lightningd: save shachain for closed channels.

We'll need this to send reestablish, and it is only small (max 47 sha256 per channel).

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

Author: rustyrussell

lightningd/closed_channel.h

@@ -28,6 +28,8 @@ struct closed_channel {
 	enum state_change state_change_cause;
 	bool leased;
 	u64 last_stable_connection;
+	/* NULL for older closed channels */
+	const struct shachain *their_shachain;
 };
 
 static inline const struct channel_id *keyof_closed_channel(const struct closed_channel *cc)

wallet/wallet.c

@@ -1745,7 +1745,7 @@ static struct channel *wallet_stmt2channel(struct wallet *w, struct db_stmt *stm
 	alias[LOCAL] = db_col_optional_scid(tmpctx, stmt, "alias_local");
 	alias[REMOTE] = db_col_optional_scid(tmpctx, stmt, "alias_remote");
 
-	ok &= wallet_shachain_load(w, db_col_u64(stmt, "shachain_remote_id"),
+ 	ok &= wallet_shachain_load(w, db_col_u64(stmt, "shachain_remote_id"),
 				   &wshachain);
 
 	remote_shutdown_scriptpubkey = db_col_arr(tmpctx, stmt,
@@ -2015,6 +2015,7 @@ static struct closed_channel *wallet_stmt2closed_channel(const tal_t *ctx,
 							 struct db_stmt *stmt)
 {
 	struct closed_channel *cc = tal(ctx, struct closed_channel);
+	struct wallet_shachain wshachain;
 
 	/* Can be missing in older dbs! */
 	cc->peer_id = db_col_optional(cc, stmt, "p.node_id", node_id);
@@ -2047,6 +2048,11 @@ static struct closed_channel *wallet_stmt2closed_channel(const tal_t *ctx,
 	cc->state_change_cause
 		= state_change_in_db(db_col_int(stmt, "state_change_reason"));
 	cc->leased = !db_col_is_null(stmt, "lease_commit_sig");
+	/* This was deleted on channel closure for older dbs! */
+	if (wallet_shachain_load(w, db_col_u64(stmt, "shachain_remote_id"), &wshachain))
+		cc->their_shachain = tal_dup(cc, struct shachain, &wshachain.chain);
+	else
+		cc->their_shachain = NULL;
 
 	return cc;
 }
@@ -2081,6 +2087,7 @@ void wallet_load_closed_channels(struct wallet *w,
 					", state_change_reason"
 					", lease_commit_sig"
 					", last_stable_connection"
+					", shachain_remote_id"
 					" FROM channels"
 					" LEFT JOIN peers p ON p.id = peer_id"
                                         " WHERE state = ?;"));
@@ -2125,6 +2132,7 @@ void wallet_load_one_closed_channel(struct wallet *w,
 					", state_change_reason"
 					", lease_commit_sig"
 					", last_stable_connection"
+					", shachain_remote_id"
 					" FROM channels"
 					" LEFT JOIN peers p ON p.id = peer_id"
                                         " WHERE channels.id = ?;"));
@@ -2836,7 +2844,10 @@ void wallet_channel_insert(struct wallet *w, struct channel *chan)
 void wallet_channel_close(struct wallet *w, u64 wallet_id)
 {
 	/* We keep the entry in the channel_configs table, since that might
-	 * help us debug some issues, and it is rather limited in size. */
+	 * help us debug some issues, and it is rather limited in size.  We
+	 * also keep shachains: it's limited and we can use it for sending
+	 * reestablish messages with enough information for nodes with lost
+	 * dbs to recover. */
 	struct db_stmt *stmt;
 
 	/* Delete entries from `channel_htlcs` */
@@ -2864,16 +2875,6 @@ void wallet_channel_close(struct wallet *w, u64 wallet_id)
 	db_bind_u64(stmt, wallet_id);
 	db_exec_prepared_v2(take(stmt));
 
-	/* Delete shachains */
-	stmt = db_prepare_v2(w->db, SQL("DELETE FROM shachains "
-					"WHERE id IN ("
-					"  SELECT shachain_remote_id "
-					"  FROM channels "
-					"  WHERE channels.id=?"
-					")"));
-	db_bind_u64(stmt, wallet_id);
-	db_exec_prepared_v2(take(stmt));
-
 	/* Delete transaction annotations */
 	stmt = db_prepare_v2(w->db, SQL("DELETE FROM transaction_annotations "
 					"WHERE channel=?"));
@@ -2916,6 +2917,19 @@ void wallet_channel_delete(struct wallet *w, const struct channel *channel)
 	assert(db_count_changes(stmt) == 2);
 	tal_free(stmt);
 
+	/* Delete shachains */
+	stmt = db_prepare_v2(w->db, SQL("DELETE FROM shachains "
+					"WHERE id IN ("
+					"  SELECT shachain_remote_id "
+					"  FROM channels "
+					"  WHERE channels.id=?"
+					")"));
+	db_bind_u64(stmt, channel->dbid);
+	db_exec_prepared_v2(stmt);
+
+	assert(db_count_changes(stmt) == 1);
+	tal_free(stmt);
+
 	stmt = db_prepare_v2(w->db, SQL("DELETE FROM channels"
 					" WHERE state = ?"
 					" AND id=?"));