channeld: handle incoming feerate changes.

We allow from the 100-confirm economical rate to 5x the immediate rate.

Closes: #243
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

channeld/channel.c

@@ -64,6 +64,9 @@ struct peer {
 	bool funding_locked[NUM_SIDES];
 	u64 next_index[NUM_SIDES];
 
+	/* Tolerable amounts for feerate (only relevant for fundee). */
+	u32 feerate_min, feerate_max;
+
 	/* Remote's current per-commit point. */
 	struct pubkey remote_per_commit;
 
@@ -430,6 +433,59 @@ static struct io_plan *handle_peer_add_htlc(struct io_conn *conn,
 	return peer_read_message(conn, &peer->pcs, peer_in);
 }
 
+static struct io_plan *handle_peer_feechange(struct io_conn *conn,
+					     struct peer *peer, const u8 *msg)
+{
+	struct channel_id channel_id;
+	u32 feerate;
+
+	if (!fromwire_update_fee(msg, NULL, &channel_id, &feerate)) {
+		peer_failed(io_conn_fd(peer->peer_conn),
+			    &peer->pcs.cs,
+			    &peer->channel_id,
+			    "Bad update_fee %s", tal_hex(msg, msg));
+	}
+
+	/* BOLT #2:
+	 *
+	 * A receiving node MUST fail the channel if the sender is not
+	 * responsible for paying the bitcoin fee.
+	 */
+	if (peer->channel->funder != REMOTE)
+		peer_failed(io_conn_fd(peer->peer_conn),
+			    &peer->pcs.cs,
+			    &peer->channel_id,
+			    "update_fee from non-funder?");
+
+	/* BOLT #2:
+	 *
+	 * A receiving node SHOULD fail the channel if the `update_fee` is too
+	 * low for timely processing, or unreasonably large.
+	 */
+	if (feerate < peer->feerate_min || feerate > peer->feerate_max)
+		peer_failed(io_conn_fd(peer->peer_conn),
+			    &peer->pcs.cs,
+			    &peer->channel_id,
+			    "update_fee %u outside range %u-%u",
+			    feerate, peer->feerate_min, peer->feerate_max);
+
+	/* BOLT #2:
+	 *
+	 * A receiving node SHOULD fail the channel if the sender cannot
+	 * afford the new fee rate on the receiving node's current commitment
+	 * transaction, but it MAY delay this check until the `update_fee` is
+	 * committed.
+	 */
+	if (!channel_update_feerate(peer->channel, feerate))
+		peer_failed(io_conn_fd(peer->peer_conn),
+			    &peer->pcs.cs,
+			    &peer->channel_id,
+			    "update_fee %u unaffordable",
+			    feerate);
+
+	return peer_read_message(conn, &peer->pcs, peer_in);
+}
+
 static struct changed_htlc *changed_htlc_arr(const tal_t *ctx,
 					     const struct htlc **changed_htlcs)
 {
@@ -446,6 +502,7 @@ static struct changed_htlc *changed_htlc_arr(const tal_t *ctx,
 
 static u8 *sending_commitsig_msg(const tal_t *ctx,
 				 u64 remote_commit_index,
+				 u32 remote_feerate,
 				 const struct htlc **changed_htlcs,
 				 const secp256k1_ecdsa_signature *commit_sig,
 				 const secp256k1_ecdsa_signature *htlc_sigs)
@@ -458,6 +515,7 @@ static u8 *sending_commitsig_msg(const tal_t *ctx,
 	 * committed to. */
 	changed = changed_htlc_arr(tmpctx, changed_htlcs);
 	msg = towire_channel_sending_commitsig(ctx, remote_commit_index,
+					       remote_feerate,
 					       changed, commit_sig, htlc_sigs);
 	tal_free(tmpctx);
 	return msg;
@@ -665,6 +723,7 @@ static void send_commit(struct peer *peer)
 	status_trace("Telling master we're about to commit...");
 	/* Tell master to save this next commit to database, then wait. */
 	msg = sending_commitsig_msg(tmpctx, peer->next_index[REMOTE],
+				    channel_feerate(peer->channel, REMOTE),
 				    changed_htlcs,
 				    &peer->next_commit_sigs->commit_sig,
 				    peer->next_commit_sigs->htlc_sigs);
@@ -798,6 +857,7 @@ static void get_shared_secret(const struct htlc *htlc,
 
 static u8 *got_commitsig_msg(const tal_t *ctx,
 			     u64 local_commit_index,
+			     u32 local_feerate,
 			     const secp256k1_ecdsa_signature *commit_sig,
 			     const secp256k1_ecdsa_signature *htlc_sigs,
 			     const struct htlc **changed_htlcs,
@@ -856,6 +916,7 @@ static u8 *got_commitsig_msg(const tal_t *ctx,
 	}
 
 	msg = towire_channel_got_commitsig(ctx, local_commit_index,
+					   local_feerate,
 					   commit_sig,
 					   htlc_sigs,
 					   added,
@@ -984,8 +1045,9 @@ static struct io_plan *handle_peer_commit_sig(struct io_conn *conn,
 		     tal_count(htlc_sigs));
 
