lnpeer: deduct jit channel fees from total amount

Deduct the just in time channel opening fees from the total amount so
htlcs don't get timed out if they come from a just in time channel with
opening fee.

Related: https://github.com/spesmilo/electrum/pull/9584

electrum/lnchannel.py

@@ -765,8 +765,15 @@ class Channel(AbstractChannel):
     def __repr__(self):
         return "Channel(%s)"%self.get_id_for_log()
 
-    def __init__(self, state: 'StoredDict', *, name=None, lnworker=None, initial_feerate=None, opening_fee=None):
+    def __init__(
-        self.opening_fee = opening_fee
+        self,
+        state: 'StoredDict', *,
+        name=None,
+        lnworker=None,
+        initial_feerate=None,
+        jit_opening_fee: Optional[int] = None,
+    ):
+        self.jit_opening_fee = jit_opening_fee
         self.name = name
         self.channel_id = bfh(state["channel_id"])
         self.short_channel_id = ShortChannelID.normalize(state["short_channel_id"])

electrum/lnpeer.py

@@ -1316,9 +1316,12 @@ class Peer(Logger, EventListener):
         # store the temp id now, so that it is recognized for e.g. 'error' messages
         self.temp_id_to_id[temp_chan_id] = None
         self._cleanup_temp_channelids()
-        channel_opening_fee = open_channel_tlvs.get('channel_opening_fee') if open_channel_tlvs else None
+        channel_opening_fee_tlv = open_channel_tlvs.get('channel_opening_fee', {})
+        channel_opening_fee = channel_opening_fee_tlv.get('channel_opening_fee')
         if channel_opening_fee:
             # todo check that the fee is reasonable
+            assert is_zeroconf
+            self.logger.info(f"just-in-time opening fee: {channel_opening_fee} msat")
             pass
 
         if self.use_anchors():
@@ -1433,7 +1436,7 @@ class Peer(Logger, EventListener):
             chan_dict,
             lnworker=self.lnworker,
             initial_feerate=feerate,
-            opening_fee = channel_opening_fee,
+            jit_opening_fee = channel_opening_fee,
         )
         chan.storage['init_timestamp'] = int(time.time())
         if isinstance(self.transport, LNTransport):
@@ -2115,8 +2118,8 @@ class Peer(Logger, EventListener):
             log_fail_reason(f"'total_msat' missing from onion")
             raise exc_incorrect_or_unknown_pd
 
-        if chan.opening_fee:
+        if chan.jit_opening_fee:
-            channel_opening_fee = chan.opening_fee['channel_opening_fee']  # type: int
+            channel_opening_fee = chan.jit_opening_fee
             total_msat -= channel_opening_fee
             amt_to_forward -= channel_opening_fee
         else:
@@ -2281,7 +2284,7 @@ class Peer(Logger, EventListener):
             self._fulfill_htlc(chan, htlc_id, preimage)
             htlc_set.htlcs.remove(mpp_htlc)
             # reset just-in-time opening fee of channel
-            chan.opening_fee = None
+            chan.jit_opening_fee = None
 
     def _fulfill_htlc(self, chan: Channel, htlc_id: int, preimage: bytes):
         assert chan.hm.is_htlc_irrevocably_added_yet(htlc_proposer=REMOTE, htlc_id=htlc_id)
@@ -3070,6 +3073,10 @@ class Peer(Logger, EventListener):
                 return OnionFailureCode.MPP_TIMEOUT, None, None
 
         if mpp_set.resolution == RecvMPPResolution.WAITING:
+            # calculate the sum of just in time channel opening fees
+            htlc_channels = [self.lnworker.get_channel_by_short_id(scid) for scid in set(h.scid for h in mpp_set.htlcs)]
+            jit_opening_fees_msat = sum((c.jit_opening_fee or 0) for c in htlc_channels)
+
             # check if set is first stage multi-trampoline payment to us
             # first stage trampoline payment:
             # is a trampoline payment + we_are_final + payment key is derived from outer onion's payment secret
@@ -3095,7 +3102,7 @@ class Peer(Logger, EventListener):
                     self.lnworker.received_mpp_htlcs[payment_key] = mpp_set._replace(
                         parent_set_key=trampoline_payment_key,
                     )
-            elif amount_msat >= total_msat:
+            elif amount_msat >= (total_msat - jit_opening_fees_msat):
                 # set mpp_set as completed as we have received the full total_msat
                 mpp_set = self.lnworker.set_mpp_resolution(
                     payment_key=payment_key,