closingd: use a more accurate fee for closing fee negotiation.

We were actually using the last commit tx's size, since we were
setting it in lightningd.  Instead, hand the min and desired feerates
to closingd, and (as it knows the weight of the closing tx), and have
it start negotiation from there.

This can be significantly less when anchor outputs are enabled: for
example in test_closing.py, the commit tx weight is 1124 Sipa, the
close is 672 Sipa!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: Protocol: Use a more accurate fee for mutual close negotiation.

closingd/closingd.c

@@ -491,6 +491,84 @@ static void closing_dev_memleak(const tal_t *ctx,
 }
 #endif /* DEVELOPER */
 
+/* Figure out what weight we actually expect for this closing tx (using zero fees
+ * gives the largest possible tx: larger values might omit outputs). */
+static size_t closing_tx_weight_estimate(u8 *scriptpubkey[NUM_SIDES],
+					 const u8 *funding_wscript,
+					 const struct amount_sat *out,
+					 struct amount_sat funding,
+					 struct amount_sat dust_limit)
+{
+	/* We create a dummy close */
+	struct bitcoin_tx *tx;
+	struct bitcoin_txid dummy_txid;
+	struct bitcoin_signature dummy_sig;
+	struct privkey dummy_privkey;
+	struct pubkey dummy_pubkey;
+	u8 **witness;
+
+	memset(&dummy_txid, 0, sizeof(dummy_txid));
+	tx = create_close_tx(tmpctx, chainparams,
+			     scriptpubkey[LOCAL], scriptpubkey[REMOTE],
+			     funding_wscript,
+			     &dummy_txid, 0,
+			     funding,
+			     out[LOCAL],
+			     out[REMOTE],
+			     dust_limit);
+
+	/* Create a signature, any signature, so we can weigh fully "signed"
+	 * tx. */
+	dummy_sig.sighash_type = SIGHASH_ALL;
+	memset(&dummy_privkey, 1, sizeof(dummy_privkey));
+	sign_hash(&dummy_privkey, &dummy_txid.shad, &dummy_sig.s);
+	pubkey_from_privkey(&dummy_privkey, &dummy_pubkey);
+	witness = bitcoin_witness_2of2(NULL, &dummy_sig, &dummy_sig,
+				       &dummy_pubkey, &dummy_pubkey);
+	bitcoin_tx_input_set_witness(tx, 0, take(witness));
+
+	return bitcoin_tx_weight(tx);
+}
+
+/* Get the minimum and desired fees */
+static void calc_fee_bounds(size_t expected_weight,
+			    u32 min_feerate,
+			    u32 desired_feerate,
+			    struct amount_sat maxfee,
+			    struct amount_sat *minfee,
+			    struct amount_sat *desiredfee)
+{
+	*minfee = amount_tx_fee(min_feerate, expected_weight);
+	*desiredfee = amount_tx_fee(desired_feerate, expected_weight);
+
+	/* Can't exceed maxfee. */
+	if (amount_sat_greater(*minfee, maxfee))
+		*minfee = maxfee;
+
+	if (amount_sat_less(*desiredfee, *minfee)) {
+		status_unusual("Our ideal fee is %s (%u sats/perkw),"
+			       " but our minimum is %s: using that",
+			       type_to_string(tmpctx, struct amount_sat, desiredfee),
+			       desired_feerate,
+			       type_to_string(tmpctx, struct amount_sat, minfee));
+		*desiredfee = *minfee;
+	}
+	if (amount_sat_greater(*desiredfee, maxfee)) {
+		status_unusual("Our ideal fee is %s (%u sats/perkw),"
+			       " but our maximum is %s: using that",
+			       type_to_string(tmpctx, struct amount_sat, desiredfee),
+			       desired_feerate,
+			       type_to_string(tmpctx, struct amount_sat, &maxfee));
+		*desiredfee = maxfee;
+	}
+
+	status_debug("Expected closing weight = %zu, fee %s (min %s, max %s)",
+		     expected_weight,
+		     type_to_string(tmpctx, struct amount_sat, desiredfee),
+		     type_to_string(tmpctx, struct amount_sat, minfee),
+		     type_to_string(tmpctx, struct amount_sat, &maxfee));
+}
+
 int main(int argc, char *argv[])
 {
 	setup_locale();
@@ -504,6 +582,7 @@ int main(int argc, char *argv[])
 	struct amount_sat funding, out[NUM_SIDES];
 	struct amount_sat our_dust_limit;
 	struct amount_sat min_fee_to_accept, commitment_fee, offer[NUM_SIDES];
+	u32 min_feerate, initial_feerate;
 	struct feerange feerange;
 	enum side opener;
 	u8 *scriptpubkey[NUM_SIDES], *funding_wscript;
@@ -531,8 +610,8 @@ int main(int argc, char *argv[])
 				    &out[LOCAL],
 				    &out[REMOTE],
 				    &our_dust_limit,
-				    &min_fee_to_accept, &commitment_fee,
+				    &min_feerate, &initial_feerate,
-				    &offer[LOCAL],
+				    &commitment_fee,
 				    &scriptpubkey[LOCAL],
 				    &scriptpubkey[REMOTE],
 				    &fee_negotiation_step,
@@ -544,6 +623,17 @@ int main(int argc, char *argv[])
 	/* stdin == requests, 3 == peer, 4 = gossip, 5 = gossip_store, 6 = hsmd */
 	per_peer_state_set_fds(notleak(pps), 3, 4, 5);
 
