gossipd: have master explicitly tell us when peer is disconnected.

Currently we intuit it from the fd being closed, but that may happen out
of order with when the master thinks it's dead.

So now if the gossip fd closes we just ignore it, and we'll get a
notification from the master when the peer is disconnected.

The notification is slightly ugly in that we have to disable it for
a channel when we manually hand the channel back to gossipd.

Note: as stands, this is racy with reconnects.  See the next patch.

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

gossipd/gossip.c

@@ -398,8 +398,8 @@ static struct io_plan *peer_init_received(struct io_conn *conn,
 		peer->broadcast_index
 			= peer->daemon->rstate->broadcasts->next_index;
 
-	/* This is a full peer now; we keep it around until its
+	/* This is a full peer now; we keep it around until master says
-	 * gossipfd closed (forget_peer) or reconnect. */
+	 * it's dead, or reconnect. */
 	peer_finalized(peer);
 
 	/* We will not have anything queued, since we're not duplex. */
@@ -845,25 +845,12 @@ static struct io_plan *owner_msg_in(struct io_conn *conn,
 		status_broken("peer %s: send us unknown msg of type %s",
 			      type_to_string(tmpctx, struct pubkey, &peer->id),
 			      gossip_wire_type_name(type));
-		/* Calls forget_peer */
 		return io_close(conn);
 	}
 
 	return daemon_conn_read_next(conn, dc);
 }
 
-static void forget_peer(struct io_conn *conn UNUSED, struct daemon_conn *dc)
-{
-	struct peer *peer = dc->ctx;
-
-	status_trace("Forgetting %s peer %s",
-		     peer->local ? "local" : "remote",
-		     type_to_string(tmpctx, struct pubkey, &peer->id));
-
-	/* Free peer. */
-	tal_free(dc->ctx);
-}
-
 /* When a peer is to be owned by another daemon, we create a socket
  * pair to send/receive gossip from it */
 static bool send_peer_with_fds(struct peer *peer, const u8 *msg)
@@ -884,7 +871,7 @@ static bool send_peer_with_fds(struct peer *peer, const u8 *msg)
 	peer->local = tal_free(peer->local);
 	peer->remote = tal(peer, struct daemon_conn);
 	daemon_conn_init(peer, peer->remote, fds[0],
-			 owner_msg_in, forget_peer);
+			 owner_msg_in, NULL);
 	peer->remote->msg_queue_cleared_cb = nonlocal_dump_gossip;
 
 	/* Peer stays around, even though caller will close conn. */
@@ -1871,6 +1858,35 @@ static struct io_plan *peer_important(struct io_conn *conn,
 	return daemon_conn_read_next(conn, &daemon->master);
 }
 
+static struct io_plan *peer_disconnected(struct io_conn *conn,
+					 struct daemon *daemon, const u8 *msg)
+{
+	struct pubkey id;
+	struct peer *peer;
+
+	if (!fromwire_gossipctl_peer_disconnected(msg, &id))
+		master_badmsg(WIRE_GOSSIPCTL_PEER_DISCONNECTED, msg);
+
+	peer = find_peer(daemon, &id);
+	if (!peer)
+		status_failed(STATUS_FAIL_INTERNAL_ERROR,
+			      "peer_disconnected unknown peer: %s",
+			      type_to_string(tmpctx, struct pubkey, &id));
+
+	/* Possible if there's a reconnect: ignore disonnect. */
+	if (peer->local) {
+		status_trace("peer_disconnected %s: reconnected, ignoring",
+			     type_to_string(tmpctx, struct pubkey, &id));
+		return daemon_conn_read_next(conn, &daemon->master);
+	}
+
+	status_trace("Forgetting remote peer %s",
+		     type_to_string(tmpctx, struct pubkey, &peer->id));
+
+	tal_free(peer);
+	return daemon_conn_read_next(conn, &daemon->master);
+}
+
 static struct io_plan *get_peers(struct io_conn *conn,
 				 struct daemon *daemon, const u8 *msg)
 {
@@ -2122,6 +2138,9 @@ static struct io_plan *recv_req(struct io_conn *conn, struct daemon_conn *master
 	case WIRE_GOSSIPCTL_PEER_IMPORTANT:
 		return peer_important(conn, daemon, master->msg_in);
 
+	case WIRE_GOSSIPCTL_PEER_DISCONNECTED:
+		return peer_disconnected(conn, daemon, master->msg_in);
+
 	case WIRE_GOSSIP_GETPEERS_REQUEST:
 		return get_peers(conn, daemon, master->msg_in);
 

gossipd/gossip_wire.csv

@@ -92,6 +92,10 @@ gossipctl_hand_back_peer,,crypto_state,struct crypto_state
 gossipctl_hand_back_peer,,len,u16
 gossipctl_hand_back_peer,,msg,len*u8
 
+# master -> gossipd: peer has disconnected.
+gossipctl_peer_disconnected,3015
+gossipctl_peer_disconnected,,id,struct pubkey
+
 # Pass JSON-RPC getnodes call through
 gossip_getnodes_request,3005
 # Can be 0 or 1 currently

lightningd/channel.c

@@ -12,13 +12,26 @@
 #include <lightningd/peer_control.h>
 #include <lightningd/subd.h>
 
+static bool connects_to_peer(struct subd *owner)
+{
+	return owner && owner->talks_to_peer;
+}
+
 void channel_set_owner(struct channel *channel, struct subd *owner)
 {
 	struct subd *old_owner = channel->owner;
 	channel->owner = owner;
 
