Merge pull request #18961 from Luap99/hosts-resolv

libpod: write /etc/{hosts,resolv.conf} once

libpod/container_internal.go

@@ -18,7 +18,6 @@ import (
 	"github.com/containers/buildah/pkg/overlay"
 	butil "github.com/containers/buildah/util"
 	"github.com/containers/common/libnetwork/etchosts"
-	"github.com/containers/common/libnetwork/resolvconf"
 	"github.com/containers/common/pkg/cgroups"
 	"github.com/containers/common/pkg/chown"
 	"github.com/containers/common/pkg/config"
@@ -961,14 +960,18 @@ func (c *Container) checkDependenciesRunning() ([]string, error) {
 }
 
 func (c *Container) completeNetworkSetup() error {
-	var nameservers []string
 	netDisabled, err := c.NetworkDisabled()
 	if err != nil {
 		return err
 	}
-	if !c.config.PostConfigureNetNS || netDisabled {
+	if netDisabled {
+		// with net=none we still want to set up /etc/hosts
+		return c.addHosts()
+	}
+	if c.config.NetNsCtr != "" {
 		return nil
 	}
+	if c.config.PostConfigureNetNS {
 		if err := c.syncContainer(); err != nil {
 			return err
 		}
@@ -978,34 +981,13 @@ func (c *Container) completeNetworkSetup() error {
 		if err := c.save(); err != nil {
 			return err
 		}
-	state := c.state
-	// collect any dns servers that the network backend tells us to use
-	for _, status := range c.getNetworkStatus() {
-		for _, server := range status.DNSServerIPs {
-			nameservers = append(nameservers, server.String())
 	}
-	}
+	// add /etc/hosts entries
-	nameservers = c.addSlirp4netnsDNS(nameservers)
+	if err := c.addHosts(); err != nil {
-
-	// check if we have a bindmount for /etc/hosts
-	if hostsBindMount, ok := state.BindMounts[config.DefaultHostsFile]; ok {
-		entries, err := c.getHostsEntries()
-		if err != nil {
 		return err
 	}
-		// add new container ips to the hosts file
-		if err := etchosts.Add(hostsBindMount, entries); err != nil {
-			return err
-		}
-	}
 
-	// check if we have a bindmount for resolv.conf
+	return c.addResolvConf()
-	resolvBindMount := state.BindMounts[resolvconf.DefaultResolvConf]
-	if len(nameservers) < 1 || resolvBindMount == "" || len(c.config.NetNsCtr) > 0 {
-		return nil
-	}
-	// write and return
-	return resolvconf.Add(resolvBindMount, nameservers)
 }
 
 // Initialize a container, creating it in the runtime

libpod/container_internal_common.go

@@ -1819,17 +1819,17 @@ func (c *Container) makeBindMounts() error {
 		// will recreate. Only do this if we aren't sharing them with
 		// another container.
 		if c.config.NetNsCtr == "" {
-			if resolvePath, ok := c.state.BindMounts["/etc/resolv.conf"]; ok {
+			if resolvePath, ok := c.state.BindMounts[resolvconf.DefaultResolvConf]; ok {
 				if err := os.Remove(resolvePath); err != nil && !os.IsNotExist(err) {
 					return fmt.Errorf("container %s: %w", c.ID(), err)
 				}
-				delete(c.state.BindMounts, "/etc/resolv.conf")
+				delete(c.state.BindMounts, resolvconf.DefaultResolvConf)
 			}
-			if hostsPath, ok := c.state.BindMounts["/etc/hosts"]; ok {
+			if hostsPath, ok := c.state.BindMounts[config.DefaultHostsFile]; ok {
 				if err := os.Remove(hostsPath); err != nil && !os.IsNotExist(err) {
 					return fmt.Errorf("container %s: %w", c.ID(), err)
 				}
-				delete(c.state.BindMounts, "/etc/hosts")
+				delete(c.state.BindMounts, config.DefaultHostsFile)
 			}
 		}
 
@@ -1851,9 +1851,9 @@ func (c *Container) makeBindMounts() error {
 
 			// The other container may not have a resolv.conf or /etc/hosts
 			// If it doesn't, don't copy them
-			resolvPath, exists := bindMounts["/etc/resolv.conf"]
+			resolvPath, exists := bindMounts[resolvconf.DefaultResolvConf]
 			if !c.config.UseImageResolvConf && exists {
-				err := c.mountIntoRootDirs("/etc/resolv.conf", resolvPath)
+				err := c.mountIntoRootDirs(resolvconf.DefaultResolvConf, resolvPath)
 
 				if err != nil {
 					return fmt.Errorf("assigning mounts to container %s: %w", c.ID(), err)
@@ -1896,31 +1896,31 @@ func (c *Container) makeBindMounts() error {
 			}
 		} else {
 			if !c.config.UseImageResolvConf {
-				if err := c.generateResolvConf(); err != nil {
+				if err := c.createResolvConf(); err != nil {
 					return fmt.Errorf("creating resolv.conf for container %s: %w", c.ID(), err)
 				}
 			}
 
 			if !c.config.UseImageHosts {
-				if err := c.createHosts(); err != nil {
+				if err := c.createHostsFile(); err != nil {
 					return fmt.Errorf("creating hosts file for container %s: %w", c.ID(), err)
 				}
 			}
 		}
 
-		if c.state.BindMounts["/etc/hosts"] != "" {
+		if c.state.BindMounts[config.DefaultHostsFile] != "" {
-			if err := c.relabel(c.state.BindMounts["/etc/hosts"], c.config.MountLabel, true); err != nil {
+			if err := c.relabel(c.state.BindMounts[config.DefaultHostsFile], c.config.MountLabel, true); err != nil {
 				return err
 			}
 		}
 
