294 lines
8.1 KiB
C
294 lines
8.1 KiB
C
#include <bitcoin/script.h>
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#include <bitcoin/tx.h>
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#include <ccan/endian/endian.h>
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#include <channeld/commit_tx.h>
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#include <common/htlc_tx.h>
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#include <common/keyset.h>
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#include <common/permute_tx.h>
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#include <common/utils.h>
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#ifndef SUPERVERBOSE
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#define SUPERVERBOSE(...)
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#endif
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static bool trim(const struct htlc *htlc,
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u32 feerate_per_kw, u64 dust_limit_satoshis,
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enum side side)
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{
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u64 htlc_fee;
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/* BOLT #3:
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*
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* - for every offered HTLC:
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* - if the HTLC amount minus the HTLC-timeout fee would be less than
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* `dust_limit_satoshis` set by the transaction owner:
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* - MUST NOT contain that output.
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* - otherwise:
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* - MUST be generated as specified in
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* [Offered HTLC Outputs](#offered-htlc-outputs).
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*/
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if (htlc_owner(htlc) == side)
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htlc_fee = htlc_timeout_fee(feerate_per_kw);
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/* BOLT #3:
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*
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* - for every received HTLC:
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* - if the HTLC amount minus the HTLC-success fee would be less than
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* `dust_limit_satoshis` set by the transaction owner:
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* - MUST NOT contain that output.
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* - otherwise:
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* - MUST be generated as specified in
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*/
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else
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htlc_fee = htlc_success_fee(feerate_per_kw);
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return htlc->msatoshi / 1000 < dust_limit_satoshis + htlc_fee;
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}
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size_t commit_tx_num_untrimmed(const struct htlc **htlcs,
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u32 feerate_per_kw, u64 dust_limit_satoshis,
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enum side side)
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{
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size_t i, n;
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for (i = n = 0; i < tal_count(htlcs); i++)
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n += !trim(htlcs[i], feerate_per_kw, dust_limit_satoshis, side);
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return n;
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}
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static void add_offered_htlc_out(struct bitcoin_tx *tx, size_t n,
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const struct htlc *htlc,
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const struct keyset *keyset)
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{
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struct ripemd160 ripemd;
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u8 *wscript;
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ripemd160(&ripemd, htlc->rhash.u.u8, sizeof(htlc->rhash.u.u8));
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wscript = htlc_offered_wscript(tx->output, &ripemd, keyset);
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tx->output[n].amount = htlc->msatoshi / 1000;
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tx->output[n].script = scriptpubkey_p2wsh(tx, wscript);
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SUPERVERBOSE("# HTLC %"PRIu64" offered amount %"PRIu64" wscript %s\n",
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htlc->id, tx->output[n].amount, tal_hex(wscript, wscript));
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tal_free(wscript);
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}
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static void add_received_htlc_out(struct bitcoin_tx *tx, size_t n,
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const struct htlc *htlc,
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const struct keyset *keyset)
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{
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struct ripemd160 ripemd;
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u8 *wscript;
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ripemd160(&ripemd, htlc->rhash.u.u8, sizeof(htlc->rhash.u.u8));
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wscript = htlc_received_wscript(tx, &ripemd, &htlc->expiry, keyset);
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tx->output[n].amount = htlc->msatoshi / 1000;
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tx->output[n].script = scriptpubkey_p2wsh(tx->output, wscript);
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SUPERVERBOSE("# HTLC %"PRIu64" received amount %"PRIu64" wscript %s\n",
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htlc->id, tx->output[n].amount, tal_hex(wscript, wscript));
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tal_free(wscript);
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}
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struct bitcoin_tx *commit_tx(const tal_t *ctx,
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const struct bitcoin_txid *funding_txid,
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unsigned int funding_txout,
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u64 funding_satoshis,
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enum side funder,
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u16 to_self_delay,
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const struct keyset *keyset,
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u32 feerate_per_kw,
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u64 dust_limit_satoshis,
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u64 self_pay_msat,
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u64 other_pay_msat,
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const struct htlc **htlcs,
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const struct htlc ***htlcmap,
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u64 obscured_commitment_number,
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enum side side)
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{
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u64 base_fee_msat;
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struct bitcoin_tx *tx;
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size_t i, n, untrimmed;
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assert(self_pay_msat + other_pay_msat <= funding_satoshis * 1000);
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/* BOLT #3:
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*
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* 1. Calculate which committed HTLCs need to be trimmed (see
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* [Trimmed Outputs](#trimmed-outputs)).
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*/
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untrimmed = commit_tx_num_untrimmed(htlcs,
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feerate_per_kw,
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dust_limit_satoshis, side);
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/* BOLT #3:
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*
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* 2. Calculate the base [commitment transaction
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* fee](#fee-calculation).
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*/
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base_fee_msat = commit_tx_base_fee(feerate_per_kw, untrimmed) * 1000;
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SUPERVERBOSE("# base commitment transaction fee = %"PRIu64"\n",
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base_fee_msat / 1000);
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/* BOLT #3:
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*
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* 3. Subtract this base fee from the funder (either `to_local` or
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* `to_remote`), with a floor of 0 (see [Fee Payment](#fee-payment)).
