dhcp: T2562: add "listen-address" CLI node for better DHCP relay support

Running ISC DHCP server as backend server for multiple pools served to relay
agents requires DHCPd to explicitly listen on give interfaces or a "transit"
subnet declaration facing the network where we receive the DHCPREQ messages on.

This implements a new "listen-address" CLI node, the given address is validated
if it is assigned to the system and upon success, a proper "subnet { }" statement
is added into dhcpd.conf

1 files changed, 8 insertions, 0 deletions

diff --git a/data/templates/dhcp-server/dhcpd.conf.tmpl b/data/templates/dhcp-server/dhcpd.conf.tmpl
index bcf425abd..56a5f4bcd 100644
--- a/data/templates/dhcp-server/dhcpd.conf.tmpl
+++ b/data/templates/dhcp-server/dhcpd.conf.tmpl
@@ -62,6 +62,14 @@ failover peer "{{ subnet_config.failover.name }}" {
 {%     endif %}
 {%   endfor %}
 {% endif %}
+{% if listen_address is defined and listen_address is not none %}
+
+# DHCP server serving relay subnet, we need a connector to the real world
+{%   for address in listen_address %}
+# Connected subnet statement for listen-address {{ address }}
+subnet {{ address | network_from_ipv4 }} netmask {{ address | netmask_from_ipv4 }} { }
+{%   endfor %}
+{% endif %}
 
 # Shared network configration(s)
 {% if shared_network_name is defined and shared_network_name is not none %}