coin_mvt: record fees for an outbound htlc

If we initialized the payment, the fees are the entire fee-chain
(final hop amount - starting hop amount)

If it's a payment we routed, the fees are the diff between the
inbound htlc and the outbound (net gain by this routing)

Added to database so data persists nicely.

lightningd/coin_mvts.c

@@ -63,25 +63,16 @@ struct channel_coin_mvt *new_channel_mvt_invoice_hout(const tal_t *ctx,
 	return new_channel_coin_mvt(ctx, &channel->cid,
 				    hout->payment_hash, &hout->partid,
 				    hout->msat, new_tag_arr(ctx, INVOICE),
-				    false, AMOUNT_MSAT(0));
+				    false, hout->fees);
 }
 
 struct channel_coin_mvt *new_channel_mvt_routed_hout(const tal_t *ctx,
 						     struct htlc_out *hout,
 						     struct channel *channel)
 {
-	struct amount_msat fees_collected;
-
-	if (!hout->in)
-		return NULL;
-
-	if (!amount_msat_sub(&fees_collected, hout->in->msat,
-			     hout->msat))
-		return NULL;
-
 	return new_channel_coin_mvt(ctx, &channel->cid,
 				    hout->payment_hash, NULL,
 				    hout->msat, new_tag_arr(ctx, ROUTED),
 				    false,
-				    fees_collected);
+				    hout->fees);
 }

lightningd/htlc_end.c

@@ -279,6 +279,7 @@ struct htlc_out *new_htlc_out(const tal_t *ctx,
 			      const u8 *onion_routing_packet,
 			      const struct pubkey *blinding,
 			      bool am_origin,
+			      struct amount_msat final_msat,
 			      u64 partid,
 			      u64 groupid,
 			      struct htlc_in *in)
@@ -310,10 +311,34 @@ struct htlc_out *new_htlc_out(const tal_t *ctx,
 	if (am_origin) {
 		hout->partid = partid;
 		hout->groupid = groupid;
+
+		/* Stash the fees (for accounting) */
+		if (!amount_msat_sub(&hout->fees, msat, final_msat))
+			return corrupt("new_htlc_out",
+				       "overflow subtract %s-%s",
+				       type_to_string(tmpctx,
+						      struct amount_msat,
+						      &msat),
+				       type_to_string(tmpctx,
+						      struct amount_msat,
+						      &final_msat));
+
 	}
 	hout->in = NULL;
-	if (in)
+	if (in) {
 		htlc_out_connect_htlc_in(hout, in);
 
+		/* Stash the fees (for accounting) */
+		if (!amount_msat_sub(&hout->fees, in->msat, msat))
+			return corrupt("new_htlc_out",
+				       "overflow subtract %s-%s",
+				       type_to_string(tmpctx,
+						      struct amount_msat,
+						      &in->msat),
+				       type_to_string(tmpctx,
+						      struct amount_msat,
+						      &msat));
+	}
+
 	return htlc_out_check(hout, "new_htlc_out");
 }

lightningd/htlc_end.h

@@ -90,6 +90,10 @@ struct htlc_out {
 	/* Is this a locally-generated payment?  Implies ->in is NULL. */
 	bool am_origin;
 
+	/* Amount of fees that this out htlc pays (if am_origin);
+	 * otherwise fees collected by routing this out */
+	struct amount_msat fees;
+
 	/* If am_origin, this is the partid of the payment. */
 	u64 partid;
 
@@ -168,6 +172,7 @@ struct htlc_out *new_htlc_out(const tal_t *ctx,
 			      const u8 *onion_routing_packet,
 			      const struct pubkey *blinding,
 			      bool am_origin,
+			      struct amount_msat final_msat,
 			      u64 partid,
 			      u64 groupid,
 			      struct htlc_in *in);

