tor-circmgr: Add a helper for extending HsCircStubs by one hop.

use tor_error::{bad_api_usage, internal};

use tor_linkspec::{CircTarget, OwnedCircTarget};

use tor_netdir::{NetDir, NetDirProvider, Relay};

use tor_proto::circuit::{self, ClientCirc};

use tor_proto::circuit::{self, CircParameters, ClientCirc};

use tor_relay_selection::{LowLevelRelayPredicate, RelayExclusion};

use tor_rtcompat::{

    scheduler::{TaskHandle, TaskSchedule},

            .into());

        }

        let params = crate::DirInfo::from(netdir).circ_params();

        self.extend_circ(circ, params, target).await

    }

    /// Try to extend a circuit to the specified target hop.

    async fn extend_circ<T>(

        &self,

        circ: HsCircStub,

        params: CircParameters,

        target: T,

    ) -> Result<Arc<ClientCirc>>

    where

        T: CircTarget,

    {

        // Estimate how long it will take to extend it one more hop, and

        // construct a timeout as appropriate.

        let n_hops = circ.n_hops();

        );

        // Make a future to extend the circuit.

        let params = crate::DirInfo::from(netdir).circ_params();

        let extend_future = circ

            .extend_ntor(&target, &params)

            .map_err(|error| Error::Protocol {