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initial_commit_tx, commit_tx: add anchor outputs if needed.

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This also means we subtract 660 satoshis more everywhere we subtract
the base fee (except for mutual close, where the base fee is still
used).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2020-08-14 03:17:02 +09:30
parent 222d018b1a
commit e7423888ba
11 changed files with 268 additions and 30 deletions
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84
channeld/commit_tx.c
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@@ -15,36 +15,41 @@
static bool trim(const struct htlc *htlc,
u32 feerate_per_kw,
struct amount_sat dust_limit,
bool option_anchor_outputs,
enum side side)
{
return htlc_is_trimmed(htlc_owner(htlc), htlc->amount,
feerate_per_kw, dust_limit, side,
false /* FIXME-anchor */);
option_anchor_outputs);
}
size_t commit_tx_num_untrimmed(const struct htlc **htlcs,
u32 feerate_per_kw,
struct amount_sat dust_limit,
bool option_anchor_outputs,
enum side side)
{
size_t i, n;
for (i = n = 0; i < tal_count(htlcs); i++)
n += !trim(htlcs[i], feerate_per_kw, dust_limit, side);
n += !trim(htlcs[i], feerate_per_kw, dust_limit,
option_anchor_outputs, side);
return n;
}
static void add_offered_htlc_out(struct bitcoin_tx *tx, size_t n,
const struct htlc *htlc,
const struct keyset *keyset)
const struct keyset *keyset,
bool option_anchor_outputs)
{
struct ripemd160 ripemd;
u8 *wscript, *p2wsh;
struct amount_sat amount = amount_msat_to_sat_round_down(htlc->amount);
ripemd160(&ripemd, htlc->rhash.u.u8, sizeof(htlc->rhash.u.u8));
wscript = htlc_offered_wscript(tx, &ripemd, keyset, false /* FIXME-anchor */);
wscript = htlc_offered_wscript(tx, &ripemd, keyset,
option_anchor_outputs);
p2wsh = scriptpubkey_p2wsh(tx, wscript);
bitcoin_tx_add_output(tx, p2wsh, wscript, amount);
SUPERVERBOSE("# HTLC %" PRIu64 " offered %s wscript %s\n", htlc->id,
@@ -55,14 +60,16 @@ static void add_offered_htlc_out(struct bitcoin_tx *tx, size_t n,
static void add_received_htlc_out(struct bitcoin_tx *tx, size_t n,
const struct htlc *htlc,
const struct keyset *keyset)
const struct keyset *keyset,
bool option_anchor_outputs)
{
struct ripemd160 ripemd;
u8 *wscript, *p2wsh;
struct amount_sat amount;
ripemd160(&ripemd, htlc->rhash.u.u8, sizeof(htlc->rhash.u.u8));
wscript = htlc_received_wscript(tx, &ripemd, &htlc->expiry, keyset, false /* FIXME-anchor */);
wscript = htlc_received_wscript(tx, &ripemd, &htlc->expiry, keyset,
option_anchor_outputs);
p2wsh = scriptpubkey_p2wsh(tx, wscript);
amount = amount_msat_to_sat_round_down(htlc->amount);
@@ -93,6 +100,7 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
const struct htlc ***htlcmap,
struct wally_tx_output *direct_outputs[NUM_SIDES],
u64 obscured_commitment_number,
bool option_anchor_outputs,
enum side side)
{
struct amount_sat base_fee;
@@ -100,6 +108,7 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
struct bitcoin_tx *tx;
size_t i, n, untrimmed;
u32 *cltvs;
bool to_local, to_remote;
struct htlc *dummy_to_local = (struct htlc *)0x01,
*dummy_to_remote = (struct htlc *)0x02;
const u8 *funding_wscript = bitcoin_redeem_2of2(tmpctx,
@@ -117,7 +126,9 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
*/
untrimmed = commit_tx_num_untrimmed(htlcs,
feerate_per_kw,
dust_limit, side);
dust_limit,
option_anchor_outputs,
side);
/* BOLT #3:
*
@@ -125,11 +136,22 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
* fee](#fee-calculation).
