chainreg: increase default CLTV value to 80 blocks (~13 hrs)

In this commit, we increase the default CTLV value to 80 blocks.
Initially this was set to 144 blocks in the early days, but then was
lowered to 40 blocks as the lnd implementation matured. By setting this
to a higher value, we increase the safety window (MTTR) when it comes to
node downtime, and also add some buffer room around time locks which may
become more stressed in the future assuming the current mempool load
remains persistent.

chainreg/chainregistry.go

@@ -128,7 +128,7 @@ const (
 
 	// DefaultBitcoinTimeLockDelta is the default forwarding time lock
 	// delta.
-	DefaultBitcoinTimeLockDelta = 40
+	DefaultBitcoinTimeLockDelta = 80
 
 	DefaultLitecoinMinHTLCInMSat  = lnwire.MilliSatoshi(1)
 	DefaultLitecoinMinHTLCOutMSat = lnwire.MilliSatoshi(1000)

docs/release-notes/release-notes-0.16.1.md

@@ -1,5 +1,10 @@
 # Release Notes
 
+## Routing
+
+* The default CLTV delta delay [has been increased from 40 blocks to 80
+  blocks](https://github.com/lightningnetwork/lnd/pull/7609).
+
 ## Wallet
 
 - The logging around transaction broadcast failures [has been improved by always

sample-lnd.conf

@@ -532,7 +532,7 @@ bitcoin.node=btcd
 ; bitcoin.feerate=1
 
 ; The CLTV delta we will subtract from a forwarded HTLC's timelock value.
-; bitcoin.timelockdelta=40
+; bitcoin.timelockdelta=80
 
 ; The seed DNS server(s) to use for initial peer discovery. Must be specified as
 ; a '<primary_dns>[,<soa_primary_dns>]' tuple where the SOA address is needed