-	if (old_owner)
+	if (old_owner) {
 		subd_release_channel(old_owner, channel);
+		if (channel->connected && !connects_to_peer(owner)) {
+			u8 *msg = towire_gossipctl_peer_disconnected(NULL,
+							     &channel->peer->id);
+			subd_send_msg(channel->peer->ld->gossip, take(msg));
+			channel->connected = false;
+		}
+	}
+	channel->connected = connects_to_peer(owner);
 }
 
 struct htlc_out *channel_has_htlc_out(struct channel *channel)
@@ -155,7 +168,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    struct changed_htlc *last_sent_commit,
 			    u32 first_blocknum,
 			    u32 min_possible_feerate,
-			    u32 max_possible_feerate)
+			    u32 max_possible_feerate,
+			    bool connected)
 {
 	struct channel *channel = tal(peer->ld, struct channel);
 
@@ -212,6 +226,7 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 	channel->first_blocknum = first_blocknum;
 	channel->min_possible_feerate = min_possible_feerate;
 	channel->max_possible_feerate = max_possible_feerate;
+	channel->connected = connected;
 	derive_channel_seed(peer->ld, &channel->seed, &peer->id, channel->dbid);
 
 	list_add_tail(&peer->channels, &channel->list);

lightningd/channel.h

@@ -96,6 +96,9 @@ struct channel {
 
 	/* Feerate range */
 	u32 min_possible_feerate, max_possible_feerate;
+
+	/* Does gossipd need to know if the owner dies? (ie. not onchaind) */
+	bool connected;
 };
 
 struct channel *new_channel(struct peer *peer, u64 dbid,
@@ -136,7 +139,8 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 			    struct changed_htlc *last_sent_commit,
 			    u32 first_blocknum,
 			    u32 min_possible_feerate,
-			    u32 max_possible_feerate);
+			    u32 max_possible_feerate,
+			    bool connected);
 
 void delete_channel(struct channel *channel);
 

lightningd/gossip_control.c

@@ -137,6 +137,7 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_MARK_CHANNEL_UNROUTABLE:
 	case WIRE_GOSSIPCTL_PEER_DISCONNECT:
 	case WIRE_GOSSIPCTL_PEER_IMPORTANT:
+	case WIRE_GOSSIPCTL_PEER_DISCONNECTED:
 	/* This is a reply, so never gets through to here. */
 	case WIRE_GOSSIPCTL_INIT_REPLY:
 	case WIRE_GOSSIP_GET_UPDATE_REPLY:

lightningd/opening_control.c

@@ -237,7 +237,9 @@ wallet_commit_channel(struct lightningd *ld,
 			      final_key_idx, false,
 			      NULL, /* No commit sent yet */
 			      uc->first_blocknum,
-			      feerate, feerate);
+			      feerate, feerate,
+			      /* We are connected */
+			      true);
 
 	/* Now we finally put it in the database. */
 	wallet_channel_insert(ld->wallet, channel);
@@ -546,7 +548,9 @@ static void opening_channel_errmsg(struct uncommitted_channel *uc,
 				   const u8 *err_for_them)
 {
 	if (peer_fd == -1) {
+		u8 *msg = towire_gossipctl_peer_disconnected(tmpctx, &uc->peer->id);
 		log_info(uc->log, "%s", desc);
+		subd_send_msg(uc->peer->ld->gossip, msg);
 		if (uc->fc)
 			command_fail(uc->fc->cmd, "%s", desc);
 	} else {

lightningd/peer_control.c

@@ -366,6 +366,9 @@ void channel_errmsg(struct channel *channel,
 					     err_for_them,
 					     tal_len(err_for_them), 0);
 
+	/* Make sure channel_fail_permanent doesn't tell gossipd we died! */
+	channel->connected = false;
+
 	/* BOLT #1:
 	 *
 	 * A sending node:

wallet/test/run-wallet.c

@@ -376,6 +376,9 @@ u8 *towire_gossipctl_peer_addrhint(const tal_t *ctx UNNEEDED, const struct pubke
 /* Generated stub for towire_gossipctl_peer_disconnect */
 u8 *towire_gossipctl_peer_disconnect(const tal_t *ctx UNNEEDED, const struct pubkey *id UNNEEDED)
 { fprintf(stderr, "towire_gossipctl_peer_disconnect called!\n"); abort(); }
+/* Generated stub for towire_gossipctl_peer_disconnected */
+u8 *towire_gossipctl_peer_disconnected(const tal_t *ctx UNNEEDED, const struct pubkey *id UNNEEDED)
+{ fprintf(stderr, "towire_gossipctl_peer_disconnected called!\n"); abort(); }
 /* Generated stub for towire_gossipctl_peer_important */
 u8 *towire_gossipctl_peer_important(const tal_t *ctx UNNEEDED, const struct pubkey *id UNNEEDED, bool important UNNEEDED)
 { fprintf(stderr, "towire_gossipctl_peer_important called!\n"); abort(); }

wallet/wallet.c

@@ -651,7 +651,9 @@ static struct channel *wallet_stmt2channel(const tal_t *ctx, struct wallet *w, s
 			   last_sent_commit,
 			   sqlite3_column_int64(stmt, 35),
 			   sqlite3_column_int(stmt, 36),
-			   sqlite3_column_int(stmt, 37));
+			   sqlite3_column_int(stmt, 37),
+			   /* Not connected */
+			   false);
 
 	return chan;
 }