+	funding_wscript = bitcoin_redeem_2of2(ctx,
+					      &funding_pubkey[LOCAL],
+					      &funding_pubkey[REMOTE]);
+
+	/* Start at what we consider a reasonable feerate for this tx. */
+	calc_fee_bounds(closing_tx_weight_estimate(scriptpubkey,
+						   funding_wscript,
+						   out, funding, our_dust_limit),
+			min_feerate, initial_feerate, commitment_fee,
+			&min_fee_to_accept, &offer[LOCAL]);
+
 	snprintf(fee_negotiation_step_str, sizeof(fee_negotiation_step_str),
 		 "%" PRIu64 "%s", fee_negotiation_step,
 		 fee_negotiation_step_unit ==
@@ -565,10 +655,6 @@ int main(int argc, char *argv[])
 					      &wrong_funding->txid),
 			       wrong_funding->n);
 
-	funding_wscript = bitcoin_redeem_2of2(ctx,
-					      &funding_pubkey[LOCAL],
-					      &funding_pubkey[REMOTE]);
-
 	peer_billboard(
 	    true,
 	    "Negotiating closing fee between %s and %s satoshi (ideal %s) "

closingd/closingd_wire.csv

@@ -17,9 +17,9 @@ msgdata,closingd_init,opener,enum side,
 msgdata,closingd_init,local_sat,amount_sat,
 msgdata,closingd_init,remote_sat,amount_sat,
 msgdata,closingd_init,our_dust_limit,amount_sat,
-msgdata,closingd_init,min_fee_satoshi,amount_sat,
+msgdata,closingd_init,min_feerate_perksipa,u32,
+msgdata,closingd_init,preferred_feerate_perksipa,u32,
 msgdata,closingd_init,fee_limit_satoshi,amount_sat,
-msgdata,closingd_init,initial_fee_satoshi,amount_sat,
 msgdata,closingd_init,local_scriptpubkey_len,u16,
 msgdata,closingd_init,local_scriptpubkey,u8,local_scriptpubkey_len
 msgdata,closingd_init,remote_scriptpubkey_len,u16,

closingd/closingd_wiregen.c

@@ -48,7 +48,7 @@ bool closingd_wire_is_defined(u16 type)
 
