Merge ~blake-rouse/maas:fix-1788780-2.3 into maas:2.3

[Blake Rouse]

LP: #1788780 - Ignore tunnel interfaces (such as those created by hypervisors) when gathering interfaces for MAAS management.

Backport of 842646142d42d95453f4b64c209f93b09f8aea7c

[Blake Rouse (blake-rouse)]

Self-approving backport.

review: Approve

diff --git a/src/provisioningserver/utils/ipaddr.py b/src/provisioningserver/utils/ipaddr.py
index 4cf6cb2..966f4d2 100644
--- a/src/provisioningserver/utils/ipaddr.py
+++ b/src/provisioningserver/utils/ipaddr.py
@@ -272,6 +272,8 @@ def get_interface_type(
             return 'ethernet.bond'
         if os.path.isfile(os.path.join(proc_net, "vlan", ifname)):
             return 'ethernet.vlan'
+        if os.path.isfile(os.path.join(sys_path, 'tun_flags')):
+            return 'ethernet.tunnel'
         device_path = os.path.join(sys_path, 'device')
         if os.path.islink(device_path):
             device_80211 = os.path.join(sys_path, 'device', 'ieee80211')
diff --git a/src/provisioningserver/utils/network.py b/src/provisioningserver/utils/network.py
index 960d3eb..b9c74a1 100644
--- a/src/provisioningserver/utils/network.py
+++ b/src/provisioningserver/utils/network.py
@@ -1138,8 +1138,20 @@ def get_all_interfaces_definition(annotate_with_monitored: bool=True) -> dict:
     interfaces = {}
     dhclient_info = get_dhclient_info()
     iproute_info = get_ip_route()
-    exclude_types = ["loopback", "ipip"]
+    exclude_types = [
+        # It doesn't make sense for MAAS to manage loopback interfaces.
+        "loopback",
+        # IPv4-in-IPv4 tunnels aren't useful for MAAS to manage.
+        "ipip",
+        # This type of interface is created when hypervisors create virtual
+        # interfaces for guests. By themselves, they're not useful for MAAS to
+        # manage.
+        "ethernet.tunnel",
+    ]
     if not running_in_container():
+        # When not running in a container, we should be able to identify
+        # any Ethernet-variant interfaces that are specific enough to be used
+        # with MAAS. So we can throw away any that can't be classified.
         exclude_types.append("ethernet")
     ipaddr_info = {
         name: ipaddr
diff --git a/src/provisioningserver/utils/tests/test_ipaddr.py b/src/provisioningserver/utils/tests/test_ipaddr.py
index 8210e52..d4206f9 100644
--- a/src/provisioningserver/utils/tests/test_ipaddr.py
+++ b/src/provisioningserver/utils/tests/test_ipaddr.py
@@ -365,7 +365,7 @@ class FakeSysProcTestCase(MAASTestCase):
     def createInterfaceType(
             self, ifname, iftype, is_bridge=False, is_vlan=False,
             is_bond=False, is_wireless=False, is_physical=False,
-            bonded_interfaces=None):
+            is_tunnel=False, bonded_interfaces=None):
         ifdir = os.path.join(self.tmp_sys_net, ifname)
         os.mkdir(ifdir)
         type_file = os.path.join(ifdir, 'type')
@@ -373,6 +373,9 @@ class FakeSysProcTestCase(MAASTestCase):
             f.write("%d\n" % iftype)
         if is_bridge:
             os.mkdir(os.path.join(ifdir, 'bridge'))
+        if is_tunnel:
+            with open(os.path.join(ifdir, "tun_flags"), 'w'):
+                pass  # Just touch.
         if is_vlan:
             with open(os.path.join(self.tmp_proc_net, "vlan", ifname), 'w'):
                 pass  # Just touch.
@@ -415,6 +418,14 @@ class TestGetInterfaceType(FakeSysProcTestCase):
             Equals('ethernet.bridge')
         )
 
+    def test__identifies_tunnel_interface(self):
+        self.createEthernetInterface('vnet0', is_tunnel=True)
+        self.assertThat(get_interface_type(
+            'vnet0', sys_class_net=self.tmp_sys_net,
+            proc_net=self.tmp_proc_net),
+            Equals('ethernet.tunnel')
+        )
+
     def test__identifies_bond_interface(self):
         self.createEthernetInterface('bond0', is_bond=True)
         self.assertThat(get_interface_type(
diff --git a/src/provisioningserver/utils/tests/test_network.py b/src/provisioningserver/utils/tests/test_network.py
index 0b08390..5b30cd4 100644
--- a/src/provisioningserver/utils/tests/test_network.py
+++ b/src/provisioningserver/utils/tests/test_network.py
@@ -1212,6 +1212,16 @@ class TestGetAllInterfacesDefinition(MAASTestCase):
         }
         self.assertInterfacesResult(ip_addr, {}, {}, MatchesDict({}))
 
+    def test__ignores_tunnel(self):
+        ip_addr = {
+            "vnet": {
+                "type": "ethernet.tunnel",
+                "flags": ["UP"],
+                "index": 2,
+            },
+        }
+        self.assertInterfacesResult(ip_addr, {}, {}, MatchesDict({}))
+
     def test__simple(self):
         ip_addr = {
             "eth0": {