[management] return nil when config is not set (#6642)

* [management] return nil when config is not set

* [management] add relay invariant test and enforce config behavior

management/internals/shared/grpc/conversion.go

@@ -47,16 +47,13 @@ func init() {
 	precomputedDeprecatedRemotePeersConstraint = constraint
 }
 
+// toNetbirdConfig converts the server configuration to the wire representation. It returns
+// nil when no server config is set (the fan-out network-map path) because clients treat any
+// non-nil config as authoritative: a config without a relay section is interpreted as relay
+// disabled and wipes the clients' relay URLs.
 func toNetbirdConfig(config *nbconfig.Config, turnCredentials *Token, relayToken *Token, extraSettings *types.ExtraSettings, settings *types.Settings) *proto.NetbirdConfig {
 	if config == nil {
-		if settings == nil {
-			return nil
-		}
-		return &proto.NetbirdConfig{
-			Metrics: &proto.MetricsConfig{
-				Enabled: settings.MetricsPushEnabled,
-			},
-		}
+		return nil
 	}
 
 	var stuns []*proto.HostConfig

management/internals/shared/grpc/conversion_test.go

@@ -8,11 +8,13 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	nbdns "github.com/netbirdio/netbird/dns"
 	"github.com/netbirdio/netbird/management/internals/controllers/network_map"
 	"github.com/netbirdio/netbird/management/internals/controllers/network_map/controller/cache"
 	nbconfig "github.com/netbirdio/netbird/management/internals/server/config"
+	"github.com/netbirdio/netbird/management/server/types"
 )
 
 func TestToProtocolDNSConfigWithCache(t *testing.T) {
@@ -263,3 +265,39 @@ func TestEncodeSessionExpiresAt(t *testing.T) {
 		assert.True(t, got.AsTime().Equal(deadline))
 	})
 }
+
+// TestToNetbirdConfig_RelayInvariant guards against the v0.74.0 relay-wipe regression.
+// Clients treat any non-nil NetbirdConfig as authoritative and interpret a missing relay
+// section as relay disabled, wiping their relay URLs. toNetbirdConfig must therefore
+// return nil when no server config is set (the fan-out network-map path) instead of a
+// partial config, and a result built from a relay-enabled config must carry the relay
+// section.
+func TestToNetbirdConfig_RelayInvariant(t *testing.T) {
+	settings := &types.Settings{MetricsPushEnabled: true}
+
+	t.Run("nil server config returns nil config", func(t *testing.T) {
+		nbCfg := toNetbirdConfig(nil, nil, nil, nil, settings)
+		assert.Nil(t, nbCfg, "fan-out updates must not carry a partial NetbirdConfig even when settings are present")
+	})
+
+	t.Run("relay-enabled config carries relay section", func(t *testing.T) {
+		cfg := &nbconfig.Config{
+			Stuns: []*nbconfig.Host{{Proto: nbconfig.UDP, URI: "stun:stun.example.com:3478"}},
+			TURNConfig: &nbconfig.TURNConfig{
+				Turns: []*nbconfig.Host{{Proto: nbconfig.UDP, URI: "turn:turn.example.com:3478", Username: "user", Password: "pass"}},
+			},
+			Relay:  &nbconfig.Relay{Addresses: []string{"rels://relay.example.com:443"}},
+			Signal: &nbconfig.Host{Proto: nbconfig.HTTP, URI: "signal.example.com:10000"},
+		}
+		relayToken := &Token{Payload: "token-payload", Signature: "token-signature"}
+
+		nbCfg := toNetbirdConfig(cfg, nil, relayToken, nil, settings)
+		require.NotNil(t, nbCfg)
+		require.NotNil(t, nbCfg.Relay, "non-nil NetbirdConfig must include the relay section")
+		assert.Equal(t, cfg.Relay.Addresses, nbCfg.Relay.Urls, "relay URLs should match the server config")
+		assert.Equal(t, relayToken.Payload, nbCfg.Relay.TokenPayload, "relay token payload should be set")
+		assert.Equal(t, relayToken.Signature, nbCfg.Relay.TokenSignature, "relay token signature should be set")
+		require.NotNil(t, nbCfg.Metrics)
+		assert.True(t, nbCfg.Metrics.Enabled, "metrics flag should carry the settings value")
+	})
+}

management/server/peer_test.go

@@ -1048,11 +1048,7 @@ func testUpdateAccountPeers(t *testing.T) {
 
 			for _, channel := range peerChannels {
 				update := <-channel
-				assert.NotNil(t, update.Update.NetbirdConfig)
-				assert.Nil(t, update.Update.NetbirdConfig.Stuns)
-				assert.Nil(t, update.Update.NetbirdConfig.Turns)
-				assert.Nil(t, update.Update.NetbirdConfig.Signal)
-				assert.Nil(t, update.Update.NetbirdConfig.Relay)
+				assert.Nil(t, update.Update.NetbirdConfig, "fan-out updates must not carry a NetbirdConfig; clients treat a config without relay as relay disabled and wipe their relay URLs")
 				assert.Equal(t, tc.peers, len(update.Update.NetworkMap.RemotePeers))
 				assert.Equal(t, tc.peers*2, len(update.Update.NetworkMap.FirewallRules))
 			}