Load nf_conntrack at boot time

Sysctl rules fined in charm config fails to be
applied in ovn enviroments because the rules are
applied before nf_conntrack is loaded.

By adding nf_conntrack to the /etc/modules file
it guarantees that it will be loaded before the
rules are applied.

Closes-Bug: #1922778
Change-Id: I51dae65cdc06e35230160bcaedda99710a72617d

hooks/nova_compute_hooks.py

@@ -24,9 +24,12 @@ import os
 import subprocess
 import grp
 import shutil
+import yaml
 
 import charmhelpers.core.unitdata as unitdata
 
+from charmhelpers.core.kernel import modprobe
+
 from charmhelpers.core.hookenv import (
     Hooks,
     config,
@@ -250,6 +253,7 @@ def config_changed():
             send_remote_restart = True
 
     sysctl_settings = config('sysctl')
+    ensure_nf_conntrack_module_loaded(sysctl_settings)
     if sysctl_settings and not is_container():
         create_sysctl(
             sysctl_settings,
@@ -330,6 +334,27 @@ def config_changed():
     check_and_start_iscsid()
 
 
+def ensure_nf_conntrack_module_loaded(sysctl_str):
+    """Loads and writes nf_conntrack to /etc/modules if present in sysctls."""
+    # abort if empty or container
+    if not sysctl_str or is_container():
+        return
+
+    try:
+        sysctl_dict = yaml.safe_load(sysctl_str)
+    except yaml.YAMLError:
+        log("Error parsing YAML sysctl_dict: {}".format(sysctl_str),
+            level=ERROR)
+        return
+
+    if any("nf_conntrack" in key for key in sysctl_dict.keys()):
+        try:
+            modprobe("nf_conntrack")
+        except Exception as e:
+            log("Failed to load or persist nf_conntrack"
+                " kernel module: {}".format(e), level=WARNING)
+
+
 def update_all_configs():
 
     CONFIGS.write_all()

unit_tests/test_nova_compute_hooks.py

@@ -453,6 +453,89 @@ class NovaComputeRelationsTests(CharmTestCase):
             user='nova'
         )
 
+    @patch.object(hooks, 'is_container')
+    @patch('yaml.safe_load')
+    def test_ensure_nf_conntrack_module_loaded_empty(
+            self, safe_load, is_container):
+        is_container.return_value = False
+        hooks.ensure_nf_conntrack_module_loaded("")
+        safe_load.assert_not_called()
+
+    @patch.object(hooks, 'is_container')
+    @patch('yaml.safe_load')
+    def test_ensure_nf_conntrack_module_loaded_container(
+            self, safe_load, is_container):
+        is_container.return_value = True
+        hooks.ensure_nf_conntrack_module_loaded("foo")
+        safe_load.assert_not_called()
+
+    @patch.object(hooks, 'modprobe')
+    @patch.object(hooks, 'is_container')
+    @patch('yaml.safe_load')
+    def test_ensure_nf_conntrack_module_loaded_failed_yaml(
+            self, safe_load, is_container, modprobe):
+        is_container.return_value = False
+        hooks.ensure_nf_conntrack_module_loaded("foo")
+        safe_load.assert_called_once_with("foo")
+        modprobe.assert_not_called()
+
+    @patch.object(hooks, 'log')
+    @patch.object(hooks, 'modprobe')
+    @patch.object(hooks, 'is_container')
+    def test_ensure_nf_conntrack_module_loaded_failed_mobprobe(
+            self, is_container, modprobe, log):
+        is_container.return_value = False
+        modprobe.side_effect = Exception("FOO")
+        data = ("{ net.ipv4.neigh.default.gc_thresh1 : 128,"
+                "net.ipv4.neigh.default.gc_thresh2 : 28672,"
+                "net.ipv4.neigh.default.gc_thresh3 : 32768,"
+                "net.ipv6.neigh.default.gc_thresh1 : 128,"
+                "net.ipv6.neigh.default.gc_thresh2 : 28672,"
+                "net.ipv6.neigh.default.gc_thresh3 : 32768,"
+                "net.nf_conntrack_max : 1000000,"
+                "net.netfilter.nf_conntrack_buckets : 204800,"
+                "net.netfilter.nf_conntrack_max : 1000000 }")
+        hooks.ensure_nf_conntrack_module_loaded(data)
+        log.assert_called_once_with(
+            "Failed to load or persist nf_conntrack kernel module: FOO",
+            level="WARNING")
+        modprobe.assert_called_once_with("nf_conntrack")
+
+    @patch.object(hooks, 'log')
+    @patch.object(hooks, 'modprobe')
+    @patch.object(hooks, 'is_container')
+    def test_ensure_nf_conntrack_module_loaded(
+            self, is_container, modprobe, log):
+        is_container.return_value = False
+        data = ("{ net.ipv4.neigh.default.gc_thresh1 : 128,"
+                "net.ipv4.neigh.default.gc_thresh2 : 28672,"
+                "net.ipv4.neigh.default.gc_thresh3 : 32768,"
+                "net.ipv6.neigh.default.gc_thresh1 : 128,"
+                "net.ipv6.neigh.default.gc_thresh2 : 28672,"
+                "net.ipv6.neigh.default.gc_thresh3 : 32768,"
+                "net.nf_conntrack_max : 1000000,"
+                "net.netfilter.nf_conntrack_buckets : 204800,"
+                "net.netfilter.nf_conntrack_max : 1000000 }")
+        hooks.ensure_nf_conntrack_module_loaded(data)
+        log.assert_not_called()
+        modprobe.assert_called_once_with("nf_conntrack")
+
+    @patch.object(hooks, 'log')
+    @patch.object(hooks, 'modprobe')
+    @patch.object(hooks, 'is_container')
+    def test_ensure_nf_conntrack_module_loaded_no_sysctl(
+            self, is_container, modprobe, log):
+        is_container.return_value = False
+        data = ("{ net.ipv4.neigh.default.gc_thresh1 : 128,"
+                "net.ipv4.neigh.default.gc_thresh2 : 28672,"
+                "net.ipv4.neigh.default.gc_thresh3 : 32768,"
+                "net.ipv6.neigh.default.gc_thresh1 : 128,"
+                "net.ipv6.neigh.default.gc_thresh2 : 28672,"
+                "net.ipv6.neigh.default.gc_thresh3 : 32768 }")
+        hooks.ensure_nf_conntrack_module_loaded(data)
+        modprobe.assert_not_called()
+        log.assert_not_called()
+
     def test_amqp_joined(self):
         hooks.amqp_joined()
         self.relation_set.assert_called_with(