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splice: signer must be informed of splice params
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The signer needs to know when the splice operation starts and the
splice parameters for each splice transaction candidate.

The channel establishment v2 (dual funding) code path already
notifies the signer via the hsmd API hsmd_ready_channel calls
However, the splicing code path does not.

Link: ElementsProject#6723
Suggested-by: @devrandom
Co-Developed-by: @devrandom
Co-Developed-by: Ken Sedgwick <ken@bonsai.com>
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
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@ksedgwic @vincenzopalazzo
ksedgwic authored and vincenzopalazzo committed Oct 4, 2023
1 parent 176a58f commit c3b56e7
Showing 1 changed file with 88 additions and 11 deletions.
99 changes: 88 additions & 11 deletions channeld/channeld.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2915,6 +2915,43 @@ static size_t calc_weight(enum tx_role role, const struct wally_psbt *psbt)
return weight;
}

/* Get the remote node amount after the splice */
static struct amount_msat remote_balance(struct peer *peer,
enum tx_role our_role,
const struct wally_psbt *psbt,
int chan_output_index,
int chan_input_index)
{
s64 relative_remote_val;
/* Current value of the remote channel balance */
struct amount_msat push_value;

/* We calculcate the `push_value` to send to the
* hsmd, that is the remote amount in the channel
* after the splice. */
switch (our_role) {
case TX_INITIATOR:
push_value = peer->channel->view[REMOTE].owed[REMOTE];
relative_remote_val = peer->splicing->accepter_relative;
break;
case TX_ACCEPTER:
push_value = peer->channel->view[REMOTE].owed[REMOTE];
relative_remote_val = peer->splicing->opener_relative;
break;
default:
/* This should never happen. Help us to early catch the tx_role change */
abort();
}

if (!amount_msat_add_sat_s64(&push_value, push_value, relative_remote_val))
status_failed(STATUS_FAIL_INTERNAL_ERROR,
"Unable to add to the amount %s the"
" value %ld",
fmt_amount_msat(tmpctx, push_value),
relative_remote_val);
return push_value;
}

/* Returns the total channel funding output amount if all checks pass.
* Otherwise, exits via peer_failed_warn. DTODO: Change to `tx_abort`. */
static struct amount_sat check_balances(struct peer *peer,
Expand Down Expand Up @@ -2973,7 +3010,6 @@ static struct amount_sat check_balances(struct peer *peer,
*
* While we're, here, adjust the output counts by splice amount.
*/

if (!amount_msat_add_sat_s64(&funding_amount, funding_amount,
peer->splicing->opener_relative))
peer_failed_warn(peer->pps, &peer->channel_id,
Expand Down Expand Up @@ -3441,6 +3477,38 @@ static struct inflight *inflights_new(struct peer *peer)
return inf;
}

static void update_hsmd_with_splice(struct peer *peer, struct inflight *inflight,
const enum tx_role our_role,
const struct amount_msat push_val)
{
u8 *msg;

/* local_upfront_shutdown_script, local_upfront_shutdown_wallet_index,
* remote_upfront_shutdown_script aren't allowed to change, so we
* don't need to gather them */
msg = towire_hsmd_ready_channel(
NULL,
peer->channel->opener == LOCAL,
inflight->amnt,
push_val,
&inflight->outpoint.txid,
inflight->outpoint.n,
peer->channel->config[LOCAL].to_self_delay,
/*local_upfront_shutdown_script*/ NULL,
/*local_upfront_shutdown_wallet_index*/ NULL,
&peer->channel->basepoints[REMOTE],
&peer->channel->funding_pubkey[REMOTE],
peer->channel->config[REMOTE].to_self_delay,
/*remote_upfront_shutdown_script*/ NULL,
peer->channel->type);

wire_sync_write(HSM_FD, take(msg));
msg = wire_sync_read(tmpctx, HSM_FD);
if (!fromwire_hsmd_ready_channel_reply(msg))
status_failed(STATUS_FAIL_HSM_IO, "Bad ready_channel_reply %s",
tal_hex(tmpctx, msg));
}

/* ACCEPTER side of the splice. Here we handle all the accepter's steps for the
* splice. Since the channel must be in STFU mode we block the daemon here until
* the splice is finished or aborted. */
Expand All @@ -3459,12 +3527,14 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
struct inflight *new_inflight;
struct wally_psbt_output *new_chan_output;
struct bitcoin_outpoint outpoint;
struct amount_msat current_push_val;
const enum tx_role our_role = TX_ACCEPTER;