 	/* Tell master daemon, then wait for ack. */
-	msg = got_commitsig_msg(tmpctx, peer->next_index[LOCAL], &commit_sig,
-				htlc_sigs, changed_htlcs, txs[0]);
+	msg = got_commitsig_msg(tmpctx, peer->next_index[LOCAL],
+				channel_feerate(peer->channel, LOCAL),
+				&commit_sig, htlc_sigs, changed_htlcs, txs[0]);
 
 	master_wait_sync_reply(tmpctx, peer, take(msg),
 			       WIRE_CHANNEL_GOT_COMMITSIG_REPLY);
@@ -1369,6 +1431,8 @@ static struct io_plan *peer_in(struct io_conn *conn, struct peer *peer, u8 *msg)
 		return handle_peer_add_htlc(conn, peer, msg);
 	case WIRE_COMMITMENT_SIGNED:
 		return handle_peer_commit_sig(conn, peer, msg);
+	case WIRE_UPDATE_FEE:
+		return handle_peer_feechange(conn, peer, msg);
 	case WIRE_REVOKE_AND_ACK:
 		return handle_peer_revoke_and_ack(conn, peer, msg);
 	case WIRE_UPDATE_FULFILL_HTLC:
@@ -1391,15 +1455,8 @@ static struct io_plan *peer_in(struct io_conn *conn, struct peer *peer, u8 *msg)
 	case WIRE_FUNDING_CREATED:
 	case WIRE_FUNDING_SIGNED:
 	case WIRE_CHANNEL_REESTABLISH:
-		goto badmessage;
-
 	case WIRE_CLOSING_SIGNED:
-	case WIRE_UPDATE_FEE:
-		peer_failed(io_conn_fd(peer->peer_conn),
-			    &peer->pcs.cs,
-			    &peer->channel_id,
-			    "Unimplemented message %u (%s)",
-			    type, wire_type_name(type));
+		goto badmessage;
 	}
 
 badmessage:
@@ -2036,6 +2093,7 @@ static void init_channel(struct peer *peer)
 				   &funding_satoshi,
 				   &peer->conf[LOCAL], &peer->conf[REMOTE],
 				   feerate_per_kw,
+				   &peer->feerate_min, &peer->feerate_max,
 				   &peer->their_commit_sig,
 				   &peer->pcs.cs,
 				   &funding_pubkey[REMOTE],
@@ -2079,14 +2137,17 @@ static void init_channel(struct peer *peer)
 	status_trace("init %s: remote_per_commit = %s, old_remote_per_commit = %s"
 		     " next_idx_local = %"PRIu64
 		     " next_idx_remote = %"PRIu64
-		     " revocations_received = %"PRIu64,
+		     " revocations_received = %"PRIu64
+		     " feerates %u/%u (range %u-%u)",
 		     side_to_str(funder),
 		     type_to_string(trc, struct pubkey,
 				    &peer->remote_per_commit),
 		     type_to_string(trc, struct pubkey,
 				    &peer->old_remote_per_commit),
 		     peer->next_index[LOCAL], peer->next_index[REMOTE],
-		     peer->revocations_received);
+		     peer->revocations_received,
+		     feerate_per_kw[LOCAL], feerate_per_kw[REMOTE],
+		     peer->feerate_min, peer->feerate_max);
 
