splice: signer must be informed of splice params

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: Ken Sedgwick <[email protected]>
Signed-off-by: Vincenzo Palazzo <[email protected]>

channeld/channeld.c

@@ -3441,6 +3441,42 @@ static struct inflight *inflights_new(struct peer *peer)
 	return inf;
 }
 
+static void update_hsmd_with_splice(struct peer *peer, struct inflight *inflight)
+{
+	u8 *msg;
+	struct amount_msat push_value;
+	/* These aren't allowed to change, so we
+	 * don't need to gather them */
+	u8 *local_upfront_shutdown_script = NULL;
+	u8 *remote_upfront_shutdown_script = NULL;
+	u32 *local_upfront_shutdown_wallet_index = NULL;
+
+	// FIXME: handle the error
+	assert(amount_sat_to_msat(&push_value, inflight->amnt));
+
+	msg = towire_hsmd_ready_channel(
+		NULL,
+		peer->channel->opener == LOCAL,
+		inflight->amnt,
+		push_value,
+		&inflight->outpoint.txid,
+		inflight->outpoint.n,
+		peer->channel->config[LOCAL].to_self_delay,
+		local_upfront_shutdown_script,
+		local_upfront_shutdown_wallet_index,
+		&peer->channel->basepoints[REMOTE],
+		&peer->channel->funding_pubkey[REMOTE],
+		peer->channel->config[REMOTE].to_self_delay,
+		remote_upfront_shutdown_script,
+		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. */
@@ -3577,6 +3613,8 @@ static void splice_accepter(struct peer *peer, const u8 *inmsg)
 	new_inflight->last_tx = NULL;
 	new_inflight->i_am_initiator = false;
 
+	update_hsmd_with_splice(peer, new_inflight);
+
 	update_view_from_inflights(peer);
 
 	peer->splice_state->count++;
@@ -3811,6 +3849,8 @@ static void splice_initiator_user_finalized(struct peer *peer)
 	new_inflight->last_tx = NULL;
 	new_inflight->i_am_initiator = true;
 
+	update_hsmd_with_splice(peer, new_inflight);
+
 	update_view_from_inflights(peer);
 
 	peer->splice_state->count++;
@@ -5160,8 +5200,7 @@ 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
@@ -5206,8 +5245,7 @@ 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);