/* Can't start a splice with another splice still active */
assert(!peer->splicing);
peer->splicing = splicing_new(peer);

ictx = new_interactivetx_context(tmpctx, TX_ACCEPTER,
ictx = new_interactivetx_context(tmpctx, our_role,
peer->pps, peer->channel_id);

if (!fromwire_splice(inmsg,
Expand Down Expand Up @@ -3520,7 +3590,6 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
* The receiver of `splice_ack`:
* - MUST begin splice negotiation.
*/

ictx->next_update_fn = next_splice_step;
ictx->desired_psbt = NULL;
ictx->pause_when_complete = false;
Expand All @@ -3543,7 +3612,7 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
new_chan_output = find_channel_output(peer, ictx->current_psbt,
&outpoint.n);

both_amount = check_balances(peer, TX_ACCEPTER, ictx->current_psbt,
both_amount = check_balances(peer, our_role, ictx->current_psbt,
outpoint.n, splice_funding_index);
new_chan_output->amount = both_amount.satoshis; /* Raw: type conv */

Expand Down Expand Up @@ -3578,6 +3647,10 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
new_inflight->last_tx = NULL;
new_inflight->i_am_initiator = false;

current_push_val = remote_balance(peer, our_role,ictx->current_psbt,
outpoint.n, splice_funding_index);
update_hsmd_with_splice(peer, new_inflight, our_role, current_push_val);

update_view_from_inflights(peer);

peer->splice_state->count++;
Expand Down Expand Up @@ -3746,8 +3819,10 @@ static void splice_initiator_user_finalized(struct peer *peer)
struct bitcoin_txid current_psbt_txid;
struct amount_sat both_amount;
struct commitsig *their_commit;
struct amount_msat current_push_val;
const enum tx_role our_role = TX_INITIATOR;

ictx = new_interactivetx_context(tmpctx, TX_INITIATOR,
ictx = new_interactivetx_context(tmpctx, our_role,
peer->pps, peer->channel_id);

ictx->next_update_fn = next_splice_step;
Expand All @@ -3774,7 +3849,7 @@ static void splice_initiator_user_finalized(struct peer *peer)
splice_funding_index = find_channel_funding_input(ictx->current_psbt,
&peer->channel->funding);

both_amount = check_balances(peer, TX_INITIATOR, ictx->current_psbt,
both_amount = check_balances(peer, our_role, ictx->current_psbt,
chan_output_index, splice_funding_index);
new_chan_output->amount = both_amount.satoshis; /* Raw: type conv */

Expand Down Expand Up @@ -3807,12 +3882,16 @@ static void splice_initiator_user_finalized(struct peer *peer)
new_inflight->last_tx = NULL;
new_inflight->i_am_initiator = true;

current_push_val = remote_balance(peer, our_role, ictx->current_psbt,
chan_output_index, splice_funding_index);
update_hsmd_with_splice(peer, new_inflight, our_role, current_push_val);

update_view_from_inflights(peer);

peer->splice_state->count++;

their_commit = interactive_send_commitments(peer, ictx->current_psbt,
TX_INITIATOR);
our_role);

new_inflight->last_tx = tal_steal(new_inflight, their_commit->tx);
new_inflight->last_sig = their_commit->commit_signature;
Expand Down Expand Up @@ -5152,8 +5231,7 @@ static void handle_funding_depth(struct peer *peer, const u8 *msg)

if (depth < peer->channel->minimum_depth) {
peer->depth_togo = peer->channel->minimum_depth - depth;
}
else {
} else {
peer->depth_togo = 0;

/* For splicing we only update the short channel id on mutual
Expand Down Expand Up @@ -5198,8 +5276,7 @@ static void handle_funding_depth(struct peer *peer, const u8 *msg)
peer_write(peer->pps, take(msg));

peer->channel_ready[LOCAL] = true;
}
else if(splicing && !peer->splice_state->locked_ready[LOCAL]) {
} else if (splicing && !peer->splice_state->locked_ready[LOCAL]) {
assert(scid);

msg = towire_splice_locked(NULL, &peer->channel_id);
Expand Down

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