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lnchannel.available_to_spend: consider both receiver's and sender's ctx

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SomberNight
2020-06-10 20:23:12 +02:00
parent 817411b889
commit 7fccd4fc5e
1 changed files with 38 additions and 47 deletions
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85
electrum/lnchannel.py
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@@ -1054,53 +1054,44 @@ class Channel(AbstractChannel):
assert type(subject) is HTLCOwner assert type(subject) is HTLCOwner
sender = subject sender = subject
receiver = subject.inverted() receiver = subject.inverted()
ctx_owner = receiver initiator = LOCAL if self.constraints.is_initiator else REMOTE # the initiator/funder pays on-chain fees
# TODO but what about the other ctx? BOLT-02 only talks about checking the receiver's ctx,
# however the channel reserve is only meaningful if we also check the sender's ctx! def consider_ctx(*, ctx_owner: HTLCOwner) -> int:
# in particular, note that dust limits can be different between the parties! ctn = self.get_next_ctn(ctx_owner)
# but due to the racy nature of this, we cannot be sure exactly what the sender's sender_balance_msat = self.balance_minus_outgoing_htlcs(whose=sender, ctx_owner=ctx_owner, ctn=ctn)
# next ctx will look like (e.g. what feerate it will use). hmmm :/ receiver_balance_msat = self.balance_minus_outgoing_htlcs(whose=receiver, ctx_owner=ctx_owner, ctn=ctn)
ctn = self.get_next_ctn(ctx_owner) sender_reserve_msat = self.config[receiver].reserve_sat * 1000
sender_balance_msat = self.balance_minus_outgoing_htlcs(whose=sender, ctx_owner=ctx_owner, ctn=ctn) receiver_reserve_msat = self.config[sender].reserve_sat * 1000
receiver_balance_msat = self.balance_minus_outgoing_htlcs(whose=receiver, ctx_owner=ctx_owner, ctn=ctn) num_htlcs_in_ctx = len(self.included_htlcs(ctx_owner, SENT, ctn=ctn) + self.included_htlcs(ctx_owner, RECEIVED, ctn=ctn))
sender_reserve_msat = self.config[receiver].reserve_sat * 1000 feerate = self.get_feerate(ctx_owner, ctn=ctn)
receiver_reserve_msat = self.config[sender].reserve_sat * 1000 ctx_fees_msat = calc_fees_for_commitment_tx(
initiator = LOCAL if self.constraints.is_initiator else REMOTE num_htlcs=num_htlcs_in_ctx,
# the initiator/funder pays on-chain fees feerate=feerate,
num_htlcs_in_ctx = len(self.included_htlcs(ctx_owner, SENT, ctn=ctn) + self.included_htlcs(ctx_owner, RECEIVED, ctn=ctn)) is_local_initiator=self.constraints.is_initiator,
feerate = self.get_feerate(ctx_owner, ctn=ctn) round_to_sat=False,
ctx_fees_msat = calc_fees_for_commitment_tx( )
num_htlcs=num_htlcs_in_ctx, htlc_fee_msat = fee_for_htlc_output(feerate=feerate)
feerate=feerate, htlc_trim_func = received_htlc_trim_threshold_sat if ctx_owner == receiver else offered_htlc_trim_threshold_sat
is_local_initiator=self.constraints.is_initiator, htlc_trim_threshold_msat = htlc_trim_func(dust_limit_sat=self.config[ctx_owner].dust_limit_sat, feerate=feerate) * 1000
round_to_sat=False, max_send_msat = sender_balance_msat - sender_reserve_msat - ctx_fees_msat[sender]
) if max_send_msat < htlc_trim_threshold_msat:
# note: if this supposed new HTLC is large enough to create an output, the initiator needs to pay for that too # there will be no corresponding HTLC output
# note: if sender != initiator, both the sender and the receiver need to "afford" the payment return max_send_msat
htlc_fee_msat = fee_for_htlc_output(feerate=feerate) if sender == initiator:
# TODO stuck channels. extra funder reserve? "fee spike buffer" (maybe only if "strict") max_send_after_htlc_fee_msat = max_send_msat - htlc_fee_msat
# see https://github.com/lightningnetwork/lightning-rfc/issues/728 max_send_msat = max(htlc_trim_threshold_msat - 1, max_send_after_htlc_fee_msat)
# note: in terms of on-chain outputs, as we are considering the htlc_receiver's ctx, this is a "received" HTLC return max_send_msat
htlc_trim_threshold_msat = received_htlc_trim_threshold_sat(dust_limit_sat=self.config[receiver].dust_limit_sat, feerate=feerate) * 1000 else:
if strict: # the receiver is the initiator, so they need to be able to pay tx fees
# also consider the other ctx, where the trim threshold is different if receiver_balance_msat - receiver_reserve_msat - ctx_fees_msat[receiver] - htlc_fee_msat < 0:
# note: the 'feerate' we use is not technically correct but we have no way max_send_msat = htlc_trim_threshold_msat - 1
# of knowing the actual future feerate ahead of time (this is a protocol bug) return max_send_msat
htlc_trim_threshold_msat = min(htlc_trim_threshold_msat,
offered_htlc_trim_threshold_sat(dust_limit_sat=self.config[sender].dust_limit_sat, feerate=feerate) * 1000) max_send_msat = min(consider_ctx(ctx_owner=receiver),
max_send_msat = sender_balance_msat - sender_reserve_msat - ctx_fees_msat[sender] consider_ctx(ctx_owner=sender))
if max_send_msat < htlc_trim_threshold_msat: max_send_msat = max(max_send_msat, 0)
# there will be no corresponding HTLC output return max_send_msat
return max_send_msat
if sender == initiator:
max_send_after_htlc_fee_msat = max_send_msat - htlc_fee_msat
max_send_msat = max(htlc_trim_threshold_msat - 1, max_send_after_htlc_fee_msat)
return max_send_msat
else:
# the receiver is the initiator, so they need to be able to pay tx fees
if receiver_balance_msat - receiver_reserve_msat - ctx_fees_msat[receiver] - htlc_fee_msat < 0:
max_send_msat = htlc_trim_threshold_msat - 1
return max_send_msat
def included_htlcs(self, subject: HTLCOwner, direction: Direction, ctn: int = None) -> Sequence[UpdateAddHtlc]: def included_htlcs(self, subject: HTLCOwner, direction: Direction, ctn: int = None) -> Sequence[UpdateAddHtlc]:
"""Returns list of non-dust HTLCs for subject's commitment tx at ctn, """Returns list of non-dust HTLCs for subject's commitment tx at ctn,