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link: also check expiry grace delta for forwarded htlcs

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Previously there was no minimum remaining blocks requirement on
forwarded htlcs, which may cause channel arbitrator to force
close the channel directly after forwarding the htlc.

Co-authored-by: Jim Posen <jim.posen@gmail.com>
This commit is contained in:
Joost Jager 2019-03-26 11:54:08 +01:00
parent d107627145
commit e6fbbaa1dc
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GPG Key ID: A61B9D4C393C59C7
1 changed files with 15 additions and 13 deletions
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28
htlcswitch/link.go
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@ -30,14 +30,16 @@ func init() {
} }
const ( const (
// expiryGraceDelta is a grace period that the timeout of incoming // expiryGraceDelta is the minimum difference between the current block
// HTLC's that pay directly to us (i.e we're the "exit node") must up // height and the CLTV we require on 1) an outgoing HTLC in order to
// hold. We'll reject any HTLC's who's timeout minus this value is less // forward as an intermediary hop, or 2) an incoming HTLC to reveal the
// that or equal to the current block height. We require this in order // preimage as the final hop. We'll reject any HTLC's who's timeout minus
// to ensure that if the extending party goes to the chain, then we'll // this value is less than or equal to the current block height. We require
// be able to claim the HTLC still. // this in order to ensure that we have sufficient time to claim or
// timeout an HTLC on chain.
// //
// TODO(roasbeef): must be < default delta // This MUST be greater than the maximum BroadcastDelta of the
// ChannelArbitrator for the outbound channel.
expiryGraceDelta = 2 expiryGraceDelta = 2
// maxCltvExpiry is the maximum outgoing time lock that the node accepts // maxCltvExpiry is the maximum outgoing time lock that the node accepts
@ -2147,14 +2149,13 @@ func (l *channelLink) HtlcSatifiesPolicy(payHash [32]byte,
return failure return failure
} }
// We want to avoid accepting an HTLC which will expire in the near // We want to avoid offering an HTLC which will expire in the near
// future, so we'll reject an HTLC if its expiration time is too close // future, so we'll reject an HTLC if the outgoing expiration time is
// to the current height. // too close to the current height.
timeDelta := policy.TimeLockDelta if outgoingTimeout-expiryGraceDelta <= heightNow {
if incomingTimeout-timeDelta <= heightNow {
l.errorf("htlc(%x) has an expiry that's too soon: "+ l.errorf("htlc(%x) has an expiry that's too soon: "+
"outgoing_expiry=%v, best_height=%v", payHash[:], "outgoing_expiry=%v, best_height=%v", payHash[:],
incomingTimeout-timeDelta, heightNow) outgoingTimeout, heightNow)
var failure lnwire.FailureMessage var failure lnwire.FailureMessage
update, err := l.cfg.FetchLastChannelUpdate( update, err := l.cfg.FetchLastChannelUpdate(
@ -2181,6 +2182,7 @@ func (l *channelLink) HtlcSatifiesPolicy(payHash [32]byte,
// the following constraint: the incoming time-lock minus our time-lock // the following constraint: the incoming time-lock minus our time-lock
// delta should equal the outgoing time lock. Otherwise, whether the // delta should equal the outgoing time lock. Otherwise, whether the
// sender messed up, or an intermediate node tampered with the HTLC. // sender messed up, or an intermediate node tampered with the HTLC.
timeDelta := policy.TimeLockDelta
if incomingTimeout-timeDelta < outgoingTimeout { if incomingTimeout-timeDelta < outgoingTimeout {
l.errorf("Incoming htlc(%x) has incorrect time-lock value: "+ l.errorf("Incoming htlc(%x) has incorrect time-lock value: "+
"expected at least %v block delta, got %v block delta", "expected at least %v block delta, got %v block delta",