WIP: issue per-path CIDs and keep track of them

quinn-proto/src/connection/mod.rs

@@ -228,8 +228,10 @@ pub struct Connection {
     /// exist.  So if multipath is supported the number of paths here will be higher than
     /// the actual number of paths in use.
     rem_cids: BTreeMap<PathId, CidQueue>,
-    // Attributes of CIDs generated by local peer
-    local_cid_state: CidState,
+    /// Attributes of CIDs generated by local endpoint
+    local_cid_state: BTreeMap<PathId, CidState>,
+    /// A map from issued CIDs to PathId, for fast lookup.
+    path_cids: BTreeMap<ConnectionId, PathId>,
     /// State of the unreliable datagram extension
     datagrams: DatagramState,
     /// Connection level statistics
@@ -242,11 +244,6 @@ pub struct Connection {
     //
     /// [`PathId`] associated with this connection if any.
     path_id: Option<PathId>,
-
-    /// A temporary map between CID and PathID.
-    // TODO(flub): This will probably be stored somewhere more cohesive with other path
-    //    data.  But is useful now because it allows us to make the logic changes.
-    path_cids: BTreeMap<ConnectionId, PathId>,
 }
 
 impl Connection {
@@ -289,18 +286,22 @@ impl Connection {
             expected_token: Bytes::new(),
             client_hello: None,
         });
+        let local_cid_state = BTreeMap::from([(
+            PathId(0),
+            CidState::new(
+                cid_gen.cid_len(),
+                cid_gen.cid_lifetime(),
+                now,
+                if pref_addr_cid.is_some() { 2 } else { 1 },
+            ),
+        )]);
 
         let mut this = Self {
             endpoint_config,
             crypto,
             handshake_cid: loc_cid,
             rem_handshake_cid: rem_cid,
-            local_cid_state: CidState::new(
-                cid_gen.cid_len(),
-                cid_gen.cid_lifetime(),
-                now,
-                if pref_addr_cid.is_some() { 2 } else { 1 },
-            ),
+            local_cid_state,
             path: PathData::new(remote, allow_mtud, None, now, path_validated, &config),
             allow_mtud,
             local_ip,