fix: should roll back configuration if failure of reload

cmd/run.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"fmt"
+	"github.com/mohae/deepcopy"
 	"github.com/okzk/sdnotify"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -120,33 +121,46 @@ loop:
 
 			// Load new config.
 			log.Warnln("[Reload] Load new config")
-			conf, includes, err := readConfig(cfgFile)
+			newConf, includes, err := readConfig(cfgFile)
 			if err != nil {
 				log.WithFields(logrus.Fields{
 					"err": err,
-				}).Errorln("Failed to reload")
+				}).Errorln("[Reload] Failed to reload")
 				sdnotify.Ready()
 				continue
 			}
 			log.Infof("Include config files: [%v]", strings.Join(includes, ", "))
 			// New logger.
-			log = logger.NewLogger(conf.Global.LogLevel, disableTimestamp)
+			log = logger.NewLogger(newConf.Global.LogLevel, disableTimestamp)
 			logrus.SetLevel(log.Level)
 
 			// New control plane.
 			obj := c.EjectBpf()
 			log.Warnln("[Reload] Load new control plane")
-			newC, err := newControlPlane(log, obj, conf)
+			newC, err := newControlPlane(log, obj, newConf)
 			if err != nil {
 				log.WithFields(logrus.Fields{
 					"err": err,
-				}).Errorln("Failed to reload")
-				sdnotify.Ready()
-				continue
+				}).Errorln("[Reload] Failed to reload; try to roll back configuration")
+				// Load last config back.
+				newC, err = newControlPlane(log, obj, conf)
+				if err != nil {
+					sdnotify.Stopping()
+					obj.Close()
+					c.Close()
+					log.WithFields(logrus.Fields{
+						"err": err,
+					}).Fatalln("[Reload] Failed to roll back configuration")
 				}
+				log.Warnln("[Reload] Last reload failed; rolled back configuration")
+			} else {
 				log.Warnln("[Reload] Stopped old control plane")
+			}
+			// Inject bpf objects into the new control plane life-cycle.
+			newC.InjectBpf(obj)
 			c.Close()
 			c = newC
+			conf = newConf
 			reloading = true
 		default:
 			break loop
@@ -160,6 +174,9 @@ loop:
 }
 
 func newControlPlane(log *logrus.Logger, bpf interface{}, conf *config.Config) (c *control.ControlPlane, err error) {
+	// Deep copy to prevent modification.
+	conf = deepcopy.Copy(conf).(*config.Config)
+
 	/// Get tag -> nodeList mapping.
 	tagToNodeList := map[string][]string{}
 	if len(conf.Node) > 0 {

control/control_plane.go

@@ -155,6 +155,8 @@ func NewControlPlane(
 	)
 	defer func() {
 		if err != nil {
+			// Flip back.
+			core.Flip()
 			_ = core.Close()
 		}
 	}()
@@ -358,6 +360,9 @@ func NewControlPlane(
 func (c *ControlPlane) EjectBpf() *bpfObjects {
 	return c.core.EjectBpf()
 }
+func (c *ControlPlane) InjectBpf(bpf *bpfObjects) {
+	c.core.InjectBpf(bpf)
+}
 
 func (c *ControlPlane) dnsUpstreamReadyCallback(raw *url.URL, dnsUpstream *dns.Upstream) (err error) {
 	// Waiting for ready.

control/control_plane_core.go

@@ -37,6 +37,7 @@ type controlPlaneCore struct {
 
 	flip       int
 	isReload   bool
+	bpfEjected bool
 }
 
 func newControlPlaneCore(log *logrus.Logger,
@@ -48,9 +49,13 @@ func newControlPlaneCore(log *logrus.Logger,
 	if isReload {
 		coreFlip = coreFlip&1 ^ 1
 	}
+	var deferFuncs []func() error
+	if !isReload {
+		deferFuncs = append(deferFuncs, bpf.Close)
+	}
 	return &controlPlaneCore{
 		log:             log,
-		deferFuncs:      []func() error{bpf.Close},
+		deferFuncs:      deferFuncs,
 		bpf:             bpf,
 		outboundId2Name: outboundId2Name,
 		kernelVersion:   kernelVersion,
@@ -59,6 +64,9 @@ func newControlPlaneCore(log *logrus.Logger,
 	}
 }
 
+func (c *controlPlaneCore) Flip() {
+	coreFlip = coreFlip&1 ^ 1
+}
 func (c *controlPlaneCore) Close() (err error) {
 	// Invoke defer funcs in reverse order.
 	for i := len(c.deferFuncs) - 1; i >= 0; i-- {
@@ -513,6 +521,18 @@ func (c *controlPlaneCore) BatchUpdateDomainRouting(cache *DnsCache) error {
 
 // EjectBpf will resect bpf from destroying life-cycle of control plane core.
 func (c *controlPlaneCore) EjectBpf() *bpfObjects {
+	if !c.bpfEjected && !c.isReload {
 		c.deferFuncs = c.deferFuncs[1:]
+	}
+	c.bpfEjected = true
 	return c.bpf
 }
+
+// InjectBpf will inject bpf back.
+func (c *controlPlaneCore) InjectBpf(bpf *bpfObjects) {
+	if c.bpfEjected {
+		c.bpfEjected = false
+		c.deferFuncs = append([]func() error{bpf.Close}, c.deferFuncs...)
+	}
+	return
+}