T5942: Make failover support dhcp-interface

* Refactor XML a little: move common dhcp-interface properties to
  separate include file
* Add failover support for dhcp-interface
* Add test for DHCP in failover protocol

8 files changed, 410 insertions, 168 deletions

diff --git a/interface-definitions/include/dhcp-interface-multi.xml.i b/interface-definitions/include/dhcp-interface-multi.xml.i
index 0db11cf79..5f5c54cfd 100644
--- a/interface-definitions/include/dhcp-interface-multi.xml.i
+++ b/interface-definitions/include/dhcp-interface-multi.xml.i
@@ -1,18 +1,8 @@
 <!-- include start from dhcp-interface-multi.xml.i -->
-<leafNode name="dhcp-interface">
-  <properties>
-    <help>DHCP interface supplying next-hop IP address</help>
-    <completionHelp>
-      <script>${vyos_completion_dir}/list_interfaces</script>
-    </completionHelp>
-    <valueHelp>
-      <format>txt</format>
-      <description>DHCP interface name</description>
-    </valueHelp>
-    <constraint>
-      #include <include/constraint/interface-name.xml.i>
-    </constraint>
-    <multi/>
-  </properties>
+    <leafNode name="dhcp-interface">
+      <properties>
+        #include <include/dhcp-interface-properties.xml.i>
+        <multi/>
+      </properties>
 </leafNode>
-<!-- include end -->
\ No newline at end of file
+<!-- include end -->
diff --git a/interface-definitions/include/dhcp-interface-properties.xml.i b/interface-definitions/include/dhcp-interface-properties.xml.i
new file mode 100644
index 000000000..b184b8f0a
--- /dev/null
+++ b/interface-definitions/include/dhcp-interface-properties.xml.i
@@ -0,0 +1,13 @@
+<!-- include end -->
+        <help>DHCP interface supplying next-hop IP address</help>
+        <completionHelp>
+          <script>${vyos_completion_dir}/list_interfaces</script>
+        </completionHelp>
+        <valueHelp>
+          <format>txt</format>
+          <description>DHCP interface name</description>
+        </valueHelp>
+        <constraint>
+          #include <include/constraint/interface-name.xml.i>
+        </constraint>
+<!-- include end -->
diff --git a/interface-definitions/include/dhcp-interface.xml.i b/interface-definitions/include/dhcp-interface.xml.i
index b5c94cb24..e056b3fe1 100644
--- a/interface-definitions/include/dhcp-interface.xml.i
+++ b/interface-definitions/include/dhcp-interface.xml.i
@@ -1,15 +1,7 @@
+<!-- include start from dhcp-interface.xml.i -->
     <leafNode name="dhcp-interface">
       <properties>
-        <help>DHCP interface supplying next-hop IP address</help>
-        <completionHelp>
-          <script>${vyos_completion_dir}/list_interfaces</script>
-        </completionHelp>
-        <valueHelp>
-          <format>txt</format>
-          <description>DHCP interface name</description>
-        </valueHelp>
-        <constraint>
-          #include <include/constraint/interface-name.xml.i>
-        </constraint>
+        #include <include/dhcp-interface-properties.xml.i>
       </properties>
     </leafNode>
+<!-- include end -->
diff --git a/interface-definitions/include/failover/common-failover.xml.i b/interface-definitions/include/failover/common-failover.xml.i
new file mode 100644
index 000000000..b147a0f8d
--- /dev/null
+++ b/interface-definitions/include/failover/common-failover.xml.i
@@ -0,0 +1,105 @@
+<!-- include start from include/failover/common-failover.xml.i -->
+<children>
+  <node name="check">
+    <properties>
+      <help>Check target options</help>
+    </properties>
+    <children>
+      <leafNode name="policy">
+        <properties>
+          <help>Policy for check targets</help>
+          <completionHelp>
+            <list>any-available all-available</list>
+          </completionHelp>
+          <valueHelp>
+            <format>all-available</format>
+            <description>All targets must be alive</description>
+          </valueHelp>
+          <valueHelp>
+            <format>any-available</format>
+            <description>Any target must be alive</description>
+          </valueHelp>
+          <constraint>
+            <regex>(all-available|any-available)</regex>
+          </constraint>
+        </properties>
+        <defaultValue>any-available</defaultValue>
+      </leafNode>
+      #include <include/port-number.xml.i>
+      <tagNode name="target">
+        <properties>
+          <help>Check target address</help>
+          <valueHelp>
+            <format>ipv4</format>
+            <description>Address to check</description>
+          </valueHelp>
+          <constraint>
+            <validator name="ipv4-address"/>
+          </constraint>
+        </properties>
+        <children>
+          #include <include/interface/vrf.xml.i>
+          #include <include/generic-interface.xml.i>
+        </children>
+      </tagNode>
+      <leafNode name="timeout">
+        <properties>
+          <help>Timeout between checks</help>
+          <valueHelp>
+            <format>u32:1-300</format>
+            <description>Timeout in seconds between checks</description>
+          </valueHelp>
+          <constraint>
+            <validator name="numeric" argument="--range 1-255"/>
+          </constraint>
+        </properties>
+        <defaultValue>10</defaultValue>
+      </leafNode>
+      <leafNode name="type">
+        <properties>
+          <help>Check type</help>
+          <completionHelp>
+            <list>arp icmp tcp</list>
+          </completionHelp>
+          <valueHelp>
+            <format>arp</format>
+            <description>Check target by ARP</description>
+          </valueHelp>
+          <valueHelp>
+            <format>icmp</format>
+            <description>Check target by ICMP</description>
+          </valueHelp>
+          <valueHelp>
+            <format>tcp</format>
+            <description>Check target by TCP</description>
+          </valueHelp>
+          <constraint>
