ipa-dns-install offer IP addresses from resolv.conf as default forwarders

In non-interactive more option --auto-forwarders can be used to do the
same. --forward option can be used to supply additional IP addresses.

https://fedorahosted.org/freeipa/ticket/5438

Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipaserver/install/dns.py

@@ -2,8 +2,11 @@
 # Copyright (C) 2015  FreeIPA Contributors see COPYING for license
 #
 
+from __future__ import absolute_import
 from __future__ import print_function
 
+# absolute import is necessary because IPA module dns clashes with python-dns
+from dns import resolver
 import sys
 
 from subprocess import CalledProcessError
@@ -230,8 +233,13 @@ def install_check(standalone, replica, options, hostname):
 
     if options.no_forwarders:
         dns_forwarders = ()
-    elif options.forwarders:
+    elif options.forwarders or options.auto_forwarders:
-        dns_forwarders = options.forwarders
+        if options.forwarders:
+            dns_forwarders = options.forwarders
+        else:
+            dns_forwarders = []
+        if options.auto_forwarders:
+            dns_forwarders += resolver.get_default_resolver().nameservers
     elif standalone or not replica:
         dns_forwarders = read_dns_forwarders()
 

ipaserver/install/installutils.py

@@ -282,6 +282,13 @@ def read_ip_addresses():
 def read_dns_forwarders():
     addrs = []
     if ipautil.user_input("Do you want to configure DNS forwarders?", True):
+        print("Following DNS servers are configured in /etc/resolv.conf: %s" %
+                ", ".join(resolver.get_default_resolver().nameservers))
+        if ipautil.user_input("Do you want to configure these servers as DNS "
+                "forwarders?", True):
+            addrs = resolver.default_resolver.nameservers[:]
+            print("All DNS servers from /etc/resolv.conf were added. You can "
+                  "enter additional addresses now:")
         while True:
             ip = ipautil.user_input("Enter an IP address for a DNS forwarder, "
                                     "or press Enter to skip", allow_empty=True)

ipaserver/install/server/common.py

@@ -167,6 +167,11 @@ class BaseServerDNS(common.Installable, core.Group, core.Composite):
         cli_name='forwarder',
     )
 
+    auto_forwarders = Knob(
+        bool, False,
+        description="Use DNS forwarders configured in /etc/resolv.conf",
+    )
+
     no_forwarders = Knob(
         bool, False,
         description="Do not add any DNS forwarders, use root servers instead",
@@ -395,6 +400,10 @@ class BaseServer(common.Installable, common.Interactive, core.Composite):
                 raise RuntimeError(
                     "You cannot specify a --forwarder option without the "
                     "--setup-dns option")
+            if self.dns.auto_forwarders:
+                raise RuntimeError(
+                    "You cannot specify a --auto-forwarders option without "
+                    "the --setup-dns option")
             if self.dns.no_forwarders:
                 raise RuntimeError(
                     "You cannot specify a --no-forwarders option without the "
@@ -415,6 +424,10 @@ class BaseServer(common.Installable, common.Interactive, core.Composite):
             raise RuntimeError(
                 "You cannot specify a --forwarder option together with "
                 "--no-forwarders")
+        elif self.dns.auto_forwarders and self.dns.no_forwarders:
+            raise RuntimeError(
+                "You cannot specify a --auto-forwarders option together with "
+                "--no-forwarders")
         elif self.dns.reverse_zones and self.dns.no_reverse:
             raise RuntimeError(
                 "You cannot specify a --reverse-zone option together with "
@@ -441,6 +454,7 @@ class BaseServer(common.Installable, common.Interactive, core.Composite):
         self.skip_schema_check = self.ca.skip_schema_check
 
         self.forwarders = self.dns.forwarders
+        self.auto_forwarders = self.dns.auto_forwarders
         self.no_forwarders = self.dns.no_forwarders
         self.reverse_zones = self.dns.reverse_zones
         self.no_reverse = self.dns.no_reverse

ipaserver/install/server/install.py

@@ -1267,10 +1267,11 @@ class Server(BaseServer):
                     "and -a options")
             if self.setup_dns:
                 #pylint: disable=no-member
-                if not self.dns.forwarders and not self.dns.no_forwarders:
+                if (not self.dns.forwarders and not self.dns.no_forwarders
+                    and not self.dns.auto_forwarders):
                     raise RuntimeError(
-                        "You must specify at least one --forwarder option or "
+                        "You must specify at least one of --forwarder, "
-                        "--no-forwarders option")
+                        "--auto-forwarders, or --no-forwarders options")
 
         if self.idmax < self.idstart:
             raise RuntimeError(

ipaserver/install/server/replicainstall.py

@@ -1199,10 +1199,11 @@ class Replica(BaseServer):
 
         if self.setup_dns:
             #pylint: disable=no-member
-            if not self.dns.forwarders and not self.dns.no_forwarders:
+            if (not self.dns.forwarders and not self.dns.no_forwarders
+                and not self.dns.auto_forwarders):
                 raise RuntimeError(
-                    "You must specify at least one --forwarder option or "
+                    "You must specify at least one of --forwarder, "
-                    "--no-forwarders option")
+                    "--auto-forwarders, or --no-forwarders options")
 
         self.password = self.dm_password