-		if c.state.BindMounts["/etc/resolv.conf"] != "" {
+		if c.state.BindMounts[resolvconf.DefaultResolvConf] != "" {
-			if err := c.relabel(c.state.BindMounts["/etc/resolv.conf"], c.config.MountLabel, true); err != nil {
+			if err := c.relabel(c.state.BindMounts[resolvconf.DefaultResolvConf], c.config.MountLabel, true); err != nil {
 				return err
 			}
 		}
-	} else if !c.config.UseImageHosts && c.state.BindMounts["/etc/hosts"] == "" {
+	} else if !c.config.UseImageHosts && c.state.BindMounts[config.DefaultHostsFile] == "" {
-		if err := c.createHosts(); err != nil {
+		if err := c.createHostsFile(); err != nil {
 			return fmt.Errorf("creating hosts file for container %s: %w", c.ID(), err)
 		}
 	}
@@ -2028,8 +2028,25 @@ rootless=%d
 	return c.makePlatformBindMounts()
 }
 
-// generateResolvConf generates a containers resolv.conf
+// createResolvConf create the resolv.conf file and bind mount it
-func (c *Container) generateResolvConf() error {
+func (c *Container) createResolvConf() error {
+	destPath := filepath.Join(c.state.RunDir, "resolv.conf")
+	f, err := os.Create(destPath)
+	if err != nil {
+		return err
+	}
+	f.Close()
+	return c.bindMountRootFile(destPath, resolvconf.DefaultResolvConf)
+}
+
+// addResolvConf add resolv.conf entries
+func (c *Container) addResolvConf() error {
+	destPath, ok := c.state.BindMounts[resolvconf.DefaultResolvConf]
+	if !ok {
+		// no resolv.conf mount, do nothing
+		return nil
+	}
+
 	var (
 		networkNameServers   []string
 		networkSearchDomains []string
@@ -2082,12 +2099,8 @@ func (c *Container) generateResolvConf() error {
 		nameservers = networkNameServers
 
 		// slirp4netns has a built in DNS forwarder.
-		// If in userns the network is not setup here, instead we need to do that in
-		// c.completeNetworkSetup() which knows the actual slirp dns ip only at that point
-		if !c.config.PostConfigureNetNS {
 		nameservers = c.addSlirp4netnsDNS(nameservers)
 	}
-	}
 
 	// Set DNS search domains
 	search := networkSearchDomains
@@ -2103,8 +2116,6 @@ func (c *Container) generateResolvConf() error {
 	options = append(options, c.runtime.config.Containers.DNSOptions...)
 	options = append(options, c.config.DNSOption...)
 
-	destPath := filepath.Join(c.state.RunDir, "resolv.conf")
-
 	var namespaces []spec.LinuxNamespace
 	if c.config.Spec.Linux != nil {
 		namespaces = c.config.Spec.Linux.Namespaces
@@ -2122,7 +2133,7 @@ func (c *Container) generateResolvConf() error {
 		return fmt.Errorf("building resolv.conf for container %s: %w", c.ID(), err)
 	}
 
-	return c.bindMountRootFile(destPath, resolvconf.DefaultResolvConf)
+	return nil
 }
 
 // Check if a container uses IPv6.
@@ -2209,36 +2220,38 @@ func (c *Container) getHostsEntries() (etchosts.HostEntries, error) {
 	return entries, nil
 }
 
-func (c *Container) createHosts() error {
+func (c *Container) createHostsFile() error {
-	var containerIPsEntries etchosts.HostEntries
+	targetFile := filepath.Join(c.state.RunDir, "hosts")
-	var err error
+	f, err := os.Create(targetFile)
-	// if we configure the netns after the container create we should not add
+	if err != nil {
-	// the hosts here since we have no information about the actual ips
+		return err
-	// instead we will add them in c.completeNetworkSetup()
+	}
-	if !c.config.PostConfigureNetNS {
+	f.Close()
-		containerIPsEntries, err = c.getHostsEntries()
+	return c.bindMountRootFile(targetFile, config.DefaultHostsFile)
+}
+
+func (c *Container) addHosts() error {
+	targetFile, ok := c.state.BindMounts[config.DefaultHostsFile]
+	if !ok {
+		// no host file nothing to do
+		return nil
+	}
+	containerIPsEntries, err := c.getHostsEntries()
 	if err != nil {
 		return fmt.Errorf("failed to get container ip host entries: %w", err)
 	}
-	}
 	baseHostFile, err := etchosts.GetBaseHostFile(c.runtime.config.Containers.BaseHostsFile, c.state.Mountpoint)
 	if err != nil {
 		return err
 	}
 
-	targetFile := filepath.Join(c.state.RunDir, "hosts")
+	return etchosts.New(&etchosts.Params{
-	err = etchosts.New(&etchosts.Params{
 		BaseFile:                 baseHostFile,
 		ExtraHosts:               c.config.HostAdd,
 		ContainerIPs:             containerIPsEntries,
 		HostContainersInternalIP: etchosts.GetHostContainersInternalIP(c.runtime.config, c.state.NetworkStatus, c.runtime.network),
 		TargetFile:               targetFile,
 	})
-	if err != nil {
-		return err
-	}
-
-	return c.bindMountRootFile(targetFile, config.DefaultHostsFile)
 }
 
 // bindMountRootFile will chown and relabel the source file to make it usable in the container.