64 lines
1.8 KiB
C
64 lines
1.8 KiB
C
#include "funding_tx.h"
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#include <assert.h>
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#include <bitcoin/script.h>
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#include <bitcoin/tx.h>
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#include <ccan/ptrint/ptrint.h>
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#include <lightningd/utxo.h>
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#include <permute_tx.h>
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#ifndef SUPERVERBOSE
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#define SUPERVERBOSE(...)
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#endif
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struct bitcoin_tx *funding_tx(const tal_t *ctx,
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u32 *outnum,
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const struct utxo *utxos,
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u64 funding_satoshis,
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const struct pubkey *local_fundingkey,
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const struct pubkey *remote_fundingkey,
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const struct pubkey *changekey,
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u64 feerate_per_kw,
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u64 dust_limit_satoshis)
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{
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struct bitcoin_tx *tx = bitcoin_tx(ctx, tal_count(utxos), 2);
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u8 *wscript;
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u64 fee, weight, input_satoshis = 0;
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size_t i;
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for (i = 0; i < tal_count(utxos); i++) {
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tx->input[i].txid = utxos[i].txid;
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tx->input[i].index = utxos[i].outnum;
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tx->input[i].amount = tal_dup(tx, u64, &utxos[i].amount);
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input_satoshis += utxos[i].amount;
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}
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tx->output[0].amount = funding_satoshis;
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wscript = bitcoin_redeem_2of2(tx, local_fundingkey, remote_fundingkey);
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SUPERVERBOSE("# funding witness script = %s\n",
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tal_hex(wscript, wscript));
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tx->output[0].script = scriptpubkey_p2wsh(tx, wscript);
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tal_free(wscript);
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assert(input_satoshis >= funding_satoshis);
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tx->output[1].script = scriptpubkey_p2wpkh(tx, changekey);
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/* Calculate what weight will be once we've signed. */
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weight = measure_tx_cost(tx) + 4 * (73 + 34);
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fee = weight * feerate_per_kw / 1000;
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/* Too small an output after fee? Drop it. */
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if (input_satoshis - funding_satoshis < dust_limit_satoshis + fee) {
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tal_resize(&tx->output, 1);
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*outnum = 0;
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} else {
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const void *map[2];
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map[0] = int2ptr(0);
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map[1] = int2ptr(1);
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tx->output[1].amount = input_satoshis - funding_satoshis - fee;
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permute_outputs(tx->output, tal_count(tx->output), map);
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*outnum = (map[0] == int2ptr(0) ? 0 : 1);
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}
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return tx;
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}
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