 /* WIRE: CLOSINGD_INIT */
 /* Begin!  (passes peer fd */
-u8 *towire_closingd_init(const tal_t *ctx, const struct chainparams *chainparams, const struct per_peer_state *pps, const struct channel_id *channel_id, const struct bitcoin_txid *funding_txid, u16 funding_txout, struct amount_sat funding_satoshi, const struct pubkey *local_fundingkey, const struct pubkey *remote_fundingkey, enum side opener, struct amount_sat local_sat, struct amount_sat remote_sat, struct amount_sat our_dust_limit, struct amount_sat min_fee_satoshi, struct amount_sat fee_limit_satoshi, struct amount_sat initial_fee_satoshi, const u8 *local_scriptpubkey, const u8 *remote_scriptpubkey, u64 fee_negotiation_step, u8 fee_negotiation_step_unit, bool dev_fast_gossip, const struct bitcoin_outpoint *shutdown_wrong_funding)
+u8 *towire_closingd_init(const tal_t *ctx, const struct chainparams *chainparams, const struct per_peer_state *pps, const struct channel_id *channel_id, const struct bitcoin_txid *funding_txid, u16 funding_txout, struct amount_sat funding_satoshi, const struct pubkey *local_fundingkey, const struct pubkey *remote_fundingkey, enum side opener, struct amount_sat local_sat, struct amount_sat remote_sat, struct amount_sat our_dust_limit, u32 min_feerate_perksipa, u32 preferred_feerate_perksipa, struct amount_sat fee_limit_satoshi, const u8 *local_scriptpubkey, const u8 *remote_scriptpubkey, u64 fee_negotiation_step, u8 fee_negotiation_step_unit, bool dev_fast_gossip, const struct bitcoin_outpoint *shutdown_wrong_funding)
 {
 	u16 local_scriptpubkey_len = tal_count(local_scriptpubkey);
 	u16 remote_scriptpubkey_len = tal_count(remote_scriptpubkey);
@@ -67,9 +67,9 @@ u8 *towire_closingd_init(const tal_t *ctx, const struct chainparams *chainparams
 	towire_amount_sat(&p, local_sat);
 	towire_amount_sat(&p, remote_sat);
 	towire_amount_sat(&p, our_dust_limit);
-	towire_amount_sat(&p, min_fee_satoshi);
+	towire_u32(&p, min_feerate_perksipa);
+	towire_u32(&p, preferred_feerate_perksipa);
 	towire_amount_sat(&p, fee_limit_satoshi);
-	towire_amount_sat(&p, initial_fee_satoshi);
 	towire_u16(&p, local_scriptpubkey_len);
 	towire_u8_array(&p, local_scriptpubkey, local_scriptpubkey_len);
 	towire_u16(&p, remote_scriptpubkey_len);
@@ -86,7 +86,7 @@ u8 *towire_closingd_init(const tal_t *ctx, const struct chainparams *chainparams
 
 	return memcheck(p, tal_count(p));
 }
-bool fromwire_closingd_init(const tal_t *ctx, const void *p, const struct chainparams **chainparams, struct per_peer_state **pps, struct channel_id *channel_id, struct bitcoin_txid *funding_txid, u16 *funding_txout, struct amount_sat *funding_satoshi, struct pubkey *local_fundingkey, struct pubkey *remote_fundingkey, enum side *opener, struct amount_sat *local_sat, struct amount_sat *remote_sat, struct amount_sat *our_dust_limit, struct amount_sat *min_fee_satoshi, struct amount_sat *fee_limit_satoshi, struct amount_sat *initial_fee_satoshi, u8 **local_scriptpubkey, u8 **remote_scriptpubkey, u64 *fee_negotiation_step, u8 *fee_negotiation_step_unit, bool *dev_fast_gossip, struct bitcoin_outpoint **shutdown_wrong_funding)
+bool fromwire_closingd_init(const tal_t *ctx, const void *p, const struct chainparams **chainparams, struct per_peer_state **pps, struct channel_id *channel_id, struct bitcoin_txid *funding_txid, u16 *funding_txout, struct amount_sat *funding_satoshi, struct pubkey *local_fundingkey, struct pubkey *remote_fundingkey, enum side *opener, struct amount_sat *local_sat, struct amount_sat *remote_sat, struct amount_sat *our_dust_limit, u32 *min_feerate_perksipa, u32 *preferred_feerate_perksipa, struct amount_sat *fee_limit_satoshi, u8 **local_scriptpubkey, u8 **remote_scriptpubkey, u64 *fee_negotiation_step, u8 *fee_negotiation_step_unit, bool *dev_fast_gossip, struct bitcoin_outpoint **shutdown_wrong_funding)
 {
 	u16 local_scriptpubkey_len;
 	u16 remote_scriptpubkey_len;
@@ -108,9 +108,9 @@ bool fromwire_closingd_init(const tal_t *ctx, const void *p, const struct chainp
  	*local_sat = fromwire_amount_sat(&cursor, &plen);
  	*remote_sat = fromwire_amount_sat(&cursor, &plen);
  	*our_dust_limit = fromwire_amount_sat(&cursor, &plen);
- 	*min_fee_satoshi = fromwire_amount_sat(&cursor, &plen);
+ 	*min_feerate_perksipa = fromwire_u32(&cursor, &plen);
+ 	*preferred_feerate_perksipa = fromwire_u32(&cursor, &plen);
  	*fee_limit_satoshi = fromwire_amount_sat(&cursor, &plen);
- 	*initial_fee_satoshi = fromwire_amount_sat(&cursor, &plen);
  	local_scriptpubkey_len = fromwire_u16(&cursor, &plen);
  	// 2nd case local_scriptpubkey
 	*local_scriptpubkey = local_scriptpubkey_len ? tal_arr(ctx, u8, local_scriptpubkey_len) : NULL;
@@ -195,4 +195,4 @@ bool fromwire_closingd_complete(const void *p)
 		return false;
 	return cursor != NULL;
 }
-// SHA256STAMP:cbcaa37f43a9705e657ef6905e276ac4b703171a3f9dcd6f6ca352e3d753a6f2
+// SHA256STAMP:a8b0af1ae87e71bc448585060b8d449c3e5f0d0f4f3ac195dcd4d84f8176ae17

