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funding_tx: permute inputs, don't re-calculate fees 

built_utxos needs to calculate fees for figuring out how many utxos to
use, so fix that logic and rely on it.

We make build_utxos return a pointer array, so funding_tx can simply hand
that to permute_inputs.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
ppa-0.6.1
Rusty Russell 8 years ago
parent
e0d9b6efdf
commit
d77e7963f9
6 changed files with 81 additions and 85 deletions
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  1. 41
      lightningd/build_utxos.c
  2. 12
      lightningd/build_utxos.h
  3. 36
      lightningd/funding_tx.c
  4. 22
      lightningd/funding_tx.h
  5. 26
      lightningd/peer_control.c
  6. 29
      lightningd/test/run-funding_tx.c

41
lightningd/build_utxos.c
View File

@ -175,39 +175,35 @@ static void unreserve_utxo(struct lightningd *ld, const struct utxo *unres)
struct tracked_utxo *utxo;
list_for_each(&ld->utxos, utxo, list) {
if (unres->outnum != utxo->utxo.outnum
|| !structeq(&unres->txid, &utxo->utxo.txid))
if (unres != &utxo->utxo)
continue;
assert(utxo->reserved);
assert(unres->amount == utxo->utxo.amount);
assert(unres->keyindex == utxo->utxo.keyindex);
assert(unres->is_p2sh == utxo->utxo.is_p2sh);
utxo->reserved = false;
return;
}
abort();
}
static void destroy_utxos(struct utxo *utxos, struct lightningd *ld)
static void destroy_utxos(const struct utxo **utxos, struct lightningd *ld)
{
size_t i;
for (i = 0; i < tal_count(utxos); i++)
unreserve_utxo(ld, &utxos[i]);
unreserve_utxo(ld, utxos[i]);
}
void confirm_utxos(struct lightningd *ld, struct utxo *utxos)
void confirm_utxos(struct lightningd *ld, const struct utxo **utxos)
{
tal_del_destructor2(utxos, destroy_utxos, ld);
}
struct utxo *build_utxos(const tal_t *ctx,
struct lightningd *ld, u64 satoshi_out,
u32 feerate_per_kw, u64 dust_limit,
u64 *change_amount, u32 *change_keyindex)
const struct utxo **build_utxos(const tal_t *ctx,
struct lightningd *ld, u64 satoshi_out,
u32 feerate_per_kw, u64 dust_limit,
u64 *change_satoshis, u32 *change_keyindex)
{
size_t i = 0;
struct utxo *utxos = tal_arr(ctx, struct utxo, 0);
const struct utxo **utxos = tal_arr(ctx, const struct utxo *, 0);
struct tracked_utxo *utxo;
/* We assume two outputs for the weight. */
u64 satoshi_in = 0, weight = (4 + (8 + 22) * 2 + 4) * 4;
@ -221,23 +217,26 @@ struct utxo *build_utxos(const tal_t *ctx,
continue;
tal_resize(&utxos, i+1);
utxos[i] = utxo->utxo;
utxos[i] = &utxo->utxo;
utxo->reserved = true;
/* Add this input's weight. */
weight += (32 + 4 + 4) * 4;
if (utxos[i].is_p2sh)
if (utxos[i]->is_p2sh)
weight += 22 * 4;
satoshi_in += utxos[i].amount;
/* Account for witness (1 byte count + sig + key */
weight += 1 + (1 + 73 + 1 + 33);
fee = weight * feerate_per_kw / 1000;
satoshi_in += utxos[i]->amount;
if (satoshi_in >= fee + satoshi_out) {
/* We simply eliminate change if it's dust. */
*change_amount = satoshi_in - (fee + satoshi_out);
if (*change_amount < dust_limit)
*change_amount = 0;
else
*change_satoshis = satoshi_in - (fee + satoshi_out);
if (*change_satoshis < dust_limit) {
*change_satoshis = 0;
*change_keyindex = 0;
} else
*change_keyindex = ld->bip32_max_index++;
return utxos;