*/
base_fee = commit_tx_base_fee(feerate_per_kw, untrimmed,
false /* FIXME-anchor */);
option_anchor_outputs);
SUPERVERBOSE("# base commitment transaction fee = %s\n",
type_to_string(tmpctx, struct amount_sat, &base_fee));
/* BOLT-a12da24dd0102c170365124782b46d9710950ac1:
* If `option_anchor_outputs` applies to the commitment
* transaction, also subtract two times the fixed anchor size
* of 330 sats from the funder (either `to_local` or
* `to_remote`).
*/
if (option_anchor_outputs
&& !amount_sat_add(&base_fee, base_fee, AMOUNT_SAT(660)))
/* Can't overflow: feerate is u32. */
abort();
/* BOLT #3:
*
* 3. Subtract this base fee from the funder (either `to_local` or
@@ -142,7 +164,8 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
struct amount_sat out = AMOUNT_SAT(0);
bool ok = true;
for (i = 0; i < tal_count(htlcs); i++) {
if (!trim(htlcs[i], feerate_per_kw, dust_limit, side))
if (!trim(htlcs[i], feerate_per_kw, dust_limit,
option_anchor_outputs, side))
ok &= amount_sat_add(&out, out, amount_msat_to_sat_round_down(htlcs[i]->amount));
}
if (amount_msat_greater_sat(self_pay, dust_limit))
@@ -155,8 +178,8 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
}
#endif
/* Worst-case sizing: both to-local and to-remote outputs. */
tx = bitcoin_tx(ctx, chainparams, 1, untrimmed + 2, 0);
/* Worst-case sizing: both to-local and to-remote outputs, and anchors. */
tx = bitcoin_tx(ctx, chainparams, 1, untrimmed + 2 + 2, 0);
/* We keep track of which outputs have which HTLCs */
*htlcmap = tal_arr(tx, const struct htlc *, tx->wtx->outputs_allocation_len);
@@ -177,9 +200,11 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
for (i = 0; i < tal_count(htlcs); i++) {
if (htlc_owner(htlcs[i]) != side)
continue;
if (trim(htlcs[i], feerate_per_kw, dust_limit, side))
if (trim(htlcs[i], feerate_per_kw, dust_limit,
option_anchor_outputs, side))
continue;
add_offered_htlc_out(tx, n, htlcs[i], keyset);
add_offered_htlc_out(tx, n, htlcs[i], keyset,
option_anchor_outputs);
(*htlcmap)[n] = htlcs[i];
cltvs[n] = abs_locktime_to_blocks(&htlcs[i]->expiry);
n++;
@@ -193,9 +218,11 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
for (i = 0; i < tal_count(htlcs); i++) {
if (htlc_owner(htlcs[i]) == side)
continue;
if (trim(htlcs[i], feerate_per_kw, dust_limit, side))
if (trim(htlcs[i], feerate_per_kw, dust_limit,
option_anchor_outputs, side))
continue;
add_received_htlc_out(tx, n, htlcs[i], keyset);
add_received_htlc_out(tx, n, htlcs[i], keyset,
option_anchor_outputs);
(*htlcmap)[n] = htlcs[i];
cltvs[n] = abs_locktime_to_blocks(&htlcs[i]->expiry);
n++;
@@ -221,7 +248,9 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
type_to_string(tmpctx, struct amount_sat, &amount),
tal_hex(tmpctx, wscript));
n++;
}
to_local = true;
} else
to_local = false;
/* BOLT #3:
*
@@ -251,6 +280,29 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
type_to_string(tmpctx, struct pubkey,
&keyset->other_payment_key));
n++;
to_remote = true;
} else
to_remote = false;
if (option_anchor_outputs) {
/* BOLT-a12da24dd0102c170365124782b46d9710950ac1 #3:
* if `to_local` exists or there are untrimmed HTLCs, add a `to_local_anchor` output
*/
if (to_local || untrimmed != 0) {
tx_add_anchor_output(tx, local_funding_key);
(*htlcmap)[n] = NULL;
n++;
}
/* BOLT-a12da24dd0102c170365124782b46d9710950ac1 #3:
* if `to_remote` exists or there are untrimmed HTLCs, add a `to_remote_anchor` output
*/
if (to_remote || untrimmed != 0) {
tx_add_anchor_output(tx, remote_funding_key);
(*htlcmap)[n] = NULL;
n++;
}
}
/* BOLT #2: