pppoe: dhcpv6-pd: T421: initial support

The following configuration will assign a /64 prefix out of a /56 delegation
to eth0. The IPv6 address assigned to eth0 will be <prefix>::ffff/64.
If you do not know the prefix size delegated to you, start with sla-len 0.

  pppoe pppoe0 {
      authentication {
          password vyos
          user vyos
      }
      description sadfas
      dhcpv6-options {
          delegate eth0 {
              interface-id 65535
              sla-id 0
              sla-len 8
          }
      }
      ipv6 {
          address {
              autoconf
          }
          enable
      }
      source-interface eth1
  }

  vyos@vyos:~$ show interfaces
  Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
  Interface        IP Address                        S/L  Description
  ---------        ----------                        ---  -----------
  eth0             2001:db8:8003:400::ffff/64        u/u

4 files changed, 115 insertions, 3 deletions

diff --git a/data/templates/dhcp-client/ipv6.tmpl b/data/templates/dhcp-client/ipv6.tmpl
index 8485c9d78..6cfe24d3e 100644
--- a/data/templates/dhcp-client/ipv6.tmpl
+++ b/data/templates/dhcp-client/ipv6.tmpl
@@ -1,10 +1,41 @@
 # generated by dhcp.py
+# man https://www.unix.com/man-page/debian/5/dhcp6c.conf/
+
 interface {{ ifname }} {
-	request domain-name-servers,domain-name;
+    request domain-name-servers;
+    request domain-name;
 {%  if dhcpv6_prm_only %}
     information-only;
 {%  endif %}
 {%  if not dhcpv6_temporary %}
-    send ia-na 0;
+    send ia-na 1; # non-temporary address
 {%  endif %}
+{%  if dhcpv6_pd %}
+    send ia-pd 2; # prefix delegation
+{%  endif %}
+};
+
+{%  if not dhcpv6_temporary %}
+id-assoc na 1 {
+    # Identity association NA
 };
+{%  endif %}
+
+{%  if dhcpv6_pd %}
+id-assoc pd 2 {
+{%  for intf in dhcpv6_pd %}
+    prefix-interface {{ intf.ifname }} {
+{%    if intf.sla_id %}
+        sla-id {{ intf.sla_id }};
+{%    endif %}
+{%    if intf.sla_len %}
+        sla-len {{ intf.sla_len }};
+{%    endif %}
+{%    if intf.if_id %}
+        ifid {{ intf.if_id  }};
+{%    endif %}
+    };
+{%  endfor %}
+};
+{%  endif %}
+
diff --git a/interface-definitions/interfaces-pppoe.xml.in b/interface-definitions/interfaces-pppoe.xml.in
index d69e0b42c..4337b6fc7 100644
--- a/interface-definitions/interfaces-pppoe.xml.in
+++ b/interface-definitions/interfaces-pppoe.xml.in
@@ -72,6 +72,59 @@
               </valueHelp>
             </properties>
           </leafNode>
+          <node name="dhcpv6-options">
+            <properties>
+              <help>DHCPv6 options</help>
+            </properties>
+            <children>
+              <tagNode name="delegate">
+                <properties>
+                  <help>Delegate IPv6 prefix from provider to this interface</help>
+                  <completionHelp>
+                    <script>${vyos_completion_dir}/list_interfaces.py --broadcast</script>
+                  </completionHelp>
+                </properties>
+                <children>
+                  <leafNode name="interface-id">
+                    <properties>
+                      <help>Interface address identifier</help>
+                      <valueHelp>
+                        <format>0-</format>
+                        <description>Used to form IPv6 interface address (default: EUI-64)</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="numeric" argument="--non-negative"/>
+                      </constraint>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="sla-id">
+                    <properties>
+                      <help>Interface site-Level aggregator (SLA)</help>
+                      <valueHelp>
+                        <format>0-128</format>
+                        <description>Decimal integer which fits in the length of SLA IDs</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="numeric" argument="--range 0-128"/>
+                      </constraint>
+                    </properties>
+                  </leafNode>
+                  <leafNode name="sla-len">
+                    <properties>
+                      <help>Site-Level aggregator (SLA) length</help>
+                      <valueHelp>
+                        <format>0-128</format>
+                        <description>Length of delegated prefix</description>
+                      </valueHelp>
+                      <constraint>
+                        <validator name="numeric" argument="--range 0-128"/>
+                      </constraint>
+                    </properties>
+                  </leafNode>
+                </children>
+              </tagNode>
+            </children>
+          </node>
           #include <include/interface-description.xml.i>
           #include <include/interface-disable.xml.i>
           #include <include/interface-vrf.xml.i>
diff --git a/python/vyos/ifconfig/dhcp.py b/python/vyos/ifconfig/dhcp.py
index 95623a76e..f8fdeb6a9 100644
--- a/python/vyos/ifconfig/dhcp.py
+++ b/python/vyos/ifconfig/dhcp.py
@@ -86,6 +86,7 @@ class _DHCPv6 (Control):
             'ifname': ifname,
             'dhcpv6_prm_only': False,
             'dhcpv6_temporary': False,
+            'dhcpv6_pd': [],
         })
         self._conf_file = f'/run/dhcp6c/dhcp6c.{ifname}.conf'
 
