Enum multistream_select::Version

pub enum Version {
    V1,
    V1Lazy,
}

Supported multistream-select protocol versions.

Variants

V1

Version 1 of the multistream-select protocol. See 1 and 2.

V1Lazy

A lazy variant of version 1 that is identical on the wire but delays sending of protocol negotiation data as much as possible.

Delaying the sending of protocol negotiation data can result in significantly fewer network roundtrips used for the negotiation, up to 0-RTT negotiation.

0-RTT negotiation is achieved if the dialer supports only a single application protocol. In that case the dialer immedidately settles on that protocol, buffering the negotiation messages to be sent with the first round of application protocol data (or an attempt is made to read from the Negotiated I/O stream).

A listener receiving a V1Lazy header will similarly delay sending of the protocol confirmation. Though typically the listener will need to read the request data before sending its response, thus triggering sending of the protocol confirmation, which, in absence of additional buffering on lower layers will result in at least two response frames to be sent.

V1Lazy is specific to rust-libp2p: While the wire protocol is identical to V1, delayed sending of protocol negotiation frames is only safe under the following assumptions:

1. The dialer is assumed to always send the first multistream-select protocol message immediately after the multistream header, without first waiting for confirmation of that header. Since the listener delays sending the protocol confirmation, a deadlock situation may otherwise occurs that is only resolved by a timeout. This assumption is trivially satisfied if both peers support and use V1Lazy.

2. When nesting multiple protocol negotiations, the listener is either known to support all of the dialer's optimistically chosen protocols or there is no intermediate protocol without a payload and none of the protocol payloads has the potential for being mistaken for a multistream-select protocol message. This avoids rare edge-cases whereby the listener may not recognize upgrade boundaries and erroneously process a request despite not supporting one of the intermediate protocols that the dialer committed to. See 1 and 2.

Trait Implementations

impl Clone for Version

fn clone(&self) -> Version

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Version

impl Debug for Version

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

Formats the value using the given formatter.

impl Default for Version

fn default() -> Self

Returns the "default value" for a type.

impl Eq for Version

impl PartialEq<Version> for Version

fn eq(&self, other: &Version) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl StructuralEq for Version

impl StructuralPartialEq for Version