salt/checks: Only check routing tables

In the previous commit, we introduce a validation of the full Service
CIDR by looking at all routes defined in the system routing tables
(obtained with `network.routes`).
This change makes the previous approach (using `network.get_route`,
similar to an `ip route get` invocation) unneeded, as we are already
comparing networks inclusion-wise.

Cherry-picked from: 1c347fc

salt/_modules/metalk8s_checks.py

@@ -212,37 +212,29 @@ def route_exists(destination, raises=True):
         raises (bool): the method will raise if there is no route for this
             destination.
     """
-    network = ipaddress.IPv4Network(destination)
-
+    dest_net = ipaddress.IPv4Network(destination)
     error = None
-    route_info = None
-    try:
-        route_info = __salt__["network.get_route"](network.network_address)
-    except Exception as exc:
-        # NOTE: if no route exists, this module may fail with an
-        # AttributeError. To be on the safe side, we catch any Exception.
-        error = "No route exists for {}".format(destination)
-
-    if route_info is not None:
-        # We found a route for the first network address in the provided
-        # `destination`. Let's verify that the whole network can be routed.
-        all_routes = __salt__["network.routes"](family="inet")
-
-        for route in all_routes:
-            if route["gateway"] == route_info["gateway"] \
-                    and route["interface"] == route_info["interface"]:
-                # The route matches the one we found, let's check if our
-                # destination is fully included in this route.
-                route_net = ipaddress.IPv4Network(
-                    "{r[destination]}/{r[netmask]}".format(r=route)
-                )
-                if _is_subnet_of(network, route_net):
-                    break
+    route_exists = False
+
+    all_routes = __salt__["network.routes"](family="inet")
+
+    for route in all_routes:
+        # Check if our destination network is fully included in this route.
+        route_net = ipaddress.IPv4Network(
+            "{r[destination]}/{r[netmask]}".format(r=route)
+        )
+        if _is_subnet_of(dest_net, route_net):
+            break
         else:
+            route_exists |= dest_net.network_address in route_net
+    else:
+        if route_exists:
             error = (
                 "A route was found for {n.network_address}, but it does not "
                 "match the full destination network {n.compressed}"
-            ).format(n=network)
+            ).format(n=dest_net)
+        else:
+            error = "No route exists for {}".format(dest_net.compressed)
 
     if error and raises:
         raise CheckError(error)

salt/tests/unit/modules/files/test_metalk8s_checks.yaml

@@ -310,36 +310,26 @@ route_exists:
   # 1. Success: Nominal (default route)
   - &route_exists_nominal
     destination: 10.96.0.0/12
-    get_route_ret:
-      gateway: &default_gw "10.10.0.1"
-      interface: &default_iface eth0
-      destination: 10.96.0.0/32
-      source: "10.10.1.2"
     routes_ret:
       - &default_route
         addr_family: inet
         destination: "0.0.0.0"
         flags: UG
-        gateway: *default_gw
-        interface: *default_iface
+        gateway: "10.10.0.1"
+        interface: eth0
         netmask: "0.0.0.0"
 
   # 2. Success: Nominal (dedicated dummy route)
   - <<: *route_exists_nominal
-    get_route_ret:
-      gateway: *default_gw
-      interface: dummy0
-      destination: 10.96.0.0/32
-      source: "10.10.1.2"
     routes_ret:
       - <<: *default_route
         interface: dummy0
         destination: "10.96.0.0"
         netmask: "255.240.0.0"
 
-  # 3. Error: Failure to get route
+  # 3. Error: No route exists
   - <<: *route_exists_nominal
-    get_route_ret: Some error when getting route
+    routes_ret: []
     error: No route exists for 10.96.0.0/12
 
   # 4. Error: Route found is too small

salt/tests/unit/modules/test_metalk8s_checks.py

@@ -162,22 +162,14 @@ def test_route_exists(
         self,
         destination,
         error=None,
-        get_route_ret=None,
         routes_ret=None,
     ):
         """
         Tests the return of `route_exists` function
         """
-        def _network_get_route(dest):
-            if isinstance(get_route_ret, dict):
-                return get_route_ret
-            raise AttributeError(get_route_ret)
-
-        network_get_route_mock = MagicMock(side_effect=_network_get_route)
         network_routes_mock = MagicMock(return_value=routes_ret)
 
         patch_dict = {
-            'network.get_route': network_get_route_mock,
             'network.routes': network_routes_mock,
         }