[relay] use exposed address for healthcheck TLS validation (#4872)

* fix(relay): use exposed address for healthcheck TLS validation

Healthcheck was using listen address (0.0.0.0) instead of exposed address
(domain name) for certificate validation, causing validation to always fail.

Now correctly uses the exposed address where the TLS certificate is valid,
matching real client connection behavior.

* - store exposedAddress directly in Relay struct instead of parsing on every call
- remove unused parseHostPort() function
- remove unused ListenAddress() method from ServiceChecker interface
- improve error logging with address context

* [relay/healthcheck] Remove QUIC health check logic, update WebSocket validation flow

Refactored health check logic by removing QUIC-specific connection validation and simplifying logic for WebSocket protocol. Adjusted certificate validation flow and improved handling of exposed addresses.

* [relay/healthcheck] Fix certificate validation status during health check

---------

Co-authored-by: Maycon Santos <mlsmaycon@gmail.com>

relay/healthcheck/healthcheck.go

@@ -6,14 +6,13 @@ import (
 	"errors"
 	"net"
 	"net/http"
+	"strings"
 	"sync"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 
 	"github.com/netbirdio/netbird/relay/protocol"
-	"github.com/netbirdio/netbird/relay/server/listener/quic"
-	"github.com/netbirdio/netbird/relay/server/listener/ws"
 )
 
 const (
@@ -27,7 +26,7 @@ const (
 
 type ServiceChecker interface {
 	ListenerProtocols() []protocol.Protocol
-	ListenAddress() string
+	ExposedAddress() string
 }
 
 type HealthStatus struct {
@@ -135,7 +134,11 @@ func (s *Server) getHealthStatus(ctx context.Context) (*HealthStatus, bool) {
 	}
 	status.Listeners = listeners
 
-	if ok := s.validateCertificate(ctx); !ok {
+	if !strings.HasPrefix(s.config.ServiceChecker.ExposedAddress(), "rels") {
+		status.CertificateValid = false
+	}
+
+	if ok := s.validateConnection(ctx); !ok {
 		status.Status = statusUnhealthy
 		status.CertificateValid = false
 		healthy = false
@@ -152,32 +155,18 @@ func (s *Server) validateListeners() ([]protocol.Protocol, bool) {
 	return listeners, true
 }
 
-func (s *Server) validateCertificate(ctx context.Context) bool {
-	listenAddress := s.config.ServiceChecker.ListenAddress()
-	if listenAddress == "" {
-		log.Warn("listen address is empty")
+func (s *Server) validateConnection(ctx context.Context) bool {
+	exposedAddress := s.config.ServiceChecker.ExposedAddress()
+	if exposedAddress == "" {
+		log.Error("exposed address is empty, cannot validate certificate")
 		return false
 	}
 
-	dAddr := dialAddress(listenAddress)
-
-	for _, proto := range s.config.ServiceChecker.ListenerProtocols() {
-		switch proto {
-		case ws.Proto:
-			if err := dialWS(ctx, dAddr); err != nil {
-				log.Errorf("failed to dial WebSocket listener: %v", err)
-				return false
-			}
-		case quic.Proto:
-			if err := dialQUIC(ctx, dAddr); err != nil {
-				log.Errorf("failed to dial QUIC listener: %v", err)
-				return false
-			}
-		default:
-			log.Warnf("unknown protocol for healthcheck: %s", proto)
-			return false
-		}
+	if err := dialWS(ctx, exposedAddress); err != nil {
+		log.Errorf("failed to dial WebSocket listener at %s: %v", exposedAddress, err)
+		return false
 	}
+
 	return true
 }
 
@@ -187,8 +176,9 @@ func dialAddress(listenAddress string) string {
 		return listenAddress // fallback, might be invalid for dialing
 	}
 
