db: store claimed per_commitment_point from option_data_loss_protect.

This means we don't try to unilaterally close after a restart, *and*
we can tell onchaind to try to use the point to recover funds when the
peer unilaterally closes.

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

lightningd/channel.c

@@ -170,7 +170,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    u32 max_possible_feerate,
 			    bool connected,
 			    const struct basepoints *local_basepoints,
-			    const struct pubkey *local_funding_pubkey)
+			    const struct pubkey *local_funding_pubkey,
+			    const struct pubkey *future_per_commitment_point)
 {
 	struct channel *channel = tal(peer->ld, struct channel);
 
@@ -231,7 +232,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->connected = connected;
 	channel->local_basepoints = *local_basepoints;
 	channel->local_funding_pubkey = *local_funding_pubkey;
-	channel->future_per_commitment_point = NULL;
+	channel->future_per_commitment_point
+		= tal_steal(channel, future_per_commitment_point);
 
 	list_add_tail(&peer->channels, &channel->list);
 	tal_add_destructor(channel, destroy_channel);

lightningd/channel.h

@@ -108,7 +108,7 @@ struct channel {
 
 	/* Do we have an "impossible" future per_commitment_point from
 	 * peer via option_data_loss_protect? */
-	struct pubkey *future_per_commitment_point;
+	const struct pubkey *future_per_commitment_point;
 };
 
 struct channel *new_channel(struct peer *peer, u64 dbid,
@@ -152,7 +152,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    u32 max_possible_feerate,
 			    bool connected,
 			    const struct basepoints *local_basepoints,
-			    const struct pubkey *local_funding_pubkey);
+			    const struct pubkey *local_funding_pubkey,
+			    const struct pubkey *future_per_commitment_point);
 
 void delete_channel(struct channel *channel);
 

lightningd/channel_control.c

@@ -114,10 +114,12 @@ static void channel_fail_fallen_behind(struct channel *channel, const u8 *msg)
 		return;
 	}
 
-	/* FIXME: Save in db! */
 	channel->future_per_commitment_point
 		= tal_dup(channel, struct pubkey, &per_commitment_point);
 
+	/* TODO(cdecker) Selectively save updated fields to DB */
+	wallet_channel_save(channel->peer->ld->wallet, channel);
+
 	/* We don't fail yet, since we want daemon to send them an error
 	 * to trigger rebroadcasting.  But make sure we set error now in
 	 * case something else goes wrong! */

lightningd/opening_control.c

@@ -202,7 +202,8 @@ wallet_commit_channel(struct lightningd *ld,
 			      /* We are connected */
 			      true,
 			      &uc->local_basepoints,
-			      &uc->local_funding_pubkey);
+			      &uc->local_funding_pubkey,
+			      NULL);
 
 	/* Now we finally put it in the database. */
 	wallet_channel_insert(ld->wallet, channel);

tests/test_connection.py

@@ -1219,6 +1219,11 @@ def test_dataloss_protection(node_factory, bitcoind):
     # l2 should still recover something!
     bitcoind.generate_block(1)
 
+    l2.daemon.wait_for_log("ERROR: Unknown commitment #2, recovering our funds!")
+
+    # Restarting l2, and it should remember from db.
+    l2.restart()
+
     l2.daemon.wait_for_log("ERROR: Unknown commitment #2, recovering our funds!")
     bitcoind.generate_block(100)
     l2.daemon.wait_for_log('WIRE_ONCHAIN_ALL_IRREVOCABLY_RESOLVED')

wallet/db.c

@@ -335,6 +335,8 @@ char *dbmigrations[] = {
     /* -- End of  PR #1398 -- */
     "ALTER TABLE invoices ADD description TEXT;",
     "ALTER TABLE payments ADD description TEXT;",
+    /* future_per_commitment_point if other side proves we're out of date -- */
+    "ALTER TABLE channels ADD future_per_commitment_point BLOB;",
     NULL,
 };
 

wallet/wallet.c

@@ -585,6 +585,7 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 	s64 final_key_idx;
 	struct basepoints local_basepoints;
 	struct pubkey local_funding_pubkey;
+	struct pubkey *future_per_commitment_point;
 
 	peer_dbid = sqlite3_column_int64(stmt, 1);
 	peer = find_peer_by_dbid(w->ld, peer_dbid);
@@ -616,6 +617,13 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 		last_sent_commit = NULL;
 	}
 
+	if (sqlite3_column_type(stmt, 40) != SQLITE_NULL) {
+		future_per_commitment_point = tal(tmpctx, struct pubkey);
+		ok &= sqlite3_column_pubkey(stmt, 40,
+					    future_per_commitment_point);
+	} else
+		future_per_commitment_point = NULL;
+
 	ok &= wallet_channel_config_load(w, sqlite3_column_int64(stmt, 3),
 					 &our_config);
 	ok &= sqlite3_column_sha256_double(stmt, 12, &funding_txid.shad);
@@ -682,7 +690,8 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 			   sqlite3_column_int(stmt, 37),
 			   /* Not connected */
 			   false,
-			   &local_basepoints, &local_funding_pubkey);
+			   &local_basepoints, &local_funding_pubkey,
+			   future_per_commitment_point);
 
 	return chan;
 }
@@ -706,7 +715,7 @@ static const char *channel_fields =
     /*30*/ "last_sent_commit_state, last_sent_commit_id, "
     /*32*/ "last_tx, last_sig, last_was_revoke, first_blocknum, "
     /*36*/ "min_possible_feerate, max_possible_feerate, "
-    /*38*/ "msatoshi_to_us_min, msatoshi_to_us_max ";
+    /*38*/ "msatoshi_to_us_min, msatoshi_to_us_max, future_per_commitment_point ";
 
 bool wallet_channels_load_active(const tal_t *ctx, struct wallet *w)
 {
@@ -966,7 +975,8 @@ void wallet_channel_save(struct wallet *w, struct channel *chan)
 			  "  old_per_commit_remote=?,"
 			  "  local_feerate_per_kw=?,"
 			  "  remote_feerate_per_kw=?,"
-			  "  channel_config_remote=?"
+			  "  channel_config_remote=?,"
+			  "  future_per_commitment_point=?"
 			  " WHERE id=?");
 	sqlite3_bind_pubkey(stmt, 1,  &chan->channel_info.remote_fundingkey);
 	sqlite3_bind_pubkey(stmt, 2,  &chan->channel_info.theirbase.revocation);
@@ -978,7 +988,11 @@ void wallet_channel_save(struct wallet *w, struct channel *chan)
 	sqlite3_bind_int(stmt, 8, chan->channel_info.feerate_per_kw[LOCAL]);
 	sqlite3_bind_int(stmt, 9, chan->channel_info.feerate_per_kw[REMOTE]);
 	sqlite3_bind_int64(stmt, 10, chan->channel_info.their_config.id);
-	sqlite3_bind_int64(stmt, 11, chan->dbid);
+	if (chan->future_per_commitment_point)
+		sqlite3_bind_pubkey(stmt, 11, chan->future_per_commitment_point);
+	else
+		sqlite3_bind_null(stmt, 11);
+	sqlite3_bind_int64(stmt, 12, chan->dbid);
 	db_exec_prepared(w->db, stmt);
 
 	/* If we have a last_sent_commit, store it */