cancel()
			delete(t.activeInterfaces, name)
		}
	}

	for _, iface := range interfaces {
		if _, exists := t.activeInterfaces[iface.Name]; !exists {
			log.Printf("[iface] add: %s", iface.Name)
			ctx, cancel := context.WithCancel(context.Background())
			t.activeInterfaces[iface.Name] = cancel
			t.startInterface(ctx, iface)
		}
	}
}

func (t *Tendrils) startInterface(ctx context.Context, iface net.Interface) {
	if !t.DisableLLDP {
		go t.listenLLDP(ctx, iface)
	}
}