closingd/closingd_wiregen.h

@@ -37,8 +37,8 @@ bool closingd_wire_is_defined(u16 type);
 
 /* WIRE: CLOSINGD_INIT */
 /*  Begin!  (passes peer fd */
-u8 *towire_closingd_init(const tal_t *ctx, const struct chainparams *chainparams, const struct per_peer_state *pps, const struct channel_id *channel_id, const struct bitcoin_txid *funding_txid, u16 funding_txout, struct amount_sat funding_satoshi, const struct pubkey *local_fundingkey, const struct pubkey *remote_fundingkey, enum side opener, struct amount_sat local_sat, struct amount_sat remote_sat, struct amount_sat our_dust_limit, struct amount_sat min_fee_satoshi, struct amount_sat fee_limit_satoshi, struct amount_sat initial_fee_satoshi, const u8 *local_scriptpubkey, const u8 *remote_scriptpubkey, u64 fee_negotiation_step, u8 fee_negotiation_step_unit, bool dev_fast_gossip, const struct bitcoin_outpoint *shutdown_wrong_funding);
+u8 *towire_closingd_init(const tal_t *ctx, const struct chainparams *chainparams, const struct per_peer_state *pps, const struct channel_id *channel_id, const struct bitcoin_txid *funding_txid, u16 funding_txout, struct amount_sat funding_satoshi, const struct pubkey *local_fundingkey, const struct pubkey *remote_fundingkey, enum side opener, struct amount_sat local_sat, struct amount_sat remote_sat, struct amount_sat our_dust_limit, u32 min_feerate_perksipa, u32 preferred_feerate_perksipa, struct amount_sat fee_limit_satoshi, const u8 *local_scriptpubkey, const u8 *remote_scriptpubkey, u64 fee_negotiation_step, u8 fee_negotiation_step_unit, bool dev_fast_gossip, const struct bitcoin_outpoint *shutdown_wrong_funding);
-bool fromwire_closingd_init(const tal_t *ctx, const void *p, const struct chainparams **chainparams, struct per_peer_state **pps, struct channel_id *channel_id, struct bitcoin_txid *funding_txid, u16 *funding_txout, struct amount_sat *funding_satoshi, struct pubkey *local_fundingkey, struct pubkey *remote_fundingkey, enum side *opener, struct amount_sat *local_sat, struct amount_sat *remote_sat, struct amount_sat *our_dust_limit, struct amount_sat *min_fee_satoshi, struct amount_sat *fee_limit_satoshi, struct amount_sat *initial_fee_satoshi, u8 **local_scriptpubkey, u8 **remote_scriptpubkey, u64 *fee_negotiation_step, u8 *fee_negotiation_step_unit, bool *dev_fast_gossip, struct bitcoin_outpoint **shutdown_wrong_funding);
+bool fromwire_closingd_init(const tal_t *ctx, const void *p, const struct chainparams **chainparams, struct per_peer_state **pps, struct channel_id *channel_id, struct bitcoin_txid *funding_txid, u16 *funding_txout, struct amount_sat *funding_satoshi, struct pubkey *local_fundingkey, struct pubkey *remote_fundingkey, enum side *opener, struct amount_sat *local_sat, struct amount_sat *remote_sat, struct amount_sat *our_dust_limit, u32 *min_feerate_perksipa, u32 *preferred_feerate_perksipa, struct amount_sat *fee_limit_satoshi, u8 **local_scriptpubkey, u8 **remote_scriptpubkey, u64 *fee_negotiation_step, u8 *fee_negotiation_step_unit, bool *dev_fast_gossip, struct bitcoin_outpoint **shutdown_wrong_funding);
 
