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The wire protocol uses this, in the assumption that we'll never see feerates in excess of 4294967 satoshi per kiloweight. So let's use that consistently internally as well. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
96 lines
3.2 KiB
C
96 lines
3.2 KiB
C
/* Commit tx without HTLC support; needed for openingd. */
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#ifndef LIGHTNING_COMMON_INITIAL_COMMIT_TX_H
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#define LIGHTNING_COMMON_INITIAL_COMMIT_TX_H
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#include "config.h"
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#include <bitcoin/pubkey.h>
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#include <common/htlc.h>
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struct keyset;
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struct sha256_double;
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/* BOLT #3:
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*
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* This obscures the number of commitments made on the channel in the
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* case of unilateral close, yet still provides a useful index for
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* both nodes (who know the `payment_basepoint`s) to quickly find a
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* revoked commitment transaction.
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*/
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u64 commit_number_obscurer(const struct pubkey *opener_payment_basepoint,
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const struct pubkey *accepter_payment_basepoint);
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/* Helper to calculate the base fee if we have this many htlc outputs */
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static inline u64 commit_tx_base_fee(u32 feerate_per_kw,
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size_t num_untrimmed_htlcs)
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{
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u64 weight;
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/* BOLT #3:
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*
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* The base fee for a commitment transaction MUST BE
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* calculated to match:
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*
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* 1. Start with `weight` = 724.
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*/
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weight = 724;
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/* BOLT #3:
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*
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* 2. For each committed HTLC, if that output is not trimmed
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* as specified in [Trimmed Outputs](#trimmed-outputs), add
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* 172 to `weight`.
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*/
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weight += 172 * num_untrimmed_htlcs;
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/* BOLT #3:
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*
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* 3. Multiply `feerate_per_kw` by `weight`, divide by 1000
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* (rounding down).
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*/
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return feerate_per_kw * weight / 1000;
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}
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/**
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* initial_commit_tx: create (unsigned) commitment tx to spend the funding tx output
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* @ctx: context to allocate transaction and @htlc_map from.
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* @funding_txid, @funding_out, @funding_satoshis: funding outpoint.
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* @funder: is the LOCAL or REMOTE paying the fee?
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* @keyset: keys derived for this commit tx.
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* @feerate_per_kw: feerate to use
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* @dust_limit_satoshis: dust limit below which to trim outputs.
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* @self_pay_msat: amount to pay directly to self
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* @other_pay_msat: amount to pay directly to the other side
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* @obscured_commitment_number: number to encode in commitment transaction
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* @side: side to generate commitment transaction for.
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*
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* We need to be able to generate the remote side's tx to create signatures,
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* but the BOLT is expressed in terms of generating our local commitment
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* transaction, so we carefully use the terms "self" and "other" here.
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*/
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struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
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const struct sha256_double *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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u64 obscured_commitment_number,
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enum side side);
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/* try_subtract_fee - take away this fee from the funder, or all if insufficient. */
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void try_subtract_fee(enum side funder, enum side side,
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u64 base_fee_msat, u64 *self_msat, u64 *other_msat);
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/* Generate the witness script for the to-self output:
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* scriptpubkey_p2wsh(ctx, wscript) gives the scriptpubkey */
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u8 *to_self_wscript(const tal_t *ctx,
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u16 to_self_delay,
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const struct keyset *keyset);
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/* To-other is simply: scriptpubkey_p2wpkh(tx, keyset->other_payment_key) */
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#endif /* LIGHTNING_COMMON_INITIAL_COMMIT_TX_H */
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