[anchor commitment] Make the anchor commitment type spec compliant #4558

halseth · 2020-08-21T11:39:19Z

This PR makes the necessary changes to the anchor commitment type to make it compliant with the final spec version as defined in lightning/bolts#688

There are two changes needed:

We set the feature bit to 20/21. This means that we now require this bit to be advertised to signal anchor support. The old bit will be ignored by new nodes.
The anchor amounts are given back to the initiator in a coop close scenario. This means that existing nodes having anchor channels will disagree on the final coop close fee if only one of the channel parties update. However if both update closing proceeds as normal. In the worst case force closing works as before.
Anchors are no longer experimental.

NOTE: Watchtowers are still not supported for anchor commitment types, and anchor support is not advertised by default but must be enabled through the --protocol.anchors option.

cfromknecht

first pass looks good

cfromknecht · 2020-08-21T19:53:50Z

lnwallet/commitment.go

+	}
+
+	if isInitiator {
+		ourBalance = ourBalance - coopCloseFee + commitFee + anchorValue


possible underflow, here and below

Pre-existing, but I think it is safe to add the extra check: ca22db6

cfromknecht · 2020-08-21T19:54:59Z

lnwallet/commitment.go

+	if isInitiator {
+		ourBalance = ourBalance - coopCloseFee + commitFee + anchorValue
+	} else {
+		theirBalance = theirBalance - coopCloseFee + commitFee + anchorValue


can be simplified with +=

maybe coopCloseFee + commitFee + anchorValue can be extracted to prevent a future bug where only one is updated

Extracted into initiatorDelta: a8ec11a

cfromknecht · 2020-08-21T19:56:29Z

lncfg/protocol.go

+
+	// Anchors should be set if we want to support opening or accepting
+	// channels having the anchor commitment type.
+	Anchors bool `long:"anchors" description:"enable support for anchor commitments (won't work with watchtowers)"`


preexisting: help message is a little misleading. it will work with watchtowers, but state updates for anchor channels won't be backed up. this should change before 0.12 though with anchor tower support in the works

Updated: 83fe313

joostjager

LGTM. Tested on regtest and inspected coop close tx. Anchor value is indeed added back to the initiator balance. Two questions:

Did you (manually) test coop closing an old-format anchor channel?
Is the itest coop closing with anchors anywhere?

lnwallet/channel.go

joostjager · 2020-08-24T06:58:40Z

lnwallet/commitment.go

+	if isInitiator {
+		ourBalance = ourBalance - coopCloseFee + commitFee + anchorValue
+	} else {
+		theirBalance = theirBalance - coopCloseFee + commitFee + anchorValue


maybe coopCloseFee + commitFee + anchorValue can be extracted to prevent a future bug where only one is updated

lnwallet/commitment.go

halseth · 2020-08-24T14:09:21Z

Did you (manually) test coop closing an old-format anchor channel?

Do you mean one node running the updated code, one node running the old code? If yes, then I tried this in one of the integration tests, and closing expectedly failed.

Is the itest coop closing with anchors anywhere?

Yes, most tests using anchors are closing the channel at the end, most notably the basic funding flow test. Checks all combinations of channel types.

cfromknecht · 2020-08-24T19:31:20Z

@halseth looks good, can squash now

joostjager · 2020-08-25T06:29:09Z

lnwallet/commitment.go

@@ -693,7 +693,12 @@ func CoopCloseBalance(chanType channeldb.ChannelType, isInitiator bool,
 		theirBalance += initiatorDelta
 	}

-	return ourBalance, theirBalance
+	if ourBalance < 0 || theirBalance < 0 {


Make clear in a comment that this is a sanity check and not supposed to be hit?

narrator: it was hit

halseth · 2020-08-26T09:26:00Z

Squashed and rebased. Removed the commit making anchors non-experimental as discussed, such that they are still behind a build tag.

cfromknecht · 2020-08-26T21:34:58Z

@halseth appears related to newly added underflow check

--- FAIL: TestCooperativeCloseDustAdherence (0.03s)
    channel_test.go:2291: unable to close channel: initiator cannot afford proposed coop close fee

halseth · 2020-08-28T10:27:49Z

@halseth appears related to newly added underflow check

--- FAIL: TestCooperativeCloseDustAdherence (0.03s)
    channel_test.go:2291: unable to close channel: initiator cannot afford proposed coop close fee

Fixed!

cfromknecht · 2020-08-28T22:37:13Z

lnwallet/channel_test.go:2285:5: `Attemtping` is a misspelling of `Attempting` (misspell)
	// Attemtping to close with this fee now should fails, since Alice

halseth · 2020-09-03T11:44:34Z

@cfromknecht Should be good now.

cfromknecht

LGTM 🤓

To be spec compliant, we require the initiator to not pay the anchor values into fees on coop close. We extract the balance calculation into commitment.go, and add back the value of the anchors to the initiator's balance.

