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Zero fee htlc: Finally add support (experimental!) #6137

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Zero fee htlc: Finally add support (experimental!) #6137

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c7153d9
hsmd: command to sign anchor spends.
rustyrussell Apr 10, 2023
2beb151
bitcoin/psbt: handle anchor spends.
rustyrussell Apr 10, 2023
d77f2e8
lightningd/chaintopology: change form of finished callback.
rustyrussell Apr 10, 2023
e20cb83
lightningd: code to spend anchor outputs if we want to boost commitme…
rustyrussell Apr 10, 2023
bada362
pytest: test CPFP using anchors.
rustyrussell Apr 10, 2023
2d33e2c
lightningd: use lowball feerate for commit_tx on anchor channels.
rustyrussell Apr 10, 2023
9b33dca
hsmd: routine to sign HTLC tx merged with our own tx.
rustyrussell Apr 10, 2023
d23c30f
onchaind: use our own inputs to add to HTLC txs (iff using anchors).
rustyrussell Apr 10, 2023
f84613b
bitcoin, common: thread zero fee option everywhere.
rustyrussell Apr 10, 2023
ab40dc0
common/channel_type: add zero-fee-anchor type.
rustyrussell Apr 10, 2023
0241ea1
lightningd: turn on experimental support for zero-fee htlc anchors.
rustyrussell Apr 10, 2023
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5 changes: 5 additions & 0 deletions .msggen.json
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Original file line number Diff line number Diff line change
Expand Up @@ -365,6 +365,7 @@
"Feerates.perkb.mutual_close": 4,
"Feerates.perkb.opening": 3,
"Feerates.perkb.penalty": 8,
"Feerates.perkb.unilateral_anchor_close": 11,
"Feerates.perkb.unilateral_close": 5
},
"FeeratesPerkbEstimates": {
Expand Down Expand Up @@ -1602,6 +1603,10 @@
"added": "pre-v0.10.1",
"deprecated": false
},
"Feerates.perkb.unilateral_anchor_close": {
"added": "v23.05",
"deprecated": false
},
"Feerates.perkb.unilateral_close": {
"added": "pre-v0.10.1",
"deprecated": false
Expand Down
26 changes: 23 additions & 3 deletions bitcoin/psbt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -603,18 +603,24 @@ bool psbt_finalize(struct wally_psbt *psbt)
tal_wally_start();

/* Wally doesn't know how to finalize P2WSH; this happens with
* option_anchor_outputs, and finalizing is trivial. */
* option_anchor_outputs, and finalizing those two cases is trivial. */
/* FIXME: miniscript! miniscript! miniscript! */
for (size_t i = 0; i < psbt->num_inputs; i++) {
struct wally_psbt_input *input = &psbt->inputs[i];
struct wally_tx_witness_stack *stack;
const struct wally_map_item *iws;

iws = wally_map_get_integer(&input->psbt_fields, /* PSBT_IN_WITNESS_SCRIPT */ 0x05);
if (!iws || !is_to_remote_anchored_witness_script(iws->value,
iws->value_len))
if (!iws)
continue;

if (!is_to_remote_anchored_witness_script(iws->value,
iws->value_len)
&& !is_anchor_witness_script(iws->value,
iws->value_len)) {
continue;
}

if (input->signatures.num_items != 1)
continue;

Expand All @@ -632,6 +638,19 @@ bool psbt_finalize(struct wally_psbt *psbt)
*
* <remote_sig>
*/
/* BOLT #3:
* #### `to_local_anchor` and `to_remote_anchor` Output (option_anchors)
*...
* <local_funding_pubkey/remote_funding_pubkey> OP_CHECKSIG OP_IFDUP
* OP_NOTIF
* OP_16 OP_CHECKSEQUENCEVERIFY
* OP_ENDIF
*...
* Spending of the output requires the following witness:
* <local_sig/remote_sig>
*/

