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// Copyright 2018 Parity Technologies (UK) Ltd. // // Permission is hereby granted, free of charge, to any person obtaining a // copy of this software and associated documentation files (the "Software"), // to deal in the Software without restriction, including without limitation // the rights to use, copy, modify, merge, publish, distribute, sublicense, // and/or sell copies of the Software, and to permit persons to whom the // Software is furnished to do so, subject to the following conditions: // // The above copyright notice and this permission notice shall be included in // all copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER // DEALINGS IN THE SOFTWARE. //! Once we are connected to a node, a *protocols handler* handles one or more specific protocols //! on this connection. //! //! This includes: how to handle incoming substreams, which protocols are supported, when to open //! a new outbound substream, and so on. //! //! Each implementation of the `ProtocolsHandler` trait handles one or more specific protocols. //! Two `ProtocolsHandler`s can be combined together with the `select()` method in order to build //! a `ProtocolsHandler` that combines both. This can be repeated multiple times in order to create //! a handler that handles all the protocols that you wish. //! //! > **Note**: A `ProtocolsHandler` handles one or more protocols in relation to a specific //! > connection with a remote. In order to handle a protocol that requires knowledge of //! > the network as a whole, see the `NetworkBehaviour` trait. use crate::PeerId; use crate::upgrade::{ InboundUpgrade, OutboundUpgrade, UpgradeError, }; use futures::prelude::*; use std::{error, fmt, time::Duration}; use tokio_io::{AsyncRead, AsyncWrite}; pub use self::dummy::DummyProtocolsHandler; pub use self::map_in::MapInEvent; pub use self::map_out::MapOutEvent; pub use self::node_handler::{NodeHandlerWrapper, NodeHandlerWrapperBuilder}; pub use self::select::{IntoProtocolsHandlerSelect, ProtocolsHandlerSelect}; mod dummy; mod map_in; mod map_out; mod node_handler; mod select; /// Handler for a set of protocols for a specific connection with a remote. /// /// This trait should be implemented on a struct that holds the state for a specific protocol /// behaviour with a specific remote. /// /// # Handling a protocol /// /// Communication with a remote over a set of protocols opened in two different ways: /// /// - Dialing, which is a voluntary process. In order to do so, make `poll()` return an /// `OutboundSubstreamRequest` variant containing the connection upgrade to use to start using a /// protocol. /// - Listening, which is used to determine which protocols are supported when the remote wants /// to open a substream. The `listen_protocol()` method should return the upgrades supported when /// listening. /// /// The upgrade when dialing and the upgrade when listening have to be of the same type, but you /// are free to return for example an `OrUpgrade` enum, or an enum of your own, containing the /// upgrade you want depending on the situation. /// /// # Shutting down /// /// Implementors of this trait should keep in mind that the connection can be closed at any time. /// When a connection is closed (either by us or by the remote) `shutdown()` is called and the /// handler continues to be processed until it produces `ProtocolsHandlerEvent::Shutdown`. Only /// then the handler is destroyed. /// /// This makes it possible for the handler to finish delivering events even after knowing that it /// is shutting down. /// /// Implementors of this trait should keep in mind that when `shutdown()` is called, the connection /// might already be closed or unresponsive. They should therefore not rely on being able to /// deliver messages. /// pub trait ProtocolsHandler { /// Custom event that can be received from the outside. type InEvent; /// Custom event that can be produced by the handler and that will be returned to the outside. type OutEvent; /// Error that can happen when polling. type Error: error::Error; /// The type of the substream that contains the raw data. type Substream: AsyncRead + AsyncWrite; /// The upgrade for the protocol or protocols handled by this handler. type InboundProtocol: InboundUpgrade<Self::Substream>; /// The upgrade for the protocol or protocols handled by this handler. type OutboundProtocol: OutboundUpgrade<Self::Substream>; /// Information about a substream. Can be sent to the handler through a `NodeHandlerEndpoint`, /// and will be passed back in `inject_substream` or `inject_outbound_closed`. type OutboundOpenInfo; /// Produces a `ConnectionUpgrade` for the protocol or protocols to accept when listening. /// /// > **Note**: You should always accept all the protocols you support, even if in a specific /// > context you wouldn't accept one in particular (eg. only allow one substream at /// > a time for a given protocol). The reason is that remotes are allowed to put the /// > list of supported protocols in a cache in order to avoid spurious queries. fn listen_protocol(&self) -> Self::InboundProtocol; /// Injects a fully-negotiated substream in the handler. /// /// This method is called when a substream has been successfully opened and negotiated. fn inject_fully_negotiated_inbound( &mut self, protocol: <Self::InboundProtocol as InboundUpgrade<Self::Substream>>::Output ); fn inject_fully_negotiated_outbound( &mut self, protocol: <Self::OutboundProtocol as OutboundUpgrade<Self::Substream>>::Output, info: Self::OutboundOpenInfo ); /// Injects an event coming from the outside in the handler. fn inject_event(&mut self, event: Self::InEvent); /// Indicates to the handler that upgrading a substream to the given protocol has failed. fn inject_dial_upgrade_error(&mut self, info: Self::OutboundOpenInfo, error: ProtocolsHandlerUpgrErr<<Self::OutboundProtocol as OutboundUpgrade<Self::Substream>>::Error>); /// Indicates to the handler that the inbound part of the muxer has been closed, and that /// therefore no more inbound substreams will be produced. fn inject_inbound_closed(&mut self); /// Returns whether the connection should be kept alive. /// /// If returns `false`, that indicates that this connection is not important and the user may /// invoke `shutdown()` if they think that they will no longer need the connection in the /// future. /// /// On the other hand, returning `true` is only an indication and doesn't mean that the user /// will not call `shutdown()`. /// /// When multiple `ProtocolsHandler` are combined together, they should use *OR* to merge the /// result of this method. /// /// The result of this method should be checked every time `poll()` is invoked. /// /// After `shutdown()` is called, the result of this method doesn't matter anymore. fn connection_keep_alive(&self) -> bool; /// Indicates to the node that it should shut down. After that, it is expected that `poll()` /// returns `Ready(ProtocolsHandlerEvent::Shutdown)` as soon as possible. /// /// This method allows an implementation to perform a graceful shutdown of the substreams, and /// send back various events. fn shutdown(&mut self); /// Should behave like `Stream::poll()`. Should close if no more event can be produced and the /// node should be closed. /// /// > **Note**: If this handler is combined with other handlers, as soon as `poll()` returns /// > `Ok(Async::Ready(ProtocolsHandlerEvent::Shutdown))`, all the other handlers /// > will receive a call to `shutdown()` and will eventually be closed and /// > destroyed. fn poll(&mut self) -> Poll<ProtocolsHandlerEvent<Self::OutboundProtocol, Self::OutboundOpenInfo, Self::OutEvent>, Self::Error>; /// Adds a closure that turns the input event into something else. #[inline] fn map_in_event<TNewIn, TMap>(self, map: TMap) -> MapInEvent<Self, TNewIn, TMap> where Self: Sized, TMap: Fn(&TNewIn) -> Option<&Self::InEvent>, { MapInEvent::new(self, map) } /// Adds a closure that turns the output event into something else. #[inline] fn map_out_event<TMap, TNewOut>(self, map: TMap) -> MapOutEvent<Self, TMap> where Self: Sized, TMap: FnMut(Self::OutEvent) -> TNewOut, { MapOutEvent::new(self, map) } /// Builds an implementation of `ProtocolsHandler` that handles both this protocol and the /// other one together. #[inline] fn select<TProto2>(self, other: TProto2) -> ProtocolsHandlerSelect<Self, TProto2> where Self: Sized, { ProtocolsHandlerSelect::new(self, other) } /// Creates a builder that will allow creating a `NodeHandler` that handles this protocol /// exclusively. #[inline] fn into_node_handler_builder(self) -> NodeHandlerWrapperBuilder<Self> where Self: Sized, { IntoProtocolsHandler::into_node_handler_builder(self) } /// Builds an implementation of `NodeHandler` that handles this protocol exclusively. /// /// > **Note**: This is a shortcut for `self.into_node_handler_builder().build()`. #[inline] #[deprecated(note = "Use into_node_handler_builder instead")] fn into_node_handler(self) -> NodeHandlerWrapper<Self> where Self: Sized, { #![allow(deprecated)] self.into_node_handler_builder().build() } } /// Event produced by a handler. #[derive(Debug, Copy, Clone, PartialEq, Eq)] pub enum ProtocolsHandlerEvent<TConnectionUpgrade, TOutboundOpenInfo, TCustom> { /// Request a new outbound substream to