+            <regex>(arp|icmp|tcp)</regex>
+          </constraint>
+        </properties>
+        <defaultValue>icmp</defaultValue>
+      </leafNode>
+    </children>
+  </node>
+  #include <include/generic-interface.xml.i>
+  <leafNode name="metric">
+    <properties>
+      <help>Route metric for this gateway</help>
+      <valueHelp>
+        <format>u32:1-255</format>
+        <description>Route metric</description>
+      </valueHelp>
+      <constraint>
+        <validator name="numeric" argument="--range 1-255"/>
+      </constraint>
+    </properties>
+    <defaultValue>1</defaultValue>
+  </leafNode>
+  <leafNode name="onlink">
+    <properties>
+      <help>The next hop is directly connected to the interface, even if it does not match interface prefix</help>
+      <valueless/>
+    </properties>
+  </leafNode>
+</children>
+<!-- include end -->
diff --git a/interface-definitions/include/failover/protocol-common-config.xml.i b/interface-definitions/include/failover/protocol-common-config.xml.i
index a106fdc74..56c9d8f90 100644
--- a/interface-definitions/include/failover/protocol-common-config.xml.i
+++ b/interface-definitions/include/failover/protocol-common-config.xml.i
@@ -22,109 +22,13 @@
           <validator name="ipv4-address"/>
         </constraint>
       </properties>
-      <children>
-        <node name="check">
-          <properties>
-            <help>Check target options</help>
-          </properties>
-          <children>
-            <leafNode name="policy">
-              <properties>
-                <help>Policy for check targets</help>
-                <completionHelp>
-                  <list>any-available all-available</list>
-                </completionHelp>
-                <valueHelp>
-                  <format>all-available</format>
-                  <description>All targets must be alive</description>
-                </valueHelp>
-                <valueHelp>
-                  <format>any-available</format>
-                  <description>Any target must be alive</description>
-                </valueHelp>
-                <constraint>
-                  <regex>(all-available|any-available)</regex>
-                </constraint>
-              </properties>
-              <defaultValue>any-available</defaultValue>
-            </leafNode>
-            #include <include/port-number.xml.i>
-            <tagNode name="target">
-              <properties>
-                <help>Check target address</help>
-                <valueHelp>
-                  <format>ipv4</format>
-                  <description>Address to check</description>
-                </valueHelp>
-                <constraint>
-                  <validator name="ipv4-address"/>
-                </constraint>
-              </properties>
-              <children>
-                #include <include/interface/vrf.xml.i>
-                #include <include/generic-interface.xml.i>
-              </children>
-            </tagNode>
-            <leafNode name="timeout">
-              <properties>
-                <help>Timeout between checks</help>
-                <valueHelp>
-                  <format>u32:1-300</format>
-                  <description>Timeout in seconds between checks</description>
-                </valueHelp>
-                <constraint>
-                  <validator name="numeric" argument="--range 1-255"/>
-                </constraint>
-              </properties>
-              <defaultValue>10</defaultValue>
-            </leafNode>
-            <leafNode name="type">
-              <properties>
-                <help>Check type</help>
-                <completionHelp>
-                  <list>arp icmp tcp</list>
-                </completionHelp>
-                <valueHelp>
-                  <format>arp</format>
-                  <description>Check target by ARP</description>
-                </valueHelp>
-                <valueHelp>
-                  <format>icmp</format>
-                  <description>Check target by ICMP</description>
-                </valueHelp>
-                <valueHelp>
-                  <format>tcp</format>
-                  <description>Check target by TCP</description>
-                </valueHelp>
-                <constraint>
-                  <regex>(arp|icmp|tcp)</regex>
-                </constraint>
-              </properties>
-              <defaultValue>icmp</defaultValue>
-            </leafNode>
-          </children>
-        </node>
-        #include <include/generic-interface.xml.i>
-        <leafNode name="metric">
-          <properties>
-            <help>Route metric for this gateway</help>
-            <valueHelp>
-              <format>u32:1-255</format>
-              <description>Route metric</description>
-            </valueHelp>
-            <constraint>
-              <validator name="numeric" argument="--range 1-255"/>
-            </constraint>
-          </properties>
-          <defaultValue>1</defaultValue>
-        </leafNode>
-        <leafNode name="onlink">
-          <properties>
-            <help>The next hop is directly connected to the interface, even if it does not match interface prefix</help>
-            <valueless/>
-          </properties>
-        </leafNode>
-      </children>
+      #include <include/failover/common-failover.xml.i>
+    </tagNode>
+    <tagNode name="dhcp-interface">
+      <properties>
+        #include <include/dhcp-interface-properties.xml.i>
+      </properties>
+      #include <include/failover/common-failover.xml.i>
     </tagNode>
   </children>
 </tagNode>
diff --git a/smoketest/scripts/cli/test_protocols_failover.py b/smoketest/scripts/cli/test_protocols_failover.py
index 26f5e87b5..132d427ec 100755
--- a/smoketest/scripts/cli/test_protocols_failover.py
+++ b/smoketest/scripts/cli/test_protocols_failover.py
@@ -34,6 +34,7 @@ config_dir_root = '/run/vyos-failover.conf.d'
 
