openingd: check with lightningd when we receive an offer.

Instead of lightningd telling us when it's ready, we ask it.
This also provides an opportunity to have a plugin hook at this point.

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

lightningd/channel.c

@@ -332,8 +332,6 @@ void channel_set_state(struct channel *channel,
 		       enum channel_state old_state,
 		       enum channel_state state)
 {
-	bool was_active = channel_active(channel);
-
 	log_info(channel->log, "State changed from %s to %s",
 		 channel_state_name(channel), channel_state_str(state));
 	if (channel->state != old_state)
@@ -344,11 +342,6 @@ void channel_set_state(struct channel *channel,
 
 	/* TODO(cdecker) Selectively save updated fields to DB */
 	wallet_channel_save(channel->peer->ld->wallet, channel);
-
-	/* If openingd is running, it might want to know we're no longer
-	 * active */
-	if (was_active && !channel_active(channel))
-		opening_peer_no_active_channels(channel->peer);
 }
 
 void channel_fail_permanent(struct channel *channel, const char *fmt, ...)

lightningd/opening_control.c

@@ -725,6 +725,20 @@ static void channel_config(struct lightningd *ld,
 	 ours->channel_reserve = AMOUNT_SAT(UINT64_MAX);
 }
 
+static void opening_got_offer(struct subd *openingd,
+			      const u8 *msg,
+			      struct uncommitted_channel *uc)
+{
+	const char *reason = NULL;
+
+	/* Tell them they can't open, if we already have open channel. */
+	if (peer_active_channel(uc->peer))
+		reason = "Already have active channel";
+
+	subd_send_msg(openingd,
+		      take(towire_opening_got_offer_reply(NULL, reason)));
+}
+
 static unsigned int openingd_msg(struct subd *openingd,
 				 const u8 *msg, const int *fds)
 {
@@ -760,10 +774,14 @@ static unsigned int openingd_msg(struct subd *openingd,
 		opening_fundee_finished(openingd, msg, fds, uc);
 		return 0;
 
+	case WIRE_OPENING_GOT_OFFER:
+		opening_got_offer(openingd, msg, uc);
+		return 0;
+
 	/* We send these! */
 	case WIRE_OPENING_INIT:
 	case WIRE_OPENING_FUNDER:
-	case WIRE_OPENING_CAN_ACCEPT_CHANNEL:
+	case WIRE_OPENING_GOT_OFFER_REPLY:
 	case WIRE_OPENING_DEV_MEMLEAK:
 	/* Replies never get here */
 	case WIRE_OPENING_DEV_MEMLEAK_REPLY:
@@ -834,21 +852,11 @@ void peer_start_openingd(struct peer *peer,
 				  uc->minimum_depth,
 				  feerate_min(peer->ld, NULL),
 				  feerate_max(peer->ld, NULL),
-				  !peer_active_channel(peer),
 				  peer->localfeatures,
 				  send_msg);
 	subd_send_msg(uc->openingd, take(msg));
 }
 
-void opening_peer_no_active_channels(struct peer *peer)
-{
-	assert(!peer_active_channel(peer));
-	if (peer->uncommitted_channel) {
-		subd_send_msg(peer->uncommitted_channel->openingd,
-			      take(towire_opening_can_accept_channel(NULL)));
-	}
-}
-
 /**
  * json_fund_channel - Entrypoint for funding a channel
  */

lightningd/opening_control.h

@@ -17,8 +17,6 @@ void peer_start_openingd(struct peer *peer,
 			 struct peer_comms *pcomms,
 			 const u8 *msg);
 
-void opening_peer_no_active_channels(struct peer *peer);
-
 void kill_uncommitted_channel(struct uncommitted_channel *uc,
 			      const char *why);
 

lightningd/test/run-invoice-select-inchan.c

@@ -290,9 +290,6 @@ enum watch_result onchaind_funding_spent(struct channel *channel UNNEEDED,
 					 const struct bitcoin_tx *tx UNNEEDED,
 					 u32 blockheight UNNEEDED)
 { fprintf(stderr, "onchaind_funding_spent called!\n"); abort(); }
-/* Generated stub for opening_peer_no_active_channels */
-void opening_peer_no_active_channels(struct peer *peer UNNEEDED)
-{ fprintf(stderr, "opening_peer_no_active_channels called!\n"); abort(); }
 /* Generated stub for param */
 bool param(struct command *cmd UNNEEDED, const char *buffer UNNEEDED,
 	   const jsmntok_t params[] UNNEEDED, ...)

openingd/opening_wire.csv

@@ -17,15 +17,29 @@ opening_init,,our_funding_pubkey,struct pubkey
 opening_init,,minimum_depth,u32
 opening_init,,min_feerate,u32
 opening_init,,max_feerate,u32
-opening_init,,can_open_channel,bool
 opening_init,,lfeatures_len,u16
 opening_init,,lfeatures,lfeatures_len*u8
 # Optional msg to send.
 opening_init,,len,u16
 opening_init,,msg,len*u8
 
-# Master->openingd: they can now open a channel if they want.
-opening_can_accept_channel,6002
+# Openingd->master: they offered channel, should we continue?
+opening_got_offer,6005
+opening_got_offer,,funding_satoshis,struct amount_sat
+opening_got_offer,,push_msat,struct amount_msat
+opening_got_offer,,dust_limit_satoshis,struct amount_sat
+opening_got_offer,,max_htlc_value_in_flight_msat,struct amount_msat
+opening_got_offer,,channel_reserve_satoshis,struct amount_sat
+opening_got_offer,,htlc_minimum_msat,struct amount_msat
+opening_got_offer,,feerate_per_kw,u32
+opening_got_offer,,to_self_delay,u16
+opening_got_offer,,max_accepted_htlcs,u16
+opening_got_offer,,channel_flags,u8
+opening_got_offer,,shutdown_len,u16
+opening_got_offer,,shutdown_scriptpubkey,shutdown_len*u8
+# master->openingd: optional rejection message
+opening_got_offer_reply,6105
+opening_got_offer_reply,,rejection,?wirestring
 
