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// Copyright 2017-2018 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.
//! Connection-oriented communication channels.
//!
//! The main entity of this module is the [`Transport`] trait, which provides an
//! interface for establishing connections with other nodes, thereby negotiating
//! any desired protocols. The rest of the module defines combinators for
//! modifying a transport through composition with other transports or protocol upgrades.
use futures::prelude::*;
use multiaddr::Multiaddr;
use std::{
error::Error,
fmt,
pin::Pin,
task::{Context, Poll},
};
pub mod and_then;
pub mod choice;
pub mod dummy;
pub mod map;
pub mod map_err;
pub mod memory;
pub mod timeout;
pub mod upgrade;
mod boxed;
mod optional;
use crate::ConnectedPoint;
pub use self::boxed::Boxed;
pub use self::choice::OrTransport;
pub use self::memory::MemoryTransport;
pub use self::optional::OptionalTransport;
pub use self::upgrade::Upgrade;
/// A transport provides connection-oriented communication between two peers
/// through ordered streams of data (i.e. connections).
///
/// Connections are established either by [listening](Transport::listen_on)
/// or [dialing](Transport::dial) on a [`Transport`]. A peer that
/// obtains a connection by listening is often referred to as the *listener* and the
/// peer that initiated the connection through dialing as the *dialer*, in
/// contrast to the traditional roles of *server* and *client*.
///
/// Most transports also provide a form of reliable delivery on the established
/// connections but the precise semantics of these guarantees depend on the
/// specific transport.
///
/// This trait is implemented for concrete connection-oriented transport protocols
/// like TCP or Unix Domain Sockets, but also on wrappers that add additional
/// functionality to the dialing or listening process (e.g. name resolution via
/// the DNS).
///
/// Additional protocols can be layered on top of the connections established
/// by a [`Transport`] through an upgrade mechanism that is initiated via
/// [`upgrade`](Transport::upgrade).
///
/// Note for implementors: Futures returned by [`Transport::dial`] should only
/// do work once polled for the first time. E.g. in the case of TCP, connecting
/// to the remote should not happen immediately on [`Transport::dial`] but only
/// once the returned [`Future`] is polled. The caller of [`Transport::dial`]
/// may call the method multiple times with a set of addresses, racing a subset
/// of the returned dials to success concurrently.
pub trait Transport {
/// The result of a connection setup process, including protocol upgrades.
///
/// Typically the output contains at least a handle to a data stream (i.e. a
/// connection or a substream multiplexer on top of a connection) that
/// provides APIs for sending and receiving data through the connection.
type Output;
/// An error that occurred during connection setup.
type Error: Error;
/// A pending [`Output`](Transport::Output) for an inbound connection,
/// obtained from the [`Transport`] stream.
///
/// After a connection has been accepted by the transport, it may need to go through
/// asynchronous post-processing (i.e. protocol upgrade negotiations). Such
/// post-processing should not block the `Listener` from producing the next
/// connection, hence further connection setup proceeds asynchronously.
/// Once a `ListenerUpgrade` future resolves it yields the [`Output`](Transport::Output)
/// of the connection setup process.
type ListenerUpgrade: Future<Output = Result<Self::Output, Self::Error>>;
/// A pending [`Output`](Transport::Output) for an outbound connection,
/// obtained from [dialing](Transport::dial).
type Dial: Future<Output = Result<Self::Output, Self::Error>>;
/// Listens on the given [`Multiaddr`] for inbound connections.
fn listen_on(&mut self, addr: Multiaddr) -> Result<ListenerId, TransportError<Self::Error>>;
/// Remove a listener.
///
/// Return `true` if there was a listener with this Id, `false`
/// otherwise.
fn remove_listener(&mut self, id: ListenerId) -> bool;
/// Dials the given [`Multiaddr`], returning a future for a pending outbound connection.
///
/// If [`TransportError::MultiaddrNotSupported`] is returned, it may be desirable to
/// try an alternative [`Transport`], if available.
fn dial(&mut self, addr: Multiaddr) -> Result<Self::Dial, TransportError<Self::Error>>;
/// As [`Transport::dial`] but has the local node act as a listener on the outgoing connection.
///
/// This option is needed for NAT and firewall hole punching.
