From 057be82cc48c3ccc256270caed4d46e66d822a24 Mon Sep 17 00:00:00 2001
From: Alex Kudentsov <43482574+alexk37@users.noreply.github.com>
Date: Wed, 7 Oct 2026 02:25:50 +0700
Subject: bgp: T9407: do not render "bgp reject-as-sets" when it is the FRR
 default

Since FRR 10.5 "bgp reject-as-sets" is the default. FRR does not print
the default in show running-config, so frr-reload never finds the line in
the running config and sends it again on every reload. The command
handler resets every BGP session of the instance (NOTIFICATION Cease,
other configuration change) whether or not the value changed,
so with "protocols bgp parameters reject-as-sets" set, every commit that
reloads FRR reset every established session, not only commits that touch
BGP.

Render only the non-default form: "no bgp reject-as-sets" when the
option is not set, as T7664 added it, and nothing when it is set. The
option is a valueless leaf, so it has no XML default to read; the
rendered "no" form already was the only place that knows what FRR's
default is. Changing the option still reaches FRR: frr-reload sends
"bgp reject-as-sets" when the option is set (the "no" line leaves the
rendered config) and "no bgp reject-as-sets" when it is deleted, and
each change resets the sessions once, as before.

Add a smoketest that reads the rendered /run/frr/config/vyos.frr.conf,
because FRR never prints the default form and vtysh cannot show it.
---
 data/templates/frr/bgpd.frr.j2 | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'data')

diff --git a/data/templates/frr/bgpd.frr.j2 b/data/templates/frr/bgpd.frr.j2
index 7671576d1..f84f10126 100644
--- a/data/templates/frr/bgpd.frr.j2
+++ b/data/templates/frr/bgpd.frr.j2
@@ -673,9 +673,11 @@ router bgp {{ system_as }} {{ 'vrf ' ~ vrf if vrf is vyos_defined }} {{ 'as-nota
 {% if parameters.no_suppress_duplicates is vyos_defined %}
  no bgp suppress-duplicates
 {% endif %}
-{% if parameters.reject_as_sets is vyos_defined %}
- bgp reject-as-sets
-{% else %}
+{# FRR 10.5+ defaults to "bgp reject-as-sets" and does not print the default
+   in show running-config. frr-reload would find the line missing on every
+   reload and send it again, and FRR resets every peer for each application.
+   Only the non-default form is rendered. #}
+{% if parameters.reject_as_sets is not vyos_defined %}
  no bgp reject-as-sets
 {% endif %}
 {% if parameters.router_id is vyos_defined and parameters.router_id is not none %}
-- 
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