 #include <common/bip32.h>
 #include <common/htlc_wire.h>

openingd/openingd.c

@@ -102,12 +102,6 @@ struct state {
 	 * as initial channels never have HTLCs. */
 	struct channel *channel;
 
-	/*~ We only allow one active channel at a time per peer.  Otherwise
-	 * all our per-peer daemons would have to handle multiple channels,
-	 * or we would need some other daemon to demux the messages.
-	 * Thus, lightningd tells is if/when there's no active channel. */
-	bool can_accept_channel;
-
 	/* Which chain we're on, so we can check/set `chain_hash` fields */
 	const struct chainparams *chainparams;
 };
@@ -971,16 +965,6 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 			    "Bad open_channel %s",
 			    tal_hex(open_channel_msg, open_channel_msg));
 
-	/* We can't handle talking about more than one channel at once. */
-	if (!state->can_accept_channel) {
-		u8 *errmsg;
-		errmsg = towire_errorfmt(NULL, &state->channel_id,
-					 "Already have active channel");
-
-		sync_crypto_write(&state->cs, PEER_FD, take(errmsg));
-		return NULL;
-	}
-
 	/* BOLT #2:
 	 *
 	 * The receiving node MUST fail the channel if:
@@ -1018,7 +1002,7 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 	if (amount_msat_greater_sat(state->push_msat, state->funding)) {
 		peer_failed(&state->cs,
 			    &state->channel_id,
-			    "Our push_msat %s"
+			    "Their push_msat %s"
 			    " would be too large for funding_satoshis %s",
 			    type_to_string(tmpctx, struct amount_msat,
 					   &state->push_msat),
@@ -1087,6 +1071,34 @@ static u8 *fundee_channel(struct state *state, const u8 *open_channel_msg)
 	if (!check_config_bounds(state, &state->remoteconf, false))
 		return NULL;
 
+	/* Check with lightningd that we can accept this?  In particular,
+	 * if we have an existing channel, we don't support it. */
+	msg = towire_opening_got_offer(NULL,
+				       state->funding,
+				       state->push_msat,
+				       state->remoteconf.dust_limit,
+				       state->remoteconf.max_htlc_value_in_flight,
+				       state->remoteconf.channel_reserve,
+				       state->remoteconf.htlc_minimum,
+				       state->feerate_per_kw,
+				       state->remoteconf.to_self_delay,
+				       state->remoteconf.max_accepted_htlcs,
+				       channel_flags,
+				       state->remote_upfront_shutdown_script);
+	wire_sync_write(REQ_FD, take(msg));
+	msg = wire_sync_read(tmpctx, REQ_FD);
+
+	if (!fromwire_opening_got_offer_reply(tmpctx, msg, &err_reason))
+		master_badmsg(WIRE_OPENING_GOT_OFFER_REPLY, msg);
+
+	/* If they give us a reason to reject, do so. */
+	if (err_reason) {
+		u8 *errmsg = towire_errorfmt(NULL, &state->channel_id,
+					     "%s", err_reason);
+		sync_crypto_write(&state->cs, PEER_FD, take(errmsg));
+		return NULL;
+	}
+
 	/* OK, we accept! */
 	msg = towire_accept_channel_option_upfront_shutdown_script(NULL, &state->channel_id,
 				    state->localconf.dust_limit,
@@ -1429,12 +1441,6 @@ static u8 *handle_master_in(struct state *state)
 				     take(utxos), &bip32_base);
 		return msg;
 
-	case WIRE_OPENING_CAN_ACCEPT_CHANNEL:
-		if (!fromwire_opening_can_accept_channel(msg))
-			master_badmsg(WIRE_OPENING_CAN_ACCEPT_CHANNEL, msg);
-		state->can_accept_channel = true;
-		return NULL;
-
 	case WIRE_OPENING_DEV_MEMLEAK:
 #if DEVELOPER
 		handle_dev_memleak(state, msg);
@@ -1445,6 +1451,8 @@ static u8 *handle_master_in(struct state *state)
 	case WIRE_OPENING_FUNDER_REPLY:
 	case WIRE_OPENING_FUNDEE:
 	case WIRE_OPENING_FUNDER_FAILED:
+	case WIRE_OPENING_GOT_OFFER:
+	case WIRE_OPENING_GOT_OFFER_REPLY:
 		break;
 	}
 
@@ -1480,7 +1488,6 @@ int main(int argc, char *argv[])
 				   &state->our_funding_pubkey,
 				   &state->minimum_depth,
 				   &state->min_feerate, &state->max_feerate,
-				   &state->can_accept_channel,
 				   &state->localfeatures,
 				   &inner))
 		master_badmsg(WIRE_OPENING_INIT, msg);

wallet/test/run-wallet.c

@@ -350,9 +350,6 @@ enum watch_result onchaind_funding_spent(struct channel *channel UNNEEDED,
 /* Generated stub for onion_type_name */
 const char *onion_type_name(int e UNNEEDED)
 { fprintf(stderr, "onion_type_name called!\n"); abort(); }
-/* Generated stub for opening_peer_no_active_channels */
-void opening_peer_no_active_channels(struct peer *peer UNNEEDED)
-{ fprintf(stderr, "opening_peer_no_active_channels called!\n"); abort(); }
 /* Generated stub for outpointfilter_add */
 void outpointfilter_add(struct outpointfilter *of UNNEEDED,
 			const struct bitcoin_txid *txid UNNEEDED, const u32 outnum UNNEEDED)