BridgeRelay: Implement more traits.

Also add a BridgeRelayWithDesc type (name tbd) to guarantee that
a bridge relay really does have a known descriptor before you
try to build a circuit with it.

Cargo.lock

@@ -3704,6 +3704,7 @@ dependencies = [
  "tor-netdoc",
  "tor-persist",
  "tor-proto",
+ "tor-protover",
  "tor-rtcompat",
  "tor-rtmock",
  "tor-units",

crates/tor-guardmgr/Cargo.toml

@@ -19,7 +19,7 @@ experimental = ["bridge-client"]
 # Support for using bridges as a client. Note that this is not the same as
 # the pt-client feature, since here we are not concerned with
 # pluggable transports necessarily.
-bridge-client = ["tor-netdoc/routerdesc"]
+bridge-client = ["tor-netdoc/routerdesc", "tor-protover"]
 # Support for pluggable transports.
 pt-client = ["bridge-client", "tor-linkspec/pt-client"]
 
@@ -51,6 +51,7 @@ tor-netdir = { path = "../tor-netdir", version = "0.6.0" }
 tor-netdoc = { path = "../tor-netdoc", version = "0.5.2" }                               # for address pattern
 tor-persist = { path = "../tor-persist", version = "0.5.1" }
 tor-proto = { path = "../tor-proto", version = "0.7.0" }
+tor-protover = { path = "../tor-protover", version = "0.3.2", optional = true }
 tor-rtcompat = { path = "../tor-rtcompat", version = "0.7.0" }
 tor-units = { path = "../tor-units", version = "0.3.1" }
 tracing = "0.1.18"

crates/tor-guardmgr/src/bridge/relay.rs

@@ -2,7 +2,7 @@
 
 use std::sync::Arc;
 
-use tor_linkspec::{HasRelayIds, RelayIdRef, RelayIdType};
+use tor_linkspec::{ChanTarget, CircTarget, HasAddrs, HasRelayIds, RelayIdRef, RelayIdType};
 
 use super::{Bridge, BridgeDesc};
 
@@ -22,11 +22,26 @@ pub struct BridgeRelay {
     desc: Option<BridgeDesc>,
 }
 
+/// A BridgeRelay that is known to have its full information available, and
+/// which is therefore usable for circuits.
+#[derive(Clone, Debug)]
+pub struct BridgeRelayWithDesc<'a>(
+    /// This will _always_ be a bridge relay with a non-None desc.
+    &'a BridgeRelay,
+);
+
 impl BridgeRelay {
     /// Return true if this BridgeRelay has a known descriptor and can be used for relays.
     pub fn has_descriptor(&self) -> bool {
         self.desc.is_some()
     }
+
+    /// If we have enough information about this relay to build a circuit through it,
+    /// return a BridgeRelayWithDesc for it.
+    // TODO pt-client rename XXXX
+    pub fn for_circuit_usage(&self) -> Option<BridgeRelayWithDesc<'_>> {
+        self.desc.is_some().then(|| BridgeRelayWithDesc(self))
+    }
 }
 
 impl HasRelayIds for BridgeRelay {
@@ -36,3 +51,43 @@ impl HasRelayIds for BridgeRelay {
             .or_else(|| self.desc.as_ref().and_then(|d| d.identity(key_type)))
     }
 }
+
+impl HasAddrs for BridgeRelay {
+    fn addrs(&self) -> &[std::net::SocketAddr] {
+        todo!()
+    }
+}
+
+impl ChanTarget for BridgeRelay {}
+
+impl<'a> HasRelayIds for BridgeRelayWithDesc<'a> {
+    fn identity(&self, key_type: RelayIdType) -> Option<RelayIdRef<'_>> {
+        self.0.identity(key_type)
+    }
+}
+impl<'a> HasAddrs for BridgeRelayWithDesc<'a> {
+    fn addrs(&self) -> &[std::net::SocketAddr] {
+        self.0.addrs()
+    }
+}
+impl<'a> ChanTarget for BridgeRelayWithDesc<'a> {}
+
+impl<'a> BridgeRelayWithDesc<'a> {
+    /// Return a reference to the BridgeDesc in this reference.
+    fn desc(&self) -> &BridgeDesc {
+        self.0
+            .desc
+            .as_ref()
+            .expect("There was supposed to be a descriptor here")
+    }
+}
+
+impl<'a> CircTarget for BridgeRelayWithDesc<'a> {
+    fn ntor_onion_key(&self) -> &tor_llcrypto::pk::curve25519::PublicKey {
+        self.desc().as_ref().ntor_onion_key()
+    }
+
+    fn protovers(&self) -> &tor_protover::Protocols {
+        self.desc().as_ref().protocols()
+    }
+}