From: Matt Corallo Date: Thu, 17 Jun 2021 22:54:46 +0000 (+0000) Subject: Clean up docs on peer_handler significantly. X-Git-Tag: v0.0.99~18^2 X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=refs%2Fheads%2F2021-06-p2p-no-deadlock;p=rust-lightning Clean up docs on peer_handler significantly. There are various typo and grammatical fixes here, as well as concrete updates to correctness. --- diff --git a/lightning/src/ln/peer_handler.rs b/lightning/src/ln/peer_handler.rs index a701200be..5546227ef 100644 --- a/lightning/src/ln/peer_handler.rs +++ b/lightning/src/ln/peer_handler.rs @@ -160,10 +160,15 @@ pub struct MessageHandler where CM::Target: ChannelMessageHandler, RM::Target: RoutingMessageHandler { /// A message handler which handles messages specific to channels. Usually this is just a - /// ChannelManager object or a ErroringMessageHandler. + /// [`ChannelManager`] object or an [`ErroringMessageHandler`]. + /// + /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager pub chan_handler: CM, /// A message handler which handles messages updating our knowledge of the network channel - /// graph. Usually this is just a NetGraphMsgHandlerMonitor object or an IgnoringMessageHandler. + /// graph. Usually this is just a [`NetGraphMsgHandler`] object or an + /// [`IgnoringMessageHandler`]. + /// + /// [`NetGraphMsgHandler`]: crate::routing::network_graph::NetGraphMsgHandler pub route_handler: RM, } @@ -173,29 +178,35 @@ pub struct MessageHandler where /// /// For efficiency, Clone should be relatively cheap for this type. /// -/// You probably want to just extend an int and put a file descriptor in a struct and implement -/// send_data. Note that if you are using a higher-level net library that may call close() itself, -/// be careful to ensure you don't have races whereby you might register a new connection with an -/// fd which is the same as a previous one which has yet to be removed via -/// PeerManager::socket_disconnected(). +/// Two descriptors may compare equal (by [`cmp::Eq`] and [`hash::Hash`]) as long as the original +/// has been disconnected, the [`PeerManager`] has been informed of the disconnection (either by it +/// having triggered the disconnection or a call to [`PeerManager::socket_disconnected`]), and no +/// further calls to the [`PeerManager`] related to the original socket occur. This allows you to +/// use a file descriptor for your SocketDescriptor directly, however for simplicity you may wish +/// to simply use another value which is guaranteed to be globally unique instead. pub trait SocketDescriptor : cmp::Eq + hash::Hash + Clone { /// Attempts to send some data from the given slice to the peer. /// /// Returns the amount of data which was sent, possibly 0 if the socket has since disconnected. - /// Note that in the disconnected case, socket_disconnected must still fire and further write - /// attempts may occur until that time. + /// Note that in the disconnected case, [`PeerManager::socket_disconnected`] must still be + /// called and further write attempts may occur until that time. /// - /// If the returned size is smaller than data.len(), a write_available event must - /// trigger the next time more data can be written. Additionally, until the a send_data event - /// completes fully, no further read_events should trigger on the same peer! + /// If the returned size is smaller than `data.len()`, a + /// [`PeerManager::write_buffer_space_avail`] call must be made the next time more data can be + /// written. Additionally, until a `send_data` event completes fully, no further + /// [`PeerManager::read_event`] calls should be made for the same peer! Because this is to + /// prevent denial-of-service issues, you should not read or buffer any data from the socket + /// until then. /// - /// If a read_event on this descriptor had previously returned true (indicating that read - /// events should be paused to prevent DoS in the send buffer), resume_read may be set - /// indicating that read events on this descriptor should resume. A resume_read of false does - /// *not* imply that further read events should be paused. + /// If a [`PeerManager::read_event`] call on this descriptor had previously returned true + /// (indicating that read events should be paused to prevent DoS in the send buffer), + /// `resume_read` may be set indicating that read events on this descriptor should resume. A + /// `resume_read` of false carries no meaning, and should not cause any action. fn send_data(&mut self, data: &[u8], resume_read: bool) -> usize; /// Disconnect the socket pointed to by this SocketDescriptor. - /// No [`PeerManager::socket_disconnected`] call need be generated as a result of this call. + /// + /// You do *not* need to call [`PeerManager::socket_disconnected`] with this socket after this + /// call (doing so is a noop). fn disconnect_socket(&mut self); } @@ -309,14 +320,25 @@ pub type SimpleArcPeerManager = PeerManager = PeerManager, &'e NetGraphMsgHandler<&'g C, &'f L>, &'f L>; -/// A PeerManager manages a set of peers, described by their SocketDescriptor and marshalls socket -/// events into messages which it passes on to its MessageHandlers. +/// A PeerManager manages a set of peers, described by their [`SocketDescriptor`] and marshalls +/// socket events into messages which it passes on to its [`MessageHandler`]. +/// +/// Locks are taken internally, so you must never assume that reentrancy from a +/// [`SocketDescriptor`] call back into [`PeerManager`] methods will not deadlock. +/// +/// Calls to [`read_event`] will decode relevant messages and pass them to the +/// [`ChannelMessageHandler`], likely doing message processing in-line. Thus, the primary form of +/// parallelism in Rust-Lightning is in calls to [`read_event`]. Note, however, that calls to any +/// [`PeerManager`] functions related to the same connection must occur only in serial, making new +/// calls only after previous ones have returned. /// /// Rather than using a plain PeerManager, it is preferable to use either a SimpleArcPeerManager /// a SimpleRefPeerManager, for conciseness. See their documentation for more details, but /// essentially you should default to using a SimpleRefPeerManager, and use a /// SimpleArcPeerManager when you require a PeerManager with a static lifetime, such as when /// you're using lightning-net-tokio. +/// +/// [`read_event`]: PeerManager::read_event pub struct PeerManager where CM::Target: ChannelMessageHandler, RM::Target: RoutingMessageHandler, @@ -397,8 +419,6 @@ impl PeerManager PeerManager where CM::Target: ChannelMessageHandler, RM::Target: RoutingMessageHandler, @@ -458,8 +478,10 @@ impl PeerManager Result, PeerHandleError> { let mut peer_encryptor = PeerChannelEncryptor::new_outbound(their_node_id.clone(), self.get_ephemeral_key()); let res = peer_encryptor.get_act_one().to_vec(); @@ -495,8 +517,10 @@ impl PeerManager Result<(), PeerHandleError> { let peer_encryptor = PeerChannelEncryptor::new_inbound(&self.our_node_secret); let pending_read_buffer = [0; 50].to_vec(); // Noise act one is 50 bytes @@ -604,12 +628,14 @@ impl PeerManager Result<(), PeerHandleError> { let mut peers = self.peers.lock().unwrap(); match peers.peers.get_mut(descriptor) { @@ -631,13 +657,16 @@ impl PeerManager Result { match self.do_read_event(peer_descriptor, data) { Ok(res) => Ok(res), @@ -1085,7 +1114,14 @@ impl PeerManager PeerManager PeerManager PeerManager