T4550: router-advert: Add deprecate-prefix & decrement-lifetimes options

DeprecatePrefix and DecrementLifetimes options in radvd is useful in a DHCPv6-PD environment to accommodate prefix changes from ISP's delegating router. Though there is currently no integration between the DHCP PD client (wide-dhcpv6-client) and radvd, it could be a good start point to have the 2 options configurable by the user.

https://phabricator.vyos.net/T4550

- deprecate-prefix: Upon shutdown, deprecate the prefix. This is useful
  in a DHCPv6 PD environment: When ISP re-assigns a new prefix,
deprecate the old prefix that was advertised.
- decrement-lifetimes: Decrement the values of the preferred and valid
  lifetimes for the prefix over time. This is also useful in a DHCPv6
  PD environment to keep the advertised prefix's lifetimes in sync with
  the prefix from delegating router.

1 files changed, 2 insertions, 0 deletions

diff --git a/data/templates/router-advert/radvd.conf.j2 b/data/templates/router-advert/radvd.conf.j2
index ed15b32f0..a464795ad 100644
--- a/data/templates/router-advert/radvd.conf.j2
+++ b/data/templates/router-advert/radvd.conf.j2
@@ -50,6 +50,8 @@ interface {{ iface }} {
         AdvValidLifetime {{ prefix_options.valid_lifetime }};
         AdvOnLink {{ 'off' if prefix_options.no_on_link_flag is vyos_defined else 'on' }};
         AdvPreferredLifetime {{ prefix_options.preferred_lifetime }};
+        DeprecatePrefix {{ 'on' if prefix_options.deprecate_prefix is vyos_defined else 'off' }};
+        DecrementLifetimes {{ 'on' if prefix_options.decrement_lifetime is vyos_defined else 'off' }};
     };
 {%             endfor %}
 {%         endif %}