From 48bb2d831bf2bd52effcab947ab786625809457a Mon Sep 17 00:00:00 2001
From: niftynei <niftynei@gmail.com>
Date: Mon, 30 Oct 2023 21:17:38 -0500
Subject: [PATCH] dual-fund: don't re-notify plugin on arrival of sigs (2nd
 time)

When we got our peer's sigs, if we were the remote, we would re-notify
the plugin, which in turn would re-send the tx-sigs to use.

In the case of CLN, we'd then
- break, because we'd re-forward the sigs to the `openchannel` plugin,
  which was then in the wrong state (MULTIFUNDCHANNEL_SIGNED)

    spenderp: plugins/spender/openchannel.c:598: json_peer_sigs: Assertion `dest->state == MULTIFUNDCHANNEL_SECURED' failed.
    spenderp: FATAL SIGNAL 6 (version 5880d59-modded)

In the case of eclair, they'd just see our 2nd TX_SIGS message and
@t-bast would complain:

	> This test works, with one minor issue: on reconnection, cln sends its tx_signatures twice (duplicate?).

This commit does two things:
	- has the openchannel / spender plugin log a broken instead of
	  crashing when the state is not what we're expecting
	- stops us from calling the `funder` plugin if this is a
	  replay/second receipt of commit-sigs.
---
 lightningd/dual_open_control.c | 22 +++++++++++++++-------
 plugins/spender/openchannel.c  |  9 ++++++++-
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/lightningd/dual_open_control.c b/lightningd/dual_open_control.c
index 6d18a3349..96754019f 100644
--- a/lightningd/dual_open_control.c
+++ b/lightningd/dual_open_control.c
@@ -1297,7 +1297,7 @@ wallet_update_channel(struct lightningd *ld,
 	return inflight;
 }
 
-static void
+static bool
 wallet_update_channel_commit(struct lightningd *ld,
 			     struct channel *channel,
 			     struct channel_inflight *inflight,
@@ -1343,10 +1343,13 @@ wallet_update_channel_commit(struct lightningd *ld,
 					       type_to_string(tmpctx, struct bitcoin_txid, &inflight_txid),
 					       type_to_string(tmpctx, struct bitcoin_txid, &txid));
 		}
-	} else {
-		inflight_set_last_tx(inflight, remote_commit, *remote_commit_sig);
-		wallet_inflight_save(ld->wallet, inflight);
+		return false;
 	}
+
+
+	inflight_set_last_tx(inflight, remote_commit, *remote_commit_sig);
+	wallet_inflight_save(ld->wallet, inflight);
+	return true;
 }
 
 
@@ -3469,6 +3472,7 @@ static void handle_commit_received(struct subd *dualopend,
 	struct openchannel2_psbt_payload *payload;
 	struct channel_inflight *inflight;
 	struct command *cmd;
+	bool updated;
 
 	if (!fromwire_dualopend_commit_rcvd(tmpctx, msg,
 					    &remote_commit,
@@ -3491,9 +3495,9 @@ static void handle_commit_received(struct subd *dualopend,
 		return;
 	}
 
-	wallet_update_channel_commit(ld, channel, inflight,
-				     remote_commit,
-				     &remote_commit_sig);
+	updated = wallet_update_channel_commit(ld, channel, inflight,
+					       remote_commit,
+					       &remote_commit_sig);
 
 	/* FIXME: handle RBF pbases */
 	if (pbase && channel->state != DUALOPEND_AWAITING_LOCKIN) {
@@ -3517,6 +3521,10 @@ static void handle_commit_received(struct subd *dualopend,
 		was_pending(command_success(cmd, response));
 		return;
 	case REMOTE:
+		if (!updated) {
+			log_info(channel->log, "Already had sigs, skipping notif");
+			return;
+		}
 		payload = tal(dualopend, struct openchannel2_psbt_payload);
 		payload->ld = ld;
 		payload->dualopend = dualopend;
diff --git a/plugins/spender/openchannel.c b/plugins/spender/openchannel.c
index 669c16be3..e3996888f 100644
--- a/plugins/spender/openchannel.c
+++ b/plugins/spender/openchannel.c
@@ -595,7 +595,14 @@ static struct command_result *json_peer_sigs(struct command *cmd,
 	if (dest->state == MULTIFUNDCHANNEL_UPDATED)
 		dest->state = MULTIFUNDCHANNEL_SIGNED_NOT_SECURED;
 	else {
-		assert(dest->state == MULTIFUNDCHANNEL_SECURED);
+		if (dest->state != MULTIFUNDCHANNEL_SECURED) {
+			plugin_log(cmd->plugin, LOG_BROKEN,
+				   "mfc %"PRIu64":`openchannel_peer_sigs` "
+				   " expected state MULTIFUNDCHANNEL_SECURED (%d),"
+				   " state is %d", dest->mfc->id,
+				   MULTIFUNDCHANNEL_SECURED,
+				   dest->state);
+		}
 		dest->state = MULTIFUNDCHANNEL_SIGNED;
 	}