VRF: T3655: proper connection tracking for VRFs

Currently, all VRFs share the same connection tracking table, which can
lead to problems:

- traffic leaks to a wrong VRF
- improper NAT rules handling when multiple VRFs contain the same IP
networks
- stateful firewall rules issues

The commit implements connection tracking zones support. Each VRF
utilizes its own zone, so connections will never mix up.

It also adds some restrictions to VRF names and assigned table numbers,
because of nftables and conntrack requirements:

- VRF name should always start from a letter (interfaces that start from
numbers are not supported in nftables rules)
- table number must be in the 100-65535 range because conntrack supports
only 65535 zones

1 files changed, 24 insertions, 0 deletions

diff --git a/src/conf_mode/vrf.py b/src/conf_mode/vrf.py
index 936561edc..fbfce646f 100755
--- a/src/conf_mode/vrf.py
+++ b/src/conf_mode/vrf.py
@@ -18,6 +18,7 @@ import os
 
 from sys import exit
 from json import loads
+from tempfile import NamedTemporaryFile
 
 from vyos.config import Config
 from vyos.configdict import node_changed
@@ -26,6 +27,7 @@ from vyos.template import render
 from vyos.template import render_to_string
 from vyos.util import call
 from vyos.util import cmd
+from vyos.util import popen
 from vyos.util import dict_search
 from vyos.util import get_interface_config
 from vyos import ConfigError
@@ -125,11 +127,17 @@ def verify(vrf):
 
     return None
 
+
 def generate(vrf):
     render(config_file, 'vrf/vrf.conf.tmpl', vrf)
     vrf['new_frr_config'] = render_to_string('frr/vrf.frr.tmpl', vrf)
+    # Render nftables zones config
+    vrf['nft_vrf_zones'] = NamedTemporaryFile().name
+    render(vrf['nft_vrf_zones'], 'firewall/nftables-vrf-zones.tmpl', vrf)
+
     return None
 
+
 def apply(vrf):
     # Documentation
     #
@@ -151,8 +159,19 @@ def apply(vrf):
             call(f'ip -4 route del vrf {tmp} unreachable default metric 4278198272')
             call(f'ip -6 route del vrf {tmp} unreachable default metric 4278198272')
             call(f'ip link delete dev {tmp}')
+            # Remove nftables conntrack zone map item
+            nft_del_element = f'delete element inet vrf_zones ct_iface_map {{ "{tmp}" }}'
+            cmd(f'nft {nft_del_element}')
 
     if 'name' in vrf:
+        # Separate VRFs in conntrack table
+        # check if table already exists
+        _, err = popen('nft list table inet vrf_zones')
+        # If not, create a table
+        if err:
+            cmd(f'nft -f {vrf["nft_vrf_zones"]}')
+            os.unlink(vrf['nft_vrf_zones'])
+
         for name, config in vrf['name'].items():
             table = config['table']
 
@@ -182,6 +201,9 @@ def apply(vrf):
             # reconfiguration.
             state = 'down' if 'disable' in config else 'up'
             vrf_if.set_admin_state(state)
+            # Add nftables conntrack zone map item
+            nft_add_element = f'add element inet vrf_zones ct_iface_map {{ "{name}" : {table} }}'
+            cmd(f'nft {nft_add_element}')
 
     # Linux routing uses rules to find tables - routing targets are then
     # looked up in those tables. If the lookup got a matching route, the
@@ -214,6 +236,8 @@ def apply(vrf):
             # clean out l3mdev-table rule if present
             if 1000 in [r.get('priority') for r in list_rules() if r.get('priority') == 1000]:
                 call(f'ip {af} rule del pref 1000')
+        # Remove VRF zones table from nftables
+        cmd('nft delete table inet vrf_zones')
 
     # add configuration to FRR
     frr_cfg = frr.FRRConfig()