Install systemd-resolved for NetworkManager

Workaround for cloud-init bug until this fix gets shipped to the
distros:
cb36bf38b8

pkg/distros/opensuse_tumbleweed.go

@@ -39,11 +39,52 @@ func (mgr *OpensuseTumbleweedTemplateManager) DownloadTemplate(version, codename
 	)
 }
 
-func (mgr *OpensuseTumbleweedTemplateManager) InstallNetworkManager(handle *guestfs.Guestfs) error {
-	args := []string{"zypper", "--non-interactive", "install", "NetworkManager"}
-	_, err := mgr.logAndRunCommand(handle, args)
+func (mgr *OpensuseTumbleweedTemplateManager) addSystemUser(handle *guestfs.Guestfs, name, comment string) error {
+	matches, err := handle.Grep("^"+name, "/etc/passwd", nil)
 	if err != nil {
-		return fmt.Errorf("Could not install NetworkManager: %w", err)
+		return fmt.Errorf("Could not grep /etc/passwd: %w", err)
+	}
+	if len(matches) > 0 {
+		return nil
+	}
+	_, err = mgr.logAndRunCommand(handle, []string{
+		"useradd",
+		"--system",
+		"--no-create-home",
+		"--home-dir", "/",
+		"--shell", "/usr/sbin/nologin",
+		"--comment", comment,
+		name,
+	})
+	if err != nil {
+		return fmt.Errorf("Could not add user %s: %w", name, err)
+	}
+	return nil
+}
+
+func (mgr *OpensuseTumbleweedTemplateManager) InstallSystemdResolved(handle *guestfs.Guestfs) error {
+	// This package contains both systemd-networkd and systemd-resolved
+	args := []string{"zypper", "--non-interactive", "install", "systemd-network"}
+	if _, err := mgr.logAndRunCommand(handle, args); err != nil {
+		return fmt.Errorf("Could not install systemd-network: %w", err)
+	}
+	// The systemd-network and systemd-resolve users don't get added for
+	// some reason, even though the systemd services need to run as them
+	if err := mgr.addSystemUser(handle, "systemd-resolve", "systemd Resolver"); err != nil {
+		return err
+	}
+	if err := mgr.addSystemUser(handle, "systemd-network", "systemd Network Management"); err != nil {
+		return err
+	}
+	// nsswitch.conf doesn't get updated either
+	args = []string{
+		"sed",
+		"-i",
+		`s/^hosts:/hosts:\t\tfiles myhostname resolve [!UNAVAIL=return] dns/`,
+		"/usr/etc/nsswitch.conf",
+	}
+	if _, err := mgr.logAndRunCommand(handle, args); err != nil {
+		return fmt.Errorf("Could not update nsswitch.conf: %w", err)
 	}
 	return nil
 }

pkg/distros/template_manager.go

@@ -56,14 +56,14 @@ type IDistroSpecificTemplateManager interface {
 	// (but does not upgrade) the packages for this distro, e.g.
 	// "sudo apt update".
 	CommandToUpdatePackageCache() []string
-	// InstallNetworkManager installs the OS-specific package for
-	// NetworkManager.
-	InstallNetworkManager(handle *guestfs.Guestfs) error
+	// InstallSystemdResolved installs the OS-specific package for
+	// systemd-resolved.
+	InstallSystemdResolved(handle *guestfs.Guestfs) error
 }
 
-func (mgr *TemplateManager) InstallNetworkManager(handle *guestfs.Guestfs) error {
+func (mgr *TemplateManager) InstallSystemdResolved(handle *guestfs.Guestfs) error {
 	// Individual distros should override this method if necessary
-	return errors.New("InstallNetworkManager: not implemented for this distro")
+	return errors.New("InstallSystemdResolved: not implemented for this distro")
 }
 
 func (mgr *TemplateManager) DownloadTemplateGeneric(filename, url string) (path string, err error) {
@@ -248,9 +248,12 @@ func (mgr *TemplateManager) logAndRunCommand(handle *guestfs.Guestfs, args []str
 }
 
 func (mgr *TemplateManager) enableSystemdUnit(handle *guestfs.Guestfs, unit string) error {
-	_, err := mgr.logAndRunCommand(handle, []string{
-		"systemctl", "enable", unit,
-	})
+	_, err := mgr.logAndRunCommand(handle, []string{"systemctl", "enable", unit})
+	return err
+}
+
+func (mgr *TemplateManager) disableSystemdUnit(handle *guestfs.Guestfs, unit string) error {
+	_, err := mgr.logAndRunCommand(handle, []string{"systemctl", "disable", unit})
 	return err
 }
 
