splice: track funding_tx_index on inflights and channel funding

Give every funding tx a stable index: 0 for the original funding
(including RBF attempts), incrementing by 1 per splice.  Threaded through
the channeld inflight, the channel, the channeld_init and
channeld_add_inflight wire messages, set on splice creation and carried
onto the channel funding when a splice locks, and persisted in the
channel_funding_inflights and channels tables.

Author: nGoline

channeld/channeld.c

@@ -483,6 +483,7 @@ static void check_mutual_splice_locked(struct peer *peer)
 		     fmt_channel(tmpctx, peer->channel));
 
 	error = channel_update_funding(peer->channel, &inflight->outpoint,
+				       inflight->funding_tx_index,
 				       inflight->amnt,
 				       inflight->splice_amnt);
 	if (error)
@@ -4362,6 +4363,7 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
 					   &peer->splicing->remote_funding_pubkey,
 					   &outpoint.txid,
 					   outpoint.n,
+					   peer->channel->funding_tx_index + 1,
 					   funding_feerate_perkw,
 					   both_amount,
 					   peer->splicing->accepter_relative,
@@ -4379,6 +4381,8 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
 		  &new_inflight->outpoint.txid, NULL);
 	new_inflight->remote_funding = peer->splicing->remote_funding_pubkey;
 	new_inflight->outpoint = outpoint;
+	/* A splice's funding tx is the parent funding's index + 1. */
+	new_inflight->funding_tx_index = peer->channel->funding_tx_index + 1;
 	new_inflight->amnt = both_amount;
 	new_inflight->psbt = clone_psbt(new_inflight, ictx->current_psbt);
 	new_inflight->splice_amnt = peer->splicing->accepter_relative;
@@ -4657,6 +4661,7 @@ static void splice_initiator_user_finalized(struct peer *peer)
 					      &peer->splicing->remote_funding_pubkey,
 					      &current_psbt_txid,
 					      chan_output_index,
+					      peer->channel->funding_tx_index + 1,
 					      peer->splicing->feerate_per_kw,
 					      amount_sat(new_chan_output->amount),
 					      peer->splicing->opener_relative,
@@ -4674,6 +4679,8 @@ static void splice_initiator_user_finalized(struct peer *peer)
 		  NULL);
 	new_inflight->remote_funding = peer->splicing->remote_funding_pubkey;
 	new_inflight->outpoint.n = chan_output_index;
+	/* A splice's funding tx is the parent funding's index + 1. */
+	new_inflight->funding_tx_index = peer->channel->funding_tx_index + 1;
 	new_inflight->amnt = amount_sat(new_chan_output->amount);
 	new_inflight->splice_amnt = peer->splicing->opener_relative;
 	new_inflight->last_tx = NULL;
@@ -6825,6 +6832,7 @@ static void init_channel(struct peer *peer)
 {
 	struct basepoints points[NUM_SIDES];
 	struct amount_sat funding_sats;
+	u32 funding_tx_index;
 	struct amount_msat local_msat;
 	struct pubkey funding_pubkey[NUM_SIDES];
 	struct channel_config conf[NUM_SIDES];
@@ -6854,6 +6862,7 @@ static void init_channel(struct peer *peer)
 				    &peer->channel_id,
 				    &funding,
 				    &funding_sats,
+				    &funding_tx_index,
 				    &minimum_depth,
 				    &peer->our_blockheight,
 				    &blockheight_states,
@@ -6968,6 +6977,7 @@ static void init_channel(struct peer *peer)
 
 	peer->channel = new_full_channel(peer, &peer->channel_id,
 					 &funding,
+					 funding_tx_index,
 					 minimum_depth,
 					 take(blockheight_states),
 					 lease_expiry,