@@ -107,7 +108,7 @@ class _DHCPv6 (Control):
             raise Exception(
                 'DHCPv6 temporary and parameters-only options are mutually exclusive!')
 
-        render(self._conf_file, 'dhcp-client/ipv6.tmpl', self.options)
+        render(self._conf_file, 'dhcp-client/ipv6.tmpl', self.options, trim_blocks=True)
         return self._cmd('systemctl restart dhcp6c@{ifname}.service'.format(**self.options))
 
     def delete(self):
diff --git a/src/conf_mode/interfaces-pppoe.py b/src/conf_mode/interfaces-pppoe.py
index e72540f66..baa07e283 100755
--- a/src/conf_mode/interfaces-pppoe.py
+++ b/src/conf_mode/interfaces-pppoe.py
@@ -36,6 +36,7 @@ default_config_data = {
     'deleted': False,
     'description': '\0',
     'disable': False,
+    'dhcpv6_pd': [],
     'intf': '',
     'idle_timeout': '',
     'ipv6_autoconf': False,
@@ -138,6 +139,27 @@ def get_config():
     if conf.exists('vrf'):
         pppoe['vrf'] = conf.return_value(['vrf'])
 
+    if conf.exists(['dhcpv6-options', 'delegate']):
+        for interface in conf.list_nodes(['dhcpv6-options', 'delegate']):
+            pd = {
+                'ifname': interface,
+                'sla_id': '',
+                'sla_len': '',
+                'if_id': ''
+            }
+            conf.set_level(base_path + [pppoe['intf'], 'dhcpv6-options', 'delegate', interface])
+
+            if conf.exists(['sla-id']):
+                pd['sla_id'] = conf.return_value(['sla-id'])
+
+            if conf.exists(['sla-len']):
+                pd['sla_len'] = conf.return_value(['sla-len'])
+
+            if conf.exists(['interface-id']):
+                pd['if_id'] = conf.return_value(['interface-id'])
+
+            pppoe['dhcpv6_pd'].append(pd)
+
     return pppoe
 
 def verify(pppoe):
@@ -201,6 +223,11 @@ def generate(pppoe):
         render(script_pppoe_ipv6_up, 'pppoe/ipv6-up.script.tmpl',
                pppoe, trim_blocks=True, permission=0o755)
 
+        if len(pppoe['dhcpv6_pd']) > 0:
+            ifname = pppoe['intf']
+            pppoe['ifname'] = ifname
+            render(f'/run/dhcp6c/dhcp6c.{ifname}.conf', 'dhcp-client/ipv6.tmpl', pppoe, trim_blocks=True)
+
     return None
 
 def apply(pppoe):