Module upgrade

Contains everything related to upgrading a connection or a substream to use a protocol.

After a connection with a remote has been successfully established or a substream successfully opened, the next step is to upgrade this connection or substream to use a protocol.

This is where the UpgradeInfo, InboundUpgrade and OutboundUpgrade traits come into play. The InboundUpgrade and OutboundUpgrade traits are implemented on types that represent a collection of one or more possible protocols for respectively an ingoing or outgoing connection or substream.

Note: Multiple versions of the same protocol are treated as different protocols. For example, /foo/1.0.0 and /foo/1.1.0 are totally unrelated as far as upgrading is concerned.

Upgrade process

An upgrade is performed in two steps:

• A protocol negotiation step. The UpgradeInfo::protocol_info method is called to determine which protocols are supported by the trait implementation. The multistream-select protocol is used in order to agree on which protocol to use amongst the ones supported.

• A handshake. After a successful negotiation, the InboundUpgrade::upgrade_inbound or OutboundUpgrade::upgrade_outbound method is called. This method will return a Future that performs a handshake. This handshake is considered mandatory, however in practice it is possible for the trait implementation to return a dummy Future that doesn’t perform any action and immediately succeeds.

After an upgrade is successful, an object of type InboundUpgrade::Output or OutboundUpgrade::Output is returned. The actual object depends on the implementation and there is no constraint on the traits that it should implement, however it is expected that it can be used by the user to control the behaviour of the protocol.

Note: You can use the apply_inbound or apply_outbound methods to try upgrade a connection or substream. However if you use the recommended Swarm or ConnectionHandler APIs, the upgrade is automatically handled for you and you don’t need to use these methods.

Structs

DeniedUpgrade

Dummy implementation of UpgradeInfo/InboundUpgrade/OutboundUpgrade that doesn’t support any protocol.

NegotiatedComplete

A Future that waits on the completion of protocol negotiation.

PendingUpgrade

Implementation of UpgradeInfo, InboundUpgrade and OutboundUpgrade that always returns a pending upgrade.

ReadyUpgrade

Implementation of UpgradeInfo, InboundUpgrade and OutboundUpgrade that directly yields the substream.

SelectUpgrade

Upgrade that combines two upgrades into one. Supports all the protocols supported by either sub-upgrade.

Enums

NegotiationError

Error that can happen when negotiating a protocol with the remote.

ProtocolError

A protocol error.

Version

Supported multistream-select versions.

Traits

InboundConnectionUpgrade

Possible upgrade on an inbound connection

InboundUpgrade

Possible upgrade on an inbound connection or substream.

OutboundConnectionUpgrade

Possible upgrade on an outbound connection

OutboundUpgrade

Possible upgrade on an outbound connection or substream.

UpgradeInfo

Common trait for upgrades that can be applied on inbound substreams, outbound substreams, or both.

Type Aliases

Negotiated