From 05bd52dbb6a01a7aa878573751a396f34c2dec48 Mon Sep 17 00:00:00 2001
From: Santhosh Manohar <santhosh@docker.com>
Date: Thu, 14 Jan 2016 09:56:32 -0800
Subject: [PATCH 1/2] Setup embedded DNS server correctly on container restart

Signed-off-by: Santhosh Manohar <santhosh@docker.com>
---
 libnetwork/resolver.go |  5 ++++-
 libnetwork/sandbox.go  | 18 ++++++++++++++----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/libnetwork/resolver.go b/libnetwork/resolver.go
index 3cd74e03ad..d395ab46b3 100644
--- a/libnetwork/resolver.go
+++ b/libnetwork/resolver.go
@@ -15,7 +15,8 @@ import (
 type Resolver interface {
 	// Start starts the name server for the container
 	Start() error
-	// Stop stops the name server for the container
+	// Stop stops the name server for the container. Stopped resolver
+	// can be reused after running the SetupFunc again.
 	Stop()
 	// SetupFunc() provides the setup function that should be run
 	// in the container's network namespace.
@@ -102,6 +103,8 @@ func (r *resolver) Stop() {
 	if r.server != nil {
 		r.server.Shutdown()
 	}
+	r.conn = nil
+	r.err = fmt.Errorf("setup not done yet")
 }
 
 func (r *resolver) SetExtServers(dns []string) {
diff --git a/libnetwork/sandbox.go b/libnetwork/sandbox.go
index 8977cf349f..9dbb100ef9 100644
--- a/libnetwork/sandbox.go
+++ b/libnetwork/sandbox.go
@@ -488,23 +488,22 @@ func (sb *sandbox) resolveName(req string, networkName string, epList []*endpoin
 }
 
 func (sb *sandbox) SetKey(basePath string) error {
-	var err error
 	if basePath == "" {
 		return types.BadRequestErrorf("invalid sandbox key")
 	}
 
 	sb.Lock()
-	osSbox := sb.osSbox
+	oldosSbox := sb.osSbox
 	sb.Unlock()
 
-	if osSbox != nil {
+	if oldosSbox != nil {
 		// If we already have an OS sandbox, release the network resources from that
 		// and destroy the OS snab. We are moving into a new home further down. Note that none
 		// of the network resources gets destroyed during the move.
 		sb.releaseOSSbox()
 	}
 
-	osSbox, err = osl.GetSandboxForExternalKey(basePath, sb.Key())
+	osSbox, err := osl.GetSandboxForExternalKey(basePath, sb.Key())
 	if err != nil {
 		return err
 	}
@@ -520,6 +519,17 @@ func (sb *sandbox) SetKey(basePath string) error {
 		}
 	}()
 
+	// If the resolver was setup before stop it and set it up in the
+	// new osl sandbox.
+	if oldosSbox != nil && sb.resolver != nil {
+		sb.resolver.Stop()
+
+		sb.osSbox.InvokeFunc(sb.resolver.SetupFunc())
+		if err := sb.resolver.Start(); err != nil {
+			log.Errorf("Resolver Setup/Start failed for container %s, %q", sb.ContainerID(), err)
+		}
+	}
+
 	for _, ep := range sb.getConnectedEndpoints() {
 		if err = sb.populateNetworkResources(ep); err != nil {
 			return err

From b48c479b17a28753ba1ad0e51a9284f208129fcb Mon Sep 17 00:00:00 2001
From: Santhosh Manohar <santhosh@docker.com>
Date: Thu, 14 Jan 2016 10:17:34 -0800
Subject: [PATCH 2/2] changelog for v0.5.6

Signed-off-by: Santhosh Manohar <santhosh@docker.com>
---
 libnetwork/CHANGELOG.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libnetwork/CHANGELOG.md b/libnetwork/CHANGELOG.md
index 98e3913327..ea136da5b4 100644
--- a/libnetwork/CHANGELOG.md
+++ b/libnetwork/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## 0.5.6 (2016-01-14)
+- Setup embedded DNS server correctly on container restart. Fixes docker/docker#19354
+
 ## 0.5.5 (2016-01-14)
 - Allow network-scoped alias to be resolved for anonymous endpoint
 - Self repair corrupted IP database that could happen in 1.9.0 & 1.9.1