///
/// See [`ConnectedPoint::Dialer`](crate::connection::ConnectedPoint::Dialer) for related option.
fn dial_as_listener(
&mut self,
addr: Multiaddr,
) -> Result<Self::Dial, TransportError<Self::Error>>;
/// Poll for [`TransportEvent`]s.
///
/// A [`TransportEvent::Incoming`] should be produced whenever a connection is received at the lowest
/// level of the transport stack. The item must be a [`ListenerUpgrade`](Transport::ListenerUpgrade)
/// future that resolves to an [`Output`](Transport::Output) value once all protocol upgrades have
/// been applied.
///
/// Transports are expected to produce [`TransportEvent::Incoming`] events only for
/// listen addresses which have previously been announced via
/// a [`TransportEvent::NewAddress`] event and which have not been invalidated by
/// an [`TransportEvent::AddressExpired`] event yet.
fn poll(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<TransportEvent<Self::ListenerUpgrade, Self::Error>>;
/// Performs a transport-specific mapping of an address `observed` by a remote onto a
/// local `listen` address to yield an address for the local node that may be reachable
/// for other peers.
///
/// This is relevant for transports where Network Address Translation (NAT) can occur
/// so that e.g. the peer is observed at a different IP than the IP of the local
/// listening address. See also [`address_translation`][crate::address_translation].
///
/// Within [`libp2p::Swarm`](<https://docs.rs/libp2p/latest/libp2p/struct.Swarm.html>) this is
/// used when extending the listening addresses of the local peer with external addresses
/// observed by remote peers.
/// On transports where this is not relevant (i.e. no NATs are present) `None` should be
/// returned for the sake of de-duplication.
///
/// Note: if the listen or observed address is not a valid address of this transport,
/// `None` should be returned as well.
fn address_translation(&self, listen: &Multiaddr, observed: &Multiaddr) -> Option<Multiaddr>;
/// Boxes the transport, including custom transport errors.
fn boxed(self) -> boxed::Boxed<Self::Output>
where
Self: Sized + Send + Unpin + 'static,
Self::Dial: Send + 'static,
Self::ListenerUpgrade: Send + 'static,
Self::Error: Send + Sync,
{
boxed::boxed(self)
}
/// Applies a function on the connections created by the transport.
fn map<F, O>(self, f: F) -> map::Map<Self, F>
where
Self: Sized,
F: FnOnce(Self::Output, ConnectedPoint) -> O,
{
map::Map::new(self, f)
}
/// Applies a function on the errors generated by the futures of the transport.
fn map_err<F, E>(self, f: F) -> map_err::MapErr<Self, F>
where
Self: Sized,
F: FnOnce(Self::Error) -> E,
{
map_err::MapErr::new(self, f)
}
/// Adds a fallback transport that is used when encountering errors
/// while establishing inbound or outbound connections.
///
/// The returned transport will act like `self`, except that if `listen_on` or `dial`
/// return an error then `other` will be tried.
fn or_transport<U>(self, other: U) -> OrTransport<Self, U>
where
Self: Sized,
U: Transport,
<U as Transport>::Error: 'static,
{
OrTransport::new(self, other)
}
/// Applies a function producing an asynchronous result to every connection
/// created by this transport.
///
/// This function can be used for ad-hoc protocol upgrades or
/// for processing or adapting the output for following configurations.
///
/// For the high-level transport upgrade procedure, see [`Transport::upgrade`].
fn and_then<C, F, O>(self, f: C) -> and_then::AndThen<Self, C>
where
Self: Sized,
C: FnOnce(Self::Output, ConnectedPoint) -> F,
F: TryFuture<Ok = O>,
<F as TryFuture>::Error: Error + 'static,
{
and_then::AndThen::new(self, f)
}
/// Begins a series of protocol upgrades via an
/// [`upgrade::Builder`](upgrade::Builder).
fn upgrade(self, version: upgrade::Version) -> upgrade::Builder<Self>
where
Self: Sized,
Self::Error: 'static,
{
upgrade::Builder::new(self, version)
}
}
/// The ID of a single listener.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub struct ListenerId(u64);
impl ListenerId {
/// Creates a new `ListenerId`.
pub fn new() -> Self {
ListenerId(rand::random())
}
}
impl Default for ListenerId {
fn default() -> Self {
Self::new()
}
}
/// Event produced by [`Transport`]s.
pub enum TransportEvent<TUpgr, TErr> {
/// A new address is being listened on.
