Configure systemd-resolved to use IPA's BIND

IPA installer now instructs systemd-resolved to use IPA's BIND DNS
server as primary DNS server.

Fixes: https://pagure.io/freeipa/issue/8275
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipaplatform/base/paths.py

@@ -388,6 +388,7 @@ class BasePathNamespace:
     CERTMONGER = '/usr/sbin/certmonger'
     NETWORK_MANAGER_CONFIG_DIR = '/etc/NetworkManager/conf.d'
     NETWORK_MANAGER_IPA_CONF = '/etc/NetworkManager/conf.d/zzz-ipa.conf'
+    SYSTEMD_RESOLVED_IPA_CONF = '/etc/systemd/resolved.conf.d/zzz-ipa.conf'
     IPA_CUSTODIA_CONF_DIR = '/etc/ipa/custodia'
     IPA_CUSTODIA_CONF = '/etc/ipa/custodia/custodia.conf'
     IPA_CUSTODIA_KEYS = '/etc/ipa/custodia/server.keys'

ipaplatform/base/services.py

@@ -57,7 +57,8 @@ wellknownservices = [
     'rpcidmapd', 'pki_tomcatd', 'chronyd', 'domainname',
     'named', 'ods_enforcerd', 'ods_signerd', 'gssproxy',
     'nfs-utils', 'sssd', 'NetworkManager', 'ipa-custodia',
-    'ipa-dnskeysyncd', 'ipa-otpd', 'ipa-ods-exporter'
+    'ipa-dnskeysyncd', 'ipa-otpd', 'ipa-ods-exporter',
+    'systemd-resolved',
 ]
 
 # The common ports for these services. This is used to wait for the

ipaplatform/base/tasks.py

@@ -24,7 +24,9 @@ This module contains default platform-specific implementations of system tasks.
 
 from __future__ import absolute_import
 
+import os
 import logging
+import textwrap
 
 from pkg_resources import parse_version
 
@@ -35,6 +37,17 @@ from ipapython.ipachangeconf import IPAChangeConf
 logger = logging.getLogger(__name__)
 
 
+# TODO: Add other masters as FallbackDNS ?
+RESOLVE1_IPA_CONF = textwrap.dedent("""
+    # auto-generated by IPA installer
+    [Resolve]
+    # use local BIND instance
+    DNS=127.0.0.1
+    # make local BIND default DNS server, add search suffixes
+    Domains=~. {searchdomains}
+""")
+
+
 class BaseTaskNamespace:
 
     def restore_context(self, filepath, force=False):
@@ -318,7 +331,21 @@ class BaseTaskNamespace:
         :param resolve1_enabled: is systemd-resolved enabled?
         :param fstore: optional file store for backup
         """
-        raise NotImplementedError
+        if resolve1_enabled:
+            # break circular import
+            from ipaplatform.services import knownservices
+
+            confd = os.path.dirname(paths.SYSTEMD_RESOLVED_IPA_CONF)
+            os.makedirs(confd, exist_ok=True)
+
+            cfg = RESOLVE1_IPA_CONF.format(
+                searchdomains=" ".join(searchdomains)
+            )
+            with open(paths.SYSTEMD_RESOLVED_IPA_CONF, "w") as f:
+                os.fchmod(f.fileno(), 0o644)
+                f.write(cfg)
+
+            knownservices["systemd-resolved"].reload_or_restart()
 
     def unconfigure_dns_resolver(self, fstore=None):
         """Unconfigure global DNS resolver (e.g. /etc/resolv.conf)
@@ -328,6 +355,12 @@ class BaseTaskNamespace:
         if fstore is not None and fstore.has_file(paths.RESOLV_CONF):
             fstore.restore_file(paths.RESOLV_CONF)
 
+        if os.path.isfile(paths.SYSTEMD_RESOLVED_IPA_CONF):
+            # break circular import
+            from ipaplatform.services import knownservices
+
+            os.unlink(paths.SYSTEMD_RESOLVED_IPA_CONF)
+            knownservices["systemd-resolved"].reload_or_restart()
 
     def configure_pkcs11_modules(self, fstore):
         """Disable p11-kit modules

ipaplatform/redhat/tasks.py

@@ -44,7 +44,6 @@ from subprocess import CalledProcessError
 from pyasn1.error import PyAsn1Error
 
 from ipapython import directivesetter
-from ipapython import dnsutil
 from ipapython import ipautil
 import ipapython.errors
 
@@ -625,6 +624,13 @@ class RedHatTaskNamespace(BaseTaskNamespace):
         assert nameservers and isinstance(nameservers, list)
         assert searchdomains and isinstance(searchdomains, list)
 
+        super().configure_dns_resolver(
+            nameservers=nameservers,
+            searchdomains=searchdomains,
+            resolve1_enabled=resolve1_enabled,
+            fstore=fstore
+        )
+
         # break circular import
         from ipaplatform.services import knownservices
 
@@ -632,7 +638,8 @@ class RedHatTaskNamespace(BaseTaskNamespace):
             fstore.backup_file(paths.RESOLV_CONF)
 
         nm = knownservices['NetworkManager']
-        if nm.is_enabled():
+        nm_enabled = nm.is_enabled()
+        if nm_enabled:
             logger.debug(
                 "Network Manager is enabled, write %s",
                 paths.NETWORK_MANAGER_IPA_CONF
@@ -658,11 +665,13 @@ class RedHatTaskNamespace(BaseTaskNamespace):
                 f.write(cfg)
             # reload NetworkManager
             nm.reload_or_restart()
-        else:
-            # no NM running, fall back to /etc/resolv.conf
+
+        if not resolve1_enabled and not nm_enabled:
+            # no NM running, no systemd-resolved detected
+            # fall back to /etc/resolv.conf
             logger.debug(
-                "Network Manager is not enabled, write %s directly.",
-                paths.RESOLV_CONF
+                "Neither Network Manager nor systemd-resolved are enabled, "
+                "write %s directly.", paths.RESOLV_CONF
             )
             cfg = [
                 "# auto-generated by IPA installer",
@@ -678,12 +687,10 @@ class RedHatTaskNamespace(BaseTaskNamespace):
 
         :param fstore: optional file store for restore
         """
+        super().unconfigure_dns_resolver(fstore=fstore)
         # break circular import
         from ipaplatform.services import knownservices
 
-        if fstore is not None and fstore.has_file(paths.RESOLV_CONF):
-            fstore.restore_file(paths.RESOLV_CONF)
-
         nm = knownservices['NetworkManager']
         if os.path.isfile(paths.NETWORK_MANAGER_IPA_CONF):
             os.unlink(paths.NETWORK_MANAGER_IPA_CONF)