channeld/channeld_wire.csv

@@ -21,6 +21,7 @@ msgdata,channeld_init,hsm_capabilities,u32,num_hsm_capabilities
 msgdata,channeld_init,channel_id,channel_id,
 msgdata,channeld_init,funding,bitcoin_outpoint,
 msgdata,channeld_init,funding_satoshi,amount_sat,
+msgdata,channeld_init,funding_tx_index,u32,
 msgdata,channeld_init,minimum_depth,u32,
 msgdata,channeld_init,our_blockheight,u32,
 msgdata,channeld_init,blockheight_states,height_states,
@@ -261,6 +262,7 @@ msgtype,channeld_add_inflight,7216
 msgdata,channeld_add_inflight,remote_funding,pubkey,
 msgdata,channeld_add_inflight,tx_id,bitcoin_txid,
 msgdata,channeld_add_inflight,tx_outnum,u32,
+msgdata,channeld_add_inflight,funding_tx_index,u32,
 msgdata,channeld_add_inflight,feerate,u32,
 msgdata,channeld_add_inflight,satoshis,amount_sat,
 msgdata,channeld_add_inflight,splice_amount,s64,

channeld/full_channel.c

@@ -74,6 +74,7 @@ static bool balance_ok(const struct balance *balance,
 struct channel *new_full_channel(const tal_t *ctx,
 				 const struct channel_id *cid,
 				 const struct bitcoin_outpoint *funding,
+				 u32 funding_tx_index,
 				 u32 minimum_depth,
 				 const struct height_states *blockheight_states,
 				 u32 lease_expiry,
@@ -93,6 +94,7 @@ struct channel *new_full_channel(const tal_t *ctx,
 	struct channel *channel = new_initial_channel(ctx,
 						      cid,
 						      funding,
+						      funding_tx_index,
 						      minimum_depth,
 						      blockheight_states,
 						      lease_expiry,

channeld/full_channel.h

@@ -36,6 +36,7 @@ struct existing_htlc;
 struct channel *new_full_channel(const tal_t *ctx,
 				 const struct channel_id *cid,
 				 const struct bitcoin_outpoint *funding,
+				 u32 funding_tx_index,
 				 u32 minimum_depth,
 				 const struct height_states *blockheight_states,
 				 u32 lease_expiry,

channeld/inflight.c

@@ -9,6 +9,7 @@ struct inflight *fromwire_inflight(const tal_t *ctx, const u8 **cursor, size_t *
 	struct inflight *inflight = tal(ctx, struct inflight);
 
 	fromwire_bitcoin_outpoint(cursor, max, &inflight->outpoint);
+	inflight->funding_tx_index = fromwire_u32(cursor, max);
 	fromwire_pubkey(cursor, max, &inflight->remote_funding);
 	inflight->amnt = fromwire_amount_sat(cursor, max);
 	inflight->remote_tx_sigs = fromwire_bool(cursor, max);
@@ -41,6 +42,7 @@ struct inflight *fromwire_inflight(const tal_t *ctx, const u8 **cursor, size_t *
 void towire_inflight(u8 **pptr, const struct inflight *inflight)
 {
 	towire_bitcoin_outpoint(pptr, &inflight->outpoint);
+	towire_u32(pptr, inflight->funding_tx_index);
 	towire_pubkey(pptr, &inflight->remote_funding);
 	towire_amount_sat(pptr, inflight->amnt);
 	towire_bool(pptr, inflight->remote_tx_sigs);

channeld/inflight.h

@@ -10,6 +10,9 @@
 struct inflight {
 	/* The new channel outpoint */
 	struct bitcoin_outpoint outpoint;
+	/* Which funding tx this is: 0 for the original funding (incl. RBF
+	 * attempts), incrementing by 1 for each splice. */
+	u32 funding_tx_index;
 	struct pubkey remote_funding;
 	struct amount_sat amnt;
 	bool remote_tx_sigs;

