Repository: Azure/WALinuxAgent
Pull request #3127 (2024-05-10 22:18:27)

Reduce the frequency of firewall telemetry (#3124)
* Reduce the frequency of firewall telemetry

* python 2: timespan.total_seconds() does not exist

* fix unit test

---------

Co-authored-by: narrieta <narrieta>
(cherry picked from commit 5302651b6608d315f46085c19fbc3693e89724dc)



Patch:
diff --git a/azurelinuxagent/common/osutil/default.py b/azurelinuxagent/common/osutil/default.py
index 3b9c504e..0a0fd0e1 100644
--- a/azurelinuxagent/common/osutil/default.py
+++ b/azurelinuxagent/common/osutil/default.py
@@ -277,16 +277,16 @@ class DefaultOSUtil(object):
 
     def enable_firewall(self, dst_ip, uid):
         """
-        It checks if every iptable rule exists and add them if not present. It returns a tuple(enable firewall success status, update rules flag)
+        It checks if every iptable rule exists and add them if not present. It returns a tuple(enable firewall success status, missing rules array)
         enable firewall success status: Returns True if every firewall rule exists otherwise False
-        update rules flag: Returns True if rules are updated otherwise False
+        missing rules: array with names of the missing rules ("ACCEPT DNS", "ACCEPT", "DROP")
         """
-        # This is to send telemetry when iptable rules updated
-        is_firewall_rules_updated = False
         # If a previous attempt failed, do not retry
         global _enable_firewall  # pylint: disable=W0603
         if not _enable_firewall:
-            return False, is_firewall_rules_updated
+            return False, []
+
+        missing_rules = []
 
         try:
             wait = self.get_firewall_will_wait()
@@ -294,10 +294,10 @@ class DefaultOSUtil(object):
             # check every iptable rule and delete others if any rule is missing
             #   and append every iptable rule to the end of the chain.
             try:
-                if not AddFirewallRules.verify_iptables_rules_exist(wait, dst_ip, uid):
+                missing_rules.extend(AddFirewallRules.get_missing_iptables_rules(wait, dst_ip, uid))
+                if len(missing_rules) > 0:
                     self.remove_firewall(dst_ip, uid, wait)
                     AddFirewallRules.add_iptables_rules(wait, dst_ip, uid)
-                    is_firewall_rules_updated = True
             except CommandError as e:
                 if e.returncode == 2:
                     self.remove_firewall(dst_ip, uid, wait)
@@ -308,14 +308,14 @@ class DefaultOSUtil(object):
                 logger.warn(ustr(error))
                 raise
 
-            return True, is_firewall_rules_updated
+            return True, missing_rules
 
         except Exception as e:
             _enable_firewall = False
             logger.info("Unable to establish firewall -- "
                         "no further attempts will be made: "
                         "{0}".format(ustr(e)))
-            return False, is_firewall_rules_updated
+            return False, missing_rules
 
     def get_firewall_list(self, wait=None):
         try:
diff --git a/azurelinuxagent/common/utils/networkutil.py b/azurelinuxagent/common/utils/networkutil.py
index 160f1751..7f698014 100644
--- a/azurelinuxagent/common/utils/networkutil.py
+++ b/azurelinuxagent/common/utils/networkutil.py
@@ -217,14 +217,22 @@ class AddFirewallRules(object):
         return False
 
     @staticmethod
-    def verify_iptables_rules_exist(wait, dst_ip, uid):
+    def get_missing_iptables_rules(wait, dst_ip, uid):
+        missing = []
+
         check_cmd_tcp_rule = AddFirewallRules.get_accept_tcp_rule(AddFirewallRules.CHECK_COMMAND, dst_ip, wait=wait)
-        check_cmd_accept_rule = AddFirewallRules.get_wire_root_accept_rule(AddFirewallRules.CHECK_COMMAND, dst_ip, uid,
-                                                                           wait=wait)
+        if not AddFirewallRules.__execute_check_command(check_cmd_tcp_rule):
+            missing.append("ACCEPT DNS")
+
+        check_cmd_accept_rule = AddFirewallRules.get_wire_root_accept_rule(AddFirewallRules.CHECK_COMMAND, dst_ip, uid, wait=wait)
+        if not AddFirewallRules.__execute_check_command(check_cmd_accept_rule):
+            missing.append("ACCEPT")
+
         check_cmd_drop_rule = AddFirewallRules.get_wire_non_root_drop_rule(AddFirewallRules.CHECK_COMMAND, dst_ip, wait=wait)
+        if not AddFirewallRules.__execute_check_command(check_cmd_drop_rule):
+            missing.append("DROP")
 
-        return AddFirewallRules.__execute_check_command(check_cmd_tcp_rule) and AddFirewallRules.__execute_check_command(check_cmd_accept_rule) \
-               and AddFirewallRules.__execute_check_command(check_cmd_drop_rule)
+        return missing
 
