Short description
Multiple issues with "Create zone from prefix" in GUI for IPv6 zones:-

1. Web page input validation allows entry of prefix with bitmask on the end, e.g. /nn. PHP script doesn't validate either and generates invalid zone, e.g. enter 2400:7700::/32, generates 2.3./.0.0.7.7.0.0.4.2.ip6.arpa. To my knowledge this is not a valid zone.

2. Algorithm does not correctly handle "packed" prefixes, i.e. prefixes where leading zeros have been removed. For my specific error I was adding a /64. Algorithm handled missing leading zeros in blocks 2 & 3 OK, i.e. nibbles 5 thru 12, but truncated the result for block 4 (nibbles 13 to 16).

Environment

• Operating system: Debian v9 (Stretch)
  

• Software version: PowerDNS v4.1.5, Opera version unknown, latest from GIT
  

• Software source: PowerDNS repository, Opera GIT
  

• Backend: PostgreSQL v9.6.10
  

Steps to reproduce

1. Enter 2001:470:d:eb3 in "Create zone from prefix" in IPv6 Zones.

Expected behaviour
Should return 3.b.e.0.d.0.0.0.0.7.4.0.1.0.0.2.ip6.arpa.

Actual behaviour
returns 3.b.e.d.0.0.0.0.7.4.0.1.0.0.2.ip6.arpa. (4th nibble from left is missing, resultant is only 15 nibbles, should be 16).

Other information
Happens on other /64 packed prefixes too.
2001:470:1f2d:14b = b.4.1.d.2.f.1.0.7.4.0.1.0.0.2.ip6.arpa.
2001:470🅱️612 = 2.1.6.b.0.0.0.0.7.4.0.1.0.0.2.ip6.arpa.