lightningd/pay.c

@@ -773,6 +773,7 @@ static bool should_use_tlv(enum route_hop_style style)
 static const u8 *send_onion(const tal_t *ctx, struct lightningd *ld,
 			    const struct onionpacket *packet,
 			    const struct route_hop *first_hop,
+			    const struct amount_msat final_amount,
 			    const struct sha256 *payment_hash,
 			    const struct pubkey *blinding,
 			    u64 partid,
@@ -786,7 +787,8 @@ static const u8 *send_onion(const tal_t *ctx, struct lightningd *ld,
 	base_expiry = get_block_height(ld->topology) + 1;
 	onion = serialize_onionpacket(tmpctx, packet);
 	return send_htlc_out(ctx, channel, first_hop->amount,
-			     base_expiry + first_hop->delay, payment_hash,
+			     base_expiry + first_hop->delay,
+			     final_amount, payment_hash,
 			     blinding, partid, groupid, onion, NULL, hout,
 			     &dont_care_about_channel_update);
 }
@@ -1047,7 +1049,8 @@ send_payment_core(struct lightningd *ld,
 		return command_failed(cmd, data);
 	}
 
-	failmsg = send_onion(tmpctx, ld, packet, first_hop, rhash, NULL, partid,
+	failmsg = send_onion(tmpctx, ld, packet, first_hop, msat,
+			     rhash, NULL, partid,
 			     group, channel, &hout);
 
 	if (failmsg) {
@@ -1211,7 +1214,8 @@ send_payment(struct lightningd *ld,
 		 n_hops, type_to_string(tmpctx, struct amount_msat, &msat));
 	packet = create_onionpacket(tmpctx, path, ROUTING_INFO_SIZE, &path_secrets);
 	return send_payment_core(ld, cmd, rhash, partid, group, &route[0],
-				 msat, total_msat, label, invstring,
+				 msat, total_msat,
+				 label, invstring,
 				 packet, &ids[n_hops - 1], ids,
 				 channels, path_secrets, local_offer_id);
 }

lightningd/peer_htlcs.c

@@ -638,6 +638,7 @@ static void htlc_offer_timeout(struct htlc_out *out)
 const u8 *send_htlc_out(const tal_t *ctx,
 			struct channel *out,
 			struct amount_msat amount, u32 cltv,
+			struct amount_msat final_msat,
 			const struct sha256 *payment_hash,
 			const struct pubkey *blinding,
 			u64 partid,
@@ -675,6 +676,7 @@ const u8 *send_htlc_out(const tal_t *ctx,
 	*houtp = new_htlc_out(out->owner, out, amount, cltv,
 			      payment_hash, onion_routing_packet,
 			      blinding, in == NULL,
+			      final_msat,
 			      partid, groupid, in);
 	tal_add_destructor(*houtp, destroy_hout_subd_died);
 
@@ -786,7 +788,8 @@ static void forward_htlc(struct htlc_in *hin,
 	}
 
 	failmsg = send_htlc_out(tmpctx, next, amt_to_forward,
-				outgoing_cltv_value, &hin->payment_hash,
+				outgoing_cltv_value, AMOUNT_MSAT(0),
+				&hin->payment_hash,
 				next_blinding, 0 /* partid */, 0 /* groupid */,
 				next_onion, hin, &hout, &needs_update_appended);
 	if (!failmsg)
@@ -1605,7 +1608,7 @@ static void remove_htlc_out(struct channel *channel, struct htlc_out *hout)
 
 		if (!mvt)
 			log_broken(channel->log,
-				   "Unable to calculate fees collected."
+				   "Unable to calculate fees."
 				   " Not logging an outbound HTLC");
 		else
 			notify_channel_mvt(channel->peer->ld, mvt);

lightningd/peer_htlcs.h

@@ -43,6 +43,7 @@ void update_per_commit_point(struct channel *channel,
 const u8 *send_htlc_out(const tal_t *ctx,
 			struct channel *out,
 			struct amount_msat amount, u32 cltv,
+			struct amount_msat final_msat,
 			const struct sha256 *payment_hash,
 			const struct pubkey *blinding,
 			u64 partid,

tests/test_plugin.py

@@ -1902,10 +1902,18 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
         {'type': 'chain_mvt', 'credit': 0, 'debit': 950000501, 'tags': ['channel_close']},
     ]
 
