Add broadcast packet tracking with rate monitoring

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ping.go

@@ -1,16 +1,143 @@
 package tendrils
 
 import (
+	"log"
 	"net"
+	"sync"
 	"time"
 
 	"golang.org/x/net/icmp"
 	"golang.org/x/net/ipv4"
 )
 
+type pendingPing struct {
+	ip       string
+	response chan bool
+}
+
+type PingManager struct {
+	mu      sync.Mutex
+	conn    *icmp.PacketConn
+	pending map[uint16]*pendingPing
+	nextID  uint16
+	minID   uint16
+}
+
+func NewPingManager() *PingManager {
+	pm := &PingManager{
+		pending: map[uint16]*pendingPing{},
+		nextID:  1000,
+		minID:   1000,
+	}
+
+	conn, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
+	if err != nil {
+		return pm
+	}
+	pm.conn = conn
+
+	go pm.readLoop()
+
+	return pm
+}
+
+func (pm *PingManager) readLoop() {
+	buf := make([]byte, 1500)
+	for {
+		n, peer, err := pm.conn.ReadFrom(buf)
+		if err != nil {
+			return
+		}
+
+		msg, err := icmp.ParseMessage(1, buf[:n])
+		if err != nil {
+			continue
+		}
+
+		if msg.Type != ipv4.ICMPTypeEchoReply {
+			continue
+		}
+
+		echo, ok := msg.Body.(*icmp.Echo)
+		if !ok {
+			continue
+		}
+
+		ipAddr, ok := peer.(*net.IPAddr)
+		if !ok {
+			continue
+		}
+
+		pm.mu.Lock()
+		id := uint16(echo.ID)
+		if p, exists := pm.pending[id]; exists {
+			if p.ip == ipAddr.IP.String() {
+				select {
+				case p.response <- true:
+				default:
+					log.Printf("[ping] late response from %s (channel full)", ipAddr.IP)
+				}
+			}
+		} else if id >= pm.minID {
+			log.Printf("[ping] late response from %s (id %d expired)", ipAddr.IP, echo.ID)
+		}
+		pm.mu.Unlock()
+	}
+}
+
+func (pm *PingManager) Ping(ipStr string, timeout time.Duration) bool {
+	if pm.conn == nil {
+		return false
+	}
+
+	pm.mu.Lock()
+	pm.nextID++
+	id := pm.nextID
+	p := &pendingPing{
+		ip:       ipStr,
+		response: make(chan bool, 1),
+	}
+	pm.pending[id] = p
+	pm.mu.Unlock()
+
+	defer func() {
+		pm.mu.Lock()
+		delete(pm.pending, id)
+		pm.mu.Unlock()
+	}()
+
+	msg := icmp.Message{
+		Type: ipv4.ICMPTypeEcho,
+		Code: 0,
+		Body: &icmp.Echo{
+			ID:   int(id),
+			Seq:  1,
+			Data: []byte("tendrils"),
+		},
+	}
+	msgBytes, err := msg.Marshal(nil)
+	if err != nil {
+		return false
+	}
+
+	ip := net.ParseIP(ipStr)
+	_, err = pm.conn.WriteTo(msgBytes, &net.IPAddr{IP: ip})
+	if err != nil {
+		return false
+	}
+
+	select {
+	case <-p.response:
+		return true
+	case <-time.After(timeout):
+		return false
+	}
+}
+
 func (t *Tendrils) pingNode(node *Node) {
 	t.nodes.mu.RLock()
 	var ips []string
+	nodeName := node.DisplayName()
 	for _, iface := range node.Interfaces {
 		for ipStr := range iface.IPs {
 			ip := net.ParseIP(ipStr)
@@ -26,63 +153,14 @@ func (t *Tendrils) pingNode(node *Node) {
 	}
 
 	for _, ipStr := range ips {
-		reachable := t.pingIP(ipStr)
+		reachable := t.ping.Ping(ipStr, 2*time.Second)
 		if reachable {
-			t.errors.ClearUnreachable(node, ipStr)
+			if t.errors.ClearUnreachable(node, ipStr) {
+				log.Printf("[ping] %s (%s) is now reachable", nodeName, ipStr)
+			}
 		} else {
-			t.errors.SetUnreachable(node, ipStr)
-		}
-	}
-}
-
-func (t *Tendrils) pingIP(ipStr string) bool {
-	conn, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
-	if err != nil {
-		return false
-	}
-	defer conn.Close()
-
-	conn.SetDeadline(time.Now().Add(500 * time.Millisecond))
-
-	ip := net.ParseIP(ipStr)
-	seq := uint16(time.Now().UnixNano() & 0xFFFF)
-
-	msg := icmp.Message{
-		Type: ipv4.ICMPTypeEcho,
-		Code: 0,
-		Body: &icmp.Echo{
-			ID:   int(seq),
-			Seq:  1,
-			Data: []byte("tendrils"),
-		},
-	}
-	msgBytes, err := msg.Marshal(nil)
-	if err != nil {
-		return false
-	}
-
-	_, err = conn.WriteTo(msgBytes, &net.IPAddr{IP: ip})
-	if err != nil {
-		return false
-	}
-
-	buf := make([]byte, 1500)
-	for {
-		n, peer, err := conn.ReadFrom(buf)
-		if err != nil {
-			return false
-		}
-
-		parsed, err := icmp.ParseMessage(1, buf[:n])
-		if err != nil {
-			continue
-		}
-
-		if parsed.Type == ipv4.ICMPTypeEchoReply {
-			if ipAddr, ok := peer.(*net.IPAddr); ok {
-				if ipAddr.IP.String() == ipStr {
-					return true
-				}
+			if t.errors.SetUnreachable(node, ipStr) {
+				log.Printf("[ping] %s (%s) is now unreachable", nodeName, ipStr)
 			}
 		}
 	}