 check_timeout = 1
 wait_timeout = 5
+wait_dhcp_timeout = 10
 
 # Use numeric value to not get ip errors while
 # /etc/iproute2/rt_protos.d/failover.conf is not installed yet
@@ -43,6 +44,9 @@ dummy_if1 = 'dum3711'
 dummy_if2 = 'dum3712'
 dummy_if3 = 'dum3713'
 
+veth_if1 = 'veth71'
+veth_if2 = 'veth72'
+
 route_prefix = '203.0.113.0/24'
 route2_prefix = '172.16.0.0/24'
 route_base_path = base_path + ['route', route_prefix]
@@ -51,6 +55,12 @@ dummy_if1_addr = '192.168.30.1'
 dummy_if2_addr = '10.0.70.1'
 dummy_if3_addr = '10.20.0.1'
 
+# These three must be in same subnet:
+dhcp_prefix = '10.133.0'
+veth_if1_addr = f'{dhcp_prefix}.1'
+dhcp_gateway_addr_1 = f'{dhcp_prefix}.99'
+dhcp_gateway_addr_2 = f'{dhcp_prefix}.117'
+
 
 class RoutesChecker:
     def __init__(self, required_routes, allow_extra=False):
@@ -101,13 +111,26 @@ class TestProtocolsFailover(VyOSUnitTestSHIM.TestCase):
         self.cli_set(['interfaces', 'dummy', dummy_if1])
         self.cli_set(['interfaces', 'dummy', dummy_if2])
         self.cli_set(['interfaces', 'dummy', dummy_if3])
+        self.cli_set(
+            ['interfaces', 'virtual-ethernet', veth_if1, 'peer-name', veth_if2]
+        )
+        self.cli_set(
+            ['interfaces', 'virtual-ethernet', veth_if2, 'peer-name', veth_if1]
+        )
 
         self.clean_and_stop_daemon()
 
