route: static: T2450: add missing "dhcp-interface" route option

As thought in the beginning the dhcp-interface route option can not be
superseeded by the interface option. When a route is installed for a DHCP
interface, that interface is usually a broadcast interface which can not be
used for plain interface-based routes.

The old Vyatta logic was migrated to Python where the current received
next-hop address from the DHCP interface is installed as next-hop address.

3 files changed, 40 insertions, 1 deletions

diff --git a/data/templates/frr/static_routes_macro.j2 b/data/templates/frr/static_routes_macro.j2
index b24232ef3..f10b58047 100644
--- a/data/templates/frr/static_routes_macro.j2
+++ b/data/templates/frr/static_routes_macro.j2
@@ -2,6 +2,12 @@
 {%   if prefix_config.blackhole is defined %}
 {{ ip_ipv6 }} route {{ prefix }} blackhole {{ prefix_config.blackhole.distance if prefix_config.blackhole.distance is defined }} {{ 'tag ' + prefix_config.blackhole.tag if prefix_config.blackhole.tag is defined }} {{ 'table ' + table if table is defined and table is not none }}
 {%   endif %}
+{%   if prefix_config.dhcp_interface is defined and prefix_config.dhcp_interface is not none %}
+{%     set next_hop = prefix_config.dhcp_interface | get_dhcp_router %}
+{%     if next_hop is defined and next_hop is not none %}
+{{ ip_ipv6 }} route {{ prefix }} {{ next_hop }}
+{%     endif %}
+{%   endif %}
 {%   if prefix_config.interface is defined and prefix_config.interface is not none %}
 {%     for interface, interface_config in prefix_config.interface.items() if interface_config.disable is not defined %}
 {{ ip_ipv6 }} route {{ prefix }} {{ interface }} {{ interface_config.distance if interface_config.distance is defined }} {{ 'nexthop-vrf ' + interface_config.vrf if interface_config.vrf is defined }} {{ 'table ' + table if table is defined and table is not none }}
diff --git a/interface-definitions/include/static-route.xml.i b/interface-definitions/include/static-route.xml.i
index 386582e09..21fcbcd3f 100644
--- a/interface-definitions/include/static-route.xml.i
+++ b/interface-definitions/include/static-route.xml.i
@@ -31,6 +31,21 @@
         </leafNode>
       </children>
     </node>
+    <leafNode name="dhcp-interface">
+      <properties>
+        <help>DHCP interface supplying next-hop IP address</help>
+        <completionHelp>
+          <script>${vyos_completion_dir}/list_interfaces.py</script>
+        </completionHelp>
+        <valueHelp>
+          <format>txt</format>
+          <description>DHCP interface name</description>
+        </valueHelp>
+        <constraint>
+          <validator name="interface-name"/>
+        </constraint>
+      </properties>
+    </leafNode>
     <tagNode name="interface">
       <properties>
         <help>Next-hop IPv4 router interface</help>
diff --git a/python/vyos/template.py b/python/vyos/template.py
index 527384d0b..22883b103 100644
--- a/python/vyos/template.py
+++ b/python/vyos/template.py
@@ -288,7 +288,6 @@ def compare_netmask(netmask1, netmask2):
     except:
         return False
 
-
 @register_filter('isc_static_route')
 def isc_static_route(subnet, router):
     # https://ercpe.de/blog/pushing-static-routes-with-isc-dhcp-server
@@ -316,3 +315,22 @@ def is_file(filename):
     if os.path.exists(filename):
         return os.path.isfile(filename)
     return False
+
+@register_filter('get_dhcp_router')
+def get_dhcp_router(interface):
+    """ Static routes can point to a router received by a DHCP reply. This
+    helper is used to get the current default router from the DHCP reply.
+
+    Returns False of no router is found, returns the IP address as string if
+    a router is found.
+    """
+    interface = interface.replace('.', '_')
+    lease_file = f'/var/lib/dhcp/dhclient_{interface}.leases'
+    if not os.path.exists(lease_file):
+        return None
+
+    from vyos.util import read_file
+    for line in read_file(lease_file).splitlines():
+        if 'option routers' in line:
+            (_, _, address) = line.split()
+            return address.rstrip(';')