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.
Concurrently dial address candidates within a single dial attempt.
Main motivation for this feature is to increase success rate on hole punching
(see https://github.com/libp2p/rust-libp2p/issues/1896#issuecomment-885894496
for details). Though, as a nice side effect, as one would expect, it does
improve connection establishment time.
Cleanups and fixes done along the way:
- Merge `pool.rs` and `manager.rs`.
- Instead of manually implementing state machines in `task.rs` use
`async/await`.
- Fix bug where `NetworkBehaviour::inject_connection_closed` is called without a
previous `NetworkBehaviour::inject_connection_established` (see
https://github.com/libp2p/rust-libp2p/issues/2242).
- Return handler to behaviour on incoming connection limit error. Missed in
https://github.com/libp2p/rust-libp2p/issues/2242.
