Enum libp2p_swarm::behaviour::NetworkBehaviourAction

pub enum NetworkBehaviourAction<TOutEvent, THandler: IntoConnectionHandler, TInEvent = <<THandler as IntoConnectionHandler>::Handler as ConnectionHandler>::InEvent> {
    GenerateEvent(TOutEvent),
    Dial {
        opts: DialOpts,
        handler: THandler,
    },
    NotifyHandler {
        peer_id: PeerId,
        handler: NotifyHandler,
        event: TInEvent,
    },
    ReportObservedAddr {
        address: Multiaddr,
        score: AddressScore,
    },
    CloseConnection {
        peer_id: PeerId,
        connection: CloseConnection,
    },
}

An action that a NetworkBehaviour can trigger in the Swarm in whose context it is executing.

Variants

GenerateEvent(TOutEvent)

Instructs the Swarm to return an event when it is being polled.

Dial

Fields

opts: DialOpts

handler: THandler

Instructs the swarm to start a dial.

On success, NetworkBehaviour::inject_connection_established is invoked. On failure, NetworkBehaviour::inject_dial_failure is invoked.

Note that the provided handler is returned to the NetworkBehaviour on connection failure and connection closing. Thus it can be used to carry state, which otherwise would have to be tracked in the NetworkBehaviour itself. E.g. a message destined to an unconnected peer can be included in the handler, and thus directly send on connection success or extracted by the NetworkBehaviour on connection failure.

Example carrying state in the handler

// Super precious message that we should better not lose.
let message = PreciousMessage("My precious message".to_string());

// Unfortunately this peer is offline, thus sending our message to it will fail.
let offline_peer = PeerId::random();

// Let's send it anyways. We should get it back in case connecting to the peer fails.
swarm.behaviour_mut().send(offline_peer, message);

block_on(async {
    // As expected, sending failed. But great news, we got our message back.
    matches!(
        swarm.next().await.expect("Infinite stream"),
        SwarmEvent::Behaviour(PreciousMessage(_))
    );
});

#[derive(Default)]
struct MyBehaviour {
    outbox_to_swarm: VecDeque<NetworkBehaviourAction<PreciousMessage, MyHandler>>,
}

impl MyBehaviour {
    fn send(&mut self, peer_id: PeerId, msg: PreciousMessage) {
        self.outbox_to_swarm
            .push_back(NetworkBehaviourAction::Dial {
                opts: DialOpts::peer_id(peer_id)
                          .condition(PeerCondition::Always)
                          .build(),
                handler: MyHandler { message: Some(msg) },
            });
    }
}
impl NetworkBehaviour for MyBehaviour {
    fn inject_dial_failure(
        &mut self,
        _: Option<PeerId>,
        handler: Self::ConnectionHandler,
        _: &DialError,
    ) {
        // As expected, sending the message failed. But lucky us, we got the handler back, thus
        // the precious message is not lost and we can return it back to the user.
        let msg = handler.message.unwrap();
        self.outbox_to_swarm
            .push_back(NetworkBehaviourAction::GenerateEvent(msg))
    }
}

NotifyHandler

Fields

peer_id: PeerId

The peer for whom a ConnectionHandler should be notified.

handler: NotifyHandler

The options w.r.t. which connection handler to notify of the event.

event: TInEvent

The event to send.

Instructs the Swarm to send an event to the handler dedicated to a connection with a peer.

If the Swarm is connected to the peer, the message is delivered to the ConnectionHandler instance identified by the peer ID and connection ID.

If the specified connection no longer exists, the event is silently dropped.

Typically the connection ID given is the same as the one passed to NetworkBehaviour::inject_event, i.e. whenever the behaviour wishes to respond to a request on the same connection (and possibly the same substream, as per the implementation of ConnectionHandler).

Note that even if the peer is currently connected, connections can get closed at any time and thus the event may not reach a handler.

ReportObservedAddr

Fields

address: Multiaddr

The observed address of the local node.

score: AddressScore

The score to associate with this observation, i.e. an indicator for the trusworthiness of this address relative to other observed addresses.

Informs the Swarm about an address observed by a remote for the local node by which the local node is supposedly publicly reachable.

It is advisable to issue ReportObservedAddr actions at a fixed frequency per node. This way address information will be more accurate over time and individual outliers carry less weight.

CloseConnection

Fields

peer_id: PeerId

The peer to disconnect.

connection: CloseConnection

Whether to close a specific or all connections to the given peer.

Instructs the Swarm to initiate a graceful close of one or all connections with the given peer.

Note: Closing a connection via NetworkBehaviourAction::CloseConnection does not inform the corresponding ConnectionHandler. Closing a connection via a ConnectionHandler can be done either in a collaborative manner across ConnectionHandlers with ConnectionHandler::connection_keep_alive or directly with ConnectionHandlerEvent::Close.

Implementations

impl<TOutEvent, THandler: IntoConnectionHandler, TInEventOld> NetworkBehaviourAction<TOutEvent, THandler, TInEventOld>

pub fn map_in<TInEventNew>(
    self,
    f: impl FnOnce(TInEventOld) -> TInEventNew
) -> NetworkBehaviourAction<TOutEvent, THandler, TInEventNew>

Map the handler event.

impl<TOutEvent, THandler: IntoConnectionHandler> NetworkBehaviourAction<TOutEvent, THandler>

pub fn map_out<E>(
    self,
    f: impl FnOnce(TOutEvent) -> E
) -> NetworkBehaviourAction<E, THandler>

Map the event the swarm will return.

impl<TInEvent, TOutEvent, THandlerOld> NetworkBehaviourAction<TOutEvent, THandlerOld>where
    THandlerOld: IntoConnectionHandler,
    <THandlerOld as IntoConnectionHandler>::Handler: ConnectionHandler<InEvent = TInEvent>,

pub fn map_handler<THandlerNew>(
    self,
    f: impl FnOnce(THandlerOld) -> THandlerNew
) -> NetworkBehaviourAction<TOutEvent, THandlerNew>where
    THandlerNew: IntoConnectionHandler,
    <THandlerNew as IntoConnectionHandler>::Handler: ConnectionHandler<InEvent = TInEvent>,

Map the handler.

impl<TInEventOld, TOutEvent, THandlerOld> NetworkBehaviourAction<TOutEvent, THandlerOld>where
    THandlerOld: IntoConnectionHandler,
    <THandlerOld as IntoConnectionHandler>::Handler: ConnectionHandler<InEvent = TInEventOld>,

pub fn map_handler_and_in<THandlerNew, TInEventNew>(
    self,
    f_handler: impl FnOnce(THandlerOld) -> THandlerNew,
    f_in_event: impl FnOnce(TInEventOld) -> TInEventNew
) -> NetworkBehaviourAction<TOutEvent, THandlerNew>where
    THandlerNew: IntoConnectionHandler,
    <THandlerNew as IntoConnectionHandler>::Handler: ConnectionHandler<InEvent = TInEventNew>,

Map the handler and handler event.

Trait Implementations

impl<TOutEvent: Debug, THandler: Debug + IntoConnectionHandler, TInEvent: Debug> Debug for NetworkBehaviourAction<TOutEvent, THandler, TInEvent>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.