[nat64] fetch NAT64 prefix from infrastructure interface and advertise it to netdata

[xuyirio]

This commit fetches the NAT64 prefix on infrastructure interface and advertise it to Network Data at medium preference.

• Use getaddrinfo_a() function to asynchronously lookup the ipv6 address of the special domain ipv4only.arpa. The infrastructure NAT64 prefix is extracted from the domain answer.
• mInfraIfNat64PrefixStaleTimer is scheduled to monitor the presence and change of infrastructure NAT64 prefix.
• EvaluateNat64Prefix evaluates whether to advertise the infrastructure prefix or the local ULA prefix or neither. When there is a new infrastructure prefix, it will withdraw the legacy one and add the new one. When the infrastructure prefix no longer exists, it will withdraw the legacy one and add the local ULA prefix. When the infrastructure prefix presents again, it will add the infrastructure prefix and withdraw the local ULA prefix.

New tests are added to test the scenarios when infrastructure NAT64 prefix exists. DNS64 on OTBR is turned on to enable bind9 with NAT64 prefix on infrastructure interface for these tests. bind9 is explicitly turned off when testing local ULA prefix. Since bind9 is conflict with other components like dnssd, all nat64 tests are moved under /nat64 directory and configured separately.

The case that two or more BRs have same infrastructure NAT64 prefix is not covered by this commit and will be followed up later.

[size-report[bot]]

Size Report of OpenThread

Merging #7619 into main(034fc826f347c0d6ad4a7ce4bdb936a284fede05).

name	branch	text	data	bss	total
ot-cli-ftd_1.1	main	462352	780	60772	523904
	#7619	462432	780	60772	523984
	+/-	+80	0	0	+80
ot-cli-mtd_1.1	main	381880	780	50564	433224
	#7619	381960	780	50564	433304
	+/-	+80	0	0	+80
ot-ncp-ftd_1.1	main	444084	780	59752	504616
	#7619	444084	780	59752	504616
	+/-	0	0	0	0
ot-ncp-mtd_1.1	main	366364	780	49544	416688
	#7619	366364	780	49544	416688
	+/-	0	0	0	0
ot-rcp_1.1	main	58136	564	19964	78664
	#7619	58136	564	19964	78664
	+/-	0	0	0	0
libopenthread-cli-ftd.a_1.1	main	45925	0	4244	50169
	#7619	45925	0	4244	50169
	+/-	0	0	0	0
libopenthread-cli-mtd.a_1.1	main	38548	0	4244	42792
	#7619	38548	0	4244	42792
	+/-	0	0	0	0
libopenthread-ftd.a_1.1	main	242776	20	39090	281886
	#7619	242836	20	39090	281946
	+/-	+60	0	0	+60
libopenthread-mtd.a_1.1	main	175987	20	28882	204889
	#7619	176047	20	28882	204949
	+/-	+60	0	0	+60
libopenthread-ncp-ftd.a_1.1	main	31597	0	5852	37449
	#7619	31597	0	5852	37449
	+/-	0	0	0	0
libopenthread-ncp-mtd.a_1.1	main	26441	0	5852	32293
	#7619	26441	0	5852	32293
	+/-	0	0	0	0
libopenthread-rcp.a_1.1	main	8894	0	4988	13882
	#7619	8894	0	4988	13882
	+/-	0	0	0	0
libopenthread-radio.a_1.1	main	15939	0	174	16113
	#7619	15939	0	174	16113
	+/-	0	0	0	0
ot-cli-ftd_1.3	main	485120	780	70468	556368
	#7619	485200	780	70468	556448
	+/-	+80	0	0	+80
ot-cli-mtd_1.3	main	397040	780	51820	449640
	#7619	397120	780	51820	449720
	+/-	+80	0	0	+80
ot-ncp-ftd_1.3	main	465812	780	69440	536032
	#7619	465812	780	69440	536032
	+/-	0	0	0	0
ot-ncp-mtd_1.3	main	380100	780	50792	431672
	#7619	380100	780	50792	431672
	+/-	0	0	0	0
ot-rcp_1.3	main	60464	564	20532	81560
	#7619	60464	564	20532	81560
	+/-	0	0	0	0
libopenthread-cli-ftd.a_1.3	main	48783	0	4244	53027
	#7619	48783	0	4244	53027
	+/-	0	0	0	0
libopenthread-cli-mtd.a_1.3	main	40812	0	4244	45056
	#7619	40812	0	4244	45056
	+/-	0	0	0	0
libopenthread-ftd.a_1.3	main	261698	20	48242	309960
	#7619	261758	20	48242	310020
	+/-	+60	0	0	+60
libopenthread-mtd.a_1.3	main	187814	20	29594	217428
	#7619	187874	20	29594	217488
	+/-	+60	0	0	+60
libopenthread-ncp-ftd.a_1.3	main	33427	0	5852	39279
	#7619	33427	0	5852	39279
	+/-	0	0	0	0
libopenthread-ncp-mtd.a_1.3	main	27807	0	5852	33659
	#7619	27807	0	5852	33659
	+/-	0	0	0	0
libopenthread-rcp.a_1.3	main	9060	0	4988	14048
	#7619	9060	0	4988	14048
	+/-	0	0	0	0
libopenthread-radio.a_1.3	main	16819	0	206	17025
	#7619	16819	0	206	17025
	+/-	0	0	0	0

