splice: Enable user splice RBF

Allow user’s to RBF existing splices. For now this is done by simple executing an additional splice command, in the future this will can also be done with dedicated RPCs.

Changelog-Added: Enabled the ability to RBF splices

Author: ddustin

channeld/channeld.c

@@ -61,6 +61,7 @@
 	((msg) == WIRE_SPLICE || \
 	(msg) == WIRE_SPLICE_ACK || \
 	(msg) == WIRE_TX_INIT_RBF || \
+	(msg) == WIRE_TX_ACK_RBF || \
 	(msg) == WIRE_TX_ABORT)
 
 #define SAT_MIN(a, b) (amount_sat_less((a), (b)) ? (a) : (b))
@@ -4097,14 +4098,41 @@ static void splice_initiator(struct peer *peer, const u8 *inmsg)
 	struct wally_psbt *psbt = peer->splicing->current_psbt;
 	u32 sequence = 0;
 	u8 *scriptPubkey;
+	enum peer_wire type;
+	struct tlv_tx_ack_rbf_tlvs *ack_rbf_tlvs;
 
-	if (!fromwire_splice_ack(inmsg,
-				 &channel_id,
-				 &peer->splicing->accepter_relative,
-				 &peer->splicing->remote_funding_pubkey))
-		peer_failed_warn(peer->pps, &peer->channel_id,
-				 "Bad wire_splice_ack %s",
-				 tal_hex(tmpctx, inmsg));
+	type = fromwire_peektype(inmsg);
+
+	if (type == WIRE_SPLICE_ACK) {
+		if (!fromwire_splice_ack(inmsg,
+					 &channel_id,
+					 &peer->splicing->accepter_relative,
+					 &peer->splicing->remote_funding_pubkey))
+			peer_failed_warn(peer->pps, &peer->channel_id,
+					 "Bad wire_splice_ack %s",
+					 tal_hex(tmpctx, inmsg));
+	} else if (type == WIRE_TX_ACK_RBF) {
+		if (!fromwire_tx_ack_rbf(tmpctx,
+					 inmsg,
+					 &channel_id,
+					 &ack_rbf_tlvs))
+			peer_failed_warn(peer->pps, &peer->channel_id,
+					 "Bad tx_ack_rbf %s",
+					 tal_hex(tmpctx, inmsg));
+
+		if (!ack_rbf_tlvs
+			|| !ack_rbf_tlvs->funding_output_contribution)
+			peer_failed_warn(peer->pps, &peer->channel_id,
+					 "tx_ack_rbf must contain tlv with a"
+					 " funding_output_contribution value");
+		peer->splicing->accepter_relative = *ack_rbf_tlvs->funding_output_contribution;
+
+		if (!last_inflight(peer))
+			peer_failed_err(peer->pps, &peer->channel_id,
+					"Can't handle tx_ack_rbf because we"
+					" have no pending splice");
+		peer->splicing->remote_funding_pubkey = last_inflight(peer)->remote_funding;
+	}
 
 	if (!channel_id_eq(&channel_id, &peer->channel_id))
 		peer_failed_warn(peer->pps, &peer->channel_id,
@@ -4538,12 +4566,29 @@ static void splice_initiator_user_signed(struct peer *peer, const u8 *inmsg)
 /* This occurs once our 'stfu' transition was successful. */
 static void handle_splice_stfu_success(struct peer *peer)
 {
-	u8 *msg = towire_splice(tmpctx,
-				&peer->channel_id,
-				peer->splicing->opener_relative,
-				peer->splicing->feerate_per_kw,
-				peer->splicing->current_psbt->fallback_locktime,
-				&peer->channel->funding_pubkey[LOCAL]);
+	u8 *msg;
+	struct tlv_tx_init_rbf_tlvs *init_rbf_tlvs;
+	if (!last_inflight(peer)) {
+		msg = towire_splice(tmpctx,
+				    &peer->channel_id,
+				    peer->splicing->opener_relative,
+				    peer->splicing->feerate_per_kw,
+				    peer->splicing->current_psbt->fallback_locktime,
+				    &peer->channel->funding_pubkey[LOCAL]);
+	}
+	else { /* RBF attempt */
+		init_rbf_tlvs = tlv_tx_init_rbf_tlvs_new(tmpctx);
+		init_rbf_tlvs->funding_output_contribution = tal(init_rbf_tlvs, s64);
+		*init_rbf_tlvs->funding_output_contribution = peer->splicing->opener_relative;
+		init_rbf_tlvs->require_confirmed_inputs = NULL;
+
+		msg = towire_tx_init_rbf(tmpctx,
+					 &peer->channel_id,
+					 peer->splicing->current_psbt->fallback_locktime,
+					 peer->splicing->feerate_per_kw,
+					 init_rbf_tlvs);
+	}
+
 	peer->splice_state->await_commitment_succcess = false;
 	peer_write(peer->pps, take(msg));
 }
@@ -4617,8 +4662,9 @@ static void handle_splice_init(struct peer *peer, const u8 *inmsg)
 		return;
 	}
 
-	status_debug("Getting handle_splice_init psbt version %d",
-		     peer->splicing->current_psbt->version);
+	status_debug("Getting handle_splice_init psbt version %d (RBF?: %s)",
+		     peer->splicing->current_psbt->version,
+		     last_inflight(peer) ? "y" : "n");
 
 	if (skip_stfu) {
 		handle_splice_stfu_success(peer);
@@ -4793,6 +4839,7 @@ static void peer_in(struct peer *peer, const u8 *msg)
 		splice_accepter(peer, msg);
 		return;
 	case WIRE_SPLICE_ACK:
+	case WIRE_TX_ACK_RBF:
 		splice_initiator(peer, msg);
 		return;
 	case WIRE_SPLICE_LOCKED:
@@ -4819,8 +4866,6 @@ static void peer_in(struct peer *peer, const u8 *msg)
 	case WIRE_TX_SIGNATURES:
 		handle_unexpected_tx_sigs(peer, msg);
 		return;
-	case WIRE_TX_ACK_RBF:
-		break;
 
 	case WIRE_CHANNEL_REESTABLISH:
 		handle_unexpected_reestablish(peer, msg);

lightningd/channel_control.c

@@ -2204,11 +2204,12 @@ static struct command_result *channel_for_splice(struct command *cmd,
 				    "abnormal owner state %s",
 				    (*channel)->owner->name);
 
-	if ((*channel)->state != CHANNELD_NORMAL)
+	if ((*channel)->state != CHANNELD_NORMAL
+		&& (*channel)->state != CHANNELD_AWAITING_SPLICE)
 		return command_fail(cmd,
 				    SPLICE_INVALID_CHANNEL_STATE,
-				    "Channel needs to be in normal state but "
-				    "is in state %s",
+				    "Channel needs to be in normal or awaiting"
+				    " splice state but is in state %s",
 				    channel_state_name(*channel));
 
 	return NULL;