lightningd/funding_tx: use struct utxos, remove signing helper.

The signing helper was really just for testing, so remove it.  But
turn the funding_tx() function into a useful one by making it take the
utxo array.

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

lightningd/funding_tx.c

@@ -2,6 +2,8 @@
 #include <assert.h>
 #include <bitcoin/script.h>
 #include <bitcoin/tx.h>
+#include <ccan/ptrint/ptrint.h>
+#include <lightningd/utxo.h>
 #include <permute_tx.h>
 
 #ifndef SUPERVERBOSE
@@ -9,9 +11,8 @@
 #endif
 
 struct bitcoin_tx *funding_tx(const tal_t *ctx,
-			      const struct sha256_double *input_txid,
+			      u32 *outnum,
-			      unsigned int input_txout,
+			      const struct utxo *utxos,
-			      u64 input_satoshis,
 			      u64 funding_satoshis,
 			      const struct pubkey *local_fundingkey,
 			      const struct pubkey *remote_fundingkey,
@@ -19,13 +20,17 @@ struct bitcoin_tx *funding_tx(const tal_t *ctx,
 			      u64 feerate_per_kw,
 			      u64 dust_limit_satoshis)
 {
-	struct bitcoin_tx *tx = bitcoin_tx(ctx, 1, 2);
+	struct bitcoin_tx *tx = bitcoin_tx(ctx, tal_count(utxos), 2);
 	u8 *wscript;
-	u64 fee, weight;
+	u64 fee, weight, input_satoshis = 0;
-
+	size_t i;
-	tx->input[0].txid = *input_txid;
+
-	tx->input[0].index = input_txout;
+	for (i = 0; i < tal_count(utxos); i++) {
-	tx->input[0].amount = tal_dup(tx, u64, &input_satoshis);
+		tx->input[i].txid = utxos[i].txid;
+		tx->input[i].index = utxos[i].outnum;
+		tx->input[i].amount = tal_dup(tx, u64, &utxos[i].amount);
+		input_satoshis += utxos[i].amount;
+	}
 
 	tx->output[0].amount = funding_satoshis;
 	wscript = bitcoin_redeem_2of2(tx, local_fundingkey, remote_fundingkey);
@@ -42,26 +47,17 @@ struct bitcoin_tx *funding_tx(const tal_t *ctx,
 	fee = weight * feerate_per_kw / 1000;
 
 	/* Too small an output after fee?  Drop it. */
-	if (input_satoshis - funding_satoshis < dust_limit_satoshis + fee)
+	if (input_satoshis - funding_satoshis < dust_limit_satoshis + fee) {
 		tal_resize(&tx->output, 1);
-	else {
+		*outnum = 0;
+	} else {
+		const void *map[2];
+		map[0] = int2ptr(0);
+		map[1] = int2ptr(1);
 		tx->output[1].amount = input_satoshis - funding_satoshis - fee;
-		permute_outputs(tx->output, tal_count(tx->output), NULL);
+		permute_outputs(tx->output, tal_count(tx->output), map);
+		*outnum = (map[0] == int2ptr(0) ? 0 : 1);
 	}
 
 	return tx;
 }
-
-void sign_funding_tx(struct bitcoin_tx *funding,
-		     const struct pubkey *inputkey,
-		     const struct privkey *input_privkey)
-{
-	secp256k1_ecdsa_signature sig;
-	u8 *subscript = scriptpubkey_p2pkh(funding, inputkey);
-
-	sign_tx_input(funding, 0, subscript, NULL, input_privkey, inputkey,
-		      &sig);
-	tal_free(subscript);
-
-	funding->input[0].script = bitcoin_redeem_p2pkh(funding, inputkey, &sig);
-}

lightningd/funding_tx.h

@@ -8,22 +8,27 @@ struct bitcoin_tx;
 struct privkey;
 struct pubkey;
 struct sha256_double;
+struct utxo;
 
