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commit_tx: make interface side-agnostic.

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It's currently written to produce "local" commit-txs, but of course we
need to produce remote ones too, for signing.

Thus instead of using "remote" and "local" we use "other" and "self",
and indicate with a single "side" flag which we're generating (because
that changes how HTLCs are interpreted).

This also adds to the tests: generate the remote view of the commit_tx
and make sure it matches!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2017-02-21 15:15:28 +10:30
parent 068cdc825f
commit e8e96e67d0
3 changed files with 177 additions and 41 deletions
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52
lightningd/commit_tx.c
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@@ -33,15 +33,15 @@ u64 commit_number_obscurer(const struct pubkey *opener_payment_basepoint,
return be64_to_cpu(obscurer);
}
static void subtract_fee(enum side funder,
u64 base_fee_msat, u64 *local_msat, u64 *remote_msat)
static void subtract_fee(enum side funder, enum side side,
u64 base_fee_msat, u64 *self_msat, u64 *other_msat)
{
u64 *funder_msat;
if (funder == LOCAL)
funder_msat = local_msat;
if (funder == side)
funder_msat = self_msat;
else
funder_msat = remote_msat;
funder_msat = other_msat;
if (*funder_msat >= base_fee_msat)
*funder_msat -= base_fee_msat;
@@ -97,7 +97,7 @@ static const struct htlc **untrimmed(const tal_t *ctx,
*/
arr = tal_arr(ctx, const struct htlc *, tal_count(htlcs));
for (i = n = 0; i < tal_count(htlcs); i++) {
if (htlc_owner(htlcs[i]) != side)
if (htlc_owner(htlcs[i]) != side)
continue;
if (htlcs[i]->msatoshi / 1000 < dust_limit_satoshis + htlc_fee)
continue;
@@ -146,16 +146,17 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
enum side funder,
u16 to_self_delay,
const struct pubkey *revocation_pubkey,
const struct pubkey *local_delayedkey,
const struct pubkey *localkey,
const struct pubkey *remotekey,
const struct pubkey *self_delayedkey,
const struct pubkey *selfkey,
const struct pubkey *otherkey,
u64 feerate_per_kw,
u64 dust_limit_satoshis,
u64 local_pay_msat,
u64 remote_pay_msat,
u64 self_pay_msat,
u64 other_pay_msat,
const struct htlc **htlcs,
const struct htlc ***htlcmap,
u64 obscured_commitment_number)
u64 obscured_commitment_number,
enum side side)
{
const tal_t *tmpctx = tal_tmpctx(ctx);
const struct htlc **offered, **received;
@@ -163,17 +164,17 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
struct bitcoin_tx *tx;
size_t i, n;
assert(local_pay_msat + remote_pay_msat <= funding_satoshis * 1000);
assert(self_pay_msat + other_pay_msat <= funding_satoshis * 1000);
/* BOLT #3:
*
* 1. Calculate which committed HTLCs need to be trimmed (see
* [Trimmed Outputs](#trimmed-outputs)).
*/
offered = untrimmed(tmpctx, htlcs, LOCAL,
offered = untrimmed(tmpctx, htlcs, side,
htlc_timeout_fee(feerate_per_kw),
dust_limit_satoshis);
received = untrimmed(tmpctx, htlcs, REMOTE,
received = untrimmed(tmpctx, htlcs, !side,
htlc_success_fee(feerate_per_kw),
dust_limit_satoshis);
@@ -195,7 +196,8 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
* 3. Subtract this base fee from the funder (either `to-local` or
* `to-remote`), with a floor of zero (see [Fee Payment](#fee-payment)).
*/
subtract_fee(funder, base_fee_msat, &local_pay_msat, &remote_pay_msat);
subtract_fee(funder, side, base_fee_msat,
&self_pay_msat, &other_pay_msat);
/* Worst-case sizing: both to-local and to-remote outputs. */
tx = bitcoin_tx(ctx, 1, tal_count(offered) + tal_count(received) + 2);
@@ -211,7 +213,7 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
n = 0;
for (i = 0; i < tal_count(offered); i++, n++) {
u8 *wscript = bitcoin_wscript_htlc_offer(tmpctx,
localkey, remotekey,
selfkey, otherkey,
&offered[i]->rhash);
tx->output[n].amount = offered[i]->msatoshi / 1000;
tx->output[n].script = scriptpubkey_p2wsh(tx, wscript);
@@ -229,7 +231,7 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
for (i = 0; i < tal_count(received); i++, n++) {
u8 *wscript = bitcoin_wscript_htlc_receive(tmpctx,
&received[i]->expiry,
localkey, remotekey,
selfkey, otherkey,
&received[i]->rhash);
tx->output[n].amount = received[i]->msatoshi / 1000;
tx->output[n].script = scriptpubkey_p2wsh(tx, wscript);
@@ -245,12 +247,12 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
* `dust-limit-satoshis`, add a [To-Local
* Output](#to-local-output).
*/
if (local_pay_msat / 1000 >= dust_limit_satoshis) {
if (self_pay_msat / 1000 >= dust_limit_satoshis) {
u8 *wscript = bitcoin_wscript_to_local(tmpctx,
to_self_delay,
revocation_pubkey,
local_delayedkey);
tx->output[n].amount = local_pay_msat / 1000;
self_delayedkey);
tx->output[n].amount = self_pay_msat / 1000;
tx->output[n].script = scriptpubkey_p2wsh(tx, wscript);
(*htlcmap)[n] = NULL;
SUPERVERBOSE("# to-local amount %"PRIu64" wscript %s\n",
@@ -265,7 +267,7 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
* `dust-limit-satoshis`, add a [To-Remote
* Output](#to-remote-output).
*/
if (remote_pay_msat / 1000 >= dust_limit_satoshis) {
if (other_pay_msat / 1000 >= dust_limit_satoshis) {
/* BOLT #3:
*
* #### To-Remote Output
@@ -273,12 +275,12 @@ struct bitcoin_tx *commit_tx(const tal_t *ctx,
* This output sends funds to the other peer, thus is a simple
* P2WPKH to `remotekey`.
*/
tx->output[n].amount = remote_pay_msat / 1000;
tx->output[n].script = scriptpubkey_p2wpkh(tx, remotekey);
tx->output[n].amount = other_pay_msat / 1000;
tx->output[n].script = scriptpubkey_p2wpkh(tx, otherkey);
(*htlcmap)[n] = NULL;
SUPERVERBOSE("# to-remote amount %"PRIu64" P2WPKH(%s)\n",
tx->output[n].amount,
type_to_string(tmpctx, struct pubkey, remotekey));
type_to_string(tmpctx, struct pubkey, otherkey));
n++;
}