AaronFiore/electrum
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lnpeer.maybe_forward_trampoline: fix cltv calculation

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follow-up b0401a6386
This commit is contained in:
SomberNight
2023-10-18 19:22:52 +00:00
parent a059a9a256
commit eca10eb04d
1 changed files with 14 additions and 5 deletions
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19
electrum/lnpeer.py
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@@ -1780,7 +1780,16 @@ class Peer(Logger):
trampoline_cltv_delta = cltv_expiry - cltv_from_onion # cltv budget
total_msat = outer_onion.hop_data.payload["payment_data"]["total_msat"]
trampoline_fee = total_msat - amt_to_forward
self.logger.info(f'trampoline cltv and fee: {trampoline_cltv_delta, trampoline_fee}')
self.logger.info(f'trampoline forwarding. fee_budget={trampoline_fee}')
self.logger.info(f'trampoline forwarding. cltv_budget={trampoline_cltv_delta}. (inc={cltv_expiry}. out={cltv_from_onion})')
# To convert abs vs rel cltvs, we need to guess blockheight used by original sender as "current blockheight".
# Blocks might have been mined since.
# - if we skew towards the past, we decrease our own cltv_budget accordingly (which is ok)
# - if we skew towards the future, we decrease the cltv_budget for the subsequent nodes in the path,
# which can result in them failing the payment.
# So we skew towards the past and guess that there has been 1 new block mined since the payment began:
local_height_of_onion_creator = self.network.get_local_height() - 1
cltv_budget_for_rest_of_route = cltv_from_onion - local_height_of_onion_creator
try:
await self.lnworker.pay_to_node(
@@ -1788,10 +1797,10 @@ class Peer(Logger):
payment_hash=payment_hash,
payment_secret=payment_secret,
amount_to_pay=amt_to_forward,
# FIXME this API (min_cltv_expiry) is bad. This is setting the cltv-delta for the last edge
# on the path to the *next trampoline* node. We should just let lnrouter set this.
# Instead, we should rewrite pay_to_node to operate on a fee-budget and cltv-budget.
min_cltv_expiry=lnutil.MIN_FINAL_CLTV_EXPIRY_FOR_INVOICE,
# FIXME this API (min_cltv_expiry) is confusing. The value will be added to local_height
# to form the abs cltv used on the last edge on the path to the *next trampoline* node.
# We should rewrite pay_to_node to operate on a cltv-budget (and fee-budget).
min_cltv_expiry=cltv_budget_for_rest_of_route,
r_tags=r_tags,
invoice_features=invoice_features,
fwd_trampoline_onion=next_trampoline_onion,