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b193eb06d3
for every new added htlc, check that adding it won't go over our 'dust budget' (which assumes a slightly higher than current feerate, as this prevents sudden feerate changes from overshooting our dust budget) note that if the feerate changes surpass the limits we've set, we immediately fail the channel.
57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
#include <common/htlc_trim.h>
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#include <common/htlc_tx.h>
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/* If this htlc too small to create an output on @side's commitment tx? */
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bool htlc_is_trimmed(enum side htlc_owner,
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struct amount_msat htlc_amount,
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u32 feerate_per_kw,
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struct amount_sat dust_limit,
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enum side side,
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bool option_anchor_outputs)
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{
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struct amount_sat htlc_fee, htlc_min;
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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 == side)
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htlc_fee = htlc_timeout_fee(feerate_per_kw,
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option_anchor_outputs);
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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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option_anchor_outputs);
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/* If these overflow, it implies htlc must be less. */
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if (!amount_sat_add(&htlc_min, dust_limit, htlc_fee))
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return true;
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return amount_msat_less_sat(htlc_amount, htlc_min);
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}
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/* Minimum amount of headroom we should use for
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* anticipated feerate adjustments */
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#define HTLC_FEE_MIN_RANGE 2530
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#define max(a, b) ((a) > (b) ? (a) : (b))
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u32 htlc_trim_feerate_ceiling(u32 feerate_per_kw)
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{
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/* Add the greater of 1.25x or 2530 sat/kw */
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return max(feerate_per_kw + feerate_per_kw / 4,
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feerate_per_kw + HTLC_FEE_MIN_RANGE);
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}
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