common: ipv6_accept_ra_interfaces sets accept_ra=2 on bridges that sysctl at boot does not see

common/defaults/main.yml

@@ -1,5 +1,9 @@
 ipv6_stable_secret_seed: "@JW7rQ^P3*f^KRkX3744DZQJb3DfMgZJJMtGc!Jmy!ECBqb^QzAMYLHD8dLvf8m%2bRSRFhgY#SXzAgnxWTvHv#ti6b5PngR^k2gHbQW*%dJ9sdeKM$H77Gymh&xamNN"
 
+# Bridges and other interfaces that appear after sysctl runs at boot and so miss the accept_ra=2 of
+# "all"; without it a forwarding host ignores the router advertisements on them.
+ipv6_accept_ra_interfaces: []
+
 # Times of the heavy disk jobs, for hosts on a shared HDD pool that keep them out of the backup window.
 disk_maintenance:
   # systemd OnCalendar for fstrim.timer; unset keeps the distribution schedule.

common/tasks/networking.yml

@@ -46,7 +46,11 @@
     dest: "/etc/sysctl.d/ipv6-slaac-override.conf"
     content: |
       net.ipv6.conf.all.accept_ra = 2
+      {% for iface in ipv6_accept_ra_interfaces %}
+      net.ipv6.conf.{{ iface }}.accept_ra = 2
+      {% endfor %}
   notify: reload_sysctl
+  tags: ipv6_accept_ra
 
 - name: Set sysctl settings for TCP BBR 
   copy: