From 4e11adfb927c22e2f977c897d56a4d243860e877 Mon Sep 17 00:00:00 2001
From: Oleksandr Kuchmystyi <o.kuchmystyi@vyos.io>
Date: Fri, 26 Jun 2026 10:23:54 +0300
Subject: bgp: T8865: Reject `vni` sub-block in VRF l2vpn-evpn when
 `advertise-all-vni` is globally active

When `advertise-all-vni` is configured in the global/default BGP instance,
VyOS generated a `vni <id>` sub-block under each VRF BGP `address-family
l2vpn evpn` context. This conflicts with advertise-all-vni: FRR already
owns all kernel VNIs and returns `% Failed to create VNI` when frr-reload.py
attempts to apply the VRF-level vni sub-block. FRR then performs an early
exit from config processing, silently dropping the entire l2vpn evpn
address-family for all subsequent VRF BGP instances.
---
 src/conf_mode/protocols_bgp.py   | 23 ++++++++++++++++++++
 src/migration-scripts/bgp/7-to-8 | 45 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 src/migration-scripts/bgp/7-to-8

(limited to 'src')

diff --git a/src/conf_mode/protocols_bgp.py b/src/conf_mode/protocols_bgp.py
index 2ec631f4c..bde6fcdd0 100755
--- a/src/conf_mode/protocols_bgp.py
+++ b/src/conf_mode/protocols_bgp.py
@@ -647,6 +647,29 @@ def verify(config_dict):
                         if 'route_target' in vni_config and 'advertise_all_vni' not in afi_config:
                             raise ConfigError('BGP EVPN "route-target" requires "advertise-all-vni" to be set!')
 
+                # T8865: Detect conflict between VRF-level "vni" sub-block and global
+                # "advertise-all-vni". When advertise-all-vni is active in the default
+                # BGP instance, FRR already owns all VNIs discovered from the kernel.
+                # Attempting to create the same VNI again via a VRF BGP "vni" sub-block
+                # causes FRR to return "% Failed to create VNI" and perform an early exit
+                # from config processing.
+                if vrf and 'vni' in afi_config:
+                    default_bgp_evpn = dict_search(
+                        'dependent_vrfs.default.protocols.bgp.address_family.l2vpn_evpn',
+                        bgp,
+                    )
+                    if (
+                        default_bgp_evpn is not None
+                        and 'deleted' not in default_bgp_evpn
+                    ):
+                        if 'advertise_all_vni' in default_bgp_evpn:
+                            raise ConfigError(
+                                'BGP EVPN "vni" sub-configuration conflicts with '
+                                '"advertise-all-vni" in the default BGP instance. '
+                                'Remove "vni" from the VRF l2vpn-evpn configuration '
+                                'or disable "advertise-all-vni" for the default BGP.'
+                            )
+
     return None
 
 def generate(config_dict):
diff --git a/src/migration-scripts/bgp/7-to-8 b/src/migration-scripts/bgp/7-to-8
new file mode 100644
index 000000000..4db4b3211
--- /dev/null
+++ b/src/migration-scripts/bgp/7-to-8
@@ -0,0 +1,45 @@
+# Copyright (C) VyOS Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+# T8865: When "address-family l2vpn-evpn advertise-all-vni" is
+# configured remove the conflicting "vni" sub-node from each affected VRF
+# because FRR returns "Failed to create VNI".
+
+from vyos.configtree import ConfigTree
+
+vrf_base = ['vrf', 'name']
+bgp_base = ['protocols', 'bgp']
+bgp_l2vpn_evpn = bgp_base + ['address-family', 'l2vpn-evpn']
+
+
+def migrate(config: ConfigTree) -> None:
+    if not config.exists(vrf_base):
+        return  # Nothing to do
+
+    # Only act when advertise-all-vni is set in the default BGP instance
+    if not config.exists(bgp_l2vpn_evpn + ['advertise-all-vni']):
+        return
+
+    for vrf in config.list_nodes(vrf_base):
+        vni_path = vrf_base + [
+            vrf,
+            'protocols',
+            'bgp',
+            'address-family',
+            'l2vpn-evpn',
+            'vni',
+        ]
+        if config.exists(vni_path):
+            config.delete(vni_path)
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