allow /etc/hosts /etc/resolv.conf and /etc/hostname to be changed

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)

daemon/container.go

@@ -849,18 +849,16 @@ func (container *Container) setupContainerDns() error {
 		daemon = container.daemon
 	)
 
-	if config.NetworkMode == "host" {
-		container.ResolvConfPath = "/etc/resolv.conf"
-		return nil
-	}
-
 	resolvConf, err := resolvconf.Get()
 	if err != nil {
 		return err
 	}
+	container.ResolvConfPath, err = container.getRootResourcePath("resolv.conf")
+	if err != nil {
+		return err
+	}
 
-	// If custom dns exists, then create a resolv.conf for the container
-	if len(config.Dns) > 0 || len(daemon.config.Dns) > 0 || len(config.DnsSearch) > 0 || len(daemon.config.DnsSearch) > 0 {
+	if config.NetworkMode != "host" && (len(config.Dns) > 0 || len(daemon.config.Dns) > 0 || len(config.DnsSearch) > 0 || len(daemon.config.DnsSearch) > 0) {
 		var (
 			dns       = resolvconf.GetNameservers(resolvConf)
 			dnsSearch = resolvconf.GetSearchDomains(resolvConf)
@@ -875,18 +873,9 @@ func (container *Container) setupContainerDns() error {
 		} else if len(daemon.config.DnsSearch) > 0 {
 			dnsSearch = daemon.config.DnsSearch
 		}
-
-		resolvConfPath, err := container.getRootResourcePath("resolv.conf")
-		if err != nil {
-			return err
-		}
-		container.ResolvConfPath = resolvConfPath
-
 		return resolvconf.Build(container.ResolvConfPath, dns, dnsSearch)
-	} else {
-		container.ResolvConfPath = "/etc/resolv.conf"
 	}
-	return nil
+	return ioutil.WriteFile(container.ResolvConfPath, resolvConf, 0644)
 }
 
 func (container *Container) initializeNetworking() error {

daemon/volumes.go

@@ -50,15 +50,15 @@ func prepareVolumesForContainer(container *Container) error {
 
 func setupMountsForContainer(container *Container) error {
 	mounts := []execdriver.Mount{
-		{container.ResolvConfPath, "/etc/resolv.conf", false, true},
+		{container.ResolvConfPath, "/etc/resolv.conf", true, true},
 	}
 
 	if container.HostnamePath != "" {
-		mounts = append(mounts, execdriver.Mount{container.HostnamePath, "/etc/hostname", false, true})
+		mounts = append(mounts, execdriver.Mount{container.HostnamePath, "/etc/hostname", true, true})
 	}
 
 	if container.HostsPath != "" {
-		mounts = append(mounts, execdriver.Mount{container.HostsPath, "/etc/hosts", false, true})
+		mounts = append(mounts, execdriver.Mount{container.HostsPath, "/etc/hosts", true, true})
 	}
 
 	// Mount user specified volumes