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htlcswitch: check for signature owed in link

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Previously the channel method FullySynced was used to decide whether to
send a new commit sig message. However, it could happen that FullySynced
was false, but that we didn't owe a commitment signature. Instead we
were waiting on the other party to send us a signature. If that
happened, we'd send out an empty commit sig. This commit modifies the
condition that triggers a new commit sig and fixes this deviation from
the spec.
This commit is contained in:
Joost Jager 2019-09-23 14:27:06 +02:00
parent 64f4421d6c
commit f59b4d62bf
No known key found for this signature in database
GPG Key ID: A61B9D4C393C59C7
3 changed files with 9 additions and 31 deletions
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4
htlcswitch/link.go
View File

@ -1103,7 +1103,7 @@ out:
// update in some time, check to see if we have any
// pending updates we need to commit due to our
// commitment chains being desynchronized.
if l.channel.FullySynced() {
if !l.channel.OweCommitment(true) {
continue
}
@ -1808,7 +1808,7 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
// If both commitment chains are fully synced from our PoV,
// then we don't need to reply with a signature as both sides
// already have a commitment with the latest accepted.
if l.channel.FullySynced() {
if !l.channel.OweCommitment(true) {
return
}

14
htlcswitch/link_test.go
View File

@ -4699,11 +4699,10 @@ func TestChannelLinkNoEmptySig(t *testing.T) {
ctx.receiveRevAndAckAliceToBob()
ctx.sendRevAndAckBobToAlice()
// The situation now is that Alice still doesn't have her two htlcs on
// the local commit tx. Bob needs to send a new signature and Alice can
// only wait for that. However, Alice's log commit timer fires and Alice
// sends a commitment tx containing no updates. THIS SHOULD NOT HAPPEN!
ctx.receiveCommitSigAliceToBob(2)
// The commit txes are not in sync, but it is Bob's turn to send a new
// signature. We don't expect Alice to send out any message. This check
// allows some time for the log commit ticker to trigger for Alice.
ctx.assertNoMsgFromAlice(time.Second)
}
// TestChannelLinkBatchPreimageWrite asserts that a link will batch preimage
@ -6109,9 +6108,8 @@ func TestChannelLinkReceiveEmptySig(t *testing.T) {
// Send RevokeAndAck Bob->Alice to ack the added htlc.
ctx.sendRevAndAckBobToAlice()
// No new updates to sign, Alice still sends out an empty sig. THIS
// SHOULD NOT HAPPEN!
ctx.receiveCommitSigAliceToBob(1)
// We received an empty commit sig, we accepted it, but there is nothing
// new to sign for us.
// No other messages are expected.
ctx.assertNoMsgFromAlice(time.Second)

22
lnwallet/channel.go
View File

@ -3535,7 +3535,7 @@ func (lc *LightningChannel) ProcessChanSyncMsg(
// but died before the signature was sent. We re-transmit our
// revocation, but also initiate a state transition to re-sync
// them.
if !lc.FullySynced() {
if lc.OweCommitment(true) {
commitSig, htlcSigs, _, err := lc.SignNextCommitment()
switch {
@ -4225,26 +4225,6 @@ func (lc *LightningChannel) oweCommitment(local bool) bool {
return oweCommitment
}
// FullySynced returns a boolean value reflecting if both commitment chains
// (remote+local) are fully in sync. Both commitment chains are fully in sync
// if the tip of each chain includes the latest committed changes from both
// sides.
func (lc *LightningChannel) FullySynced() bool {
lc.RLock()
defer lc.RUnlock()
lastLocalCommit := lc.localCommitChain.tip()
lastRemoteCommit := lc.remoteCommitChain.tip()
localUpdatesSynced := (lastLocalCommit.ourMessageIndex ==
lastRemoteCommit.ourMessageIndex)
remoteUpdatesSynced := (lastLocalCommit.theirMessageIndex ==
lastRemoteCommit.theirMessageIndex)
return localUpdatesSynced && remoteUpdatesSynced
}
// RevokeCurrentCommitment revokes the next lowest unrevoked commitment
// transaction in the local commitment chain. As a result the edge of our
// revocation window is extended by one, and the tail of our local commitment