T6411: CGNAT fix sequences for external address ranges

[sever-sever]

Change Summary

Fix the bug where address external allocation was not rely on sequences of the external IP addresses (if set)

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/T6411

Related PR(s)

Component(s) name

cgnat

Proposed changes

How to test

Initial configuration:

set nat cgnat pool external ext-01 external-port-range '1024-65535'
set nat cgnat pool external ext-01 per-user-limit port '10000'
set nat cgnat pool external ext-01 range 192.168.122.121/32
set nat cgnat pool external ext-01 range 198.51.100.23/32 seq '3'
set nat cgnat pool external ext-01 range 203.0.113.102/32 seq '10'
set nat cgnat pool internal int-01 range '100.64.0.0/28'
set nat cgnat rule 10 source pool 'int-01'
set nat cgnat rule 10 translation pool 'ext-01'

Before the fix external address allocation not rely on the seq

vyos@r4# run show nat cgnat allocation 
Internal IP    External IP      Port range
-------------  ---------------  ------------
100.64.0.0     192.168.122.121  1024-11023
100.64.0.1     192.168.122.121  11024-21023
100.64.0.2     192.168.122.121  21024-31023
100.64.0.3     192.168.122.121  31024-41023
100.64.0.4     192.168.122.121  41024-51023
100.64.0.5     192.168.122.121  51024-61023
100.64.0.6     198.51.100.23    1024-11023
100.64.0.7     198.51.100.23    11024-21023
100.64.0.8     198.51.100.23    21024-31023
100.64.0.9     198.51.100.23    31024-41023
100.64.0.10    198.51.100.23    41024-51023
100.64.0.11    198.51.100.23    51024-61023
100.64.0.12    203.0.113.102    1024-11023
100.64.0.13    203.0.113.102    11024-21023
100.64.0.14    203.0.113.102    21024-31023
100.64.0.15    203.0.113.102    31024-41023
[edit]
vyos@r4#

After the fix, we see correctly external address allocations correctly based on sequences

vyos@r4# run show nat cgnat allocation 
Internal IP    External IP      Port range
-------------  ---------------  ------------
100.64.0.0     198.51.100.23    1024-11023
100.64.0.1     198.51.100.23    11024-21023
100.64.0.2     198.51.100.23    21024-31023
100.64.0.3     198.51.100.23    31024-41023
100.64.0.4     198.51.100.23    41024-51023
100.64.0.5     198.51.100.23    51024-61023
100.64.0.6     203.0.113.102    1024-11023
100.64.0.7     203.0.113.102    11024-21023
100.64.0.8     203.0.113.102    21024-31023
100.64.0.9     203.0.113.102    31024-41023
100.64.0.10    203.0.113.102    41024-51023
100.64.0.11    203.0.113.102    51024-61023
100.64.0.12    192.168.122.121  1024-11023
100.64.0.13    192.168.122.121  11024-21023
100.64.0.14    192.168.122.121  21024-31023
100.64.0.15    192.168.122.121  31024-41023
[edit]
vyos@r4# 

Smoketest result

vyos@r4:~$ /usr/libexec/vyos/tests/smoke/cli/test_cgnat.py
test_cgnat (__main__.TestCGNAT.test_cgnat) ... ok
test_cgnat_sequence (__main__.TestCGNAT.test_cgnat_sequence) ... ok

----------------------------------------------------------------------
Ran 2 tests in 26.153s

OK
vyos@r4:~$ 

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