[test] fix potential backbone name conflict when running cert suite

[zesonzhang]

background

#10550 has introduced a new way to support multiple backbone nework in otbr docker test. Though it works good while running a single test, a bug exists when running cert-suite, which runs a batch of tests in parallel.

cert-suite allocates the name of the backbone interfaces dynamically by setting env PORT_OFFSET for each test, so there is potentially conflict exists if we hard code the backbone_network name in TOPOLOGY. This PR is targeting to fix this potential naming conflict.

how to fix

We fix it by assigning a number for backbone_network_id in each BR definition in TOPOLOGY, instead of setting a fixed backbone network name. The final backbone network name is decided by both PORT_OFFSET env and the number of backbone_network (in backbone{PORT_OFFSET}.{backbone_network} format)

For example, if PORT_OFFSET is 0 and backbone_network_id is 1, then backbone network name will be backbone0.1. For the tests that only use one backbone network and the backbone_network_id is not given, the backbone network name is by default backbone{PORT_OFFSET}.0.

New test case format

class NewTestCase(thread_cert.TestCase):
    ...
    BR = 1
    ...
    TOPOLOGY = {
        BR: {
            ...
	    'is_otbr': True,
	    'backbone_network_id': <backbone-id>,
	    ...
	}
	...
    }
    ...

<backbone-id> is any integer from 0, for each BR inside a single test, if <backbone-id> is different, the BR use different backbone interfaces; the same <backbone-id> inside a single test case means the same backbone network interface.

'backbone_network_id': <backbone-id> is optional for single backbone test cases, when it's not given while defining a otbr node, the backbone is default as backbone{PORT_OFFSET}.0.

For developers, if you are defining a new test which has multiple backbone interfaces, please ensure backbone_network_id is explicitly defined in each BR, otherwize an error is reported.

[size-report]

Size Report of OpenThread

Merging #10596 into main(ddbc99b).

name	branch	text	data	bss	total
ot-cli-ftd	main	467752	856	66364	534972
	#10596	467752	856	66364	534972
	+/-	0	0	0	0
ot-ncp-ftd	main	437076	760	61592	499428
	#10596	437076	760	61592	499428
	+/-	0	0	0	0
libopenthread-ftd.a	main	236728	95	40302	277125
	#10596	236728	95	40302	277125
	+/-	0	0	0	0
libopenthread-cli-ftd.a	main	57973	0	8075	66048
	#10596	57973	0	8075	66048
	+/-	0	0	0	0
libopenthread-ncp-ftd.a	main	32541	0	5924	38465
	#10596	32541	0	5924	38465
	+/-	0	0	0	0
ot-cli-mtd	main	365584	760	51236	417580
	#10596	365584	760	51236	417580
	+/-	0	0	0	0
ot-ncp-mtd	main	348276	760	46480	395516
	#10596	348276	760	46480	395516
	+/-	0	0	0	0
libopenthread-mtd.a	main	159091	0	25190	184281
	#10596	159091	0	25190	184281
	+/-	0	0	0	0
libopenthread-cli-mtd.a	main	39795	0	8059	47854
	#10596	39795	0	8059	47854
	+/-	0	0	0	0
libopenthread-ncp-mtd.a	main	25349	0	5924	31273
	#10596	25349	0	5924	31273
	+/-	0	0	0	0
ot-cli-ftd-br	main	552528	864	131228	684620
	#10596	552528	864	131228	684620
	+/-	0	0	0	0
libopenthread-ftd-br.a	main	325655	100	105142	430897
	#10596	325655	100	105142	430897
	+/-	0	0	0	0
libopenthread-cli-ftd-br.a	main	72104	0	8099	80203
	#10596	72104	0	8099	80203
	+/-	0	0	0	0
ot-rcp	main	62504	564	20636	83704
	#10596	62504	564	20636	83704
	+/-	0	0	0	0
libopenthread-rcp.a	main	9750	0	5060	14810
	#10596	9750	0	5060	14810
	+/-	0	0	0	0
libopenthread-radio.a	main	19257	0	222	19479
	#10596	19257	0	222	19479
	+/-	0	0	0	0

[zesonzhang]

To Reviewers: I have separated this PR into multiple small commits which can make it much easy to review. Please kindly review by each commit. Thanks!

The link to the first commit: f2fba25

@bukepo @superwhd

[zesonzhang]

@bukepo @superwhd PR is updated and ready for review, please kindly take a look, thanks!

[Irving-cl]

LGTM. Some small suggestions.

[zesonzhang]

@Irving-cl @superwhd @bukepo This PR is ready to be reviewed, please kindly take a look, thank!

[superwhd]

LGTM 👍

Left a nonblocking minor question.

[bukepo]

keeping this line to ensure it will never be None, which can simply the _construct_backbone_network_name

[zesonzhang]

The backbone_network_id is None for non otbr/host nodes by design in this PR. It can be strange (though no harm) to assign a default backbone network id for a non-BR node. Any thoughts?

[zesonzhang]

Hi @jwhui , this PR is ready to be merged as a single commit, thanks!