add support for disabling relay via environment variable

client/internal/connect.go

@@ -290,6 +290,10 @@ func (c *ConnectClient) run(mobileDependency MobileDependency, runningChan chan
 			return wrapErr(err)
 		}
 
+		if relayClient.IsDisableRelay() {
+			relayURLs = []string{}
+		}
+
 		relayManager := relayClient.NewManager(engineCtx, relayURLs, myPrivateKey.PublicKey().String(), engineConfig.MTU)
 		c.statusRecorder.SetRelayMgr(relayManager)
 		if len(relayURLs) > 0 {

client/internal/engine.go

@@ -942,7 +942,9 @@ func (e *Engine) handleRelayUpdate(update *mgmProto.RelayConfig) error {
 			return fmt.Errorf("update relay token: %w", err)
 		}
 
-		e.relayManager.UpdateServerURLs(update.Urls)
+		if !relayClient.IsDisableRelay() {
+			e.relayManager.UpdateServerURLs(update.Urls)
+		}
 
 		// Just in case the agent started with an MGM server where the relay was disabled but was later enabled.
 		// We can ignore all errors because the guard will manage the reconnection retries.

client/internal/peer/ice/agent.go

@@ -12,6 +12,7 @@ import (
 	log "github.com/sirupsen/logrus"
 
 	"github.com/netbirdio/netbird/client/internal/stdnet"
+	relayClient "github.com/netbirdio/netbird/shared/relay/client"
 )
 
 const (
@@ -125,6 +126,10 @@ func GenerateICECredentials() (string, string, error) {
 }
 
 func CandidateTypes() []ice.CandidateType {
+	if relayClient.IsDisableRelay() {
+		return []ice.CandidateType{ice.CandidateTypeHost, ice.CandidateTypeServerReflexive, ice.CandidateTypeRelay}
+	}
+
 	if hasICEForceRelayConn() {
 		return []ice.CandidateType{ice.CandidateTypeRelay}
 	}

shared/relay/client/env.go

@@ -0,0 +1,15 @@
+package client
+
+import (
+	"os"
+	"strconv"
+)
+
+const (
+	envKeyNBDebugDisableRelay = "NB_DEBUG_DISABLE_RELAY"
+)
+
+func IsDisableRelay() bool {
+	v, _ := strconv.ParseBool(os.Getenv(envKeyNBDebugDisableRelay))
+	return v
+}