/* i.e. in both cases, this is the same thing */
wally_tx_witness_stack_init_alloc(2, &stack);
wally_tx_witness_stack_add(stack,
input->signatures.items[0].value,
Expand All @@ -640,6 +659,7 @@ bool psbt_finalize(struct wally_psbt *psbt)
iws->value,
iws->value_len);
wally_psbt_input_set_final_witness(input, stack);
wally_tx_witness_stack_free(stack);
}

ok = (wally_psbt_finalize(psbt) == WALLY_OK);
Expand Down
44 changes: 36 additions & 8 deletions bitcoin/script.c
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Original file line number Diff line number Diff line change
Expand Up @@ -606,7 +606,8 @@ u8 *bitcoin_wscript_htlc_offer_ripemd160(const tal_t *ctx,
const struct pubkey *remotehtlckey,
const struct ripemd160 *payment_ripemd,
const struct pubkey *revocationkey,
bool option_anchor_outputs)
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx)
{
u8 *script = tal_arr(ctx, u8, 0);
struct ripemd160 ripemd;
Expand Down Expand Up @@ -638,7 +639,7 @@ u8 *bitcoin_wscript_htlc_offer_ripemd160(const tal_t *ctx,
add_op(&script, OP_EQUALVERIFY);
add_op(&script, OP_CHECKSIG);
add_op(&script, OP_ENDIF);
if (option_anchor_outputs) {
if (option_anchor_outputs || option_anchors_zero_fee_htlc_tx) {
add_number(&script, 1);
add_op(&script, OP_CHECKSEQUENCEVERIFY);
add_op(&script, OP_DROP);
Expand All @@ -653,15 +654,17 @@ u8 *bitcoin_wscript_htlc_offer(const tal_t *ctx,
const struct pubkey *remotehtlckey,
const struct sha256 *payment_hash,
const struct pubkey *revocationkey,
bool option_anchor_outputs)
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx)
{
struct ripemd160 ripemd;

ripemd160(&ripemd, payment_hash->u.u8, sizeof(payment_hash->u));
return bitcoin_wscript_htlc_offer_ripemd160(ctx, localhtlckey,
remotehtlckey,
&ripemd, revocationkey,
option_anchor_outputs);
option_anchor_outputs,
option_anchors_zero_fee_htlc_tx);
}

/* BOLT #3:
Expand Down Expand Up @@ -717,7 +720,8 @@ u8 *bitcoin_wscript_htlc_receive_ripemd(const tal_t *ctx,
const struct pubkey *remotehtlckey,
const struct ripemd160 *payment_ripemd,
const struct pubkey *revocationkey,
bool option_anchor_outputs)
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx)
{
u8 *script = tal_arr(ctx, u8, 0);
struct ripemd160 ripemd;
Expand Down Expand Up @@ -752,7 +756,7 @@ u8 *bitcoin_wscript_htlc_receive_ripemd(const tal_t *ctx,
add_op(&script, OP_DROP);
add_op(&script, OP_CHECKSIG);
add_op(&script, OP_ENDIF);
if (option_anchor_outputs) {
if (option_anchor_outputs || option_anchors_zero_fee_htlc_tx) {
add_number(&script, 1);
add_op(&script, OP_CHECKSEQUENCEVERIFY);
add_op(&script, OP_DROP);
Expand All @@ -768,15 +772,17 @@ u8 *bitcoin_wscript_htlc_receive(const tal_t *ctx,
const struct pubkey *remotehtlckey,
const struct sha256 *payment_hash,
const struct pubkey *revocationkey,
bool option_anchor_outputs)
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx)
{
struct ripemd160 ripemd;

ripemd160(&ripemd, payment_hash->u.u8, sizeof(payment_hash->u));
return bitcoin_wscript_htlc_receive_ripemd(ctx, htlc_abstimeout,
localhtlckey, remotehtlckey,
&ripemd, revocationkey,
option_anchor_outputs);
option_anchor_outputs,
option_anchors_zero_fee_htlc_tx);
}

/* BOLT #3:
Expand Down Expand Up @@ -874,9 +880,31 @@ u8 *bitcoin_wscript_anchor(const tal_t *ctx,
add_op(&script, OP_CHECKSEQUENCEVERIFY);
add_op(&script, OP_ENDIF);

assert(is_anchor_witness_script(script, tal_bytelen(script)));
return script;
}

bool is_anchor_witness_script(const u8 *script, size_t script_len)
{
if (script_len != 34 + 1 + 1 + 1 + 1 + 1 + 1)
return false;
if (script[0] != OP_PUSHBYTES(33))
return false;
if (script[34] != OP_CHECKSIG)
return false;
if (script[35] != OP_IFDUP)
return false;
if (script[36] != OP_NOTIF)
return false;
if (script[37] != 0x50 + 16)
return false;
if (script[38] != OP_CHECKSEQUENCEVERIFY)
return false;
if (script[39] != OP_ENDIF)
return false;
return true;
Comment on lines +889 to +905
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A template comparison system would be nice here, but probably overkill 🤔

