This commit removes the `Network` abstraction, thus managing `Listeners`
and the connection `Pool` in `Swarm` directly. This is done under the
assumption that noone uses the `Network` abstraction directly, but
instead everyone always uses it through `Swarm`. Both `Listeners` and
`Pool` are moved from `libp2p-core` into `libp2p-swarm`. Given that they
are no longer exposed via `Network`, they can be treated as an
implementation detail of `libp2p-swarm` and `Swarm`.
This change does not include any behavioural changes.
This change has the followin benefits:
- Removal of `NetworkEvent`, which was mostly an isomorphism of
`SwarmEvent`.
- Removal of the never-directly-used `Network` abstraction.
- Removal of now obsolete verbose `Peer` (`core/src/network/peer.rs`)
construct.
- Removal of `libp2p-core` `DialOpts`, which is a direct mapping of
`libp2p-swarm` `DialOpts`.
- Allowing breaking changes to the connection handling and `Swarm` API
interface without a breaking change in `libp2p-core` and thus a
without a breaking change in `/transport` protocols.
This change enables the following potential future changes:
- Removal of `NodeHandler` and `ConnectionHandler`. Thus allowing to
rename `ProtocolsHandler` into `ConnectionHandler`.
- Moving `NetworkBehaviour` and `ProtocolsHandler` into `libp2p-core`,
having `libp2p-xxx` protocol crates only depend on `libp2p-core` and
thus allowing general breaking changes to `Swarm` without breaking all
`libp2p-xxx` crates.
Allows `NetworkBehaviour` implementations to dial a peer, but instruct
the dialed connection to be upgraded as if it were the listening
endpoint.
This is needed when establishing direct connections through NATs and/or
Firewalls (hole punching). When hole punching via TCP (QUIC is different
but similar) both ends dial the other at the same time resulting in a
simultaneously opened TCP connection. To disambiguate who is the dialer
and who the listener there are two options:
1. Use the Simultaneous Open Extension of Multistream Select. See
[sim-open] specification and [sim-open-rust] Rust implementation.
2. Disambiguate the role (dialer or listener) based on the role within
the DCUtR [dcutr] protocol. More specifically the node initiating the
DCUtR process will act as a listener and the other as a dialer.
This commit enables (2), i.e. enables the DCUtR protocol to specify the
role used once the connection is established.
While on the positive side (2) requires one round trip less than (1), on
the negative side (2) only works for coordinated simultaneous dials.
I.e. when a simultaneous dial happens by chance, and not coordinated via
DCUtR, the connection attempt fails when only (2) is in place.
[sim-open]: https://github.com/libp2p/specs/blob/master/connections/simopen.md
[sim-open-rust]: https://github.com/libp2p/rust-libp2p/pull/2066
[dcutr]: https://github.com/libp2p/specs/blob/master/relay/DCUtR.md
Enable a `NetworkBehaviour` or a user via `Swarm::dial` to override the
dial concurrency factor per dial. This is especially relevant in the
case of libp2p-autonat where one wants to probe addresses in sequence to
reduce the amount of work a remote peer can force onto the local node.
To enable the above, this commit also:
- Introduces `libp2p_core::DialOpts` mirroring `libp2p_swarm::DialOpts`.
Passed as an argument to `Network::dial`.
- Removes `Peer::dial` in favor of `Network::dial`.
- Simplifies `Swarm::dial_with_handler`.
The introduction of `libp2p_core::DialOpts` will be useful beyond this
feature, e.g. for https://github.com/libp2p/rust-libp2p/pull/2363.
In the long run I would like to move and merge `libp2p_core::Network`
and `libp2p_core::Pool` into `libp2p_swarm::Swarm` thus deduplicating
`libp2p_core::DialOpts` and `libp2p_swarm::DialOpts`.
Fixes#2385.
Enable advanced dialing requests both on `Swarm` and via
`NetworkBehaviourAction`. Users can now trigger a dial with a specific
set of addresses, optionally extended via
`NetworkBehaviour::addresses_of_peer`. In addition the whole process is
now modelled in a type safe way via the builder pattern.
Example of a `NetworkBehaviour` requesting a dial to a specific peer
with a set of addresses additionally extended through
`NetworkBehaviour::addresses_of_peer`:
```rust
NetworkBehaviourAction::Dial {
opts: DialOpts::peer_id(peer_id)
.condition(PeerCondition::Always)
.addresses(addresses)
.extend_addresses_through_behaviour()
.build(),
handler,
}
```
Example of a user requesting a dial to an unknown peer with a single
address via `Swarm`:
```rust
swarm1.dial(
DialOpts::unknown_peer_id()
.address(addr2.clone())
.build()
)
```
