[mle] suppress Announce response to orphan child on same channel and PAN ID

[abtink]

This commit updates MLE to skip sending an Announce response when receiving an Announce message from a detached/orphan device and the included channel and PAN ID in the received Announce message are the same as the current network's channel and PAN ID.

---

Related to SPEC-1165.

Fixes #8542

[codecov]

Codecov Report

Merging #9388 (6b3792e) into main (830572f) will increase coverage by 0.05%.
The diff coverage is 81.81%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9388      +/-   ##
==========================================
+ Coverage   85.71%   85.76%   +0.05%     
==========================================
  Files         555      555              
  Lines       73260    73268       +8     
==========================================
+ Hits        62793    62837      +44     
+ Misses      10467    10431      -36     

Files Changed	Coverage Δ
src/core/thread/mle.cpp	89.15% <81.81%> (+0.16%)	⬆️

... and 25 files with indirect coverage changes

[size-report]

Size Report of OpenThread

Merging #9388 into main(830572f).

name	branch	text	data	bss	total
ot-cli-ftd	main	460944	760	63148	524852
	#9388	460976	760	63148	524884
	+/-	+32	0	0	+32
ot-ncp-ftd	main	432548	760	58312	491620
	#9388	432580	760	58312	491652
	+/-	+32	0	0	+32
libopenthread-ftd.a	main	230633	0	37110	267743
	#9388	230665	0	37110	267775
	+/-	+32	0	0	+32
libopenthread-cli-ftd.a	main	55761	0	8051	63812
	#9388	55761	0	8051	63812
	+/-	0	0	0	0
libopenthread-ncp-ftd.a	main	31497	0	5852	37349
	#9388	31497	0	5852	37349
	+/-	0	0	0	0
ot-cli-mtd	main	361016	760	51132	412908
	#9388	361048	760	51132	412940
	+/-	+32	0	0	+32
ot-ncp-mtd	main	344700	760	46304	391764
	#9388	344732	760	46304	391796
	+/-	+32	0	0	+32
libopenthread-mtd.a	main	154540	0	25102	179642
	#9388	154572	0	25102	179674
	+/-	+32	0	0	+32
libopenthread-cli-mtd.a	main	39029	0	8043	47072
	#9388	39029	0	8043	47072
	+/-	0	0	0	0
libopenthread-ncp-mtd.a	main	24377	0	5852	30229
	#9388	24377	0	5852	30229
	+/-	0	0	0	0
ot-cli-ftd-br	main	528112	768	130764	659644
	#9388	528144	768	130764	659676
	+/-	+32	0	0	+32
libopenthread-ftd-br.a	main	292561	5	104702	397268
	#9388	292593	5	104702	397300
	+/-	+32	0	0	+32
libopenthread-cli-ftd-br.a	main	68962	0	8075	77037
	#9388	68962	0	8075	77037
	+/-	0	0	0	0
ot-rcp	main	61880	564	20532	82976
	#9388	61880	564	20532	82976
	+/-	0	0	0	0
libopenthread-rcp.a	main	9182	0	4988	14170
	#9388	9182	0	4988	14170
	+/-	0	0	0	0
libopenthread-radio.a	main	18528	0	206	18734
	#9388	18528	0	206	18734
	+/-	0	0	0	0

[EskoDijk]

This looks good; as it avoids sending announce triggered by devices that are on the same PANID and channel.

I was wondering where the code is that will use a mAlternateChannel/PanId from a received announce to do some attach attempt(s) with? Could not find it easily.

[EskoDijk]

Suggested change

	bool isFromOrhpan;
	bool isFromOrphan;

[abtink]

Thanks. Fixed it in new push

[abtink]

I was wondering where the code is that will use a mAlternateChannel/PanId from a received announce to do some attach attempt(s) with? Could not find it easily.

@EskoDijk , I think you mean this part:

openthread/src/core/thread/mle.cpp

Lines 3744 to 3757 in 830572f

	VerifyOrExit(!IsDetached() || (Get<Mac::Mac>().GetPanChannel() != channel) ||
	(Get<Mac::Mac>().GetPanId() != panId));
	if (mAttachState == kAttachStateProcessAnnounce)
	{
	VerifyOrExit(mAlternateTimestamp < timestamp.GetSeconds());
	}
	mAlternateTimestamp = timestamp.GetSeconds();
	mAlternateChannel = channel;
	mAlternatePanId = panId;
	SetAttachState(kAttachStateProcessAnnounce);
	mAttachTimer.Start(kAnnounceProcessTimeout);
	mAttachCounter = 0;

which uses mAttachTimer to add delay before processing it from timer callback:

openthread/src/core/thread/mle.cpp

Lines 1472 to 1474 in 830572f

	case kAttachStateProcessAnnounce:
	ProcessAnnounce();
	break;

which then calls:

openthread/src/core/thread/mle.cpp

Lines 3840 to 3860 in 830572f

	void Mle::ProcessAnnounce(void)
	{
	uint8_t newChannel = mAlternateChannel;
	uint16_t newPanId = mAlternatePanId;
	OT_ASSERT(mAttachState == kAttachStateProcessAnnounce);
	LogNote("Processing Announce - channel %d, panid 0x%02x", newChannel, newPanId);
	Stop(kKeepNetworkDatasets);
	// Save the current/previous channel and pan-id
	mAlternateChannel = Get<Mac::Mac>().GetPanChannel();
	mAlternatePanId = Get<Mac::Mac>().GetPanId();
	mAlternateTimestamp = 0;
	IgnoreError(Get<Mac::Mac>().SetPanChannel(newChannel));
	Get<Mac::Mac>().SetPanId(newPanId);
	IgnoreError(Start(kAnnounceAttach));
	}

[EskoDijk]

@abtink Yes, this was the code I was looking for; thanks. Looks good now with the update.