12
lightningd/build_utxos.h
View File

@ -5,12 +5,12 @@
#include <lightningd/utxo.h>
/* Reserves UTXOs to build tx which pays this amount; returns NULL if
* impossible. *change_amount 0 if no change needed. */
struct utxo *build_utxos(const tal_t *ctx,
struct lightningd *ld, u64 satoshi_out,
u32 feerate_per_kw, u64 dust_limit,
u64 *change_amount, u32 *change_keyindex);
* impossible. *change_satoshis 0 if no change needed. */
const struct utxo **build_utxos(const tal_t *ctx,
struct lightningd *ld, u64 satoshi_out,
u32 feerate_per_kw, u64 dust_limit,
u64 *change_satoshis, u32 *change_keyindex);
/* Once we've spent them, mark them confirmed. */
void confirm_utxos(struct lightningd *ld, struct utxo *utxos);
void confirm_utxos(struct lightningd *ld, const struct utxo **utxos);
#endif /* LIGHTNING_LIGHTNINGD_BUILD_UTXOS_H */

36
lightningd/funding_tx.c
View File

@ -12,24 +12,22 @@
struct bitcoin_tx *funding_tx(const tal_t *ctx,
u32 *outnum,
const struct utxo *utxos,
const struct utxo **utxomap,
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)
u64 change_satoshis,
const struct pubkey *changekey)
{
struct bitcoin_tx *tx = bitcoin_tx(ctx, tal_count(utxos), 2);
struct bitcoin_tx *tx = bitcoin_tx(ctx, tal_count(utxomap),
change_satoshis ? 2 : 1);
u8 *wscript;
u64 fee, weight, input_satoshis = 0;
size_t i;
for (i = 0; i < tal_count(utxos); i++) {
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;
for (i = 0; i < tal_count(utxomap); i++) {
tx->input[i].txid = utxomap[i]->txid;
tx->input[i].index = utxomap[i]->outnum;
tx->input[i].amount = tal_dup(tx, u64, &utxomap[i]->amount);
}
tx->output[0].amount = funding_satoshis;
@ -39,25 +37,19 @@ struct bitcoin_tx *funding_tx(const tal_t *ctx,
tx->output[0].script = scriptpubkey_p2wsh(tx, wscript);
tal_free(wscript);
assert(input_satoshis >= funding_satoshis);
tx->output[1].script = scriptpubkey_p2wpkh(tx, changekey);
/* Calculate what weight will be once we've signed. */
weight = measure_tx_cost(tx) + 4 * (73 + 34);
fee = weight * feerate_per_kw / 1000;
/* Too small an output after fee? Drop it. */
if (input_satoshis - funding_satoshis < dust_limit_satoshis + fee) {
tal_resize(&tx->output, 1);
*outnum = 0;
} else {
if (change_satoshis != 0) {
const void *map[2];
map[0] = int2ptr(0);
map[1] = int2ptr(1);
tx->output[1].amount = input_satoshis - funding_satoshis - fee;
tx->output[1].amount = change_satoshis;
permute_outputs(tx->output, tal_count(tx->output), map);
*outnum = (map[0] == int2ptr(0) ? 0 : 1);
} else {
*outnum = 0;
}
permute_inputs(tx->input, tal_count(tx->input), (const void **)utxomap);
return tx;
}

22
lightningd/funding_tx.h
View File

@ -13,22 +13,20 @@ struct utxo;
/**
* 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.
* @outnum: (out) txout (0 or 1) which is the funding output.
* @utxomap: (in/out) tal_arr of UTXO pointers to spend (permuted to match)
* @funding_satoshis: (in) satoshis to output.
* @local_fundingkey: (in) local key for 2of2 funding output.
* @remote_fundingkey: (in) remote key for 2of2 funding output.
* @change_satoshis: (in) amount to send as change.
* @changekey: (in) key to send change to (only used if change_satoshis != 0).
*/
struct bitcoin_tx *funding_tx(const tal_t *ctx,
u32 *outnum,
const struct utxo *utxos,
const struct utxo **utxomap,
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);
u64 change_satoshis,
const struct pubkey *changekey);
#endif /* LIGHTNING_LIGHTNINGD_FUNDING_TX_H */