+    l3_l2_mvts = [
+        {'type': 'chain_mvt', 'credit': 0, 'debit': 0, 'tags': ['channel_open']},
+        {'type': 'channel_mvt', 'credit': 100000000, 'debit': 0, 'tags': ['invoice'], 'fees': '0msat'},
+        {'type': 'channel_mvt', 'credit': 0, 'debit': 50000501, 'tags': ['invoice'], 'fees': '501msat'},
+        {'type': 'chain_mvt', 'credit': 0, 'debit': 49999499, 'tags': ['channel_close']},
+    ]
+
+    coin_plugin = os.path.join(os.getcwd(), 'tests/plugins/coin_movements.py')
     l1, l2, l3 = node_factory.line_graph(3, opts=[
         {'may_reconnect': True},
-        {'may_reconnect': True, 'plugin': os.path.join(os.getcwd(), 'tests/plugins/coin_movements.py')},
-        {'may_reconnect': True},
+        {'may_reconnect': True, 'plugin': coin_plugin},
+        {'may_reconnect': True, 'plugin': coin_plugin},
     ], wait_for_announce=True)
 
     bitcoind.generate_block(5)
@@ -1977,12 +1985,14 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
     bitcoind.generate_block(6)
     sync_blockheight(bitcoind, [l2])
     l2.daemon.wait_for_log('{}.*FUNDING_TRANSACTION/FUNDING_OUTPUT->MUTUAL_CLOSE depth'.format(l3.info['id']))
+    l3.daemon.wait_for_log('Resolved FUNDING_TRANSACTION/FUNDING_OUTPUT by MUTUAL_CLOSE')
 
     # Ending channel balance should be zero
     assert account_balance(l2, chanid_1) == 0
     assert account_balance(l2, chanid_3) == 0
 
     # Verify we recorded all the movements we expect
+    check_coin_moves(l3, chanid_3, l3_l2_mvts, chainparams)
     check_coin_moves(l2, chanid_1, l1_l2_mvts, chainparams)
     check_coin_moves(l2, chanid_3, l2_l3_mvts, chainparams)
 

wallet/db.c

@@ -868,6 +868,7 @@ static struct migration dbmigrations[] = {
 	[BUILD_ASSERT_OR_ZERO( 9 == RCVD_REMOVE_ACK_REVOCATION) +
 	 BUILD_ASSERT_OR_ZERO(19 == SENT_REMOVE_ACK_REVOCATION)],
      NULL},
+    {SQL("ALTER TABLE channel_htlcs ADD fees_msat BIGINT DEFAULT 0"), NULL},
 };
 
 /* Leak tracking. */

wallet/wallet.c

@@ -2372,8 +2372,9 @@ void wallet_htlc_save_out(struct wallet *wallet,
 		" malformed_onion,"
 		" partid,"
 		" groupid,"
+		" fees_msat,"
 		" min_commit_num"
-		") VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, 0, ?, ?, ?);"));
+		") VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, 0, ?, ?, ?, ?);"));
 
 	db_bind_u64(stmt, 0, chan->dbid);
 	db_bind_u64(stmt, 1, out->key.id);
@@ -2403,7 +2404,9 @@ void wallet_htlc_save_out(struct wallet *wallet,
 		db_bind_u64(stmt, 10, out->partid);
 		db_bind_u64(stmt, 11, out->groupid);
 	}
-	db_bind_u64(stmt, 12, min_u64(chan->next_index[LOCAL]-1,
+
+	db_bind_amount_msat(stmt, 12, &out->fees);
+	db_bind_u64(stmt, 13, min_u64(chan->next_index[LOCAL]-1,
 				      chan->next_index[REMOTE]-1));
 
 	db_exec_prepared_v2(stmt);
@@ -2598,6 +2601,7 @@ static bool wallet_stmt2htlc_out(struct wallet *wallet,
 		out->failmsg = db_col_arr(out, stmt, "localfailmsg", u8);
 
 	out->in = NULL;
+	db_col_amount_msat(stmt, "fees_msat", &out->fees);
 
 	if (!db_col_is_null(stmt, "origin_htlc")) {
 		u64 in_id = db_col_u64(stmt, "origin_htlc");
@@ -2737,6 +2741,7 @@ bool wallet_htlcs_load_out_for_channel(struct wallet *wallet,
 					     ", partid"
 					     ", localfailmsg"
 					     ", groupid"
+					     ", fees_msat"
 					     " FROM channel_htlcs"
 					     " WHERE direction = ?"
 					     " AND channel_id = ?"