[nat64] use OwningList to manage active mappings

[abtink]

This change updates the management of active NAT64 mappings to use an OwningList.

To support this, the Mapping struct now inherits from InstanceLocatorInit and includes a new Free() method. This method encapsulates the logic for releasing the associated IPv4 address and the Mapping entry back to their corresponding pools.

This new design simplifies the Translator class by removing the redundant ReleaseMapping(), ReleaseMappings(), and ReleaseExpiredMappings() methods. All mapping cleanup operations are now handled by the OwningList class (which invokes Mapping::Free() on entries as they are removed).

[github-actions]

Merging #11878 into main

name	branch	text	data	bss	total
ot-cli-ftd	853bbd1	479608	860	66548	547016
	5f95614	479608	860	66548	547016
	+/-	+0	+0	+0	+0
ot-ncp-ftd	853bbd1	445324	764	61792	507880
	5f95614	445324	764	61792	507880
	+/-	+0	+0	+0	+0
ot-cli-mtd	853bbd1	372352	764	51020	424136
	5f95614	372352	764	51020	424136
	+/-	+0	+0	+0	+0
ot-ncp-mtd	853bbd1	353452	764	46288	400504
	5f95614	353452	764	46288	400504
	+/-	+0	+0	+0	+0
ot-cli-ftd-br	853bbd1	581376	868	135332	717576
	5f95614	581312	868	135332	717512
	+/-	-64	+0	+0	-64
ot-rcp	853bbd1	63136	568	20804	84508
	5f95614	63136	568	20804	84508
	+/-	+0	+0	+0	+0

Library files

name	branch	text	data	bss	total
libopenthread-ftd.a	853bbd1	246826	95	40326	287247
	5f95614	246826	95	40326	287247
	+/-	+0	+0	+0	+0
libopenthread-cli-ftd.a	853bbd1	60843	0	8083	68926
	5f95614	60843	0	8083	68926
	+/-	+0	+0	+0	+0
libopenthread-ncp-ftd.a	853bbd1	33257	0	5948	39205
	5f95614	33257	0	5948	39205
	+/-	+0	+0	+0	+0
libopenthread-mtd.a	853bbd1	165183	0	24822	190005
	5f95614	165183	0	24822	190005
	+/-	+0	+0	+0	+0
libopenthread-cli-mtd.a	853bbd1	41134	0	8059	49193
	5f95614	41134	0	8059	49193
	+/-	+0	+0	+0	+0
libopenthread-ncp-mtd.a	853bbd1	25785	0	5948	31733
	5f95614	25785	0	5948	31733
	+/-	+0	+0	+0	+0
libopenthread-ftd-br.a	853bbd1	350343	100	109078	459521
	5f95614	350272	100	109078	459450
	+/-	-71	+0	+0	-71
libopenthread-cli-ftd-br.a	853bbd1	78409	0	8115	86524
	5f95614	78409	0	8115	86524
	+/-	+0	+0	+0	+0
libopenthread-rcp.a	853bbd1	9932	0	5060	14992
	5f95614	9932	0	5060	14992
	+/-	+0	+0	+0	+0
libopenthread-radio.a	853bbd1	19423	0	238	19661
	5f95614	19423	0	238	19661
	+/-	+0	+0	+0	+0

[abtink]

/gemini review

[gemini-code-assist]

Code Review

This pull request refactors the management of active NAT64 mappings to use an OwningList, which simplifies the code by encapsulating mapping cleanup logic within the Mapping::Free method. This is a great improvement that removes several manual mapping release methods from the Translator class. The changes are well-implemented and align with the goal of simplification. I have one minor suggestion to improve code readability by refactoring a conditional statement to avoid an empty if block.

[codecov]

Codecov Report

❌ Patch coverage is 38.46154% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.44%. Comparing base (853bbd1) to head (b7bcde6).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/core/net/nat64_translator.cpp	27.27%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11878      +/-   ##
==========================================
- Coverage   75.25%   69.44%   -5.81%     
==========================================
  Files         644      644              
  Lines       98754   102434    +3680     
==========================================
- Hits        74313    71134    -3179     
- Misses      24441    31300    +6859     

Files with missing lines	Coverage Δ
src/core/net/nat64_translator.hpp	36.36% <100.00%> (-51.14%)	⬇️
src/core/net/nat64_translator.cpp	23.20% <27.27%> (-51.06%)	⬇️

... and 190 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull Request Overview

This change refactors the NAT64 translator to use OwningList for managing active mappings, replacing manual memory management with automatic cleanup. The Mapping struct is enhanced to handle its own resource deallocation through a new Free() method, eliminating the need for multiple release methods in the Translator class.

• Replaces LinkedList<Mapping> with OwningList<Mapping> for automatic memory management
• Adds Free() method to Mapping struct to encapsulate cleanup logic
• Removes redundant release methods (ReleaseMapping, ReleaseMappings, ReleaseExpiredMappings)

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/core/net/nat64_translator.hpp	Updates class structure to use OwningList, adds Free() method to Mapping, removes manual release methods
src/core/net/nat64_translator.cpp	Implements Mapping::Free() method, updates mapping pool initialization, replaces manual cleanup calls with OwningList methods

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}