dhclient: T5724: run user hooks using run_hookdir

[gavol]

Change Summary

Execute user hooks using run_hookdir instead of run-parts.

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/T5724

Component(s) name

dhcp

Proposed changes

User hooks are executed using run_hookdir (defined in the /sbin/dhclient-script script) instead of run-parts. That allows user hooks to modify variables set by the dhcp client (e.g., the new_routers variable to avoid the installation of the default routes).

How to test

Pre-condition: at least one interface (eth0 for simplicity) receiving IP via dhcp and configured to install the default root.

Add a very simple user hook in /config/scripts/dhcp-client/pre-hooks.d:

RUN="yes"
if [ "$RUN" = "yes" ]; then
    case "$reason" in
        BOUND|RENEW|REBIND|REBOOT)
        new_routers=""
        ;;
    esac
fi

Force a dhcp renewal and then check the content of the /var/lib/dhcp/dhclient_eth0.lease file: the new_routers variable should point to an empty string when reason is BOUND or RENEW or REBIND or REBOOT.

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

[c-po]

@Mergifyio backport sagitta

[mergify]

backport sagitta

✅ Backports have been created

• #2473 dhclient: T5724: run user hooks using run_hookdir (backport #2472) has been created for branch sagitta