[simonlingoogle]

DNS64 on OTBR is turned on to enable bind9 with NAT64 prefix on infrastructure interface for these tests. bind9 is explicitly turned off when testing local ULA prefix. Since bind9 is conflict with other components like dnssd, all nat64 tests are moved under /nat64 directory and configured separately.

Does it mean that the current NAT64 solution on OTBR does not work with other 1.3 features? I think eventually we want them to co-work. How do we resolve the gaps?

[xuyirio]

DNS64 on OTBR is turned on to enable bind9 with NAT64 prefix on infrastructure interface for these tests. bind9 is explicitly turned off when testing local ULA prefix. Since bind9 is conflict with other components like dnssd, all nat64 tests are moved under /nat64 directory and configured separately.

Does it mean that the current NAT64 solution on OTBR does not work with other 1.3 features? I think eventually we want them to co-work. How do we resolve the gaps?

The bind9 is enabled here for testing only that a DNS server w/ NAT64 prefix is needed on infrastructure interface. The DNS servers in /etc/resolv.conf is expected to be managed by upstream network service (e.g. generated by dhcpcd) rather than we configure a local server. I expect that other OTBR components work w/ the upstream configured DNS servers?

[codecov[bot]]

Codecov Report

Merging #7619 (189b71f) into main (034fc82) will decrease coverage by 0.05%. The diff coverage is 91.94%.

:exclamation: Current head 189b71f differs from pull request most recent head 861f180. Consider uploading reports for the commit 861f180 to get more accurate results

@@            Coverage Diff             @@
##             main    #7619      +/-   ##
==========================================
- Coverage   85.43%   85.38%   -0.06%     
==========================================
  Files         505      510       +5     
  Lines       70125    70830     +705     
==========================================
+ Hits        59911    60477     +566     
- Misses      10214    10353     +139     

Impacted Files	Coverage Δ
examples/platforms/simulation/infra_if.c	0.00% <0.00%> (ø)
src/core/border_router/infra_if.hpp	100.00% <ø> (ø)
src/core/border_router/routing_manager.hpp	62.79% <ø> (-1.66%)	:arrow_down:
src/posix/platform/infra_if.hpp	50.00% <ø> (ø)
tests/unit/test_platform.cpp	46.73% <ø> (ø)
src/posix/platform/infra_if.cpp	89.76% <85.71%> (-1.11%)	:arrow_down:
src/core/border_router/routing_manager.cpp	88.17% <98.03%> (+3.45%)	:arrow_up:
src/cli/cli.cpp	79.56% <100.00%> (-1.60%)	:arrow_down:
src/core/api/border_routing_api.cpp	48.38% <100.00%> (+17.61%)	:arrow_up:
src/core/api/ip6_api.cpp	80.37% <100.00%> (-2.32%)	:arrow_down:
... and 66 more

[xuyirio]

@wgtdkp @abtink Could you help review this PR? Thanks!