+	// When listening on all interfaces, show localhost for better readability
 	if host == "" || host == "::" || host == "0.0.0.0" {
-		host = "0.0.0.0"
+		host = "localhost"
 	}
 
 	return net.JoinHostPort(host, port)

relay/healthcheck/quic.go

@@ -1,31 +0,0 @@
-package healthcheck
-
-import (
-	"context"
-	"crypto/tls"
-	"fmt"
-	"time"
-
-	"github.com/quic-go/quic-go"
-
-	tlsnb "github.com/netbirdio/netbird/shared/relay/tls"
-)
-
-func dialQUIC(ctx context.Context, address string) error {
-	tlsConfig := &tls.Config{
-		InsecureSkipVerify: false, // Keep certificate validation enabled
-		NextProtos:         []string{tlsnb.NBalpn},
-	}
-
-	conn, err := quic.DialAddr(ctx, address, tlsConfig, &quic.Config{
-		MaxIdleTimeout:  30 * time.Second,
-		KeepAlivePeriod: 10 * time.Second,
-		EnableDatagrams: true,
-	})
-	if err != nil {
-		return fmt.Errorf("failed to connect to QUIC server: %w", err)
-	}
-
-	_ = conn.CloseWithError(0, "availability check complete")
-	return nil
-}

relay/healthcheck/ws.go

@@ -3,6 +3,7 @@ package healthcheck
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/coder/websocket"
 
@@ -10,12 +11,19 @@ import (
 )
 
 func dialWS(ctx context.Context, address string) error {
-	url := fmt.Sprintf("wss://%s%s", address, relay.WebSocketURLPath)
+	addressSplit := strings.Split(address, "/")
+	scheme := "ws"
+	if addressSplit[0] == "rels:" {
+		scheme = "wss"
+	}
+	url := fmt.Sprintf("%s://%s%s", scheme, addressSplit[2], relay.WebSocketURLPath)
 
 	conn, resp, err := websocket.Dial(ctx, url, nil)
 	if resp != nil {
 		defer func() {
-			_ = resp.Body.Close()
+			if resp.Body != nil {
+				_ = resp.Body.Close()
+			}
 		}()
 
 	}

relay/server/relay.go

@@ -51,10 +51,11 @@ type Relay struct {
 	metricsCancel context.CancelFunc
 	validator     Validator
 
-	store       *store.Store
-	notifier    *store.PeerNotifier
-	instanceURL string
-	preparedMsg *preparedMsg
+	store          *store.Store
+	notifier       *store.PeerNotifier
+	instanceURL    string
+	exposedAddress string
+	preparedMsg    *preparedMsg
 
 	closed  bool
 	closeMu sync.RWMutex
@@ -87,12 +88,13 @@ func NewRelay(config Config) (*Relay, error) {
 	}
 
 	r := &Relay{
-		metrics:       m,
-		metricsCancel: metricsCancel,
-		validator:     config.AuthValidator,
-		instanceURL:   config.instanceURL,
-		store:         store.NewStore(),
-		notifier:      store.NewPeerNotifier(),
+		metrics:        m,
+		metricsCancel:  metricsCancel,
+		validator:      config.AuthValidator,
+		instanceURL:    config.instanceURL,
+		exposedAddress: config.ExposedAddress,
+		store:          store.NewStore(),
+		notifier:       store.NewPeerNotifier(),
 	}
 
 	r.preparedMsg, err = newPreparedMsg(r.instanceURL)
@@ -178,3 +180,8 @@ func (r *Relay) Shutdown(ctx context.Context) {
 func (r *Relay) InstanceURL() string {
 	return r.instanceURL
 }
+
+// ExposedAddress returns the exposed address (domain:port) where clients connect
+func (r *Relay) ExposedAddress() string {
+	return r.exposedAddress
+}

relay/server/server.go

@@ -28,8 +28,6 @@ type ListenerConfig struct {
 // It is the gate between the WebSocket listener and the Relay server logic.
 // In a new HTTP connection, the server will accept the connection and pass it to the Relay server via the Accept method.
 type Server struct {
-	listenAddr string
-
 	relay       *Relay
 	listeners   []listener.Listener
 	listenerMux sync.Mutex
@@ -62,8 +60,6 @@ func NewServer(config Config) (*Server, error) {
 
 // Listen starts the relay server.
 func (r *Server) Listen(cfg ListenerConfig) error {
-	r.listenAddr = cfg.Address
-
 	wSListener := &ws.Listener{
 		Address:   cfg.Address,
 		TLSConfig: cfg.TLSConfig,
@@ -139,6 +135,6 @@ func (r *Server) ListenerProtocols() []protocol.Protocol {
 	return result
 }
 
-func (r *Server) ListenAddress() string {
-	return r.listenAddr
+func (r *Server) ExposedAddress() string {
+	return r.relay.ExposedAddress()
 }