Setup external DNS servers after daemon restart with live-restore

Signed-off-by: Santhosh Manohar <santhosh@docker.com>

libnetwork/sandbox.go

@@ -728,7 +728,7 @@ func (sb *sandbox) restoreOslSandbox() error {
 			}
 		}
 		if ep.needResolver() {
-			sb.startResolver()
+			sb.startResolver(true)
 		}
 	}
 
@@ -761,7 +761,7 @@ func (sb *sandbox) populateNetworkResources(ep *endpoint) error {
 	ep.Unlock()
 
 	if ep.needResolver() {
-		sb.startResolver()
+		sb.startResolver(false)
 	}
 
 	if i != nil && i.srcName != "" {

libnetwork/sandbox_dns_unix.go

@@ -21,7 +21,7 @@ const (
 	filePerm      = 0644
 )
 
-func (sb *sandbox) startResolver() {
+func (sb *sandbox) startResolver(restore bool) {
 	sb.resolverOnce.Do(func() {
 		var err error
 		sb.resolver = NewResolver(sb)
@@ -31,10 +31,16 @@ func (sb *sandbox) startResolver() {
 			}
 		}()
 
-		err = sb.rebuildDNS()
-		if err != nil {
-			log.Errorf("Updating resolv.conf failed for container %s, %q", sb.ContainerID(), err)
-			return
+		// In the case of live restore container is already running with
+		// right resolv.conf contents created before. Just update the
+		// external DNS servers from the restored sandbox for embedded
+		// server to use.
+		if !restore {
+			err = sb.rebuildDNS()
+			if err != nil {
+				log.Errorf("Updating resolv.conf failed for container %s, %q", sb.ContainerID(), err)
+				return
+			}
 		}
 		sb.resolver.SetExtServers(sb.extDNS)
 

libnetwork/sandbox_dns_windows.go

@@ -8,7 +8,7 @@ import (
 
 // Stub implementations for DNS related functions
 
-func (sb *sandbox) startResolver() {
+func (sb *sandbox) startResolver(bool) {
 }
 
 func (sb *sandbox) setupResolutionFiles() error {

libnetwork/sandbox_store.go

@@ -27,6 +27,7 @@ type sbState struct {
 	dbExists   bool
 	Eps        []epState
 	EpPriority map[string]int
+	ExtDNS     []string
 }
 
 func (sbs *sbState) Key() []string {
@@ -113,6 +114,10 @@ func (sbs *sbState) CopyTo(o datastore.KVObject) error {
 		dstSbs.Eps = append(dstSbs.Eps, eps)
 	}
 
+	for _, dns := range sbs.ExtDNS {
+		dstSbs.ExtDNS = append(dstSbs.ExtDNS, dns)
+	}
+
 	return nil
 }
 
@@ -126,6 +131,7 @@ func (sb *sandbox) storeUpdate() error {
 		ID:         sb.id,
 		Cid:        sb.containerID,
 		EpPriority: sb.epPriority,
+		ExtDNS:     sb.extDNS,
 	}
 
 retry:
@@ -198,6 +204,7 @@ func (c *controller) sandboxCleanup(activeSandboxes map[string]interface{}) {
 			dbIndex:     sbs.dbIndex,
 			isStub:      true,
 			dbExists:    true,
+			extDNS:      sbs.ExtDNS,
 		}
 
 		msg := " for cleanup"