NewAddress {
/// The listener that is listening on the new address.
listener_id: ListenerId,
/// The new address that is being listened on.
listen_addr: Multiaddr,
},
/// An address is no longer being listened on.
AddressExpired {
/// The listener that is no longer listening on the address.
listener_id: ListenerId,
/// The new address that is being listened on.
listen_addr: Multiaddr,
},
/// A connection is incoming on one of the listeners.
Incoming {
/// The listener that produced the upgrade.
listener_id: ListenerId,
/// The produced upgrade.
upgrade: TUpgr,
/// Local connection address.
local_addr: Multiaddr,
/// Address used to send back data to the incoming client.
send_back_addr: Multiaddr,
},
/// A listener closed.
ListenerClosed {
/// The ID of the listener that closed.
listener_id: ListenerId,
/// Reason for the closure. Contains `Ok(())` if the stream produced `None`, or `Err`
/// if the stream produced an error.
reason: Result<(), TErr>,
},
/// A listener errored.
///
/// The listener will continue to be polled for new events and the event
/// is for informational purposes only.
ListenerError {
/// The ID of the listener that errored.
listener_id: ListenerId,
/// The error value.
error: TErr,
},
}
impl<TUpgr, TErr> TransportEvent<TUpgr, TErr> {
/// In case this [`TransportEvent`] is an upgrade, apply the given function
/// to the upgrade and produce another transport event based the the function's result.
pub fn map_upgrade<U>(self, map: impl FnOnce(TUpgr) -> U) -> TransportEvent<U, TErr> {
match self {
TransportEvent::Incoming {
listener_id,
upgrade,
local_addr,
send_back_addr,
} => TransportEvent::Incoming {
listener_id,
upgrade: map(upgrade),
local_addr,
send_back_addr,
},
TransportEvent::NewAddress {
listen_addr,
listener_id,
} => TransportEvent::NewAddress {
listen_addr,
listener_id,
},
TransportEvent::AddressExpired {
listen_addr,
listener_id,
} => TransportEvent::AddressExpired {
listen_addr,
listener_id,
},
TransportEvent::ListenerError { listener_id, error } => {
TransportEvent::ListenerError { listener_id, error }
}
TransportEvent::ListenerClosed {
listener_id,
reason,
} => TransportEvent::ListenerClosed {
listener_id,
reason,
},
}
}
/// In case this [`TransportEvent`] is an [`ListenerError`](TransportEvent::ListenerError),
/// or [`ListenerClosed`](TransportEvent::ListenerClosed) apply the given function to the
/// error and produce another transport event based on the function's result.
pub fn map_err<E>(self, map_err: impl FnOnce(TErr) -> E) -> TransportEvent<TUpgr, E> {
match self {
TransportEvent::Incoming {
listener_id,
upgrade,
local_addr,
send_back_addr,
} => TransportEvent::Incoming {
listener_id,
upgrade,
local_addr,
send_back_addr,
},
TransportEvent::NewAddress {
listen_addr,
listener_id,
} => TransportEvent::NewAddress {
listen_addr,
listener_id,
},
TransportEvent::AddressExpired {
listen_addr,
listener_id,
} => TransportEvent::AddressExpired {
listen_addr,
listener_id,
},
TransportEvent::ListenerError { listener_id, error } => TransportEvent::ListenerError {
listener_id,
error: map_err(error),
},
TransportEvent::ListenerClosed {
listener_id,
reason,
} => TransportEvent::ListenerClosed {
listener_id,
reason: reason.map_err(map_err),
},
}
}
/// Returns `true` if this is an [`Incoming`](TransportEvent::Incoming) transport event.
pub fn is_upgrade(&self) -> bool {
matches!(self, TransportEvent::Incoming { .. })
}
/// Try to turn this transport event into the upgrade parts of the
/// incoming connection.
///
/// Returns `None` if the event is not actually an incoming connection,
/// otherwise the upgrade and the remote address.
pub fn into_incoming(self) -> Option<(TUpgr, Multiaddr)> {
if let TransportEvent::Incoming {
upgrade,
send_back_addr,
..
} = self
{
Some((upgrade, send_back_addr))
} else {
None
}
}
/// Returns `true` if this is a [`TransportEvent::NewAddress`].
pub fn is_new_address(&self) -> bool {
matches!(self, TransportEvent::NewAddress { .. })
}
/// Try to turn this transport event into the new `Multiaddr`.
///
/// Returns `None` if the event is not actually a [`TransportEvent::NewAddress`],
/// otherwise the address.
pub fn into_new_address(self) -> Option<Multiaddr> {
if let TransportEvent::NewAddress { listen_addr, .. } = self {
Some(listen_addr)
} else {
None
}
}
/// Returns `true` if this is an [`TransportEvent::AddressExpired`].
pub fn is_address_expired(&self) -> bool {
matches!(self, TransportEvent::AddressExpired { .. })
}
/// Try to turn this transport event into the expire `Multiaddr`.
///
/// Returns `None` if the event is not actually a [`TransportEvent::AddressExpired`],
/// otherwise the address.
pub fn into_address_expired(self) -> Option<Multiaddr> {
if let TransportEvent::AddressExpired { listen_addr, .. } = self {
Some(listen_addr)
} else {
None
}
}
/// Returns `true` if this is an [`TransportEvent::ListenerError`] transport event.
pub fn is_listener_error(&self) -> bool {
matches!(self, TransportEvent::ListenerError { .. })
}
/// Try to turn this transport event into the listener error.
///
/// Returns `None` if the event is not actually a [`TransportEvent::ListenerError`]`,
/// otherwise the error.
pub fn into_listener_error(self) -> Option<TErr> {
if let TransportEvent::ListenerError { error, .. } = self {
Some(error)
} else {
None
}
}
}
impl<TUpgr, TErr: fmt::Debug> fmt::Debug for TransportEvent<TUpgr, TErr> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
match self {
TransportEvent::NewAddress {
listener_id,
listen_addr,
} => f
.debug_struct("TransportEvent::NewAddress")
.field("listener_id", listener_id)
.field("listen_addr", listen_addr)
.finish(),
TransportEvent::AddressExpired {
listener_id,
listen_addr,
} => f
.debug_struct("TransportEvent::AddressExpired")
.field("listener_id", listener_id)
.field("listen_addr", listen_addr)
.finish(),
TransportEvent::Incoming {
listener_id,
local_addr,
..
} => f
.debug_struct("TransportEvent::Incoming")
.field("listener_id", listener_id)
.field("local_addr", local_addr)
.finish(),
TransportEvent::ListenerClosed {
listener_id,
reason,
} => f
.debug_struct("TransportEvent::Closed")
.field("listener_id", listener_id)
.field("reason", reason)
.finish(),
TransportEvent::ListenerError { listener_id, error } => f
.debug_struct("TransportEvent::ListenerError")
.field("listener_id", listener_id)
.field("error", error)
.finish(),
}
}
}
/// An error during [dialing][Transport::dial] or [listening][Transport::listen_on]
/// on a [`Transport`].
#[derive(Debug, Clone)]
pub enum TransportError<TErr> {
/// The [`Multiaddr`] passed as parameter is not supported.
///
/// Contains back the same address.
MultiaddrNotSupported(Multiaddr),
/// Any other error that a [`Transport`] may produce.
Other(TErr),
}
impl<TErr> TransportError<TErr> {
/// Applies a function to the the error in [`TransportError::Other`].
pub fn map<TNewErr>(self, map: impl FnOnce(TErr) -> TNewErr) -> TransportError<TNewErr> {
match self {
TransportError::MultiaddrNotSupported(addr) => {
TransportError::MultiaddrNotSupported(addr)
}
TransportError::Other(err) => TransportError::Other(map(err)),
}
}
}
impl<TErr> fmt::Display for TransportError<TErr>
where
TErr: fmt::Display,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
TransportError::MultiaddrNotSupported(addr) => {
write!(f, "Multiaddr is not supported: {}", addr)
}
TransportError::Other(_) => Ok(()),
}
}
}
impl<TErr> Error for TransportError<TErr>
where
TErr: Error + 'static,
{
fn source(&self) -> Option<&(dyn Error + 'static)> {
match self {
TransportError::MultiaddrNotSupported(_) => None,
TransportError::Other(err) => Some(err),
}
}
}