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

12
lightningd/build_utxos.h
View File

@ -5,12 +5,12 @@
#include <lightningd/utxo.h> #include <lightningd/utxo.h>
/* Reserves UTXOs to build tx which pays this amount; returns NULL if /* Reserves UTXOs to build tx which pays this amount; returns NULL if
* impossible. *change_amount 0 if no change needed. */ * impossible. *change_satoshis 0 if no change needed. */
struct utxo *build_utxos(const tal_t *ctx, const struct utxo **build_utxos(const tal_t *ctx,
struct lightningd *ld, u64 satoshi_out, struct lightningd *ld, u64 satoshi_out,
u32 feerate_per_kw, u64 dust_limit, u32 feerate_per_kw, u64 dust_limit,
u64 *change_amount, u32 *change_keyindex); u64 *change_satoshis, u32 *change_keyindex);
/* Once we've spent them, mark them confirmed. */ /* 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 */ #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, struct bitcoin_tx *funding_tx(const tal_t *ctx,
u32 *outnum, u32 *outnum,
const struct utxo *utxos, const struct utxo **utxomap,
u64 funding_satoshis, u64 funding_satoshis,
const struct pubkey *local_fundingkey, const struct pubkey *local_fundingkey,
const struct pubkey *remote_fundingkey, const struct pubkey *remote_fundingkey,
const struct pubkey *changekey, u64 change_satoshis,
u64 feerate_per_kw, const struct pubkey *changekey)
u64 dust_limit_satoshis)
{ {
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; u8 *wscript;
u64 fee, weight, input_satoshis = 0;
size_t i; size_t i;
for (i = 0; i < tal_count(utxos); i++) { for (i = 0; i < tal_count(utxomap); i++) {
tx->input[i].txid = utxos[i].txid; tx->input[i].txid = utxomap[i]->txid;
tx->input[i].index = utxos[i].outnum; tx->input[i].index = utxomap[i]->outnum;
tx->input[i].amount = tal_dup(tx, u64, &utxos[i].amount); tx->input[i].amount = tal_dup(tx, u64, &utxomap[i]->amount);
input_satoshis += utxos[i].amount;
} }
tx->output[0].amount = funding_satoshis; 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); tx->output[0].script = scriptpubkey_p2wsh(tx, wscript);
tal_free(wscript); tal_free(wscript);
assert(input_satoshis >= funding_satoshis);
tx->output[1].script = scriptpubkey_p2wpkh(tx, changekey); tx->output[1].script = scriptpubkey_p2wpkh(tx, changekey);
/* Calculate what weight will be once we've signed. */ if (change_satoshis != 0) {
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 {
const void *map[2]; const void *map[2];
map[0] = int2ptr(0); map[0] = int2ptr(0);
map[1] = int2ptr(1); 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); permute_outputs(tx->output, tal_count(tx->output), map);
*outnum = (map[0] == int2ptr(0) ? 0 : 1); *outnum = (map[0] == int2ptr(0) ? 0 : 1);
} else {
*outnum = 0;
} }
permute_inputs(tx->input, tal_count(tx->input), (const void **)utxomap);
return tx; 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. * funding_tx: create a P2WSH funding transaction for a channel.
* @ctx: context to tal from. * @ctx: context to tal from.
* @outnum: txout (0 or 1) which is the funding output. * @outnum: (out) txout (0 or 1) which is the funding output.
* @utxo: tal_arr of UTXO to spend as inputs. * @utxomap: (in/out) tal_arr of UTXO pointers to spend (permuted to match)
* @funding_satoshis: satoshis to output. * @funding_satoshis: (in) satoshis to output.
* @local_fundingkey: local key for 2of2 funding output. * @local_fundingkey: (in) local key for 2of2 funding output.
* @remote_fundingkey: remote key for 2of2 funding output. * @remote_fundingkey: (in) remote key for 2of2 funding output.
* @changekey: key to send change to (if any). * @change_satoshis: (in) amount to send as change.
* @feerate_per_kw: feerate for transaction. * @changekey: (in) key to send change to (only used if change_satoshis != 0).
* @dust_limit_satoshis: dust limit to trim change output by.
*/ */
struct bitcoin_tx *funding_tx(const tal_t *ctx, struct bitcoin_tx *funding_tx(const tal_t *ctx,
u32 *outnum, u32 *outnum,
const struct utxo *utxos, const struct utxo **utxomap,
u64 funding_satoshis, u64 funding_satoshis,
const struct pubkey *local_fundingkey, const struct pubkey *local_fundingkey,
const struct pubkey *remote_fundingkey, const struct pubkey *remote_fundingkey,
const struct pubkey *changekey, u64 change_satoshis,
u64 feerate_per_kw, const struct pubkey *changekey);
u64 dust_limit_satoshis);
#endif /* LIGHTNING_LIGHTNINGD_FUNDING_TX_H */ #endif /* LIGHTNING_LIGHTNINGD_FUNDING_TX_H */

26
lightningd/peer_control.c
View File

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

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

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

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