+        self.clean_dhclient_lease_files = set()
+        self.need_dhcp_dir_cleanup = False
+
     def tearDown(self):
+        self.cli_delete(['interfaces', 'virtual-ethernet', veth_if2])
+        self.cli_delete(['interfaces', 'virtual-ethernet', veth_if1])
         self.cli_delete(['interfaces', 'dummy', dummy_if3])
         self.cli_delete(['interfaces', 'dummy', dummy_if2])
         self.cli_delete(['interfaces', 'dummy', dummy_if1])
+        self.cli_delete(['service', 'dhcp-server'])
+        self.cli_delete(['service', 'dns'])
 
         self.clean_and_stop_daemon()
 
@@ -503,5 +526,120 @@ class TestProtocolsFailover(VyOSUnitTestSHIM.TestCase):
         self.assertTrue(res, f"No routes should have been left, got: {output}")
 
 
+    def test_04_dhcp(self):
+        res, output = self.wait_for_ip_output(
+            f'route show proto {failover_protocol_value}',
+            [],
+            timeout=wait_timeout,
+        )
+        self.assertTrue(
+            res, f"No failover routes must exist before test, last result: {output}"
+        )
+
+        # Setup DHCP server
+        self.cli_set(
+            [
+                'interfaces',
+                'virtual-ethernet',
+                veth_if1,
+                'address',
+                f'{dhcp_prefix}.1/24',
+            ]
+        )
+        self.cli_set(['interfaces', 'virtual-ethernet', veth_if1, 'description', 'LAN'])
+
+        service_base = [
+            'service',
+            'dhcp-server',
+            'shared-network-name',
+            'LAN',
+            'subnet',
+            f'{dhcp_prefix}.0/24',
+        ]
+        self.cli_set(service_base + ['option', 'name-server', f'{dhcp_prefix}.1'])
+        self.cli_set(service_base + ['option', 'domain-name', 'vyos'])
+        self.cli_set(service_base + ['lease', '86400'])
+        self.cli_set(service_base + ['range', '0', 'start', f'{dhcp_prefix}.9'])
+        self.cli_set(service_base + ['range', '0', 'stop', f'{dhcp_prefix}.254'])
+        self.cli_set(service_base + ['subnet-id', '1952'])
+
+        self.cli_set(['service', 'dns', 'forwarding', 'cache-size', '0'])
+        self.cli_set(
+            ['service', 'dns', 'forwarding', 'listen-address', f'{dhcp_prefix}.1']
+        )
+        self.cli_set(
+            ['service', 'dns', 'forwarding', 'allow-from', f'{dhcp_prefix}.0/24']
+        )
+        # End setup DHCP server
+
+        # Setting first DHCP Gateway address
+        self.cli_set(service_base + ['option', 'default-router', dhcp_gateway_addr_1])
+
+        self.cli_set(
+            ['interfaces', 'dummy', dummy_if1, 'address', dummy_if1_addr + '/24']
+        )
+        self.cli_set(
+            ['interfaces', 'dummy', dummy_if2, 'address', dummy_if2_addr + '/24']
+        )
+        self.cli_set(['interfaces', 'virtual-ethernet', veth_if2, 'address', 'dhcp'])
+        self.cli_set(route_base_path + ['dhcp-interface', veth_if2])
+        base_dhcp_interface = route_base_path + ['dhcp-interface', veth_if2]
+        self.cli_set(base_dhcp_interface + ['metric', '30'])
+        self.cli_set(
+            base_dhcp_interface
+            + [
+                'check',
+                'target',
+                dummy_if1_addr,
+                'interface',
+                dummy_if1,
+            ]
+        )
+        self.cli_set(base_dhcp_interface + ['check', 'timeout', str(check_timeout)])
+        self.cli_commit()
+
+        # Now vyos-failover must be launched, it should create route to first dhcp address
+        checker = RoutesChecker([{'dst': route_prefix, 'gateway': dhcp_gateway_addr_1}])
+        res, output = self.wait_for_ip_output(
+            f"route show proto {failover_protocol_value}",
+            checker,
+            timeout=wait_dhcp_timeout,
+        )
+        self.assertTrue(
+            res,
+            f"Route must have been created via fist dhcp address. Checker error: {checker.error}",
+        )
+
+        # Change DHCP gateway address
+        renew_cmd = ['renew', 'dhcp', 'interface', veth_if2]
+        self.cli_set(service_base + ['option', 'default-router', dhcp_gateway_addr_2])
+        self.cli_commit()
+        self.op_mode(renew_cmd)
+
+        checker = RoutesChecker([{'dst': route_prefix, 'gateway': dhcp_gateway_addr_2}])
+        res, output = self.wait_for_ip_output(
+            f"route show proto {failover_protocol_value}",
+            checker,
+            timeout=wait_dhcp_timeout,
+        )
+        self.assertTrue(
+            res,
+            f"Route must have been created via second dhcp address. Checker error: {checker.error}",
+        )
+
+        # DHCP server down
+        self.cli_delete(['service', 'dhcp-server'])
+        self.cli_delete(['service', 'dns'])
+        self.cli_commit()
+        self.op_mode(renew_cmd)
+
+        res, output = self.wait_for_ip_output(
+            f'route show proto {failover_protocol_value}',
+            [],
+            timeout=wait_dhcp_timeout,
+        )
+        self.assertTrue(res, f"Route must have been deleted, last result: {output}")
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)
diff --git a/src/conf_mode/protocols_failover.py b/src/conf_mode/protocols_failover.py
index 956c060f4..752bd6011 100755
--- a/src/conf_mode/protocols_failover.py
+++ b/src/conf_mode/protocols_failover.py
@@ -85,38 +85,60 @@ def verify(failover):
     if 'route' not in failover:
         raise ConfigError(f'Failover "route" is mandatory!')
 
