From 5a54f450bdc5f659f9e8dfae27d931cebe9d462c Mon Sep 17 00:00:00 2001
From: Christian Decker <decker.christian@gmail.com>
Date: Thu, 9 Jun 2022 13:34:33 +0200
Subject: [PATCH] openingd: Pass `reserve` down to openingd when funding

---
 lightningd/opening_control.c | 19 ++++++++++---------
 openingd/openingd.c          | 18 +++++++++++++-----
 openingd/openingd_wire.csv   |  1 +
 3 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/lightningd/opening_control.c b/lightningd/opening_control.c
index 6ba7c4097..bd0887947 100644
--- a/lightningd/opening_control.c
+++ b/lightningd/opening_control.c
@@ -1256,15 +1256,16 @@ static struct command_result *json_fundchannel_start(struct command *cmd,
 	} else
 		upfront_shutdown_script_wallet_index = NULL;
 
-	fc->open_msg
-		= towire_openingd_funder_start(fc,
-					  *amount,
-					  fc->push,
-					  fc->our_upfront_shutdown_script,
-					  upfront_shutdown_script_wallet_index,
-					  *feerate_per_kw,
-					  &tmp_channel_id,
-					  fc->channel_flags);
+	fc->open_msg = towire_openingd_funder_start(
+			fc,
+			*amount,
+			fc->push,
+			fc->our_upfront_shutdown_script,
+			upfront_shutdown_script_wallet_index,
+			*feerate_per_kw,
+			&tmp_channel_id,
+			fc->channel_flags,
+			fc->uc->reserve);
 
 	if (socketpair(AF_LOCAL, SOCK_STREAM, 0, fds) != 0) {
 		return command_fail(cmd, FUND_MAX_EXCEEDED,
diff --git a/openingd/openingd.c b/openingd/openingd.c
index d05152e4c..60237f09f 100644
--- a/openingd/openingd.c
+++ b/openingd/openingd.c
@@ -99,6 +99,8 @@ struct state {
 	struct channel_type *channel_type;
 
 	struct feature_set *our_features;
+
+	struct amount_sat *reserve;
 };
 
 /*~ If we can't agree on parameters, we fail to open the channel.
@@ -245,10 +247,6 @@ static u8 *opening_negotiate_msg(const tal_t *ctx, struct state *state,
 
 static bool setup_channel_funder(struct state *state)
 {
-	/*~ For symmetry, we calculate our own reserve even though lightningd
-	 * could do it for the we-are-funding case. */
-	set_reserve(state, state->localconf.dust_limit);
-
 #if DEVELOPER
 	/* --dev-force-tmp-channel-id specified */
 	if (dev_force_tmp_channel_id)
@@ -329,6 +327,15 @@ static u8 *funder_channel_start(struct state *state, u8 channel_flags)
 	if (!setup_channel_funder(state))
 		return NULL;
 
+	/* If we have a reserve override we use that, otherwise we'll
+	 * use our default of 1% of the funding value. */
+	if (state->reserve != NULL) {
+		set_reserve_absolute(state, state->localconf.dust_limit,
+				     *state->reserve);
+	} else {
+		set_reserve(state, state->localconf.dust_limit);
+	}
+
 	if (!state->upfront_shutdown_script[LOCAL])
 		state->upfront_shutdown_script[LOCAL]
 			= no_upfront_shutdown_script(state,
@@ -1352,7 +1359,8 @@ static u8 *handle_master_in(struct state *state)
 						    &state->local_upfront_shutdown_wallet_index,
 						    &state->feerate_per_kw,
 						    &state->channel_id,
-						    &channel_flags))
+						    &channel_flags,
+						    &state->reserve))
 			master_badmsg(WIRE_OPENINGD_FUNDER_START, msg);
 		msg = funder_channel_start(state, channel_flags);
 
diff --git a/openingd/openingd_wire.csv b/openingd/openingd_wire.csv
index d81dfff44..4f77446f2 100644
--- a/openingd/openingd_wire.csv
+++ b/openingd/openingd_wire.csv
@@ -80,6 +80,7 @@ msgdata,openingd_funder_start,upfront_shutdown_wallet_index,?u32,
 msgdata,openingd_funder_start,feerate_per_kw,u32,
 msgdata,openingd_funder_start,temporary_channel_id,channel_id,
 msgdata,openingd_funder_start,channel_flags,u8,
+msgdata,openingd_funder_start,reserve,?amount_sat,
 
 # openingd->master: send back output script for 2-of-2 funding output
 msgtype,openingd_funder_start_reply,6102