configdep: T5839: remove trivially redundant config dependency calls

[jestabro]

Change Summary

NOTE: this requires vyos/vyatta-cfg#74

NOTE: this should not be backported until it has had a bit of time in 1.5

Remove redundant calls to config dependencies in two steps:
(1) remove trivial redundancies produced by multiple calls to set_dependents within a given config-mode script
(2) add a global list of dependencies under vyos-configd and execute in that context, when script is called with vyos-configd support

The case (1) is necessary as set_dependents can be called conditionally; a simple example, used below for demonstration, is that of firewall.py wherein dependents ["system_conntrack", "nat", "policy_route"] are added if 'group' is present (group-resync), and ["system_conntrack"] is added unconditionally.

An important consideration is that adjusting the script logic to avoid redundancies is fragile and prone to error and NOT recommended, in favor of a proper solution, provided here.

The case (2) is necessary as otherwise, scripts process local dependency lists without knowledge of other script calls, for examples, firewall 'group-resync' will call ["system_conntrack", "nat", "policy_route"], which will incur nat.py calling ["system_conntrack"] subsequently. Again, one should not need to handle the logic of execution from with the logic of dependency.

Example below:

set firewall group address-group AG address '198.122.100.137'
set nat source rule 10 outbound-interface name 'eth1'
set nat source rule 10 source group address-group 'AG'
set nat source rule 10 translation address 'masquerade'

Without any redundancy pruning:

--- including set_dependents calls:

vyos@vyos# commit
set_dependents: caller nat, dependents ['system_conntrack']
calling: system_conntrack
set_dependents: caller firewall, dependents ['system_conntrack', 'nat', 'policy_route']
set_dependents: caller firewall, dependents ['system_conntrack', 'nat', 'policy_route', 'system_conntrack']
calling: system_conntrack
calling: nat
set_dependents: caller nat, dependents ['system_conntrack']
calling: system_conntrack
calling: policy_route
calling: system_conntrack

--- limiting to the resulting script calls:

calling: system_conntrack
calling: system_conntrack
calling: nat
calling: system_conntrack
calling: policy_route
calling: system_conntrack

With intra-script dependency pruning:

--- including set_dependents calls

vyos@vyos# commit
set_dependents: caller nat, dependents ['system_conntrack']
calling: system_conntrack
set_dependents: caller firewall, dependents ['system_conntrack', 'nat', 'policy_route']
set_dependents: caller firewall, dependents ['nat', 'policy_route', 'system_conntrack']
calling: nat
set_dependents: caller nat, dependents ['system_conntrack']
calling: system_conntrack
calling: policy_route
calling: system_conntrack

--- with result:

calling: system_conntrack
calling: nat
calling: system_conntrack
calling: policy_route
calling: system_conntrack

With global dependency list:

--- scripts set dependencies as before:

vyos@vyos# commit
set_dependents: caller nat, dependents ['system_conntrack']
set_dependents: caller firewall, dependents ['system_conntrack', 'nat', 'policy_route']
set_dependents: caller firewall, dependents ['nat', 'policy_route', 'system_conntrack']

--- dependents are called under vyos-configd:

journalctl -u vyos-configd|grep calling
...: calling: nat
...: calling: policy_route
...: calling: system_conntrack

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T5839
• https://vyos.dev/T5660

Related PR(s)

vyos/vyatta-cfg#74

Component(s) name

Proposed changes

How to test

Smoketest result

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly