147 lines
5.2 KiB
C
147 lines
5.2 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/chainparams.h>
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#include <bitcoin/pubkey.h>
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#include <common/htlc.h>
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#include <common/utils.h>
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struct bitcoin_txid;
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struct keyset;
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struct wally_tx_output;
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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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/* The base weight of a commitment tx */
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static inline size_t commit_tx_base_weight(size_t num_untrimmed_htlcs,
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bool option_anchor_outputs)
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{
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size_t weight;
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/* BOLT #3:
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*
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* The base fee for a commitment transaction:
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* - MUST be calculated to match:
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* 1. Start with `weight` = 724 (1124 if `option_anchors` applies).
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*/
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if (option_anchor_outputs)
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weight = 1124;
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else
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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 as
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* specified in [Trimmed Outputs](#trimmed-outputs), add 172
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* to `weight`.
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*/
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weight += 172 * num_untrimmed_htlcs;
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if (chainparams->is_elements) {
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/* Each transaction has surjection and rangeproof (both empty
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* for us as long as we use unblinded L-BTC transactions). */
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weight += 2 * 4;
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/* Inputs have 6 bytes of blank proofs attached. This TX only
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* has a single input. */
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weight += 6;
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/* Each direct output has a bit more weight to it */
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weight += (32 + 1 + 1 + 1) * 4 * 2; /* Elements added fields */
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/* Each HTLC output also carries a bit more weight */
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weight += (32 + 1 + 1 + 1) * 4 * num_untrimmed_htlcs;
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/* For elements we also need to add the fee output and the
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* overhead for rangeproofs into the mix. */
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weight += (8 + 1) * 4; /* Bitcoin style output */
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weight += (32 + 1 + 1 + 1) * 4; /* Elements added fields */
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}
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return weight;
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}
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/* Helper to calculate the base fee if we have this many htlc outputs */
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static inline struct amount_sat commit_tx_base_fee(u32 feerate_per_kw,
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size_t num_untrimmed_htlcs,
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bool option_anchor_outputs)
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{
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return amount_tx_fee(feerate_per_kw,
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commit_tx_base_weight(num_untrimmed_htlcs,
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option_anchor_outputs));
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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: funding outpoint.
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* @funding_wscript: scriptPubkey of the funding output
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* @funding_keys: funding bitcoin keys
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* @opener: 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: dust limit below which to trim outputs.
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* @self_pay: amount to pay directly to self
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* @other_pay: amount to pay directly to the other side
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* @self_reserve: reserve the other side insisted we have
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* @obscured_commitment_number: number to encode in commitment transaction
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* @direct_outputs: If non-NULL, fill with pointers to the direct (non-HTLC) outputs (or NULL if none).
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* @side: side to generate commitment transaction for.
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* @option_anchor_outputs: does option_anchor_outputs apply to this channel?
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* @err_reason: When NULL is returned, this will point to a human readable reason.
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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 bitcoin_txid *funding_txid,
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unsigned int funding_txout,
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struct amount_sat funding,
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const struct pubkey funding_key[NUM_SIDES],
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enum side opener,
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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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struct amount_sat dust_limit,
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struct amount_msat self_pay,
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struct amount_msat other_pay,
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struct amount_sat self_reserve,
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u64 obscured_commitment_number,
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struct wally_tx_output *direct_outputs[NUM_SIDES],
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enum side side,
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u32 csv_lock,
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bool option_anchor_outputs,
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char** err_reason);
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/* try_subtract_fee - take away this fee from the opener (and return true), or all if insufficient (and return false). */
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bool try_subtract_fee(enum side opener, enum side side,
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struct amount_sat base_fee,
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struct amount_msat *self,
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struct amount_msat *other);
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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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u32 csv,
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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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/* If we determine we need one, append this anchor output */
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void tx_add_anchor_output(struct bitcoin_tx *tx,
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const struct pubkey *funding_key);
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#endif /* LIGHTNING_COMMON_INITIAL_COMMIT_TX_H */
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