* protocols/gossipsub: Fix inconsistency in mesh peer tracking (libp2p#2189)

Co-authored-by: Age Manning <Age@AgeManning.com>

* misc/metrics: Add auxiliary crate to record events as OpenMetrics (libp2p#2063)

This commit adds an auxiliary crate recording protocol and Swarm events
and exposing them as metrics in the OpenMetrics format.

* README: Mention security@ipfs.io

* examples/: Add file sharing example (libp2p#2186)

Basic file sharing application with peers either providing or locating
and getting files by name.

While obviously showcasing how to build a basic file sharing
application, the actual goal of this example is **to show how to
integrate rust-libp2p into a larger application**.

Architectural properties

- Clean clonable async/await interface ([`Client`]) to interact with the
network layer.

- Single task driving the network layer, no locks required.

* examples/README: Give an overview over the many examples (libp2p#2194)

* protocols/kad: Enable filtering of (provider) records (libp2p#2163)

Introduce `KademliaStoreInserts` option, which allows to filter records.

Co-authored-by: Max Inden <mail@max-inden.de>

* swarm/src/protocols_handler: Impl ProtocolsHandler on either::Either (libp2p#2192)

Implement ProtocolsHandler on either::Either representing either of two
ProtocolsHandler implementations.

Co-authored-by: Thomas Eizinger <thomas@eizinger.io>

* *: Make libp2p-core default features optional (libp2p#2181)

Co-authored-by: Max Inden <mail@max-inden.de>

* core/: Remove DisconnectedPeer::set_connected and Pool::add (libp2p#2195)

This logic seems to be a leftover of
libp2p#889 and unused today.

* protocols/gossipsub: Use ed25519 in tests (libp2p#2197)

With f2905c0 the secp256k1 feature is
disabled by default. Instead of enabling it in the dev-dependency,
simply use ed25519.

* build(deps): Update minicbor requirement from 0.10 to 0.11 (libp2p#2200)

Updates the requirements on [minicbor](https://gitlab.com/twittner/minicbor) to permit the latest version.
- [Release notes](https://gitlab.com/twittner/minicbor/tags)
- [Changelog](https://gitlab.com/twittner/minicbor/blob/master/CHANGELOG.md)
- [Commits](https://gitlab.com/twittner/minicbor/compare/minicbor-v0.10.0...minicbor-v0.11.0)

---
updated-dependencies:
- dependency-name: minicbor
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

* build(deps): Update salsa20 requirement from 0.8 to 0.9 (libp2p#2206)

* build(deps): Update salsa20 requirement from 0.8 to 0.9

Updates the requirements on [salsa20](https://github.com/RustCrypto/stream-ciphers) to permit the latest version.
- [Release notes](https://github.com/RustCrypto/stream-ciphers/releases)
- [Commits](RustCrypto/stream-ciphers@ctr-v0.8.0...salsa20-v0.9.0)

---
updated-dependencies:
- dependency-name: salsa20
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

* *: Bump pnet to v0.22

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Max Inden <mail@max-inden.de>

* *: Dial with handler and return handler on error and closed (libp2p#2191)

Require `NetworkBehaviourAction::{DialPeer,DialAddress}` to contain a
`ProtocolsHandler`. This allows a behaviour to attach custom state to its
handler. The behaviour would no longer need to track this state separately
during connection establishment, thus reducing state required in a behaviour.
E.g. in the case of `libp2p-kad` the behaviour can include a `GetRecord` request
in its handler, or e.g. in the case of `libp2p-request-response` the behaviour
can include the first request in the handler.

Return `ProtocolsHandler` on connection error and close. This allows a behaviour
to extract its custom state previously included in the handler on connection
failure and connection closing. E.g. in the case of `libp2p-kad` the behaviour
could extract the attached `GetRecord` from the handler of the failed connection
and then start another connection attempt with a new handler with the same
`GetRecord` or bubble up an error to the user.

Co-authored-by: Thomas Eizinger <thomas@eizinger.io>

* core/: Remove deprecated read/write functions (libp2p#2213)

Co-authored-by: Max Inden <mail@max-inden.de>

* protocols/ping: Revise naming of symbols (libp2p#2215)

Co-authored-by: Max Inden <mail@max-inden.de>

* protocols/rendezvous: Implement protocol (libp2p#2107)

Implement the libp2p rendezvous protocol.

> A lightweight mechanism for generalized peer discovery. It can be used for
bootstrap purposes, real time peer discovery, application specific routing, and
so on.

Co-authored-by: rishflab <rishflab@hotmail.com>
Co-authored-by: Daniel Karzel <daniel@comit.network>

* core/src/network/event.rs: Fix typo (libp2p#2218)

* protocols/mdns: Do not fire all timers at the same time. (libp2p#2212)

Co-authored-by: Max Inden <mail@max-inden.de>

* misc/metrics/src/kad: Set query_duration lowest bucket to 0.1 sec (libp2p#2219)

Probability for a Kademlia query to return in less than 100 milliseconds
is low, thus increasing the lower bucket to improve accuracy within the
higher ranges.

* misc/metrics/src/swarm: Expose role on connections_closed (libp2p#2220)

Expose whether closed connection was a Dialer or Listener.

* .github/workflows/ci.yml: Use clang 11 (libp2p#2233)

* protocols/rendezvous: Update prost (libp2p#2226)

Co-authored-by: Max Inden <mail@max-inden.de>

* *: Fix clippy warnings (libp2p#2227)

* swarm-derive/: Make event_process = false the default (libp2p#2214)

Co-authored-by: Max Inden <mail@max-inden.de>

Co-authored-by: Max Inden <mail@max-inden.de>
Co-authored-by: Age Manning <Age@AgeManning.com>
Co-authored-by: Ruben De Smet <ruben.de.smet@rubdos.be>
Co-authored-by: Thomas Eizinger <thomas@eizinger.io>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: rishflab <rishflab@hotmail.com>
Co-authored-by: Daniel Karzel <daniel@comit.network>
Co-authored-by: David Craven <david@craven.ch>

Co-authored-by: Max Inden <mail@max-inden.de>