small clean-up re max CLTV delta for LN

electrum/lnpeer.py

@@ -1027,13 +1027,16 @@ class Peer(Logger):
         assert amount_msat > 0, "amount_msat is not greater zero"
         if not chan.can_send_update_add_htlc():
             raise PaymentFailure("Channel cannot send update_add_htlc")
+        local_height = self.network.get_local_height()
         # create onion packet
-        final_cltv = self.network.get_local_height() + min_final_cltv_expiry
+        final_cltv = local_height + min_final_cltv_expiry
         hops_data, amount_msat, cltv = calc_hops_data_for_payment(route, amount_msat, final_cltv)
         assert final_cltv <= cltv, (final_cltv, cltv)
         secret_key = os.urandom(32)
         onion = new_onion_packet([x.node_id for x in route], secret_key, hops_data, associated_data=payment_hash)
         # create htlc
+        if cltv > local_height + lnutil.NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE:
+            raise PaymentFailure(f"htlc expiry too far into future. (in {cltv-local_height} blocks)")
         htlc = UpdateAddHtlc(amount_msat=amount_msat, payment_hash=payment_hash, cltv_expiry=cltv, timestamp=int(time.time()))
         htlc = chan.add_htlc(htlc)
         chan.set_onion_key(htlc.htlc_id, secret_key)

electrum/lnrouter.py

@@ -31,6 +31,7 @@ from .util import bh2u, profiler
 from .logging import Logger
 from .lnutil import NUM_MAX_EDGES_IN_PAYMENT_PATH, ShortChannelID
 from .channel_db import ChannelDB, Policy
+from .lnutil import NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE
 
 if TYPE_CHECKING:
     from .lnchannel import Channel
@@ -99,8 +100,7 @@ def is_route_sane_to_use(route: LNPaymentRoute, invoice_amount_msat: int, min_fi
         cltv += route_edge.cltv_expiry_delta
     total_fee = amt - invoice_amount_msat
     # TODO revise ad-hoc heuristics
-    # cltv cannot be more than 2 months
-    if cltv > 60 * 144:
+    if cltv > NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE:
         return False
     if not is_fee_sane(total_fee, payment_amount_msat=invoice_amount_msat):
         return False

electrum/lnutil.py

@@ -193,7 +193,7 @@ NBLOCK_OUR_CLTV_EXPIRY_DELTA = 144
 OUR_FEE_BASE_MSAT = 1000
 OUR_FEE_PROPORTIONAL_MILLIONTHS = 1
 
-NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE = 4032
+NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE = 28 * 144
 
 
 # When we open a channel, the remote peer has to support at least this

electrum/lnworker.py

@@ -1040,7 +1040,7 @@ class LNWallet(LNWorker):
             addr.amount = Decimal(amount_sat) / COIN
         if addr.amount is None:
             raise InvoiceError(_("Missing amount"))
-        if addr.get_min_final_cltv_expiry() > 60 * 144:
+        if addr.get_min_final_cltv_expiry() > lnutil.NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE:
             raise InvoiceError("{}\n{}".format(
                 _("Invoice wants us to risk locking funds for unreasonably long."),
                 f"min_final_cltv_expiry: {addr.get_min_final_cltv_expiry()}"))