+    def _verify_route_item(item_config, item_description, interface_mandatory):
+        if interface_mandatory and 'interface' not in item_config:
+            raise ConfigError(
+                f'Interface for route "{route}" {item_description} is mandatory!'
+            )
+
+        if not item_config.get('check'):
+            raise ConfigError(f'Check target for {item_description} is mandatory!')
+
+        if 'target' not in item_config['check']:
+            raise ConfigError(f'Check target for {item_description} is mandatory!')
+
+        check_type = item_config['check']['type']
+        if check_type == 'tcp' and 'port' not in item_config['check']:
+            raise ConfigError(
+                f'Check port for {item_description} and type TCP is mandatory!'
+            )
+
+        errors = {
+            'icmp': {},
+            'tcp': {
+                'interface': 'Check target "interface" option does nothing for type TCP. Use "vrf" if needed',
+            },
+            'arp': {
+                'vrf': 'Check target "vrf" option is incompatible with type ARP, use "interface" option if needed',
+            },
+        }
+
+        for target, target_config in item_config['check']['target'].items():
+            for key, msg in errors[check_type].items():
+                if key in target_config:
+                    raise ConfigError(msg)
+
     for route, route_config in failover['route'].items():
-        if not route_config.get('next_hop'):
-            raise ConfigError(f'Next-hop for "{route}" is mandatory!')
-
-        for next_hop, next_hop_config in route_config.get('next_hop').items():
-            if 'interface' not in next_hop_config:
-                raise ConfigError(f'Interface for route "{route}" next-hop "{next_hop}" is mandatory!')
-
-            if not next_hop_config.get('check'):
-                raise ConfigError(f'Check target for next-hop "{next_hop}" is mandatory!')
-
-            if 'target' not in next_hop_config['check']:
-                raise ConfigError(f'Check target for next-hop "{next_hop}" is mandatory!')
-
-            check_type = next_hop_config['check']['type']
-            if check_type == 'tcp' and 'port' not in next_hop_config['check']:
-                raise ConfigError(f'Check port for next-hop "{next_hop}" and type TCP is mandatory!')
-
-            errors = {
-                'icmp': {},
-                'tcp': {
-                    'interface': 'Check target "interface" option does nothing for type TCP. Use "vrf" if needed',
-                },
-                'arp': {
-                    'vrf': 'Check target "vrf" option is incompatible with type ARP, use "interface" option if needed',
-                },
-            }
-
-            for target, target_config in next_hop_config['check']['target'].items():
-                for key, msg in errors[check_type].items():
-                    if key in target_config:
-                        raise ConfigError(msg)
+        if not route_config.get('next_hop') and not route_config.get('dhcp_interface'):
+            raise ConfigError(
+                f'Either next-hop or dhcp-interface for "{route}" is mandatory!'
+            )
+
+        if route_config.get('next_hop'):
+            for next_hop, next_hop_config in route_config.get('next_hop').items():
+                _verify_route_item(
+                    next_hop_config, f'next-hop "{next_hop}"', interface_mandatory=True
+                )
+
+        if route_config.get('dhcp_interface'):
+            for dhcp_interface, dhcp_interface_config in route_config.get(
+                'dhcp_interface'
+            ).items():
+                _verify_route_item(
+                    dhcp_interface_config,
+                    f'dhcp-interface "{dhcp_interface}"',
+                    interface_mandatory=False,
+                )
 
