Add insert support to iptables. (#1180)

Add insert support to iptables.

system/iptables.py

@@ -56,6 +56,14 @@ options:
     required: false
     default: present
     choices: [ "present", "absent" ]
+  action:
+    version_added: "2.2"
+    description:
+      - Whether the rule should be appended at the bottom or inserted at the
+        top. If the rule already exists the chain won't be modified.
+    required: false
+    default: append
+    choices: [ "append", "insert" ]
   ip_version:
     description:
       - Which version of the IP protocol this rule should apply to.
@@ -372,6 +380,11 @@ def append_rule(iptables_path, module, params):
     module.run_command(cmd, check_rc=True)
 
 
+def insert_rule(iptables_path, module, params):
+    cmd = push_arguments(iptables_path, '-I', params)
+    module.run_command(cmd, check_rc=True)
+
+
 def remove_rule(iptables_path, module, params):
     cmd = push_arguments(iptables_path, '-D', params)
     module.run_command(cmd, check_rc=True)
@@ -383,6 +396,7 @@ def main():
         argument_spec=dict(
             table=dict(required=False, default='filter', choices=['filter', 'nat', 'mangle', 'raw', 'security']),
             state=dict(required=False, default='present', choices=['present', 'absent']),
+            action=dict(required=False, default='append', type='str', choices=['append', 'insert']),
             ip_version=dict(required=False, default='ipv4', choices=['ipv4', 'ipv6']),
             chain=dict(required=True, default=None, type='str'),
             protocol=dict(required=False, default=None, type='str'),
@@ -422,6 +436,7 @@ def main():
         rule=' '.join(construct_rule(module.params)),
         state=module.params['state'],
     )
+    insert = (module.params['action'] == 'insert')
     ip_version = module.params['ip_version']
     iptables_path = module.get_bin_path(BINS[ip_version], True)
     rule_is_present = check_present(iptables_path, module, module.params)
@@ -439,6 +454,9 @@ def main():
         module.exit_json(**args)
 
     if should_be_present:
+        if insert:
+            insert_rule(iptables_path, module, module.params)
+        else:
             append_rule(iptables_path, module, module.params)
     else:
         remove_rule(iptables_path, module, module.params)