}

bool scripteq(const u8 *s1, const u8 *s2)
{
memcheck(s1, tal_count(s1));
Expand Down
15 changes: 11 additions & 4 deletions bitcoin/script.h
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Original file line number Diff line number Diff line change
Expand Up @@ -98,7 +98,8 @@ u8 *bitcoin_wscript_htlc_offer(const tal_t *ctx,
const struct pubkey *remotehtlckey,
const struct sha256 *payment_hash,
const struct pubkey *revocationkey,
bool option_anchor_outputs);
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx);
u8 **bitcoin_witness_htlc_timeout_tx(const tal_t *ctx,
const struct bitcoin_signature *localsig,
const struct bitcoin_signature *remotesig,
Expand All @@ -109,7 +110,8 @@ u8 *bitcoin_wscript_htlc_receive(const tal_t *ctx,
const struct pubkey *remotekey,
const struct sha256 *payment_hash,
const struct pubkey *revocationkey,
bool option_anchor_outputs);
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx);
u8 **bitcoin_witness_htlc_success_tx(const tal_t *ctx,
const struct bitcoin_signature *localsig,
const struct bitcoin_signature *remotesig,
Expand All @@ -122,14 +124,16 @@ u8 *bitcoin_wscript_htlc_offer_ripemd160(const tal_t *ctx,
const struct pubkey *remotehtlckey,
const struct ripemd160 *payment_ripemd,
const struct pubkey *revocationkey,
bool option_anchor_outputs);
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx);
u8 *bitcoin_wscript_htlc_receive_ripemd(const tal_t *ctx,
const struct abs_locktime *htlc_abstimeout,
const struct pubkey *localkey,
const struct pubkey *remotekey,
const struct ripemd160 *payment_ripemd,
const struct pubkey *revocationkey,
bool option_anchor_outputs);
bool option_anchor_outputs,
bool option_anchors_zero_fee_htlc_tx);

/* BOLT #3 HTLC-success/HTLC-timeout output */
u8 *bitcoin_wscript_htlc_tx(const tal_t *ctx,
Expand Down Expand Up @@ -159,6 +163,9 @@ bool is_known_scripttype(const u8 *script);
/* Is this a to-remote witness script (used for option_anchor_outputs)? */
bool is_to_remote_anchored_witness_script(const u8 *script, size_t script_len);

/* Is this an anchor witness script? */
bool is_anchor_witness_script(const u8 *script, size_t script_len);

/* Are these two scripts equal? */
bool scripteq(const u8 *s1, const u8 *s2);

