elements: Fix transaction handling for elements transactions

Skipping coinbase transactions and ensuring that the transaction is serialized
correctly when sending it onwards.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

bitcoin/tx.c

@@ -97,6 +97,9 @@ const u8 *bitcoin_tx_output_get_script(const tal_t *ctx,
 	u8 *res;
 	assert(outnum < tx->wtx->num_outputs);
 	output = &tx->wtx->outputs[outnum];
+	if (output->features & WALLY_TX_IS_COINBASE)
+		return NULL;
+
 	res = tal_arr(ctx, u8, output->script_len);
 	memcpy(res, output->script, output->script_len);
 	return res;
@@ -220,7 +223,10 @@ static void push_tx(const struct bitcoin_tx *tx,
         if (bip144 && uses_witness(tx))
 		flag |= WALLY_TX_FLAG_USE_WITNESS;
 
-	res = wally_tx_get_length(tx->wtx, flag, &len);
+	if (is_elements)
+		flag |= WALLY_TX_FLAG_USE_ELEMENTS;
+
+	res = wally_tx_get_length(tx->wtx, flag & WALLY_TX_FLAG_USE_WITNESS, &len);
 	assert(res == WALLY_OK);
 	serialized = tal_arr(tmpctx, u8, len);
 

lightningd/chaintopology.c

@@ -654,6 +654,9 @@ static void topo_add_utxos(struct chain_topology *topo, struct block *b)
 	for (size_t i = 0; i < tal_count(b->full_txs); i++) {
 		const struct bitcoin_tx *tx = b->full_txs[i];
 		for (size_t j = 0; j < tx->wtx->num_outputs; j++) {
+			if (tx->wtx->outputs[j].features & WALLY_TX_IS_COINBASE)
+				continue;
+
 			const u8 *script = bitcoin_tx_output_get_script(tmpctx, tx, j);
 			struct amount_sat amt = bitcoin_tx_output_get_amount(tx, j);
 

wallet/txfilter.c

@@ -103,6 +103,9 @@ bool txfilter_match(const struct txfilter *filter, const struct bitcoin_tx *tx)
 	for (size_t i = 0; i < tx->wtx->num_outputs; i++) {
 		const u8 *oscript = bitcoin_tx_output_get_script(tmpctx, tx, i);
 
+		if (!oscript)
+			continue;
+
 		if (scriptpubkeyset_get(&filter->scriptpubkeyset, oscript))
 			return true;
 	}

wallet/wallet.c

@@ -1498,11 +1498,13 @@ int wallet_extract_owned_outputs(struct wallet *w, const struct bitcoin_tx *tx,
 		struct utxo *utxo;
 		u32 index;
 		bool is_p2sh;
-		const u8 *script = bitcoin_tx_output_get_script(tmpctx, tx, output);
+		const u8 *script;
 
+		script = bitcoin_tx_output_get_script(tmpctx, tx, output);
+		if (!script)
+			continue;
 
-		if (!wallet_can_spend(w, script, &index,
-				      &is_p2sh))
+		if (!wallet_can_spend(w, script, &index, &is_p2sh))
 			continue;
 
 		utxo = tal(w, struct utxo);