     @staticmethod
     def __execute_firewall_commands(dst_ip, uid, command=APPEND_COMMAND, firewalld_command="", wait=""):
diff --git a/azurelinuxagent/ga/env.py b/azurelinuxagent/ga/env.py
index f03bdb20..3d5887e6 100644
--- a/azurelinuxagent/ga/env.py
+++ b/azurelinuxagent/ga/env.py
@@ -16,7 +16,7 @@
 #
 # Requires Python 2.6+ and Openssl 1.0+
 #
-
+import datetime
 import re
 import os
 import socket
@@ -105,6 +105,9 @@ class EnableFirewall(PeriodicOperation):
         self._protocol = protocol
         self._try_remove_legacy_firewall_rule = False
         self._is_first_setup = True
+        self._reset_count = 0
+        self._report_after = datetime.datetime.min
+        self._report_period = None  # None indicates "report immediately"
 
     def _operation(self):
         # If the rules ever change we must reset all rules and start over again.
@@ -118,19 +121,32 @@ class EnableFirewall(PeriodicOperation):
             self._osutil.remove_legacy_firewall_rule(dst_ip=self._protocol.get_endpoint())
             self._try_remove_legacy_firewall_rule = True
 
-        firewall_state = self._get_firewall_state()
-
-        success, is_firewall_rules_updated = self._osutil.enable_firewall(dst_ip=self._protocol.get_endpoint(), uid=os.getuid())
+        success, missing_firewall_rules = self._osutil.enable_firewall(dst_ip=self._protocol.get_endpoint(), uid=os.getuid())
 
-        if is_firewall_rules_updated:
+        if len(missing_firewall_rules) > 0:
             if self._is_first_setup:
-                msg = "Created Azure fabric firewall rules:\n{0}".format(self._get_firewall_state())
+                msg = "Created firewall rules for the Azure Fabric:\n{0}".format(self._get_firewall_state())
                 logger.info(msg)
                 add_event(op=WALAEventOperation.Firewall, message=msg)
             else:
-                msg = "Reset Azure fabric firewall rules.\nInitial state:\n{0}\nCurrent state:\n{1}".format(firewall_state, self._get_firewall_state())
-                logger.info(msg)
-                add_event(op=WALAEventOperation.ResetFirewall, message=msg)
+                self._reset_count += 1
+                # We report immediately (when period is None) the first 5 instances, then we switch the period to every few hours
+                if self._report_period is None:
+                    msg = "Some firewall rules were missing: {0}. Re-created all the rules:\n{1}".format(missing_firewall_rules, self._get_firewall_state())
+                    if self._reset_count >= 5:
+                        self._report_period = datetime.timedelta(hours=3)
+                        self._reset_count = 0
+                        self._report_after = datetime.datetime.now() + self._report_period
+                elif datetime.datetime.now() >= self._report_after:
+                    msg = "Some firewall rules were missing: {0}. This has happened {1} time(s) since the last report. Re-created all the rules:\n{2}".format(
+                        missing_firewall_rules, self._reset_count, self._get_firewall_state())
+                    self._reset_count = 0
+                    self._report_after = datetime.datetime.now() + self._report_period
+                else:
+                    msg = ""
+                if msg != "":
+                    logger.info(msg)
+                    add_event(op=WALAEventOperation.ResetFirewall, message=msg)
 
         add_periodic(
             logger.EVERY_HOUR,


Test patch:
diff --git a/tests/common/osutil/test_default.py b/tests/common/osutil/test_default.py
index 0814d112..7cb5501c 100644
--- a/tests/common/osutil/test_default.py
+++ b/tests/common/osutil/test_default.py
@@ -822,13 +822,13 @@ Match host 192.168.1.2\n\
                 success, _ = osutil.DefaultOSUtil().enable_firewall(dst_ip=mock_iptables.destination, uid=mock_iptables.uid)
 
                 self.assertTrue(success, "Enabling the firewall was not successful")
-                # Exactly 8 calls have to be made.
-                # First check rule, delete 4 rules,
+                # Exactly 10 calls have to be made.
+                # First check 3 rules, delete 4 rules,
                 # and Append the IPTable 3 rules.
-                self.assertEqual(len(mock_iptables.command_calls), 8,
+                self.assertEqual(len(mock_iptables.command_calls), 10,
                                  "Incorrect number of calls to iptables: [{0}]".format(mock_iptables.command_calls))
                 for command in mock_iptables.command_calls:
-                    self.assertNotIn("-w", command, "The -w option should have been used in {0}".format(command))
+                    self.assertNotIn("-w", command, "The -w option sh       ould have been used in {0}".format(command))
 
                 self.assertTrue(osutil._enable_firewall, "The firewall should not have been disabled")