26
lightningd/peer_control.c
View File

@ -516,7 +516,7 @@ struct funding_channel {
struct peer *peer;
struct command *cmd;
u64 satoshi;
struct utxo *utxos;
const struct utxo **utxomap;
u64 change;
u32 change_keyindex;
struct crypto_state *cs;
@ -553,15 +553,22 @@ static void opening_release_tx(struct subdaemon *opening, const u8 *resp,
struct funding_channel *fc)
{
u8 *msg;
size_t i;
/* FIXME: marshal code wants array, not array of pointers. */
struct utxo *utxos = tal_arr(fc, struct utxo, tal_count(fc->utxomap));
peer_set_condition(fc->peer, "Getting HSM to sign funding tx");
/* Get HSM to sign the funding tx. */
for (i = 0; i < tal_count(fc->utxomap); i++)
utxos[i] = *fc->utxomap[i];
msg = towire_hsmctl_sign_funding(fc, fc->satoshi, fc->change,
fc->change_keyindex,
&fc->local_fundingkey,
&fc->remote_fundingkey,
fc->utxos);
utxos);
tal_free(utxos);
subdaemon_req(fc->peer->ld->hsm, take(msg), -1, NULL,
opening_got_hsm_funding_sig, fc);
}
@ -584,14 +591,13 @@ static void opening_gen_funding(struct subdaemon *opening, const u8 *resp,
return;
}
bitcoin_pubkey(fc->peer->ld, &changekey, fc->change_keyindex);
if (fc->change)
bitcoin_pubkey(fc->peer->ld, &changekey, fc->change_keyindex);
/* FIXME: Real feerate! */
/* FIXME: Real dust limit! */
fc->funding_tx = funding_tx(fc, &outnum, fc->utxos, fc->satoshi,
fc->funding_tx = funding_tx(fc, &outnum, fc->utxomap, fc->satoshi,
&fc->local_fundingkey,
&fc->remote_fundingkey,
&changekey, 15000, 546);
fc->change, &changekey);
bitcoin_txid(fc->funding_tx, &txid);
msg = towire_opening_open_funding(fc, &txid, outnum);
@ -809,9 +815,9 @@ static void json_fund_channel(struct command *cmd,
/* Try to do this now, so we know if insufficient funds. */
/* FIXME: Feerate & dustlimit */
fc->utxos = build_utxos(fc, ld, fc->satoshi, 15000, 600,
&fc->change, &fc->change_keyindex);
if (!fc->utxos) {
fc->utxomap = build_utxos(fc, ld, fc->satoshi, 15000, 600,
&fc->change, &fc->change_keyindex);
if (!fc->utxomap) {
command_fail(cmd, "Cannot afford funding transaction");
return;
}

29
lightningd/test/run-funding_tx.c
View File

@ -39,12 +39,13 @@ int main(void)
{
tal_t *tmpctx = tal_tmpctx(NULL);
struct bitcoin_tx *input, *funding;
u64 feerate_per_kw;
u64 fee;
struct pubkey local_funding_pubkey, remote_funding_pubkey;
struct privkey input_privkey;
struct pubkey inputkey;
bool testnet;
struct utxo *utxo = tal_arr(tmpctx, struct utxo, 1);
struct utxo utxo;
const struct utxo **utxomap = tal_arr(tmpctx, const struct utxo *, 1);
u64 funding_satoshis;
u32 funding_outnum;
u8 *subscript;
@ -89,26 +90,26 @@ int main(void)
&remote_funding_pubkey))
abort();
bitcoin_txid(input, &utxo->txid);
utxo->outnum = 0;
utxo->amount = 5000000000;
bitcoin_txid(input, &utxo.txid);
utxo.outnum = 0;
utxo.amount = 5000000000;
funding_satoshis = 10000000;
feerate_per_kw = 15000;
fee = 13920;
printf("input[0] txid: %s\n",
tal_hexstr(tmpctx, &utxo->txid, sizeof(utxo->txid)));
printf("input[0] input: %u\n", utxo->outnum);
printf("input[0] satoshis: %"PRIu64"\n", utxo->amount);
tal_hexstr(tmpctx, &utxo.txid, sizeof(utxo.txid)));
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, &funding_outnum, utxo,
utxomap[0] = &utxo;
funding = funding_tx(tmpctx, &funding_outnum, utxomap,
funding_satoshis,
&local_funding_pubkey,
&remote_funding_pubkey,
&inputkey,
feerate_per_kw,
0);
printf("# feerate_per_kw: %"PRIu64"\n", feerate_per_kw);
utxo.amount - fee - funding_satoshis,
&inputkey);
printf("# fee: %"PRIu64"\n", fee);
printf("change satoshis: %"PRIu64"\n",
funding->output[!funding_outnum].amount);

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