use correct feerate when sweeping htlcs

fixes #6131

electrum/lnchannel.py

@@ -838,6 +838,7 @@ class Channel(AbstractChannel):
             _script, htlc_tx = make_htlc_tx_with_open_channel(chan=self,
                                                               pcp=self.config[REMOTE].next_per_commitment_point,
                                                               subject=REMOTE,
+                                                              ctn=next_remote_ctn,
                                                               htlc_direction=direction,
                                                               commit=pending_remote_commitment,
                                                               ctx_output_idx=ctx_output_idx,
@@ -886,17 +887,19 @@ class Channel(AbstractChannel):
                                   htlc_direction=direction,
                                   pcp=pcp,
                                   ctx=pending_local_commitment,
-                                  ctx_output_idx=ctx_output_idx)
+                                  ctx_output_idx=ctx_output_idx,
+                                  ctn=next_local_ctn)
         with self.db_lock:
             self.hm.recv_ctx()
             self.config[LOCAL].current_commitment_signature=sig
             self.config[LOCAL].current_htlc_signatures=htlc_sigs_string
 
     def _verify_htlc_sig(self, *, htlc: UpdateAddHtlc, htlc_sig: bytes, htlc_direction: Direction,
-                         pcp: bytes, ctx: Transaction, ctx_output_idx: int) -> None:
+                         pcp: bytes, ctx: Transaction, ctx_output_idx: int, ctn: int) -> None:
         _script, htlc_tx = make_htlc_tx_with_open_channel(chan=self,
                                                           pcp=pcp,
                                                           subject=LOCAL,
+                                                          ctn=ctn,
                                                           htlc_direction=htlc_direction,
                                                           commit=ctx,
                                                           ctx_output_idx=ctx_output_idx,

electrum/lnsweep.py

@@ -41,6 +41,7 @@ def create_sweeptxs_for_watchtower(chan: 'Channel', ctx: Transaction, per_commit
     Sweep 'to_local', and all the HTLCs (two cases: directly from ctx, or from HTLC tx).
     """
     # prep
+    ctn = extract_ctn_from_tx_and_chan(ctx, chan)
     pcp = ecc.ECPrivkey(per_commitment_secret).get_public_key_bytes(compressed=True)
     this_conf, other_conf = get_ordered_channel_configs(chan=chan, for_us=False)
     other_revocation_privkey = derive_blinded_privkey(other_conf.revocation_basepoint.privkey,
@@ -72,6 +73,7 @@ def create_sweeptxs_for_watchtower(chan: 'Channel', ctx: Transaction, per_commit
         htlc_tx_witness_script, htlc_tx = make_htlc_tx_with_open_channel(chan=chan,
                                                                          pcp=pcp,
                                                                          subject=REMOTE,
+                                                                         ctn=ctn,
                                                                          htlc_direction=htlc_direction,
                                                                          commit=ctx,
                                                                          htlc=htlc,
@@ -85,7 +87,6 @@ def create_sweeptxs_for_watchtower(chan: 'Channel', ctx: Transaction, per_commit
             is_revocation=True,
             config=chan.lnworker.config)
 
-    ctn = extract_ctn_from_tx_and_chan(ctx, chan)
     htlc_to_ctx_output_idx_map = map_htlcs_to_ctx_output_idxs(chan=chan,
                                                               ctx=ctx,
                                                               pcp=pcp,
@@ -425,9 +426,11 @@ def create_htlctx_that_spends_from_our_ctx(chan: 'Channel', our_pcp: bytes,
                                            ctx_output_idx: int) -> Tuple[bytes, Transaction]:
     assert (htlc_direction == RECEIVED) == bool(preimage), 'preimage is required iff htlc is received'
     preimage = preimage or b''
+    ctn = extract_ctn_from_tx_and_chan(ctx, chan)
     witness_script, htlc_tx = make_htlc_tx_with_open_channel(chan=chan,
                                                              pcp=our_pcp,
                                                              subject=LOCAL,
+                                                             ctn=ctn,
                                                              htlc_direction=htlc_direction,
                                                              commit=ctx,
                                                              htlc=htlc,

electrum/lnutil.py

@@ -564,7 +564,7 @@ def map_htlcs_to_ctx_output_idxs(*, chan: 'Channel', ctx: Transaction, pcp: byte
             for htlc_relative_idx, ctx_output_idx in enumerate(sorted(inverse_map))}
 
 
-def make_htlc_tx_with_open_channel(*, chan: 'Channel', pcp: bytes, subject: 'HTLCOwner',
+def make_htlc_tx_with_open_channel(*, chan: 'Channel', pcp: bytes, subject: 'HTLCOwner', ctn: int,
                                    htlc_direction: 'Direction', commit: Transaction, ctx_output_idx: int,
                                    htlc: 'UpdateAddHtlc', name: str = None) -> Tuple[bytes, PartialTransaction]:
     amount_msat, cltv_expiry, payment_hash = htlc.amount_msat, htlc.cltv_expiry, htlc.payment_hash
@@ -580,7 +580,7 @@ def make_htlc_tx_with_open_channel(*, chan: 'Channel', pcp: bytes, subject: 'HTL
     is_htlc_success = htlc_direction == RECEIVED
     witness_script_of_htlc_tx_output, htlc_tx_output = make_htlc_tx_output(
         amount_msat = amount_msat,
-        local_feerate = chan.get_next_feerate(LOCAL if for_us else REMOTE),
+        local_feerate = chan.get_feerate(subject, ctn=ctn),
         revocationpubkey=other_revocation_pubkey,
         local_delayedpubkey=delayedpubkey,
         success = is_htlc_success,