 /* WIRE: CLOSINGD_RECEIVED_SIGNATURE */
 /*  We received an offer */
@@ -56,4 +56,4 @@ bool fromwire_closingd_complete(const void *p);
 
 
 #endif /* LIGHTNING_CLOSINGD_CLOSINGD_WIREGEN_H */
-// SHA256STAMP:cbcaa37f43a9705e657ef6905e276ac4b703171a3f9dcd6f6ca352e3d753a6f2
+// SHA256STAMP:a8b0af1ae87e71bc448585060b8d449c3e5f0d0f4f3ac195dcd4d84f8176ae17

lightningd/closing_control.c

@@ -197,8 +197,8 @@ void peer_start_closingd(struct channel *channel,
 {
 	u8 *initmsg;
 	u32 feerate;
-	struct amount_sat minfee, startfee, feelimit;
 	struct amount_msat their_msat;
+	struct amount_sat feelimit;
 	int hsmfd;
 	struct lightningd *ld = channel->peer->ld;
 	u32 final_commit_feerate;
@@ -247,10 +247,6 @@ void peer_start_closingd(struct channel *channel,
 	feelimit = commit_tx_base_fee(final_commit_feerate, 0,
 				      channel->option_anchor_outputs);
 
-	/* Pick some value above slow feerate (or min possible if unknown) */
-	minfee = commit_tx_base_fee(feerate_min(ld, NULL), 0,
-				    channel->option_anchor_outputs);
-
 	/* If we can't determine feerate, start at half unilateral feerate. */
 	feerate = mutual_close_feerate(ld->topology);
 	if (!feerate) {
@@ -258,13 +254,6 @@ void peer_start_closingd(struct channel *channel,
 		if (feerate < feerate_floor())
 			feerate = feerate_floor();
 	}
-	startfee = commit_tx_base_fee(feerate, 0,
-				      channel->option_anchor_outputs);
-
-	if (amount_sat_greater(startfee, feelimit))
-		startfee = feelimit;
-	if (amount_sat_greater(minfee, feelimit))
-		minfee = feelimit;
 
 	/* BOLT #3:
 	 *
@@ -298,7 +287,7 @@ void peer_start_closingd(struct channel *channel,
 				       amount_msat_to_sat_round_down(channel->our_msat),
 				       amount_msat_to_sat_round_down(their_msat),
 				       channel->our_config.dust_limit,
-				       minfee, feelimit, startfee,
+				       feerate_min(ld, NULL), feerate, feelimit,
 				       channel->shutdown_scriptpubkey[LOCAL],
 				       channel->shutdown_scriptpubkey[REMOTE],
 				       channel->closing_fee_negotiation_step,

tests/test_closing.py

@@ -5,7 +5,7 @@ from shutil import copyfile
 from pyln.testing.utils import SLOW_MACHINE
 from utils import (
     only_one, sync_blockheight, wait_for, TIMEOUT,
-    account_balance, first_channel_id, basic_fee, TEST_NETWORK,
+    account_balance, first_channel_id, closing_fee, TEST_NETWORK,
     scriptpubkey_addr
 )
 
