dualopend: tell lightningd about new channel as soon as it's locked in.

Once we send funding_locked, gossipd could start seeing channel_updates
from the peer (which get sent so we can use the channel in routehints
even before it's announcable).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/dual_open_control.c

@@ -22,6 +22,7 @@
 #include <lightningd/channel_control.h>
 #include <lightningd/closing_control.h>
 #include <lightningd/dual_open_control.h>
+#include <lightningd/gossip_control.h>
 #include <lightningd/hsm_control.h>
 #include <lightningd/json.h>
 #include <lightningd/notification.h>
@@ -1368,6 +1369,24 @@ static void handle_channel_closed(struct subd *dualopend,
 			  "Start closingd");
 }
 
+static void handle_local_private_channel(struct subd *dualopend,
+					 const u8 *msg)
+{
+	struct amount_sat capacity;
+	u8 *features;
+
+	if (!fromwire_dualopend_local_private_channel(msg, msg, &capacity,
+						      &features)) {
+		channel_internal_error(dualopend->channel,
+				       "bad dualopend_local_private_channel %s",
+				       tal_hex(msg, msg));
+		return;
+	}
+
+	tell_gossipd_local_private_channel(dualopend->ld, dualopend->channel,
+					   capacity, features);
+}
+
 struct channel_send {
 	const struct wally_tx *wtx;
 	struct channel *channel;
@@ -2991,7 +3010,9 @@ static unsigned int dual_opend_msg(struct subd *dualopend,
 		case WIRE_DUALOPEND_FAIL_FALLEN_BEHIND:
 			channel_fail_fallen_behind(dualopend, msg);
 			return 0;
-
+		case WIRE_DUALOPEND_LOCAL_PRIVATE_CHANNEL:
+			handle_local_private_channel(dualopend, msg);
+			return 0;
 		/* Messages we send */
 		case WIRE_DUALOPEND_INIT:
 		case WIRE_DUALOPEND_REINIT:

openingd/dualopend.c

@@ -3396,6 +3396,38 @@ static void send_funding_locked(struct state *state)
 	billboard_update(state);
 }
 
+/* FIXME: Maybe cache this? */
+static struct amount_sat channel_size(struct state *state)
+{
+	u32 funding_outnum;
+	const u8 *funding_wscript =
+		bitcoin_redeem_2of2(tmpctx,
+				    &state->our_funding_pubkey,
+				    &state->their_funding_pubkey);
+
+	if (!find_txout(state->tx_state->psbt,
+			scriptpubkey_p2wsh(tmpctx, funding_wscript),
+			&funding_outnum)) {
+		open_err_fatal(state, "Cannot fund txout");
+	}
+
+	return psbt_output_get_amount(state->tx_state->psbt, funding_outnum);
+}
+
+static void tell_gossipd_new_channel(struct state *state)
+{
+	u8 *msg;
+	const u8 *annfeatures = get_agreed_channelfeatures(tmpctx,
+							   state->our_features,
+							   state->their_features);
+
+	/* Tell lightningd about local channel. */
+	msg = towire_dualopend_local_private_channel(NULL,
+						     channel_size(state),
+						     annfeatures);
+ 	wire_sync_write(REQ_FD, take(msg));
+}
+
 static u8 *handle_funding_depth(struct state *state, u8 *msg)
 {
 	u32 depth;
@@ -3410,6 +3442,9 @@ static u8 *handle_funding_depth(struct state *state, u8 *msg)
 	/* We check this before we arrive here, but for sanity */
 	assert(state->minimum_depth <= depth);
 
+	/* Tell gossipd the new channel exists before we tell peer. */
+	tell_gossipd_new_channel(state);
+
 	send_funding_locked(state);
 	if (state->funding_locked[REMOTE])
 		return towire_dualopend_channel_locked(state);
@@ -3665,6 +3700,7 @@ static u8 *handle_master_in(struct state *state)
 	case WIRE_DUALOPEND_FAIL_FALLEN_BEHIND:
 	case WIRE_DUALOPEND_DRY_RUN:
 	case WIRE_DUALOPEND_VALIDATE_LEASE:
+	case WIRE_DUALOPEND_LOCAL_PRIVATE_CHANNEL:
 		break;
 	}
 

openingd/dualopend_wire.csv

@@ -238,3 +238,9 @@ msgdata,dualopend_validate_lease,their_pubkey,pubkey,
 
 msgtype,dualopend_validate_lease_reply,7127
 msgdata,dualopend_validate_lease_reply,err_msg,?wirestring,
+
+# Tell gossipd about this (as-yet) unannounced channel
+msgtype,dualopend_local_private_channel,7015
+msgdata,dualopend_local_private_channel,capacity,amount_sat,
+msgdata,dualopend_local_private_channel,len,u16,
+msgdata,dualopend_local_private_channel,features,u8,len