[client] Add local Prometheus metrics endpoint (#6689)

client/internal/profilemanager/config.go

@@ -103,6 +103,9 @@ type ConfigInput struct {
 	DNSLabels domain.List
 
 	MTU *uint16
+
+	LocalMetricsEnabled *bool
+	LocalMetricsAddress *string
 }
 
 // Config Configuration type
@@ -144,6 +147,11 @@ type Config struct {
 
 	DNSLabels domain.List
 
+	// LocalMetricsEnabled enables the local Prometheus /metrics endpoint.
+	LocalMetricsEnabled bool
+	// LocalMetricsAddress is the listen address of the local /metrics endpoint.
+	LocalMetricsAddress string
+
 	// SSHKey is a private SSH key in a PEM format
 	SSHKey string
 
@@ -388,6 +396,18 @@ func (config *Config) apply(input ConfigInput) (updated bool, err error) {
 		updated = true
 	}
 
+	if input.LocalMetricsEnabled != nil && *input.LocalMetricsEnabled != config.LocalMetricsEnabled {
+		log.Infof("switching local metrics to %t", *input.LocalMetricsEnabled)
+		config.LocalMetricsEnabled = *input.LocalMetricsEnabled
+		updated = true
+	}
+
+	if input.LocalMetricsAddress != nil && *input.LocalMetricsAddress != config.LocalMetricsAddress {
+		log.Infof("switching local metrics address to %s", *input.LocalMetricsAddress)
+		config.LocalMetricsAddress = *input.LocalMetricsAddress
+		updated = true
+	}
+
 	if input.NetworkMonitor != nil && (config.NetworkMonitor == nil || *input.NetworkMonitor != *config.NetworkMonitor) {
 		log.Infof("switching Network Monitor to %t", *input.NetworkMonitor)
 		config.NetworkMonitor = input.NetworkMonitor
@@ -718,6 +738,12 @@ func (config *Config) applyMDMPolicy(policy *mdm.Policy) {
 	applyBool(mdm.KeyDisableAutoConnect, func(v bool) { config.DisableAutoConnect = v })
 	applyBool(mdm.KeyRosenpassEnabled, func(v bool) { config.RosenpassEnabled = v })
 	applyBool(mdm.KeyRosenpassPermissive, func(v bool) { config.RosenpassPermissive = v })
+	applyBool(mdm.KeyEnableLocalMetrics, func(v bool) { config.LocalMetricsEnabled = v })
+
+	if v, ok := policy.GetString(mdm.KeyLocalMetricsAddress); ok {
+		config.LocalMetricsAddress = v
+		logApplied(mdm.KeyLocalMetricsAddress, v)
+	}
 
 	if v, ok := policy.GetInt(mdm.KeyWireguardPort); ok {
 		// REG_DWORD is 32-bit; UDP port range is 1-65535. Clamp at the

client/internal/profilemanager/config_mdm_test.go

@@ -130,6 +130,32 @@ func TestApply_MDMBoolKeysOverrideOnDiskValue(t *testing.T) {
 	assert.True(t, cfg.Policy().HasKey(mdm.KeyRosenpassEnabled))
 }
 
+func TestApply_MDMLocalMetrics(t *testing.T) {
+	tmp := filepath.Join(t.TempDir(), "config.json")
+
+	// Seed without MDM.
+	withMDMPolicy(t, mdm.NewPolicy(nil))
+	_, err := UpdateOrCreateConfig(ConfigInput{
+		ConfigPath:          tmp,
+		LocalMetricsEnabled: boolPtr(false),
+	})
+	require.NoError(t, err)
+
+	withMDMPolicy(t, mdm.NewPolicy(map[string]any{
+		mdm.KeyEnableLocalMetrics:  true,
+		mdm.KeyLocalMetricsAddress: "127.0.0.1:9292",
+	}))
+
+	cfg, err := UpdateOrCreateConfig(ConfigInput{ConfigPath: tmp})
+	require.NoError(t, err)
+	require.NotNil(t, cfg)
+
+	assert.True(t, cfg.LocalMetricsEnabled, "MDM override should flip on-disk false to true")
+	assert.Equal(t, "127.0.0.1:9292", cfg.LocalMetricsAddress)
+	assert.True(t, cfg.Policy().HasKey(mdm.KeyEnableLocalMetrics))
+	assert.True(t, cfg.Policy().HasKey(mdm.KeyLocalMetricsAddress))
+}
+
 func TestApply_MDMLazyConnection(t *testing.T) {
 	cases := []struct {
 		name string