commit_tx: keep permutation map.

This lets us map the HTLCs back to outputs when txs occur onchain.

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

commit_tx.c

@@ -42,7 +42,8 @@ struct bitcoin_tx *create_commit_tx(const tal_t *ctx,
 				    unsigned int anchor_index,
 				    u64 anchor_satoshis,
 				    const struct sha256 *rhash,
-				    const struct channel_state *cstate)
+				    const struct channel_state *cstate,
+				    int **map)
 {
 	struct bitcoin_tx *tx;
 	const u8 *redeemscript;
@@ -95,6 +96,7 @@ struct bitcoin_tx *create_commit_tx(const tal_t *ctx,
 	assert(num == tx->output_count);
 	assert(total <= anchor_satoshis);
 
-	permute_outputs(tx->output, tx->output_count, NULL);
+	*map = tal_arr(ctx, int, tx->output_count);
+	permute_outputs(tx->output, tx->output_count, *map);
 	return tx;
 }

commit_tx.h

@@ -20,5 +20,6 @@ struct bitcoin_tx *create_commit_tx(const tal_t *ctx,
 				    unsigned int anchor_index,
 				    u64 anchor_satoshis,
 				    const struct sha256 *rhash,
-				    const struct channel_state *cstate);
+				    const struct channel_state *cstate,
+				    int **map);
 #endif

daemon/packets.c

@@ -304,7 +304,8 @@ void queue_pkt_commit(struct peer *peer)
 				  peer->anchor.index,
 				  peer->anchor.satoshis,
 				  &ci->revocation_hash,
-				  ci->cstate);
+				  ci->cstate,
+				  &ci->map);
 
 	log_debug(peer->log, "Signing tx for %u/%u msatoshis, %zu/%zu htlcs",
 		  ci->cstate->a.pay_msat,
@@ -693,7 +694,8 @@ Pkt *accept_pkt_commit(struct peer *peer, const Pkt *pkt)
 				  peer->anchor.index,
 				  peer->anchor.satoshis,
 				  &ci->revocation_hash,
-				  ci->cstate);
+				  ci->cstate,
+				  &ci->map);
 
 	/* BOLT #2:
 	 *

daemon/peer.c

@@ -1330,7 +1330,8 @@ bool setup_first_commit(struct peer *peer)
 					       peer->anchor.index,
 					       peer->anchor.satoshis,
 					       &peer->us.commit->revocation_hash,
-					       peer->us.commit->cstate);
+					       peer->us.commit->cstate,
+					       &peer->us.commit->map);
 
 	peer->them.commit->tx = create_commit_tx(peer->them.commit,
 						 &peer->them.finalkey,
@@ -1340,7 +1341,8 @@ bool setup_first_commit(struct peer *peer)
 						 peer->anchor.index,
 						 peer->anchor.satoshis,
 						 &peer->them.commit->revocation_hash,
-						 peer->them.commit->cstate);
+						 peer->them.commit->cstate,
+						 &peer->them.commit->map);
 
 	peer->us.staging_cstate = copy_funding(peer, peer->us.commit->cstate);
 	peer->them.staging_cstate = copy_funding(peer, peer->them.commit->cstate);

daemon/peer.h

@@ -63,6 +63,8 @@ struct commit_info {
 	struct channel_state *cstate;
 	/* Other side's signature for this commit tx. */
 	struct bitcoin_signature sig;
+	/* Map for permutation: see commit_tx.c */
+	int *map;
 	/* Revocation preimage (if known). */
 	struct sha256 *revocation_preimage;
 };

permute_tx.c

@@ -2,7 +2,7 @@
 #include <stdbool.h>
 #include <string.h>
 
-static void init_map(size_t *map, size_t len)
+static void init_map(int *map, size_t len)
 {
 	size_t i;
 
@@ -15,10 +15,10 @@ static void init_map(size_t *map, size_t len)
 
 /* This map says where things ended up, eg. 0 might be in slot 3.  we
  * want to change it so map[0] = 3. */
-static void invert_map(size_t *map, size_t len)
+static void invert_map(int *map, size_t len)
 {
 	if (map) {
-		size_t i, newmap[len];
+		int i, newmap[len];
 
 		memset(newmap, 0, sizeof(newmap));
 		for (i = 0; i < len; i++) {
@@ -59,7 +59,7 @@ static size_t find_best_in(struct bitcoin_tx_input *inputs, size_t num)
 	return best;
 }
 
-static void swap_inputs(struct bitcoin_tx_input *inputs, size_t *map,
+static void swap_inputs(struct bitcoin_tx_input *inputs, int *map,
 			size_t i1, size_t i2)
 {
 	struct bitcoin_tx_input tmpinput;
@@ -78,7 +78,7 @@ static void swap_inputs(struct bitcoin_tx_input *inputs, size_t *map,
 
 void permute_inputs(struct bitcoin_tx_input *inputs,
 		    size_t num_inputs,
-		    size_t *map)
+		    int *map)
 {
 	size_t i;
 
@@ -94,7 +94,7 @@ void permute_inputs(struct bitcoin_tx_input *inputs,
 	invert_map(map, num_inputs);
 }
 
-static void swap_outputs(struct bitcoin_tx_output *outputs, size_t *map,
+static void swap_outputs(struct bitcoin_tx_output *outputs, int *map,
 			size_t i1, size_t i2)
 {
 	struct bitcoin_tx_output tmpoutput;
@@ -146,7 +146,7 @@ static size_t find_best_out(struct bitcoin_tx_output *outputs, size_t num)
 
 void permute_outputs(struct bitcoin_tx_output *outputs,
 		     size_t num_outputs,
-		     size_t *map)
+		     int *map)
 {
 	size_t i;
 

permute_tx.h

@@ -8,9 +8,9 @@
  */
 void permute_inputs(struct bitcoin_tx_input *inputs,
 		    size_t num_inputs,
-		    size_t *map);
+		    int *map);
 
 void permute_outputs(struct bitcoin_tx_output *outputs,
 		     size_t num_outputs,
-		     size_t *map);
+		     int *map);
 #endif /* LIGHTNING_PERMUTE_TX_H */