From fd503cdcfb8138b1c181916050c4c0d5cc826ae7 Mon Sep 17 00:00:00 2001
From: Gris Ge <fge@redhat.com>
Date: Thu, 19 Mar 2020 22:14:12 +0800
Subject: [PATCH] dns: support static DNS with dynamic IP

Added the support of static DNS configuration with dynamic IP interface as
long as specified interface has `InterfaceIP.AUTO_DNS` set to False.

When choosing interface to storing DNS configuration, the interface with
static address and gateway is preferred over dynamic interface with
`InterfaceIP.AUTO_DNS` set to False.

Added Unit test cases and integration test cases.

Signed-off-by: Gris Ge <fge@redhat.com>
---
 libnmstate/metadata.py |  6 +-----
 libnmstate/nm/dns.py   | 34 +++++++++++++++++++++++++++++-----
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/libnmstate/metadata.py b/libnmstate/metadata.py
index 37d6b96..b268ba3 100644
--- a/libnmstate/metadata.py
+++ b/libnmstate/metadata.py
@@ -242,12 +242,8 @@ def _generate_dns_metadata(desired_state, current_state):
     if _dns_config_not_changed(desired_state, current_state):
         _preserve_current_dns_metadata(desired_state, current_state)
     else:
-        ifaces_routes = {
-            ifname: [r.to_dict() for r in routes]
-            for ifname, routes in desired_state.config_iface_routes.items()
-        }
         ipv4_iface, ipv6_iface = nm.dns.find_interfaces_for_name_servers(
-            ifaces_routes
+            desired_state
         )
         _save_dns_metadata(
             desired_state,
diff --git a/libnmstate/nm/dns.py b/libnmstate/nm/dns.py
index 008b034..0ab28e4 100644
--- a/libnmstate/nm/dns.py
+++ b/libnmstate/nm/dns.py
@@ -27,6 +27,8 @@ from libnmstate.nm import active_connection as nm_ac
 from libnmstate.nm import route as nm_route
 from libnmstate.schema import DNS
 from libnmstate.schema import Interface
+from libnmstate.schema import InterfaceIP
+from libnmstate.schema import InterfaceIPv6
 
 
 DNS_DEFAULT_PRIORITY_VPN = 50
@@ -123,17 +125,26 @@ def get_dns_config_iface_names(acs_and_ipv4_profiles, acs_and_ipv6_profiles):
     return iface_names
 
 
-def find_interfaces_for_name_servers(iface_routes):
+def find_interfaces_for_name_servers(desired_state):
     """
     Find interfaces to store the DNS configurations:
         * Interface with static gateway configured.
+        * Interface with dynamic IP and auto-dns: False.
     Return two interface names for IPv4 and IPv6 name servers.
     The interface name will be None if failed to find proper interface.
     """
-    return (
-        nm_route.get_static_gateway_iface(Interface.IPV4, iface_routes),
-        nm_route.get_static_gateway_iface(Interface.IPV6, iface_routes),
-    )
+    iface_routes = {
+        ifname: [r.to_dict() for r in routes]
+        for ifname, routes in desired_state.config_iface_routes.items()
+    }
+    ipv4_iface = nm_route.get_static_gateway_iface(
+        Interface.IPV4, iface_routes
+    ) or _get_auto_dns_false_iface(Interface.IPV4, desired_state.interfaces)
+
+    ipv6_iface = nm_route.get_static_gateway_iface(
+        Interface.IPV6, iface_routes
+    ) or _get_auto_dns_false_iface(Interface.IPV6, desired_state.interfaces)
+    return ipv4_iface, ipv6_iface
 
 
 def get_indexed_dns_config_by_iface(
@@ -179,3 +190,16 @@ def _get_ip_profile_dns_config(ip_profile):
         DNS.SEARCH: ip_profile.props.dns_search,
         DNS_METADATA_PRIORITY: ip_profile.props.dns_priority,
     }
+
+
+def _get_auto_dns_false_iface(family, iface_states):
+    for iface_name, iface_state in iface_states.items():
+        ip_state = iface_state.get(family, {})
+        if ip_state.get(InterfaceIP.ENABLED) and not ip_state.get(
+            InterfaceIP.AUTO_DNS
+        ):
+            if ip_state.get(InterfaceIP.DHCP) or ip_state.get(
+                InterfaceIPv6.AUTOCONF
+            ):
+                return iface_name
+    return None
-- 
2.18.2