df: push back psbt to validate iff peer requests confirmed inputs

`openchannel_init` takes a psbt, which we pipe over to dualopend
process.

If the peer requests that they'll only accept confirmed inputs, we need
to go validate those before we continue.

This wires up the harness for this (validation check yet tc)

lightningd/dual_open_control.c

@@ -2941,6 +2941,31 @@ static struct command_result *json_openchannel_init(struct command *cmd,
 	return command_still_pending(cmd);
 }
 
+static void handle_validate_inputs(struct subd *dualopend,
+				   const u8 *msg)
+{
+	struct wally_psbt *psbt;
+	enum tx_role role_to_validate;
+
+	if (!fromwire_dualopend_validate_inputs(msg, msg,
+						&psbt,
+						&role_to_validate)) {
+		channel_internal_error(dualopend->channel,
+				       "Bad DUALOPEND_VALIDATE_INPUTS: %s",
+				       tal_hex(msg, msg));
+		return;
+	}
+
+	/* FIXME: actually validate inputs on psbt */
+	log_debug(dualopend->ld->log,
+		  "validating psbt for role: %s",
+		  role_to_validate == TX_INITIATOR ?
+			"initiator" : "accepter");
+
+	subd_send_msg(dualopend,
+		      take(towire_dualopend_validate_inputs_reply(NULL)));
+}
+
 static void
 channel_fail_fallen_behind(struct subd* dualopend, const u8 *msg)
 {
@@ -3268,13 +3293,17 @@ static unsigned int dual_opend_msg(struct subd *dualopend,
 		case WIRE_DUALOPEND_LOCAL_PRIVATE_CHANNEL:
 			handle_local_private_channel(dualopend, msg);
 			return 0;
+		case WIRE_DUALOPEND_VALIDATE_INPUTS:
+			handle_validate_inputs(dualopend, msg);
+			return 0;
 		/* Messages we send */
 		case WIRE_DUALOPEND_INIT:
 		case WIRE_DUALOPEND_REINIT:
 		case WIRE_DUALOPEND_OPENER_INIT:
 		case WIRE_DUALOPEND_RBF_INIT:
 		case WIRE_DUALOPEND_GOT_OFFER_REPLY:
 		case WIRE_DUALOPEND_GOT_RBF_OFFER_REPLY:
+		case WIRE_DUALOPEND_VALIDATE_INPUTS_REPLY:
 		case WIRE_DUALOPEND_RBF_VALID:
 		case WIRE_DUALOPEND_VALIDATE_LEASE_REPLY:
 		case WIRE_DUALOPEND_FAIL:

openingd/dualopend.c

@@ -3182,6 +3182,23 @@ static void opener_start(struct state *state, u8 *msg)
 		return;
 	}
 
+	/* We need to check that the inputs we've already provided
+	 * via the API are confirmed :/ */
+	if (state->require_confirmed_inputs) {
+		msg = towire_dualopend_validate_inputs(NULL, tx_state->psbt,
+						       state->our_role);
+		wire_sync_write(REQ_FD, take(msg));
+		msg = wire_sync_read(tmpctx, REQ_FD);
+
+		if (!fromwire_dualopend_validate_inputs_reply(msg)) {
+			if (!fromwire_dualopend_fail(msg, msg, &err_reason))
+				master_badmsg(fromwire_peektype(msg), msg);
+			/* We abort, because we don't have valid inputs */
+			open_abort(state, "%s", err_reason);
+			return;
+		}
+	}
+
 	/* BOLT-f53ca2301232db780843e894f55d95d512f297f9 #2:
 	 * The sending node:
 	 * - if is the *opener*:
@@ -3974,6 +3991,7 @@ static u8 *handle_master_in(struct state *state)
 	case WIRE_DUALOPEND_RBF_VALID:
 	case WIRE_DUALOPEND_VALIDATE_LEASE_REPLY:
 	case WIRE_DUALOPEND_DEV_MEMLEAK_REPLY:
+	case WIRE_DUALOPEND_VALIDATE_INPUTS_REPLY:
 
 	/* Messages we send */
 	case WIRE_DUALOPEND_GOT_OFFER:
@@ -3991,6 +4009,7 @@ static u8 *handle_master_in(struct state *state)
 	case WIRE_DUALOPEND_DRY_RUN:
 	case WIRE_DUALOPEND_VALIDATE_LEASE:
 	case WIRE_DUALOPEND_LOCAL_PRIVATE_CHANNEL:
+	case WIRE_DUALOPEND_VALIDATE_INPUTS:
 		break;
 	}
 	status_failed(STATUS_FAIL_MASTER_IO,

openingd/dualopend_wire.csv

@@ -245,6 +245,14 @@ msgdata,dualopend_dry_run,their_funding,amount_sat,
 # must go last because of embedded tu32
 msgdata,dualopend_dry_run,lease_rates,?lease_rates,
 
+# dualopend -> master: are inputs in this psbt confirmed?
+msgtype,dualopend_validate_inputs,7029
+msgdata,dualopend_validate_inputs,psbt,wally_psbt,
+msgdata,dualopend_validate_inputs,side,enum tx_role,
+
+# master -> dualopend: confirms inputs are valid
+msgtype,dualopend_validate_inputs_reply,7030
+
 # dualopend -> master:  validate liqudity offer sig
 msgtype,dualopend_validate_lease,7027
 msgdata,dualopend_validate_lease,sig,secp256k1_ecdsa_signature,