Also modify the test to check for this condition.

halseth requested a review from Roasbeef as a code owner August 21, 2020 11:39

halseth changed the title ~~[anchor commitment] Make the anchor commitment type spec~~ [anchor commitment] Make the anchor commitment type spec compliant Aug 21, 2020

halseth force-pushed the anchors-spec branch from 4a8b9e3 to f6c5079 Compare August 21, 2020 11:49

halseth added this to the 0.12.0 milestone Aug 21, 2020

halseth requested review from joostjager and cfromknecht and removed request for Roasbeef August 21, 2020 11:53

cfromknecht reviewed Aug 21, 2020

View reviewed changes

joostjager reviewed Aug 24, 2020

View reviewed changes

halseth force-pushed the anchors-spec branch from f6c5079 to 929cb61 Compare August 24, 2020 13:50

halseth requested review from cfromknecht and joostjager August 24, 2020 13:53

cfromknecht added the v0.12 label Aug 24, 2020

joostjager approved these changes Aug 25, 2020

View reviewed changes

halseth force-pushed the anchors-spec branch from 929cb61 to 2ed2a3a Compare August 26, 2020 09:24

halseth modified the milestones: 0.12.0, 0.11.1 Aug 26, 2020

cfromknecht added the v0.11.1 label Aug 27, 2020

halseth force-pushed the anchors-spec branch from 2ed2a3a to 850f8ff Compare August 28, 2020 10:27

halseth force-pushed the anchors-spec branch from 850f8ff to 1ea3da2 Compare August 31, 2020 06:20

cfromknecht approved these changes Sep 11, 2020

View reviewed changes

halseth added 6 commits September 11, 2020 11:10

channeldb: correct anchor comment

517fcd6

lnwire: update anchor bit to spec

724f439

lnwallet: extract coop close balance calc into method

07a57ae

lnwallet: add anchor size back to balance on coop close

09a126b

To be spec compliant, we require the initiator to not pay the anchor values into fees on coop close. We extract the balance calculation into commitment.go, and add back the value of the anchors to the initiator's balance.

lnwallet: check coop close fee negative balance

a48c369

Also modify the test to check for this condition.

peer/brontide: fix pubkey log

bf18929

halseth force-pushed the anchors-spec branch from 1ea3da2 to bf18929 Compare September 11, 2020 09:11

cfromknecht merged commit c704c57 into lightningnetwork:master Sep 11, 2020

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[anchor commitment] Make the anchor commitment type spec compliant #4558

[anchor commitment] Make the anchor commitment type spec compliant #4558

halseth commented Aug 21, 2020 •

edited

Loading

cfromknecht left a comment

cfromknecht Aug 21, 2020

halseth Aug 24, 2020

cfromknecht Aug 21, 2020

joostjager Aug 24, 2020

halseth Aug 24, 2020

cfromknecht Aug 21, 2020

halseth Aug 24, 2020

joostjager left a comment

joostjager Aug 24, 2020

halseth commented Aug 24, 2020 •

edited

Loading

cfromknecht commented Aug 24, 2020

joostjager Aug 25, 2020

halseth Aug 26, 2020

cfromknecht Aug 27, 2020

halseth commented Aug 26, 2020

cfromknecht commented Aug 26, 2020

halseth commented Aug 28, 2020

cfromknecht commented Aug 28, 2020

halseth commented Sep 3, 2020

cfromknecht left a comment

[anchor commitment] Make the anchor commitment type spec compliant #4558

[anchor commitment] Make the anchor commitment type spec compliant #4558

Conversation

halseth commented Aug 21, 2020 • edited Loading

cfromknecht left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

joostjager left a comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

halseth commented Aug 24, 2020 • edited Loading

cfromknecht commented Aug 24, 2020

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

halseth commented Aug 26, 2020

cfromknecht commented Aug 26, 2020

halseth commented Aug 28, 2020

cfromknecht commented Aug 28, 2020

halseth commented Sep 3, 2020

cfromknecht left a comment

Choose a reason for hiding this comment

halseth commented Aug 21, 2020 •

edited

Loading

halseth commented Aug 24, 2020 •

edited

Loading