@@ -22,7 +22,7 @@ import unittest
 def test_closing(node_factory, bitcoind, chainparams):
     l1, l2 = node_factory.line_graph(2)
     chan = l1.get_channel_scid(l2)
-    fee = basic_fee(3750) if not chainparams['elements'] else 4477
+    fee = closing_fee(3750, 2) if not chainparams['elements'] else 3603
 
     l1.pay(l2, 200000000)
 
@@ -377,7 +377,7 @@ def closing_negotiation_step(node_factory, bitcoind, chainparams, opts):
         """Binary search to find feerate"""
         assert minimum != maximum
         mid = (minimum + maximum) // 2
-        mid_fee = basic_fee(mid)
+        mid_fee = closing_fee(mid, 1)
         if mid_fee > target:
             return feerate_for(target, minimum, mid)
         elif mid_fee < target:
@@ -452,11 +452,11 @@ def test_closing_negotiation_step_30pct(node_factory, bitcoind, chainparams):
     opts['fee_negotiation_step'] = '30%'
 
     opts['close_initiated_by'] = 'opener'
-    opts['expected_close_fee'] = 20537 if not chainparams['elements'] else 33870
+    opts['expected_close_fee'] = 20537 if not chainparams['elements'] else 26046
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
     opts['close_initiated_by'] = 'peer'
-    opts['expected_close_fee'] = 20233 if not chainparams['elements'] else 33366
+    opts['expected_close_fee'] = 20233 if not chainparams['elements'] else 25657
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
 
@@ -466,11 +466,11 @@ def test_closing_negotiation_step_50pct(node_factory, bitcoind, chainparams):
     opts['fee_negotiation_step'] = '50%'
 
     opts['close_initiated_by'] = 'opener'
-    opts['expected_close_fee'] = 20334 if not chainparams['elements'] else 33533
+    opts['expected_close_fee'] = 20334 if not chainparams['elements'] else 25789
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
     opts['close_initiated_by'] = 'peer'
-    opts['expected_close_fee'] = 20334 if not chainparams['elements'] else 33533
+    opts['expected_close_fee'] = 20334 if not chainparams['elements'] else 25789
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
 
@@ -480,7 +480,7 @@ def test_closing_negotiation_step_100pct(node_factory, bitcoind, chainparams):
     opts['fee_negotiation_step'] = '100%'
 
     opts['close_initiated_by'] = 'opener'
-    opts['expected_close_fee'] = 20001 if not chainparams['elements'] else 32985
+    opts['expected_close_fee'] = 20001 if not chainparams['elements'] else 25366
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
     # The close fee of 20499 looks strange in this case - one would expect
@@ -489,7 +489,7 @@ def test_closing_negotiation_step_100pct(node_factory, bitcoind, chainparams):
     # * the opener is always first to propose, he uses 50% step, so he proposes 20500
     # * the range is narrowed to [20001, 20499] and the peer proposes 20499
     opts['close_initiated_by'] = 'peer'
-    opts['expected_close_fee'] = 20499 if not chainparams['elements'] else 33808
+    opts['expected_close_fee'] = 20499 if not chainparams['elements'] else 25998
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
 
@@ -499,11 +499,11 @@ def test_closing_negotiation_step_1sat(node_factory, bitcoind, chainparams):
     opts['fee_negotiation_step'] = '1'
 
     opts['close_initiated_by'] = 'opener'
-    opts['expected_close_fee'] = 20989 if not chainparams['elements'] else 34621
+    opts['expected_close_fee'] = 20989 if not chainparams['elements'] else 26624
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
     opts['close_initiated_by'] = 'peer'
-    opts['expected_close_fee'] = 20010 if not chainparams['elements'] else 32995
+    opts['expected_close_fee'] = 20010 if not chainparams['elements'] else 25373
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
 
@@ -513,11 +513,11 @@ def test_closing_negotiation_step_700sat(node_factory, bitcoind, chainparams):
     opts['fee_negotiation_step'] = '700'
 
     opts['close_initiated_by'] = 'opener'
-    opts['expected_close_fee'] = 20151 if not chainparams['elements'] else 33459
+    opts['expected_close_fee'] = 20151 if not chainparams['elements'] else 25650
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
     opts['close_initiated_by'] = 'peer'
-    opts['expected_close_fee'] = 20499 if not chainparams['elements'] else 33746
+    opts['expected_close_fee'] = 20499 if not chainparams['elements'] else 25998
     closing_negotiation_step(node_factory, bitcoind, chainparams, opts)
 
