core-lightning/common/close_tx.c
darosior 273029f244 wallet: set nLockTime to the tip for withdrawal transactions
This sets the nLockTime to the tip (and accordingly each input's nSequence to
0xfffffffe) for withdrawal transactions.

Even if the anti fee-sniping argument might not be valid until some time yet,
this makes our regular wallet transactions far less distinguishable from
bitcoind's ones since it now defaults to using native Segwit transactions
(like us). Moreover other wallets are likely to implement this (if they
haven't already).

Changelog-Added: wallet: withdrawal transactions now sets nlocktime to the current tip.
2020-02-03 00:45:27 +00:00

69 lines
1.7 KiB
C

#include "bitcoin/script.h"
#include "bitcoin/tx.h"
#include "close_tx.h"
#include "permute_tx.h"
#include <assert.h>
struct bitcoin_tx *create_close_tx(const tal_t *ctx,
const struct chainparams *chainparams,
const u8 *our_script,
const u8 *their_script,
const struct bitcoin_txid *anchor_txid,
unsigned int anchor_index,
struct amount_sat funding,
struct amount_sat to_us,
struct amount_sat to_them,
struct amount_sat dust_limit)
{
struct bitcoin_tx *tx;
size_t num_outputs = 0;
struct amount_sat total_out;
u8 *script;
assert(amount_sat_add(&total_out, to_us, to_them));
assert(amount_sat_less_eq(total_out, funding));
/* BOLT #3:
*
* ## Closing Transaction
*
* Note that there are two possible variants for each node.
*
* * version: 2
* * locktime: 0
* * txin count: 1
*/
/* Now create close tx: one input, two outputs. */
tx = bitcoin_tx(ctx, chainparams, 1, 2, 0);
/* Our input spends the anchor tx output. */
bitcoin_tx_add_input(tx, anchor_txid, anchor_index,
BITCOIN_TX_DEFAULT_SEQUENCE, funding, NULL);
if (amount_sat_greater_eq(to_us, dust_limit)) {
script =
tal_dup_arr(tx, u8, our_script, tal_count(our_script), 0);
/* One output is to us. */
bitcoin_tx_add_output(tx, script, to_us);
num_outputs++;
}
if (amount_sat_greater_eq(to_them, dust_limit)) {
script = tal_dup_arr(tx, u8, their_script,
tal_count(their_script), 0);
/* Other output is to them. */
bitcoin_tx_add_output(tx, script, to_them);
num_outputs++;
}
/* Can't have no outputs at all! */
if (num_outputs == 0)
return tal_free(tx);
permute_outputs(tx, NULL, NULL);
elements_tx_add_fee_output(tx);
assert(bitcoin_tx_check(tx));
return tx;
}