* libp2p-ping improvements.
* re #950: Removes use of the `OneShotHandler`, but still sending each
ping over a new substream, as seems to be intentional since #828.
* re #842: Adds an integration test that exercises the ping behaviour through
a Swarm, requiring the RTT to be below a threshold. This requires disabling
Nagle's algorithm as it can interact badly with delayed ACKs (and has been
observed to do so in the context of the new ping example and integration test).
* re #864: Control of the inbound and outbound (sub)stream protocol upgrade
timeouts has been moved from the `NodeHandlerWrapperBuilder` to the
`ProtocolsHandler`. That may also alleviate the need for a custom timeout
on an `OutboundSubstreamRequest` as a `ProtocolsHandler` is now free to
adjust these timeouts over time.
Other changes:
* A new ping example.
* Documentation improvements.
* More documentation improvements.
* Add PingPolicy and ensure no event is dropped.
* Remove inbound_timeout/outbound_timeout.
As per review comment, the inbound timeout is now configured
as part of the `listen_protocol` and the outbound timeout as
part of the `OutboundSubstreamRequest`.
* Simplify and generalise.
Generalise `ListenProtocol` to `SubstreamProtocol`, reusing it in
the context of `ProtocolsHandlerEvent::OutboundSubstreamRequest`.
* Doc comments for SubstreamProtocol.
* Adapt to changes in master.
* Relax upper bound for ping integration test rtt.
For "slow" CI build machines?
Replace the listener and address pair returned from `Transport::listen_on` with just a listener that produces `ListenerEvent` values which include upgrades as well as address changes.
* Consolidate keypairs in core.
Introduce the concept of a node's identity keypair in libp2p-core,
instead of only the public key:
* New module: libp2p_core::identity with submodules for the currently
supported key types. An identity::Keypair and identity::PublicKey
support the creation and verification of signatures. The public key
supports encoding/decoding according to the libp2p specs.
* The secio protocol is simplified as a result of moving code to libp2p-core.
* The noise protocol is slightly simplified by consolidating ed25519
keypairs in libp2p-core and using x25519-dalek for DH. Furthermore,
Ed25519 to X25519 keypair conversion is now complete and tested.
Generalise over the DH keys in the noise protocol.
Generalise over the DH keys and thus DH parameter in handshake patterns
of the Noise protocol, such that it is easy to support other DH schemes
in the future, e.g. X448.
* Address new review comments.
* Fix the dialing priority system
* Bump libp2p-core to 0.3.1
* Cancel dialing attempt if we don't have priority
* Add test for simultaneous dialing
* Improve test
* Fix test stuck forever