     return None
 
diff --git a/src/helpers/vyos-failover.py b/src/helpers/vyos-failover.py
index d255f2303..de89f20d0 100755
--- a/src/helpers/vyos-failover.py
+++ b/src/helpers/vyos-failover.py
@@ -21,6 +21,7 @@ import signal
 import time
 
 from collections import namedtuple
+from vyos.template import get_dhcp_router
 from vyos.utils.process import rc_cmd
 from vyos.utils.process import run
 from pathlib import Path
@@ -170,6 +171,7 @@ NextHopNamedTuple = namedtuple(
     'NextHopConfig',
     [
         'route',
+        'dhcp_interface',
         'next_hop',
         'vrf',
         'vrf_opt',
@@ -187,7 +189,9 @@ NextHopNamedTuple = namedtuple(
 )
 
 
-def get_nexthop_config_vars(destination, vrf, vrf_opt, nexthop_config, next_hop):
+def get_nexthop_config_vars(
+    destination, vrf, vrf_opt, nexthop_config, next_hop, dhcp_interface
+):
     port = nexthop_config.get('check').get('port')
 
     targets = tuple(
@@ -215,10 +219,13 @@ def get_nexthop_config_vars(destination, vrf, vrf_opt, nexthop_config, next_hop)
 
     return NextHopNamedTuple(
         route=destination,
+        dhcp_interface=dhcp_interface,
         next_hop=next_hop,
         vrf=vrf,
         vrf_opt=vrf_opt,
-        conf_iface=nexthop_config.get('interface'),
+        # For next-hop interface is mandatory
+        # For dhcp-interface it may be not given, then dhcp-interface is used
+        conf_iface=nexthop_config.get('interface', dhcp_interface),
         conf_metric=int(nexthop_config.get('metric')),
         port=port,
         port_opt=f'port {port}' if port else '',
@@ -245,10 +252,22 @@ RouteNamedTuple = namedtuple(
 
 def get_route_config(route, route_config, config_path, vrf):
     vrf_opt = f'vrf {vrf}' if vrf else ''
-    nexthops = tuple(
-        get_nexthop_config_vars(route, vrf, vrf_opt, nexthop_config, next_hop)
-        for next_hop, nexthop_config in route_config.get('next_hop').items()
-    )
+    nexthops = []
+    if route_config.get('next_hop'):
+        nexthops.extend(
+            get_nexthop_config_vars(route, vrf, vrf_opt, nexthop_config, next_hop, None)
+            for next_hop, nexthop_config in route_config.get('next_hop').items()
+        )
+    if route_config.get('dhcp_interface'):
+        nexthops.extend(
+            get_nexthop_config_vars(
+                route, vrf, vrf_opt, dhcp_nexthop_config, None, interface
+            )
+            for interface, dhcp_nexthop_config in route_config.get(
+                'dhcp_interface'
+            ).items()
+        )
+    nexthops = tuple(nexthops)
     return RouteNamedTuple(
         destination=route,
         vrf=vrf,
@@ -399,6 +418,55 @@ def update_configuration(last_modification_times, all_routes, config_dir):
     print_debug(f"All routes: {all_routes}")
 