 	/* First commit is used for opening: if we've sent 0, we're on
 	 * index 1. */

channeld/channel_wire.csv

@@ -14,6 +14,8 @@ channel_init,,our_config,struct channel_config
 channel_init,,their_config,struct channel_config
 # FIXME: Fix generate-wire.py to allow NUM_SIDES*u32 here.
 channel_init,,feerate_per_kw,2*u32
+channel_init,,feerate_min,u32
+channel_init,,feerate_max,u32
 channel_init,,first_commit_sig,secp256k1_ecdsa_signature
 channel_init,,crypto_state,struct crypto_state
 channel_init,,remote_fundingkey,struct pubkey
@@ -118,6 +120,7 @@ channel_got_funding_locked,,next_per_commit_point,struct pubkey
 # When we send a commitment_signed message, tell master.
 channel_sending_commitsig,1020
 channel_sending_commitsig,,commitnum,u64
+channel_sending_commitsig,,feerate,u32
 # SENT_ADD_COMMIT, SENT_REMOVE_ACK_COMMIT, SENT_ADD_ACK_COMMIT, SENT_REMOVE_COMMIT
 channel_sending_commitsig,,num_changed,u16
 channel_sending_commitsig,,changed,num_changed*struct changed_htlc
@@ -131,6 +134,7 @@ channel_sending_commitsig_reply,1120
 # When we have a commitment_signed message, tell master to remember.
 channel_got_commitsig,1021
 channel_got_commitsig,,commitnum,u64
+channel_got_commitsig,,feerate,u32
 channel_got_commitsig,,signature,secp256k1_ecdsa_signature
 channel_got_commitsig,,num_htlcs,u16
 channel_got_commitsig,,htlc_signature,num_htlcs*secp256k1_ecdsa_signature

lightningd/peer_control.c

@@ -2108,6 +2108,8 @@ static bool peer_start_channeld(struct peer *peer,
 				      &peer->our_config,
 				      &peer->channel_info->their_config,
 				      peer->channel_info->feerate_per_kw,
+				      get_feerate(peer->ld->topology, FEERATE_NORMAL),
+				      get_feerate(peer->ld->topology, FEERATE_IMMEDIATE) * 5,
 				      peer->last_sig,
 				      cs,
 				      &peer->channel_info->remote_fundingkey,

lightningd/peer_htlcs.c

@@ -990,6 +990,7 @@ static bool peer_save_commitsig_sent(struct peer *peer, u64 commitnum)
 void peer_sending_commitsig(struct peer *peer, const u8 *msg)
 {
 	u64 commitnum;
+	u32 feerate;
 	struct changed_htlc *changed_htlcs;
 	size_t i, maxid = 0, num_local_added = 0;
 	secp256k1_ecdsa_signature commit_sig;
@@ -997,6 +998,7 @@ void peer_sending_commitsig(struct peer *peer, const u8 *msg)
 
 	if (!fromwire_channel_sending_commitsig(msg, msg, NULL,
 						&commitnum,
+						&feerate,
 						&changed_htlcs,
 						&commit_sig, &htlc_sigs)) {
 		peer_internal_error(peer, "bad channel_sending_commitsig %s",
@@ -1033,6 +1035,9 @@ void peer_sending_commitsig(struct peer *peer, const u8 *msg)
 		peer->next_htlc_id += num_local_added;
 	}
 
+	/* Update their feerate. */
+	peer->channel_info->feerate_per_kw[REMOTE] = feerate;
+
 	if (!peer_save_commitsig_sent(peer, commitnum))
 		return;
 
@@ -1109,6 +1114,7 @@ static bool peer_sending_revocation(struct peer *peer,
 void peer_got_commitsig(struct peer *peer, const u8 *msg)
 {
 	u64 commitnum;
+	u32 feerate;
 	secp256k1_ecdsa_signature commit_sig;
 	secp256k1_ecdsa_signature *htlc_sigs;
 	struct added_htlc *added;
@@ -1121,6 +1127,7 @@ void peer_got_commitsig(struct peer *peer, const u8 *msg)
 
 	if (!fromwire_channel_got_commitsig(msg, msg, NULL,
 					    &commitnum,
+					    &feerate,
 					    &commit_sig,
 					    &htlc_sigs,
 					    &added,
@@ -1137,8 +1144,8 @@ void peer_got_commitsig(struct peer *peer, const u8 *msg)
 
 	log_debug(peer->log,
 		  "got commitsig %"PRIu64
-		  ": %zu added, %zu fulfilled, %zu failed, %zu changed",
-		  commitnum, tal_count(added), tal_count(fulfilled),
+		  ": feerate %u, %zu added, %zu fulfilled, %zu failed, %zu changed",
+		  commitnum, feerate, tal_count(added), tal_count(fulfilled),
 		  tal_count(failed), tal_count(changed));
 
 	/* FIXME: store commit & htlc signature information. */
@@ -1166,6 +1173,12 @@ void peer_got_commitsig(struct peer *peer, const u8 *msg)
 		}
 	}
 
+	/* Update both feerates: if we're funder, REMOTE should already be
+	 * that feerate, if we're not, we're about to ACK anyway. */
+	peer->channel_info->feerate_per_kw[LOCAL]
+		= peer->channel_info->feerate_per_kw[REMOTE]
+		= feerate;
+
 	/* Since we're about to send revoke, bump state again. */
 	if (!peer_sending_revocation(peer, added, fulfilled, failed, changed))
 		return;