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*/
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try_subtract_fee(funder, side, base_fee_msat,
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&self_pay_msat, &other_pay_msat);
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#ifdef PRINT_ACTUAL_FEE
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{
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u64 satoshis_out = 0;
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for (i = n = 0; i < tal_count(htlcs); i++) {
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if (!trim(htlcs[i], feerate_per_kw, dust_limit_satoshis,
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side))
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satoshis_out += htlcs[i]->msatoshi / 1000;
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}
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if (self_pay_msat / 1000 >= dust_limit_satoshis)
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satoshis_out += self_pay_msat / 1000;
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if (other_pay_msat / 1000 >= dust_limit_satoshis)
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satoshis_out += other_pay_msat / 1000;
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SUPERVERBOSE("# actual commitment transaction fee = %"PRIu64"\n",
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funding_satoshis - satoshis_out);
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}
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#endif
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/* Worst-case sizing: both to-local and to-remote outputs. */
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tx = bitcoin_tx(ctx, 1, untrimmed + 2);
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/* We keep track of which outputs have which HTLCs */
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if (htlcmap)
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*htlcmap = tal_arr(tx, const struct htlc *,
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tal_count(tx->output));
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/* This could be done in a single loop, but we follow the BOLT
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* literally to make comments in test vectors clearer. */
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n = 0;
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/* BOLT #3:
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*
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* 3. For every offered HTLC, if it is not trimmed, add an
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* [offered HTLC output](#offered-htlc-outputs).
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*/
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for (i = 0; i < tal_count(htlcs); i++) {
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if (htlc_owner(htlcs[i]) != side)
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continue;
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if (trim(htlcs[i], feerate_per_kw, dust_limit_satoshis, side))
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continue;
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add_offered_htlc_out(tx, n, htlcs[i], keyset);
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if (htlcmap)
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(*htlcmap)[n++] = htlcs[i];
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}
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/* BOLT #3:
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*
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* 4. For every received HTLC, if it is not trimmed, add an
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* [received HTLC output](#received-htlc-outputs).
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*/
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for (i = 0; i < tal_count(htlcs); i++) {
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if (htlc_owner(htlcs[i]) == side)
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continue;
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if (trim(htlcs[i], feerate_per_kw, dust_limit_satoshis, side))
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continue;
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add_received_htlc_out(tx, n, htlcs[i], keyset);
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if (htlcmap)
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(*htlcmap)[n++] = htlcs[i];
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}
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/* BOLT #3:
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*
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* 5. If the `to_local` amount is greater or equal to
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* `dust_limit_satoshis`, add a [`to_local`
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* output](#to-local-output).
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*/
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if (self_pay_msat / 1000 >= dust_limit_satoshis) {
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u8 *wscript = to_self_wscript(tmpctx, to_self_delay,keyset);
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tx->output[n].amount = self_pay_msat / 1000;
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tx->output[n].script = scriptpubkey_p2wsh(tx, wscript);
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if (htlcmap)
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(*htlcmap)[n] = NULL;
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SUPERVERBOSE("# to-local amount %"PRIu64" wscript %s\n",
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tx->output[n].amount,
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tal_hex(tmpctx, wscript));
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n++;
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}
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/* BOLT #3:
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*
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* 6. If the `to_remote` amount is greater or equal to
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* `dust_limit_satoshis`, add a [`to_remote`
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* output](#to-remote-output).
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*/
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if (other_pay_msat / 1000 >= dust_limit_satoshis) {
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/* BOLT #3:
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*
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* #### `to_remote` Output
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*
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* This output sends funds to the other peer and thus is a simple
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* P2WPKH to `remotepubkey`.
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*/
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tx->output[n].amount = other_pay_msat / 1000;
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tx->output[n].script = scriptpubkey_p2wpkh(tx,
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&keyset->other_payment_key);
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if (htlcmap)
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(*htlcmap)[n] = NULL;
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SUPERVERBOSE("# to-remote amount %"PRIu64" P2WPKH(%s)\n",
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tx->output[n].amount,
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type_to_string(tmpctx, struct pubkey,
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&keyset->other_payment_key));
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n++;
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}
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assert(n <= tal_count(tx->output));
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tal_resize(&tx->output, n);
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if (htlcmap)
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tal_resize(htlcmap, n);
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/* BOLT #3:
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*
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* 7. Sort the outputs into [BIP 69
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* order](#transaction-input-and-output-ordering)
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*/
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permute_outputs(tx->output, tal_count(tx->output),
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htlcmap ? (const void **)*htlcmap : NULL);
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/* BOLT #3:
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*
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* ## Commitment Transaction
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*
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* * version: 2
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*/
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assert(tx->version == 2);
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/* BOLT #3:
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*
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* * locktime: upper 8 bits are 0x20, lower 24 bits are the lower
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* 24 bits of the obscured commitment transaction number
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*/
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tx->lock_time
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= (0x20000000 | (obscured_commitment_number & 0xFFFFFF));
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/* BOLT #3:
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*
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* * txin count: 1
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* * `txin[0]` outpoint: `txid` and `output_index` from
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* `funding_created` message
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*/
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tx->input[0].txid = *funding_txid;
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tx->input[0].index = funding_txout;
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/* BOLT #3:
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*
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* * `txin[0]` sequence: upper 8 bits are 0x80, lower 24 bits are
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* upper 24 bits of the obscured commitment transaction number
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*/
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tx->input[0].sequence_number
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= (0x80000000 | ((obscured_commitment_number>>24) & 0xFFFFFF));
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/* Input amount needed for signature code. */
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tx->input[0].amount = tal_dup(tx->input, u64, &funding_satoshis);
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return tx;
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}
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