Puppet hieradata does not properly interpret an IPv4-mapped IPv6 address

[Tara Nath Subedi]

Brief Description
-----------------
IPv6 IPv4-mapped prefix of ::ffff is being interpreted by puppet as a Hiera parameter reference, causing a Hiera parameter lookup error.

To support interoperating with IPv4 systems on IPv6 deployments it is necessary to configure IPv4-mapped IPv6 addresses. Specifically, this is required for DNS entries that cannot use host entries as an alternative.

Severity
--------
Major: System/Feature is usable but degraded

Steps to Reproduce
------------------
To simply reproduce the Puppet error, a DNS configuration using the following can be configured.

system dns-modify nameservers=::ffff:10.10.10.1

Expected Behavior
------------------
The hiera data must be formatted with an expanded value that is not interpreted as a hiera data parameter reference.

Example:

import netaddr
a = netaddr.IPAddress("::ffff:10.10.10.1")
a.format(netaddr.ipv6_full)

'0:0:0:0:0:ffff:a0a:a01'

Actual Behavior
----------------
Puppet error is generated.

Reproducibility
---------------
Reproducible - 100%

System Configuration
--------------------
Any IPv6-based system.

Branch/Pull Time/Commit
-----------------------
STX master 2023-12-11_10:44:56

Last Pass
---------
Never - new test scenario.

Timestamp/Logs
--------------
Example Log Error

2023-12-11T12:44:56.292 Error: 2023-12-11 12:44:56 +0000 Evaluation Error: Error while evaluating a Function Call, Lookup of key 'platform::dns::resolv::servers' failed:
Value for key 'platform::dns::resolv::servers', in hash returned from data_hash function 'yaml_data', when using location '/tmp/puppet/hieradata/system.yaml', has wrong type,
expects Puppet::LookupValue, got Array[Any, 2, 2] (file: /usr/share/puppet/modules/platform/manifests/dns.pp, line: 79, column: 3) on node controller-0

Test Activity
-------------
Validating dual-stack deployment configuration

Workaround
----------
Manually update database with expanded notation that eliminates leading colons.

sudo -u postgres psql -d sysinv -c "update i_dns set nameservers='0:0:0:0:0:ffff:10.10.10.1';"

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/config/+/906302

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/config/+/906302
Committed: https://opendev.org/starlingx/config/commit/51fe2ced224a18ca7e4201e89ceb1515fb76851a
Submitter: "Zuul (22348)"
Branch: master

commit 51fe2ced224a18ca7e4201e89ceb1515fb76851a
Author: Tara Subedi <email address hidden>
Date: Fri Jan 19 11:24:08 2024 -0500

    Puppet hieradata does not properly interpret an IPv4-mapped IPv6

    IPv6 IPv4-mapped prefix ::ffff is being interpreted by puppet as
    a Hiera parameter reference, causing a Hiera parameter lookup
    error. "puppet lookup platform::dns::resolv::servers" shows error
    when the value in yaml file leads with ::. This commit fixes the
    issue by putting the value in quote on yaml dump.

    TEST PLAN:
        PASS: Bootstrap with dns_servers ::ffff:10.10.10.1
        PASS: system dns-modify nameservers=::ffff:10.10.10.1

    Closes-Bug: 2050307
    Change-Id: I40cf7a02b22db7fa1c51414a802b969a395db61f
    Signed-off-by: Tara Nath Subedi <email address hidden>