 

tests/test_plugin.py

@@ -1884,8 +1884,8 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
             {'type': 'chain_mvt', 'credit': 1000000000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'channel_mvt', 'credit': 0, 'debit': 100000000, 'tag': 'routed'},
             {'type': 'channel_mvt', 'credit': 50000501, 'debit': 0, 'tag': 'routed'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 4477501, 'tag': 'chain_fees'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 4271501, 'tag': 'chain_fees'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 945523000, 'tag': 'withdrawal'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 945729000, 'tag': 'withdrawal'},
         ]
 
         l2_wallet_mvts = [
@@ -1898,7 +1898,7 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
             {'type': 'chain_mvt', 'credit': 0, 'debit': 8092000, 'tag': 'chain_fees'},
             {'type': 'chain_mvt', 'credit': 991908000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'chain_mvt', 'credit': 100001000, 'debit': 0, 'tag': 'deposit'},
-            {'type': 'chain_mvt', 'credit': 945523000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'chain_mvt', 'credit': 945729000, 'debit': 0, 'tag': 'deposit'},
         ]
     elif EXPERIMENTAL_FEATURES:
         # option_anchor_outputs
@@ -1906,8 +1906,8 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
             {'type': 'chain_mvt', 'credit': 1000000000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'channel_mvt', 'credit': 0, 'debit': 100000000, 'tag': 'routed'},
             {'type': 'channel_mvt', 'credit': 50000501, 'debit': 0, 'tag': 'routed'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 4215501, 'tag': 'chain_fees'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 2520501, 'tag': 'chain_fees'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 945785000, 'tag': 'withdrawal'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 947480000, 'tag': 'withdrawal'},
         ]
 
         l2_wallet_mvts = [
@@ -1921,15 +1921,15 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
             {'type': 'chain_mvt', 'credit': 0, 'debit': 4567000, 'tag': 'chain_fees'},
             {'type': 'chain_mvt', 'credit': 995433000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'chain_mvt', 'credit': 100001000, 'debit': 0, 'tag': 'deposit'},
-            {'type': 'chain_mvt', 'credit': 945785000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'chain_mvt', 'credit': 947480000, 'debit': 0, 'tag': 'deposit'},
         ]
     else:
         l2_l3_mvts = [
             {'type': 'chain_mvt', 'credit': 1000000000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'channel_mvt', 'credit': 0, 'debit': 100000000, 'tag': 'routed'},
             {'type': 'channel_mvt', 'credit': 50000501, 'debit': 0, 'tag': 'routed'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 2715501, 'tag': 'chain_fees'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 2520501, 'tag': 'chain_fees'},
-            {'type': 'chain_mvt', 'credit': 0, 'debit': 947285000, 'tag': 'withdrawal'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 947480000, 'tag': 'withdrawal'},
         ]
 
         l2_wallet_mvts = [
@@ -1943,7 +1943,7 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
             {'type': 'chain_mvt', 'credit': 0, 'debit': 4567000, 'tag': 'chain_fees'},
             {'type': 'chain_mvt', 'credit': 995433000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'chain_mvt', 'credit': 100001000, 'debit': 0, 'tag': 'deposit'},
-            {'type': 'chain_mvt', 'credit': 947285000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'chain_mvt', 'credit': 947480000, 'debit': 0, 'tag': 'deposit'},
         ]
 
     l1, l2, l3 = node_factory.line_graph(3, opts=[

tests/utils.py

@@ -151,6 +151,12 @@ def basic_fee(feerate):
     return (weight * feerate) // 1000
 
 
+def closing_fee(feerate, num_outputs):
+    assert num_outputs == 1 or num_outputs == 2
+    weight = 424 + 124 * num_outputs
+    return (weight * feerate) // 1000
+
+
 def scriptpubkey_addr(scriptpubkey):
     if 'addresses' in scriptpubkey:
         return scriptpubkey['addresses'][0]