dhcpv6-server: T3493: adds prefix range validation and fixes typos in…

[Giggum]

… select ConfigError messages

Change Summary

1. Adds detection for when prefix-delegation start and prefix-delegation stop addresses are not within the IPv6 subnet defined. A ConfigError message is raised for both cases.

2. Updates typos in select ConfigError messages (e.g. then -> than, multipe -> multiple)

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/T3493

Related PR(s)

Component(s) name

dhcpv6-server service

Proposed changes

How to test

Test 1 - that prefix start address is not within subnet

set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 address-range start 2001:db8:3456::100 stop '2001:db8:3456::1ff'
set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 name-server '2001:db8:daad::1'
set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 prefix-delegation start 2001:db8:290::500 prefix-length '64'
set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 prefix-delegation start 2001:db8:290::500 stop '2001:db8:290::5ff

Output:
Prefix delegation start address "2001:db8:290::500" is not in subnet
"2001:db8:3456::/64"

Test 2 - that prefix stop address is not within subnet

set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 address-range start 2001:db8:3456::100 stop '2001:db8:3456::1ff'
set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 name-server '2001:db8:daad::1'
set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 prefix-delegation start 2001:db8:3456::500 prefix-length '64'
set service dhcpv6-server shared-network-name VyOS-DHCPv6 subnet 2001:db8:3456::/64 prefix-delegation start 2001:db8:3456::500 stop '2001:db8:290::5ff'

Output:
Prefix delegation stop address "2001:db8:290::5ff" is not in subnet
"2001:db8:3456::/64"

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