openingd: Set minimum_depth=0 if peer is allowed to do zeroconf

Creates a copy of `our_features` for the uncommitted channel so we can
customize it per peer.

lightningd/opening_common.c

@@ -48,6 +48,10 @@ new_uncommitted_channel(struct peer *peer)
 	uc->transient_billboard = NULL;
 	uc->dbid = wallet_get_channel_dbid(ld->wallet);
 
+	/* Need to have a copy since these might end up being
+	 * peer-specific. */
+	uc->our_features = feature_set_dup(uc, ld->our_features);
+
 	uc->log = new_log(uc, ld->log_book, &uc->peer->id,
 			  "chan#%"PRIu64, uc->dbid);
 
@@ -163,3 +167,10 @@ void channel_config(struct lightningd *ld,
 	 /* This is filled in by lightning_openingd, for consistency. */
 	 ours->channel_reserve = AMOUNT_SAT(UINT64_MAX);
 }
+
+bool opening_zeroconf_allow(struct lightningd *ld, struct node_id *peer)
+{
+	/* FIXME: Actually read the options from `ld` and return
+	 * `true` if we were configured to do so. */
+	return true;
+}

lightningd/opening_common.h

@@ -58,6 +58,10 @@ struct uncommitted_channel {
 
 	/* Our channel config. */
 	struct channel_config our_config;
+
+	/* Features we propose to this peer. This is a copy of
+	 * ld->our_features, but customized for this specific peer. */
+	struct feature_set *our_features;
 };
 
 struct funding_channel {
@@ -123,4 +127,18 @@ void channel_config(struct lightningd *ld,
 		    u32 *max_to_self_delay,
 		    struct amount_msat *min_effective_htlc_capacity);
 
+/**
+ * Are we ok with this peer opening a zeroconf channel?
+ *
+ * Determines whether we'd be happy to open or accept a zeroconf
+ * channel with this peers. It is used to selectively apply the
+ * `option_zeroconf` to the `init` message we'll send to the peer when
+ * a connection is established. This is sticky, as in it applies to
+ * all channels we'll open or accept on this connection. Notice that
+ * this does not differentiate between opening of accepting a channel,
+ * and that's because the accepter doesn't get a say in the channel
+ * negotiation.
+ */
+bool opening_zeroconf_allow(struct lightningd *ld, struct node_id *peer);
+
 #endif /* LIGHTNING_LIGHTNINGD_OPENING_COMMON_H */

lightningd/opening_control.c

@@ -7,6 +7,7 @@
 #include <common/addr.h>
 #include <common/blockheight_states.h>
 #include <common/configdir.h>
+#include <common/features.h>
 #include <common/fee_states.h>
 #include <common/json_command.h>
 #include <common/json_helpers.h>
@@ -896,6 +897,10 @@ bool peer_start_openingd(struct peer *peer, struct peer_fd *peer_fd)
 	 *     reasonable to avoid double-spending of the funding transaction.
 	 */
 	uc->minimum_depth = peer->ld->config.anchor_confirms;
+#ifdef EXPERIMENTAL_FEATURES /* zeroconf */
+	if (opening_zeroconf_allow(peer->ld, &peer->id)) {
+		uc->minimum_depth = 0;
+	}
 
 	msg = towire_openingd_init(NULL,
 				  chainparams,