dhcpv6-pd: T2677: optimize CLI interface for PD configuration

The current CLI did not support multiple prefix-delegations per interface. Some
ISPs only send one /64 to a client per prefix-delegation request, but they
allow the customer to request multiple prefixes.

The 'dhcpv6-options prefix-delegation' node has been renamed and converted to a
tag node named 'dhcpv6-options pd'. The tag node specifies a PD request (>=0).

In the past the user needed to know what prefix will be assigned and required
to calculate the sla-len by himself. The 'sla-len' node was dropped and is now
calculated in the background from the 'dhcpv6-options pd 0 length' node.

It is no longer mandatory to supply the 'sla-id' node, if sla-id is not
specified it is 'guessed' by counting upwards.

Example configuration:
----------------------

  ethernet eth1 {
       address dhcpv6
       dhcpv6-options {
           pd 0 {
               length 56
               interface eth2 {
                   address 1
               }
           }
       }
   }

This will request a /56 assignment from the ISP and will delegate a /64 network
to interface eth2. VyOS will use the interface address ::1 on the delegate
interface (eth2) as its local address.

1 files changed, 1 insertions, 1 deletions

diff --git a/interface-definitions/include/dhcp-options.xml.i b/interface-definitions/include/dhcp-options.xml.i
index 0f71d9321..9989291fc 100644
--- a/interface-definitions/include/dhcp-options.xml.i
+++ b/interface-definitions/include/dhcp-options.xml.i
@@ -1,6 +1,6 @@
 <node name="dhcp-options">
   <properties>
-    <help>DHCP options</help>
+    <help>DHCP client settings/options</help>
   </properties>
   <children>
     <leafNode name="client-id">