-/* Create funding tx which spends a single P2PKH input, produces a
+/**
- * P2WPKH change output (if over dust limit). */
+ * funding_tx: create a P2WSH funding transaction for a channel.
+ * @ctx: context to tal from.
+ * @outnum: txout (0 or 1) which is the funding output.
+ * @utxo: tal_arr of UTXO to spend as inputs.
+ * @funding_satoshis: satoshis to output.
+ * @local_fundingkey: local key for 2of2 funding output.
+ * @remote_fundingkey: remote key for 2of2 funding output.
+ * @changekey: key to send change to (if any).
+ * @feerate_per_kw: feerate for transaction.
+ * @dust_limit_satoshis: dust limit to trim change output by.
+ */
 struct bitcoin_tx *funding_tx(const tal_t *ctx,
-			      const struct sha256_double *input_txid,
+			      u32 *outnum,
-			      unsigned int input_txout,
+			      const struct utxo *utxos,
-			      u64 input_satoshis,
 			      u64 funding_satoshis,
 			      const struct pubkey *local_fundingkey,
 			      const struct pubkey *remote_fundingkey,
 			      const struct pubkey *changekey,
 			      u64 feerate_per_kw,
 			      u64 dust_limit_satoshis);
-
-void sign_funding_tx(struct bitcoin_tx *funding,
-		     const struct pubkey *inputkey,
-		     const struct privkey *input_privkey);
-
 #endif /* LIGHTNING_LIGHTNINGD_FUNDING_TX_H */

lightningd/test/run-funding_tx.c

@@ -39,16 +39,16 @@ int main(void)
 {
 	tal_t *tmpctx = tal_tmpctx(NULL);
 	struct bitcoin_tx *input, *funding;
-	struct sha256_double txid;
 	u64 feerate_per_kw;
 	struct pubkey local_funding_pubkey, remote_funding_pubkey;
 	struct privkey input_privkey;
 	struct pubkey inputkey;
 	bool testnet;
-	unsigned int input_txout;
+	struct utxo *utxo = tal_arr(tmpctx, struct utxo, 1);
-	u64 input_satoshis;
 	u64 funding_satoshis;
-	int funding_outnum;
+	u32 funding_outnum;
+	u8 *subscript;
+	secp256k1_ecdsa_signature sig;
 
 	secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
 						 | SECP256K1_CONTEXT_SIGN);
@@ -89,32 +89,37 @@ int main(void)
 				&remote_funding_pubkey))
 		abort();
 
-	bitcoin_txid(input, &txid);
+	bitcoin_txid(input, &utxo->txid);
-	input_txout = 0;
+	utxo->outnum = 0;
-	input_satoshis = 5000000000;
+	utxo->amount = 5000000000;
 	funding_satoshis = 10000000;
 	feerate_per_kw = 15000;
 
-	printf("input[0] txid: %s\n", tal_hexstr(tmpctx, &txid, sizeof(txid)));
+	printf("input[0] txid: %s\n",
-	printf("input[0] input: %u\n", input_txout);
+	       tal_hexstr(tmpctx, &utxo->txid, sizeof(utxo->txid)));
-	printf("input[0] satoshis: %"PRIu64"\n", input_satoshis);
+	printf("input[0] input: %u\n", utxo->outnum);
+	printf("input[0] satoshis: %"PRIu64"\n", utxo->amount);
 	printf("funding satoshis: %"PRIu64"\n", funding_satoshis);
 
-	funding = funding_tx(tmpctx, &txid, input_txout, input_satoshis,
+	funding = funding_tx(tmpctx, &funding_outnum, utxo,
 			     funding_satoshis,
 			     &local_funding_pubkey,
 			     &remote_funding_pubkey,
 			     &inputkey,
 			     feerate_per_kw,
 			     0);
-	funding_outnum = (funding->output[0].amount == funding_satoshis ? 0 : 1);
 	printf("# feerate_per_kw: %"PRIu64"\n", feerate_per_kw);
 	printf("change satoshis: %"PRIu64"\n",
 	       funding->output[!funding_outnum].amount);
 
 	printf("funding output: %u\n", funding_outnum);
 
-	sign_funding_tx(funding, &inputkey, &input_privkey);
+	subscript = scriptpubkey_p2pkh(funding, &inputkey);
+	sign_tx_input(funding, 0, subscript, NULL, &input_privkey, &inputkey,
+		      &sig);
+
+	funding->input[0].script = bitcoin_redeem_p2pkh(funding, &inputkey,
+							&sig);
 	printf("funding tx: %s\n",
 	       tal_hex(tmpctx, linearize_tx(tmpctx, funding)));