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.

2 files changed, 59 insertions, 3 deletions

diff --git a/src/conf_mode/interfaces-pppoe.py b/src/conf_mode/interfaces-pppoe.py
index 928113b49..901ea769c 100755
--- a/src/conf_mode/interfaces-pppoe.py
+++ b/src/conf_mode/interfaces-pppoe.py
@@ -15,7 +15,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import os
-import jmespath
 
 from sys import exit
 from copy import deepcopy
@@ -104,8 +103,7 @@ def generate(pppoe):
     render(script_pppoe_ipv6_up, 'pppoe/ipv6-up.script.tmpl',
            pppoe, trim_blocks=True, permission=0o755)
 
-    tmp = jmespath.search('dhcpv6_options.prefix_delegation.interface', pppoe)
-    if tmp and len(tmp) > 0:
+    if 'dhcpv6_options' in pppoe and 'pd' in pppoe['dhcpv6_options']:
         # ipv6.tmpl relies on ifname - this should be made consitent in the
         # future better then double key-ing the same value
         render(config_wide_dhcp6c, 'dhcp-client/ipv6.tmpl', pppoe, trim_blocks=True)
diff --git a/src/migration-scripts/interfaces/11-to-12 b/src/migration-scripts/interfaces/11-to-12
new file mode 100755
index 000000000..0dad24642
--- /dev/null
+++ b/src/migration-scripts/interfaces/11-to-12
@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2020 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# - rename 'dhcpv6-options prefix-delegation' from single node to a new tag node
+#   'dhcpv6-options pd 0'
+# - delete 'sla-len' from CLI - value is calculated on demand
+
+from sys import exit, argv
+from vyos.configtree import ConfigTree
+
+if __name__ == '__main__':
+    if (len(argv) < 1):
+        print("Must specify file name!")
+        exit(1)
+
+    file_name = argv[1]
+    with open(file_name, 'r') as f:
+        config_file = f.read()
+
+    config = ConfigTree(config_file)
+
+    for type in config.list_nodes(['interfaces']):
+        for interface in config.list_nodes(['interfaces', type]):
+            # cache current config tree
+            base_path = ['interfaces', type, interface, 'dhcpv6-options']
+            old_base = base_path + ['prefix-delegation']
+            new_base = base_path + ['pd']
+            if config.exists(old_base):
+                config.set(new_base)
+                config.set_tag(new_base)
+                config.copy(old_base, new_base + ['0'])
+                config.delete(old_base)
+
+                for pd in config.list_nodes(new_base):
+                    for tmp in config.list_nodes(new_base + [pd, 'interface']):
+                        sla_config = new_base + [pd, 'interface', tmp, 'sla-len']
+                        if config.exists(sla_config):
+                            config.delete(sla_config)
+
+    try:
+        with open(file_name, 'w') as f:
+            f.write(config.to_string())
+    except OSError as e:
+        print("Failed to save the modified config: {}".format(e))
+        exit(1)