channeld/test/run-full_channel.c

@@ -492,7 +492,7 @@ int main(int argc, const char *argv[])
 	feerate_per_kw[LOCAL] = feerate_per_kw[REMOTE] = 15000;
 	derive_channel_id(&cid, &funding);
 	lchannel = new_full_channel(tmpctx, &cid,
-				    &funding, 0,
+				    &funding, 0, 0,
 				    take(new_height_states(NULL, LOCAL, &blockheight)),
 				    0, /* No channel lease */
 				    funding_amount, to_local,
@@ -505,7 +505,7 @@ int main(int argc, const char *argv[])
 				    &remote_funding_pubkey,
 				    take(channel_type_static_remotekey(NULL)), false, LOCAL);
 	rchannel = new_full_channel(tmpctx, &cid,
-				    &funding, 0,
+				    &funding, 0, 0,
 				    take(new_height_states(NULL, REMOTE, &blockheight)),
 				    0, /* No channel lease */
 				    funding_amount, to_remote,

common/initial_channel.c

@@ -12,6 +12,7 @@
 struct channel *new_initial_channel(const tal_t *ctx,
 				    const struct channel_id *cid,
 				    const struct bitcoin_outpoint *funding,
+				    u32 funding_tx_index,
 				    u32 minimum_depth,
 				    const struct height_states *height_states TAKES,
 				    u32 lease_expiry,
@@ -46,6 +47,7 @@ struct channel *new_initial_channel(const tal_t *ctx,
 
 	channel->cid = *cid;
 	channel->funding = *funding;
+	channel->funding_tx_index = funding_tx_index;
 	channel->funding_sats = funding_sats;
 	channel->minimum_depth = minimum_depth;
 	channel->lease_expiry = lease_expiry;
@@ -156,6 +158,7 @@ struct bitcoin_tx *initial_channel_tx(const tal_t *ctx,
 
 const char *channel_update_funding(struct channel *channel,
 				   const struct bitcoin_outpoint *funding,
+				   u32 funding_tx_index,
 				   struct amount_sat funding_sats,
 				   s64 splice_amnt)
 {
@@ -164,6 +167,7 @@ const char *channel_update_funding(struct channel *channel,
 
 	channel->funding = *funding;
 	channel->funding_sats = funding_sats;
+	channel->funding_tx_index = funding_tx_index;
 
 	if (splice_amnt * 1000 + channel->view[LOCAL].owed[LOCAL].millisatoshis < 0) /* Raw: splicing */
 		return tal_fmt(tmpctx, "Channel funding update would make local"

common/initial_channel.h

@@ -39,6 +39,10 @@ struct channel {
 	/* Funding txid and output. */
 	struct bitcoin_outpoint funding;
 
+	/* Which funding tx this is: 0 for the original funding (incl. RBF
+	 * attempts), incrementing by 1 for each splice. */
+	u32 funding_tx_index;
+
 	/* Keys used to spend funding tx. */
 	struct pubkey funding_pubkey[NUM_SIDES];
 
@@ -88,6 +92,7 @@ struct channel {
  * @ctx: tal context to allocate return value from.
  * @cid: The channel's id.
  * @funding: The commitment transaction id/outnum
+ * @funding_tx_index: 0 for the original funding, +1 for each splice.
  * @minimum_depth: The minimum confirmations needed for funding transaction.
  * @height_states: The blockheight update states.
  * @lease_expiry: Block the lease expires.
@@ -109,6 +114,7 @@ struct channel {
 struct channel *new_initial_channel(const tal_t *ctx,
 				    const struct channel_id *cid,
 				    const struct bitcoin_outpoint *funding,
+				    u32 funding_tx_index,
 				    u32 minimum_depth,
 				    const struct height_states *height_states TAKES,
 				    u32 lease_expiry,
@@ -154,6 +160,7 @@ struct bitcoin_tx *initial_channel_tx(const tal_t *ctx,
  */
 const char *channel_update_funding(struct channel *channel,
 				   const struct bitcoin_outpoint *funding,
+				   u32 funding_tx_index,
 				   struct amount_sat funding_sats,
 				   s64 splice_amnt);
 

devtools/mkcommit.c

@@ -399,7 +399,7 @@ int main(int argc, char *argv[])
 
 	channel = new_full_channel(NULL,
 				   &cid,
-				   &funding, 1,
+				   &funding, 0, 1,
 				   take(new_height_states(NULL, fee_payer,
 							  &blockheight)),
 				   0, /* Defaults to no lease */