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funding+htlcswitch: dynamically update short chan id of existing link

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In this commit, we fix an existing bug that would result in some
payments getting “stuck”. This would happen if one side restarted
before the channel was fully locked in. In this case, since upon
re-connection, the link will get added to the switch with a *short
channel ID of zero*. If A then tries to make a multi-hop payment
through B, B will fail to forward the payment, as it’ll mistakenly
think that the payment originated from a local-subsystem as the channel
ID is zero. A short channel ID of zero is used to map local payments
back to their caller.

With fix this by allowing the funding manager to dynamically update the
short channel ID of a link after it discovers the short channel ID.

In this commit, we fix a second instance of reported “stuck” payments
by users.
This commit is contained in:
Olaoluwa Osuntokun
2018-02-03 18:14:09 -08:00
parent 71a837630a
commit 30dbbd69a0
7 changed files with 145 additions and 14 deletions
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42
htlcswitch/link.go
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@@ -196,6 +196,9 @@ type channelLink struct {
// updates.
channel *lnwallet.LightningChannel
// shortChanID is the most up to date short channel ID for the link.
shortChanID lnwire.ShortChannelID
// cfg is a structure which carries all dependable fields/handlers
// which may affect behaviour of the service.
cfg ChannelLinkConfig
@@ -236,6 +239,8 @@ type channelLink struct {
logCommitTimer *time.Timer
logCommitTick <-chan time.Time
sync.RWMutex
wg sync.WaitGroup
quit chan struct{}
}
@@ -248,6 +253,7 @@ func NewChannelLink(cfg ChannelLinkConfig, channel *lnwallet.LightningChannel,
link := &channelLink{
cfg: cfg,
channel: channel,
shortChanID: channel.ShortChanID(),
mailBox: newMemoryMailBox(),
linkControl: make(chan interface{}),
// TODO(roasbeef): just do reserve here?
@@ -1090,6 +1096,8 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
l.channel.ChannelPoint(), len(htlcsToForward))
for _, packet := range htlcsToForward {
if err := l.cfg.Switch.forward(packet); err != nil {
// TODO(roasbeef): cancel back htlc
// under certain conditions?
log.Errorf("channel link(%v): "+
"unhandled error while forwarding "+
"htlc packet over htlc "+
@@ -1161,7 +1169,37 @@ func (l *channelLink) Peer() Peer {
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) ShortChanID() lnwire.ShortChannelID {
return l.channel.ShortChanID()
l.RLock()
defer l.RUnlock()
return l.shortChanID
}
// UpdateShortChanID updates the short channel ID for a link. This may be
// required in the event that a link is created before the short chan ID for it
// is known, or a re-org occurs, and the funding transaction changes location
// within the chain.
//
// NOTE: Part of the ChannelLink interface.
func (l *channelLink) UpdateShortChanID(sid lnwire.ShortChannelID) {
l.Lock()
defer l.Unlock()
log.Infof("Updating short chan ID for ChannelPoint(%v)", l)
l.shortChanID = sid
go func() {
err := l.cfg.UpdateContractSignals(&contractcourt.ContractSignals{
HtlcUpdates: l.htlcUpdates,
ShortChanID: l.channel.ShortChanID(),
})
if err != nil {
log.Errorf("Unable to update signals for "+
"ChannelLink(%v)", l)
}
}()
return
}
// ChanID returns the channel ID for the channel link. The channel ID is a more
@@ -1806,5 +1844,5 @@ func (l *channelLink) sendMalformedHTLCError(htlcIndex uint64,
func (l *channelLink) fail(format string, a ...interface{}) {
reason := errors.Errorf(format, a...)
log.Error(reason)
l.cfg.Peer.Disconnect(reason)
go l.cfg.Peer.Disconnect(reason)
}