policy: T2199: Migrate policy route to XML/Python

1 files changed, 154 insertions, 0 deletions

diff --git a/src/conf_mode/policy-route.py b/src/conf_mode/policy-route.py
new file mode 100755
index 000000000..d098be68d
--- /dev/null
+++ b/src/conf_mode/policy-route.py
@@ -0,0 +1,154 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2021 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+
+from json import loads
+from sys import exit
+
+from vyos.config import Config
+from vyos.template import render
+from vyos.util import cmd
+from vyos.util import dict_search_args
+from vyos.util import run
+from vyos import ConfigError
+from vyos import airbag
+airbag.enable()
+
+mark_offset = 0x7FFFFFFF
+nftables_conf = '/run/nftables_policy.conf'
+
+def get_config(config=None):
+    if config:
+        conf = config
+    else:
+        conf = Config()
+    base = ['policy']
+
+    if not conf.exists(base + ['route']) and not conf.exists(base + ['ipv6-route']):
+        return None
+
+    policy = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True,
+                                    no_tag_node_value_mangle=True)
+
+    return policy
+
+def verify(policy):
+    # bail out early - looks like removal from running config
+    if not policy:
+        return None
+
+    for route in ['route', 'ipv6_route']:
+        if route in policy:
+            for name, pol_conf in policy[route].items():
+                if 'rule' in pol_conf:
+                    for rule_id, rule_conf in pol_conf.items():
+                        icmp = 'icmp' if route == 'route' else 'icmpv6'
+                        if icmp in rule_conf:
+                            icmp_defined = False
+                            if 'type_name' in rule_conf[icmp]:
+                                icmp_defined = True
+                                if 'code' in rule_conf[icmp] or 'type' in rule_conf[icmp]:
+                                    raise ConfigError(f'{name} rule {rule_id}: Cannot use ICMP type/code with ICMP type-name')
+                            if 'code' in rule_conf[icmp]:
+                                icmp_defined = True
+                                if 'type' not in rule_conf[icmp]:
+                                    raise ConfigError(f'{name} rule {rule_id}: ICMP code can only be defined if ICMP type is defined')
+                            if 'type' in rule_conf[icmp]:
+                                icmp_defined = True
+
+                            if icmp_defined and 'protocol' not in rule_conf or rule_conf['protocol'] != icmp:
+                                raise ConfigError(f'{name} rule {rule_id}: ICMP type/code or type-name can only be defined if protocol is ICMP')
+                        if 'set' in rule_conf:
+                            if 'tcp_mss' in rule_conf['set']:
+                                tcp_flags = dict_search_args(rule_conf, 'tcp', 'flags')
+                                if not tcp_flags or 'SYN' not in tcp_flags.split(","):
+                                    raise ConfigError(f'{name} rule {rule_id}: TCP SYN flag must be set to modify TCP-MSS')
+                        if 'tcp' in rule_conf:
+                            if 'flags' in rule_conf['tcp']:
+                                if 'protocol' not in rule_conf or rule_conf['protocol'] != 'tcp':
+                                    raise ConfigError(f'{name} rule {rule_id}: TCP flags can only be set if protocol is set to TCP')
+
+
+    return None
+
+def generate(policy):
+    if not policy:
+        if os.path.exists(nftables_conf):
+            os.unlink(nftables_conf)
+        return None
+
+    if not os.path.exists(nftables_conf):
+        policy['first_install'] = True
+
+    render(nftables_conf, 'firewall/nftables-policy.tmpl', policy)
+    return None
+
+def apply_table_marks(policy):
+    for route in ['route', 'ipv6_route']:
+        if route in policy:
+            for name, pol_conf in policy[route].items():
+                if 'rule' in pol_conf:
+                    for rule_id, rule_conf in pol_conf['rule'].items():
+                        set_table = dict_search_args(rule_conf, 'set', 'table')
+                        if set_table:
+                            if set_table == 'main':
+                                set_table = '254'
+                            table_mark = mark_offset - int(set_table)
+                            cmd(f'ip rule add fwmark {table_mark} table {set_table}')
+
+def cleanup_table_marks():
+    json_rules = cmd('ip -j -N rule list')
+    rules = loads(json_rules)
+    for rule in rules:
+        if 'fwmark' not in rule or 'table' not in rule:
+            continue
+        fwmark = rule['fwmark']
+        table = int(rule['table'])
+        if fwmark[:2] == '0x':
+            fwmark = int(fwmark, 16)
+        if (int(fwmark) == (mark_offset - table)):
+            cmd(f'ip rule del fwmark {fwmark} table {table}')
+
+def apply(policy):
+    if not policy or 'first_install' not in policy:
+        run(f'nft flush table ip mangle')
+        run(f'nft flush table ip6 mangle')
+
+    if not policy:
+        cleanup_table_marks()
+        return None
+
+    install_result = run(f'nft -f {nftables_conf}')
+    if install_result == 1:
+        raise ConfigError('Failed to apply policy based routing')
+
+    if 'first_install' not in policy:
+        cleanup_table_marks()
+
+    apply_table_marks(policy)
+
+    return None
+
+if __name__ == '__main__':
+    try:
+        c = get_config()
+        verify(c)
+        generate(c)
+        apply(c)
+    except ConfigError as e:
+        print(e)
+        exit(1)