channel: Add struct scb_chan in channel and making last tx optional.

lightningd/channel.c

@@ -212,6 +212,7 @@ struct channel *new_unsaved_channel(struct peer *peer,
 	channel->openchannel_signed_cmd = NULL;
 	channel->state = DUALOPEND_OPEN_INIT;
 	channel->owner = NULL;
+	channel->scb = NULL;
 	memset(&channel->billboard, 0, sizeof(channel->billboard));
 	channel->billboard.transient = tal_fmt(channel, "%s",
 					       "Empty channel init'd");
@@ -419,6 +420,14 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->owner = NULL;
 	memset(&channel->billboard, 0, sizeof(channel->billboard));
 	channel->billboard.transient = tal_strdup(channel, transient_billboard);
+	channel->scb = tal(channel, struct scb_chan);
+	channel->scb->id = dbid;
+	channel->scb->addr = peer->addr;
+	channel->scb->node_id = peer->id;
+	channel->scb->funding = *funding;
+	channel->scb->cid = *cid;
+	channel->scb->funding_sats = funding_sats;
+	channel->scb->type = channel_type_dup(channel->scb, type);
 
 	if (!log) {
 		channel->log = new_log(channel,
@@ -447,9 +456,11 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->our_msat = our_msat;
 	channel->msat_to_us_min = msat_to_us_min;
 	channel->msat_to_us_max = msat_to_us_max;
-	channel->last_tx = tal_steal(channel, last_tx);
+        channel->last_tx = tal_steal(channel, last_tx);
-	channel->last_tx->chainparams = chainparams;
+	if (channel->last_tx) {
-	channel->last_tx_type = TX_UNKNOWN;
+		channel->last_tx->chainparams = chainparams;
+		channel->last_tx_type = TX_UNKNOWN;
+	}
 	channel->last_sig = *last_sig;
 	channel->last_htlc_sigs = tal_steal(channel, last_htlc_sigs);
 	channel->channel_info = *channel_info;

lightningd/channel.h

@@ -3,6 +3,7 @@
 #include "config.h"
 #include <common/channel_id.h>
 #include <common/channel_type.h>
+#include <common/scb_wiregen.h>
 #include <common/tx_roles.h>
 #include <common/utils.h>
 #include <lightningd/channel_state.h>
@@ -260,6 +261,10 @@ struct channel {
 
 	/* Latest channel_update, for use in error messages. */
 	u8 *channel_update;
+
+	/* `Channel-shell` of this channel
+	 * (Minimum information required to backup this channel). */
+	struct scb_chan *scb;
 };
 
 /* For v2 opens, a channel that has not yet been committed/saved to disk */

lightningd/dual_open_control.c

@@ -1228,6 +1228,14 @@ wallet_commit_channel(struct lightningd *ld,
 					     &commitment_feerate);
 	channel->min_possible_feerate = commitment_feerate;
 	channel->max_possible_feerate = commitment_feerate;
+	channel->scb = tal(channel, struct scb_chan);
+	channel->scb->id = channel->dbid;
+	channel->scb->addr = channel->peer->addr;
+	channel->scb->node_id = channel->peer->id;
+	channel->scb->funding = *funding;
+	channel->scb->cid = channel->cid;
+	channel->scb->funding_sats = total_funding;
+	channel->scb->type = channel_type_dup(channel->scb, channel->type);
 
 	/* We are connected */
 	channel->connected = true;

wallet/wallet.c

@@ -1114,6 +1114,7 @@ wallet_stmt2inflight(struct wallet *w, struct db_stmt *stmt,
 	struct amount_msat lease_fee;
 	struct bitcoin_outpoint funding;
 	struct bitcoin_signature last_sig;
+	struct bitcoin_tx *last_tx;
 	struct channel_inflight *inflight;
 
 	secp256k1_ecdsa_signature *lease_commit_sig;
@@ -1149,12 +1150,19 @@ wallet_stmt2inflight(struct wallet *w, struct db_stmt *stmt,
 		db_col_ignore(stmt, "lease_fee");
 	}
 
+	/* last_tx is null for stub channels used for recovering funds through
+	 * Static channel backups. */
+	if (!db_col_is_null(stmt, "last_tx"))
+		last_tx = db_col_psbt_to_tx(tmpctx, stmt, "last_tx");
+	else
+		last_tx = NULL;
+
 	inflight = new_inflight(chan, &funding,
 				db_col_int(stmt, "funding_feerate"),
 				funding_sat,
 				our_funding_sat,
 				db_col_psbt(tmpctx, stmt, "funding_psbt"),
-				db_col_psbt_to_tx(tmpctx, stmt, "last_tx"),
+				last_tx,
 				last_sig,
 				db_col_int(stmt, "lease_expiry"),
 				lease_commit_sig,
@@ -1260,6 +1268,7 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 	struct bitcoin_outpoint funding;
 	struct bitcoin_outpoint *shutdown_wrong_funding;
 	struct bitcoin_signature last_sig;
+	struct bitcoin_tx *last_tx;
 	u8 *remote_shutdown_scriptpubkey;
 	u8 *local_shutdown_scriptpubkey;
 	struct changed_htlc *last_sent_commit;
@@ -1445,6 +1454,13 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 	else
 		type = channel_type_none(NULL);
 
+	/* last_tx is null for stub channels used for recovering funds through
+	 * Static channel backups. */
+	if (!db_col_is_null(stmt, "last_tx"))
+		last_tx = db_col_psbt_to_tx(tmpctx, stmt, "last_tx");
+	else
+		last_tx = NULL;
+
 	chan = new_channel(peer, db_col_u64(stmt, "id"),
 			   &wshachain,
 			   db_col_int(stmt, "state"),
@@ -1469,7 +1485,7 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 			   our_msat,
 			   msat_to_us_min, /* msatoshi_to_us_min */
 			   msat_to_us_max, /* msatoshi_to_us_max */
-			   db_col_psbt_to_tx(tmpctx, stmt, "last_tx"),
+			   last_tx,
 			   &last_sig,
 			   wallet_htlc_sigs_load(tmpctx, w,
 						 db_col_u64(stmt, "id"),