Add neighbor tracking system with LLDP integration

CLAUDE.md

@@ -4,4 +4,5 @@
 - Prepend log messages with [ERROR] if applicable
 - Don't mention claude in commit messages. Keep them to a single, short, descriptive sentence
 - Always push after commiting
-- Use git add -A so you don't miss files when committing
+- Use git add -A so you don't miss files when committing
+- Never use go build -- use go run instead

lldp.go

@@ -53,4 +53,31 @@ func (t *Tendrils) handleLLDPPacket(ifaceName string, packet gopacket.Packet) {
 
 	log.Printf("[%s] lldp packet received: ChassisID=%x PortID=%s TTL=%d",
 		ifaceName, lldp.ChassisID.ID, lldp.PortID.ID, lldp.TTL)
+
+	if len(lldp.ChassisID.ID) == 6 {
+		mac := net.HardwareAddr(lldp.ChassisID.ID)
+		if !isBroadcastOrZero(mac) {
+			t.neighbors.Update(nil, []net.HardwareAddr{mac}, "lldp:"+ifaceName)
+		}
+	}
+}
+
+func isBroadcastOrZero(mac net.HardwareAddr) bool {
+	if len(mac) != 6 {
+		return true
+	}
+
+	allZero := true
+	allFF := true
+
+	for _, b := range mac {
+		if b != 0x00 {
+			allZero = false
+		}
+		if b != 0xff {
+			allFF = false
+		}
+	}
+
+	return allZero || allFF
 }

neighbors.go

@@ -0,0 +1,169 @@
+package tendrils
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"sort"
+	"sync"
+)
+
+type Neighbor struct {
+	IPs  map[string]net.IP
+	MACs map[string]net.HardwareAddr
+}
+
+func (n *Neighbor) String() string {
+	var macs []string
+	for _, mac := range n.MACs {
+		macs = append(macs, mac.String())
+	}
+	sort.Strings(macs)
+
+	var ips []string
+	for _, ip := range n.IPs {
+		ips = append(ips, ip.String())
+	}
+	sort.Strings(ips)
+
+	return fmt.Sprintf("{macs=%v ips=%v}", macs, ips)
+}
+
+type Neighbors struct {
+	mu        sync.RWMutex
+	neighbors map[int]*Neighbor
+	ipIndex   map[string]int
+	macIndex  map[string]int
+	nextID    int
+}
+
+func NewNeighbors() *Neighbors {
+	return &Neighbors{
+		neighbors: map[int]*Neighbor{},
+		ipIndex:   map[string]int{},
+		macIndex:  map[string]int{},
+		nextID:    1,
+	}
+}
+
+func (n *Neighbors) Update(ips []net.IP, macs []net.HardwareAddr, source string) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	if len(ips) == 0 && len(macs) == 0 {
+		return
+	}
+
+	existingIDs := map[int]bool{}
+
+	for _, ip := range ips {
+		if id, exists := n.ipIndex[ip.String()]; exists {
+			existingIDs[id] = true
+		}
+	}
+
+	for _, mac := range macs {
+		if id, exists := n.macIndex[mac.String()]; exists {
+			existingIDs[id] = true
+		}
+	}
+
+	var targetID int
+	if len(existingIDs) == 0 {
+		targetID = n.nextID
+		n.nextID++
+		n.neighbors[targetID] = &Neighbor{
+			IPs:  map[string]net.IP{},
+			MACs: map[string]net.HardwareAddr{},
+		}
+	} else if len(existingIDs) == 1 {
+		for id := range existingIDs {
+			targetID = id
+		}
+	} else {
+		var ids []int
+		for id := range existingIDs {
+			ids = append(ids, id)
+		}
+		targetID = ids[0]
+		var merging []string
+		for i := 1; i < len(ids); i++ {
+			merging = append(merging, n.neighbors[ids[i]].String())
+			n.mergeNeighbors(targetID, ids[i])
+		}
+		log.Printf("[%s] merged neighbors %v into %s", source, merging, n.neighbors[targetID])
+	}
+
+	neighbor := n.neighbors[targetID]
+	var added []string
+
+	for _, ip := range ips {
+		ipKey := ip.String()
+		if _, exists := neighbor.IPs[ipKey]; !exists {
+			added = append(added, "ip="+ipKey)
+		}
+		neighbor.IPs[ipKey] = ip
+		n.ipIndex[ipKey] = targetID
+	}
+
+	for _, mac := range macs {
+		macKey := mac.String()
+		if _, exists := neighbor.MACs[macKey]; !exists {
+			added = append(added, "mac="+macKey)
+		}
+		neighbor.MACs[macKey] = mac
+		n.macIndex[macKey] = targetID
+	}
+
+	if len(added) > 0 {
+		log.Printf("[%s] updated %s +%v", source, neighbor, added)
+	}
+}
+
+func (n *Neighbors) mergeNeighbors(keepID, mergeID int) {
+	keep := n.neighbors[keepID]
+	merge := n.neighbors[mergeID]
+
+	for ipKey, ip := range merge.IPs {
+		keep.IPs[ipKey] = ip
+		n.ipIndex[ipKey] = keepID
+	}
+
+	for macKey, mac := range merge.MACs {
+		keep.MACs[macKey] = mac
+		n.macIndex[macKey] = keepID
+	}
+
+	delete(n.neighbors, mergeID)
+}
+
+func (n *Neighbors) GetByIP(ipv4 net.IP) *Neighbor {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+
+	if id, exists := n.ipIndex[ipv4.String()]; exists {
+		return n.neighbors[id]
+	}
+	return nil
+}
+
+func (n *Neighbors) GetByMAC(mac net.HardwareAddr) *Neighbor {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+
+	if id, exists := n.macIndex[mac.String()]; exists {
+		return n.neighbors[id]
+	}
+	return nil
+}
+
+func (n *Neighbors) All() []*Neighbor {
+	n.mu.RLock()
+	defer n.mu.RUnlock()
+
+	result := make([]*Neighbor, 0, len(n.neighbors))
+	for _, neighbor := range n.neighbors {
+		result = append(result, neighbor)
+	}
+	return result
+}

tendrils.go

@@ -9,11 +9,13 @@ import (
 
 type Tendrils struct {
 	activeInterfaces map[string]context.CancelFunc
+	neighbors        *Neighbors
 }
 
 func New() *Tendrils {
 	return &Tendrils{
 		activeInterfaces: map[string]context.CancelFunc{},
+		neighbors:        NewNeighbors(),
 	}
 }