 
+def process_dhcp_interface(nhc, nexthop_by_dhcp_nexthop):
+    """
+    Processes NextHopNamedTuple with dhcp_interface != None
+    Return NextHopNamedTuple with next_hop equal to DHCP gateway of nhc.
+        If there is no gateway for nhc, return None
+
+    Args:
+        nhc(NextHopNamedTuple): configuration with dhcp_interface
+        nexthop_by_dhcp_nexthop(dict): dict with previous returned values
+    """
+    cur_dhcpgw = get_dhcp_router(nhc.dhcp_interface)
+    if not cur_dhcpgw:
+        cur_dhcpgw = False
+
+    if nhc in nexthop_by_dhcp_nexthop:
+        prev_dhcpgw = nexthop_by_dhcp_nexthop[nhc].next_hop
+    else:
+        prev_dhcpgw = False
+
+    # Equal - do nothing, just return previous value
+    if prev_dhcpgw == cur_dhcpgw:
+        if not cur_dhcpgw:
+            return None
+        return nexthop_by_dhcp_nexthop[nhc]
+
+    print_debug(
+        f"DHCP Gateway changed for interface {nhc.dhcp_interface} from '{prev_dhcpgw}' to '{cur_dhcpgw}'"
+    )
+
+    # dhcpgw differ and there was previous dhcpgw
+    if prev_dhcpgw:
+        prevnhc = nexthop_by_dhcp_nexthop.pop(nhc)
+        print_debug(
+            f"Deleting previous nexthop {prevnhc} because of DHCP interface change"
+        )
+        ip_args = get_ip_command_args(prevnhc)
+        if is_route_exists(ip_args):
+            delete_route(ip_args)
+
+    newnhc = None
+    # dhcpgw differ and there is new dhcpgw
+    if cur_dhcpgw:
+        newnhc = nhc._replace(next_hop=cur_dhcpgw, dhcp_interface=None)
+        print_debug(f"Saving new nexthop {newnhc} because of DHCP interface change")
+        nexthop_by_dhcp_nexthop[nhc] = newnhc
+
+    return newnhc
+
+
 if __name__ == '__main__':
     print_debug(f"{my_name} started")
 
@@ -426,6 +494,11 @@ if __name__ == '__main__':
     signal.signal(signal.SIGINT, kill_handler)
     signal.signal(signal.SIGTERM, kill_handler)
 
+    # keys: NextHopNamedTuple with dhcp_interface != None
+    # values: NextHopNamedTuple with next_hop != None
+    # Translates nexthop with dhcp_interface to ususal nexthop
+    nexthop_by_dhcp_nexthop = {}
+
     had_sleeps = True
     while not kill_called:
         # Check in case daemon was launched without routes
@@ -443,6 +516,11 @@ if __name__ == '__main__':
             vrf_opt = route_config.vrf_opt
 
             for nhc in route_config.nexthops:
+                if nhc.dhcp_interface:
+                    nhc = process_dhcp_interface(nhc, nexthop_by_dhcp_nexthop)
+                    if not nhc:
+                        continue
+
                 next_hop = nhc.next_hop
                 ip_args = get_ip_command_args(nhc)
 
@@ -478,7 +556,7 @@ if __name__ == '__main__':
                             f'    [ TARGET_FAIL ] target checks fails for [{nhc.pretty_targets}], do nothing'
                         )
                         journal.send(
-                            f'Check fail for route {route} target {nhc.pretty_targets} proto {nhc.proto} '
+                            f'Check fail for route {route} interface "{nhc.conf_iface}" target {nhc.pretty_targets} proto {nhc.proto} '
                             f'{nhc.port_opt}',
                             SYSLOG_IDENTIFIER=my_name,
                         )