be opened with the remote. OutboundSubstreamRequest { /// The upgrade to apply on the substream. upgrade: TConnectionUpgrade, /// User-defined information, passed back when the substream is open. info: TOutboundOpenInfo, }, /// Perform a graceful shutdown of the connection to the remote. /// /// Should be returned after `shutdown()` has been called. Shutdown, /// Other event. Custom(TCustom), } /// Event produced by a handler. impl<TConnectionUpgrade, TOutboundOpenInfo, TCustom> ProtocolsHandlerEvent<TConnectionUpgrade, TOutboundOpenInfo, TCustom> { /// If this is an `OutboundSubstreamRequest`, maps the `info` member from a `TOutboundOpenInfo` to something else. #[inline] pub fn map_outbound_open_info<F, I>( self, map: F, ) -> ProtocolsHandlerEvent<TConnectionUpgrade, I, TCustom> where F: FnOnce(TOutboundOpenInfo) -> I, { match self { ProtocolsHandlerEvent::OutboundSubstreamRequest { upgrade, info } => { ProtocolsHandlerEvent::OutboundSubstreamRequest { upgrade, info: map(info), } } ProtocolsHandlerEvent::Shutdown => ProtocolsHandlerEvent::Shutdown, ProtocolsHandlerEvent::Custom(val) => ProtocolsHandlerEvent::Custom(val), } } /// If this is an `OutboundSubstreamRequest`, maps the protocol (`TConnectionUpgrade`) to something else. #[inline] pub fn map_protocol<F, I>( self, map: F, ) -> ProtocolsHandlerEvent<I, TOutboundOpenInfo, TCustom> where F: FnOnce(TConnectionUpgrade) -> I, { match self { ProtocolsHandlerEvent::OutboundSubstreamRequest { upgrade, info } => { ProtocolsHandlerEvent::OutboundSubstreamRequest { upgrade: map(upgrade), info, } } ProtocolsHandlerEvent::Shutdown => ProtocolsHandlerEvent::Shutdown, ProtocolsHandlerEvent::Custom(val) => ProtocolsHandlerEvent::Custom(val), } } /// If this is a `Custom` event, maps the content to something else. #[inline] pub fn map_custom<F, I>( self, map: F, ) -> ProtocolsHandlerEvent<TConnectionUpgrade, TOutboundOpenInfo, I> where F: FnOnce(TCustom) -> I, { match self { ProtocolsHandlerEvent::OutboundSubstreamRequest { upgrade, info } => { ProtocolsHandlerEvent::OutboundSubstreamRequest { upgrade, info } } ProtocolsHandlerEvent::Shutdown => ProtocolsHandlerEvent::Shutdown, ProtocolsHandlerEvent::Custom(val) => ProtocolsHandlerEvent::Custom(map(val)), } } } /// Error that can happen on an outbound substream opening attempt. #[derive(Debug)] pub enum ProtocolsHandlerUpgrErr<TUpgrErr> { /// The opening attempt timed out before the negotiation was fully completed. Timeout, /// There was an error in the timer used. Timer, /// The remote muxer denied the attempt to open a substream. MuxerDeniedSubstream, /// Error while upgrading the substream to the protocol we want. Upgrade(UpgradeError<TUpgrErr>), } impl<TUpgrErr> fmt::Display for ProtocolsHandlerUpgrErr<TUpgrErr> where TUpgrErr: fmt::Display, { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match self { ProtocolsHandlerUpgrErr::Timeout => { write!(f, "Timeout error while opening a substream") }, ProtocolsHandlerUpgrErr::Timer => { write!(f, "Timer error while opening a substream") }, ProtocolsHandlerUpgrErr::MuxerDeniedSubstream => { write!(f, "Remote muxer denied our attempt to open a substream") }, ProtocolsHandlerUpgrErr::Upgrade(err) => write!(f, "{}", err), } } } impl<TUpgrErr> error::Error for ProtocolsHandlerUpgrErr<TUpgrErr> where TUpgrErr: error::Error + 'static { fn source(&self) -> Option<&(dyn error::Error + 'static)> { match self { ProtocolsHandlerUpgrErr::Timeout => None, ProtocolsHandlerUpgrErr::Timer => None, ProtocolsHandlerUpgrErr::MuxerDeniedSubstream => None, ProtocolsHandlerUpgrErr::Upgrade(err) => Some(err), } } } /// Prototype for a `ProtocolsHandler`. pub trait IntoProtocolsHandler { /// The protocols handler. type Handler: ProtocolsHandler; /// Builds the protocols handler. /// /// The `PeerId` is the id of the node the handler is going to handle. fn into_handler(self, remote_peer_id: &PeerId) -> Self::Handler; /// Builds an implementation of `IntoProtocolsHandler` that handles both this protocol and the /// other one together. #[inline] fn select<TProto2>(self, other: TProto2) -> IntoProtocolsHandlerSelect<Self, TProto2> where Self: Sized, { IntoProtocolsHandlerSelect::new(self, other) } /// Creates a builder that will allow creating a `NodeHandler` that handles this protocol /// exclusively. #[inline] fn into_node_handler_builder(self) -> NodeHandlerWrapperBuilder<Self> where Self: Sized, { NodeHandlerWrapperBuilder::new(self, Duration::from_secs(10), Duration::from_secs(10), Duration::from_secs(5)) } } impl<T> IntoProtocolsHandler for T where T: ProtocolsHandler { type Handler = Self; #[inline] fn into_handler(self, _: &PeerId) -> Self { self } }