@@ -440,6 +443,35 @@ func (mgr *TemplateManager) setNetworkManagerOptions(handle *guestfs.Guestfs) er
 			return fmt.Errorf("Could not create %s: %w", cfgFilePath, err)
 		}
 	}
+	// A bug was introduced in cloud-init commit 5942f40 which causes the DHCP
+	// server identifier in the dhclient lease file to be ignored. It is fixed by
+	// https://github.com/canonical/cloud-init/commit/cb36bf38b823f811a3e938ccffc03d7d13190095,
+	// but as of this writing (2024-01-13), this fix is not present in any official
+	// distro packages yet.
+	// As a workaround, we will install systemd-resolved, whose NSS module
+	// nss-resolve has a higher priority than "dns" for the "hosts" database in
+	// nsswitch.conf. This allows cloud-init to resolve the "data-server" host name
+	// (by querying the CloudStack DNS server instead of the ones which we wrote in
+	// /etc/resolv.conf), so it will not need to read any DHCP lease files.
+	// We can remove this workaround once the aforementioned fix gets shipped to
+	// all of the distros which we support.
+	resolvedIsPresent, err := handle.Is_file("/lib/systemd/systemd-resolved", nil)
+	if err != nil {
+		return fmt.Errorf("Could not determine if /lib/systemd/systemd-resolved is a file: %w", err)
+	}
+	if !resolvedIsPresent {
+		if err = mgr.impl.InstallSystemdResolved(handle); err != nil {
+			return err
+		}
+		if err = mgr.enableSystemdUnit(handle, "systemd-resolved"); err != nil {
+			return err
+		}
+		// Make sure that systemd-networkd isn't enabled or else it'll interfere
+		// with NetworkManager
+		if err = mgr.disableSystemdUnit(handle, "systemd-networkd"); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
@@ -466,20 +498,6 @@ func (mgr *TemplateManager) addSystemdNetworkdCloudInitSnippet(handle *guestfs.G
 	return handle.Write(path, getResource("systemd-networkd-cloud-init"))
 }
 
-func (mgr *TemplateManager) installAndEnableNetworkManager(handle *guestfs.Guestfs) error {
-	isInstalled, err := handle.Is_file("/lib/systemd/system/NetworkManager.service", nil)
-	if err != nil {
-		return err
-	}
-	if !isInstalled {
-		err = mgr.impl.InstallNetworkManager(handle)
-		if err != nil {
-			return err
-		}
-	}
-	return mgr.enableSystemdUnit(handle, "NetworkManager.service")
-}
-
 func (mgr *TemplateManager) setupCommonNetworkConfigs(handle *guestfs.Guestfs) error {
 	usesNetworkManager, err := mgr.usesNetworkManager(handle)
 	if err != nil {
@@ -502,12 +520,7 @@ func (mgr *TemplateManager) setupCommonNetworkConfigs(handle *guestfs.Guestfs) e
 	if usesEtcNetworkInterfaces {
 		return mgr.setDhclientOptions(handle)
 	}
-	mgr.logger.Info().Msg("Could not determine network backend, resorting to installing NetworkManager")
-	err = mgr.installAndEnableNetworkManager(handle)
-	if err != nil {
-		return err
-	}
-	return mgr.setNetworkManagerOptions(handle)
+	return errors.New("Could not determine network backend")
 }
 
 func (mgr *TemplateManager) setupIpv6Scripts(handle *guestfs.Guestfs) (err error) {