Expand Down
3 changes: 3 additions & 0 deletions bitcoin/test/run-bitcoin_block_from_hex.c
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,9 @@ u8 fromwire_u8(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
/* Generated stub for fromwire_u8_array */
void fromwire_u8_array(const u8 **cursor UNNEEDED, size_t *max UNNEEDED, u8 *arr UNNEEDED, size_t num UNNEEDED)
{ fprintf(stderr, "fromwire_u8_array called!\n"); abort(); }
/* Generated stub for is_anchor_witness_script */
bool is_anchor_witness_script(const u8 *script UNNEEDED, size_t script_len UNNEEDED)
{ fprintf(stderr, "is_anchor_witness_script called!\n"); abort(); }
/* Generated stub for is_to_remote_anchored_witness_script */
bool is_to_remote_anchored_witness_script(const u8 *script UNNEEDED, size_t script_len UNNEEDED)
{ fprintf(stderr, "is_to_remote_anchored_witness_script called!\n"); abort(); }
Expand Down
3 changes: 3 additions & 0 deletions bitcoin/test/run-psbt-from-tx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,9 @@ struct amount_sat amount_tx_fee(u32 fee_per_kw UNNEEDED, size_t weight UNNEEDED)
void fromwire_sha256_double(const u8 **cursor UNNEEDED, size_t *max UNNEEDED,
struct sha256_double *sha256d UNNEEDED)
{ fprintf(stderr, "fromwire_sha256_double called!\n"); abort(); }
/* Generated stub for is_anchor_witness_script */
bool is_anchor_witness_script(const u8 *script UNNEEDED, size_t script_len UNNEEDED)
{ fprintf(stderr, "is_anchor_witness_script called!\n"); abort(); }
/* Generated stub for is_to_remote_anchored_witness_script */
bool is_to_remote_anchored_witness_script(const u8 *script UNNEEDED, size_t script_len UNNEEDED)
{ fprintf(stderr, "is_to_remote_anchored_witness_script called!\n"); abort(); }
Expand Down
3 changes: 3 additions & 0 deletions bitcoin/test/run-tx-encode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,9 @@ u8 fromwire_u8(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
/* Generated stub for fromwire_u8_array */
void fromwire_u8_array(const u8 **cursor UNNEEDED, size_t *max UNNEEDED, u8 *arr UNNEEDED, size_t num UNNEEDED)
{ fprintf(stderr, "fromwire_u8_array called!\n"); abort(); }
/* Generated stub for is_anchor_witness_script */
bool is_anchor_witness_script(const u8 *script UNNEEDED, size_t script_len UNNEEDED)
{ fprintf(stderr, "is_anchor_witness_script called!\n"); abort(); }
/* Generated stub for is_to_remote_anchored_witness_script */
bool is_to_remote_anchored_witness_script(const u8 *script UNNEEDED, size_t script_len UNNEEDED)
{ fprintf(stderr, "is_to_remote_anchored_witness_script called!\n"); abort(); }
Expand Down
16 changes: 11 additions & 5 deletions channeld/channeld.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1074,9 +1074,11 @@ static struct bitcoin_signature *calc_commitsigs(const tal_t *ctx,
wscript = bitcoin_tx_output_get_witscript(tmpctx, txs[0],
txs[i+1]->wtx->inputs[0].index);
msg = towire_hsmd_sign_remote_htlc_tx(NULL, txs[i + 1], wscript,
&peer->remote_per_commit,
&peer->remote_per_commit,
channel_has(peer->channel,
OPT_ANCHOR_OUTPUTS));
OPT_ANCHOR_OUTPUTS)
|| channel_has(peer->channel,
OPT_ANCHORS_ZERO_FEE_HTLC_TX));

msg = hsm_req(tmpctx, take(msg));
if (!fromwire_hsmd_sign_tx_reply(msg, &htlc_sigs[i]))
Expand Down Expand Up @@ -1605,7 +1607,8 @@ static void handle_peer_commit_sig(struct peer *peer, const u8 *msg)
/* SIGHASH_ALL is implied. */
commit_sig.sighash_type = SIGHASH_ALL;
htlc_sigs = unraw_sigs(tmpctx, raw_sigs,
channel_has(peer->channel, OPT_ANCHOR_OUTPUTS));
channel_has(peer->channel, OPT_ANCHOR_OUTPUTS)
|| channel_has(peer->channel, OPT_ANCHORS_ZERO_FEE_HTLC_TX));

txs =
channel_txs(tmpctx, &htlc_map, NULL,
Expand Down Expand Up @@ -3848,9 +3851,12 @@ static void init_channel(struct peer *peer)
peer->dev_fast_gossip = dev_fast_gossip;
#endif

status_debug("option_static_remotekey = %u, option_anchor_outputs = %u",
status_debug("option_static_remotekey = %u,"
" option_anchor_outputs = %u"
" option_anchors_zero_fee_htlc_tx = %u",
channel_type_has(channel_type, OPT_STATIC_REMOTEKEY),
channel_type_has(channel_type, OPT_ANCHOR_OUTPUTS));
channel_type_has(channel_type, OPT_ANCHOR_OUTPUTS),
channel_type_has(channel_type, OPT_ANCHORS_ZERO_FEE_HTLC_TX));

/* Keeping an array of pointers is better since it allows us to avoid
* extra allocations later. */
Expand Down
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