core/: Merge pending and established connection limits

Merge pending and established limits for both incoming and outgoing
connections. More specifically merge
`ConnectionLimits::with_max_pending_incoming` with
`ConnectionLimits::with_max_established_incoming` and
`ConnectionLimits::with_max_pending_outgoing` with
`ConnectionLimits::with_max_established_outgoing`. Connection limits are
checked on `Network::dial` for outgoing and on `Network::accept` for
incoming connections.

This (a) simplifies connection limits from an implementations and user
perspective and (b) simplifies returning a connection handler on limit
error as limits can only be exceeded at the start of dialing and
accepting. See [1].

[1]: libp2p#2242 (comment)

core/CHANGELOG.md

@@ -1,6 +1,13 @@
 # 0.30.0 [unreleased]
 
-- Add `ConnectionLimit::with_max_established` (see [PR 2137]).
+- Add `ConnectionLimits::with_max_established` (see [PR 2137]).
+
+- Merge pending and established limits for both incoming and outgoing connections. More specifically
+  merge `ConnectionLimits::with_max_pending_incoming` with
+  `ConnectionLimits::with_max_established_incoming` and
+  `ConnectionLimits::with_max_pending_outgoing` with
+  `ConnectionLimits::with_max_established_outgoing`. Connection limits are checked on
+  `Network::dial` for outgoing and on `Network::accept` for incoming connections.
 
 - Add `Keypair::to_protobuf_encoding` (see [PR 2142]).
 
@@ -22,11 +29,6 @@
 
 - Remove `DisconnectedPeer::set_connected` and `Pool::add` (see [PR 2195]).
 
-- Report `ConnectionLimit` error through `ConnectionError` and thus through
-  `NetworkEvent::ConnectionClosed` instead of previously through
-  `PendingConnectionError` and thus `NetworkEvent::{IncomingConnectionError,
-  DialError}` (see [PR 2191]).
-
 - Report abortion of pending connection through `DialError`,
   `UnknownPeerDialError` or `IncomingConnectionError` (see [PR 2191]).
 

core/src/connection/error.rs

@@ -18,7 +18,6 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-use crate::connection::ConnectionLimit;
 use crate::transport::TransportError;
 use std::{fmt, io};
 
@@ -29,10 +28,6 @@ pub enum ConnectionError<THandlerErr> {
     // TODO: Eventually this should also be a custom error?
     IO(io::Error),
 
-    /// The connection was dropped because the connection limit
-    /// for a peer has been reached.
-    ConnectionLimit(ConnectionLimit),
-
     /// The connection handler produced an error.
     Handler(THandlerErr),
 }
@@ -45,9 +40,6 @@ where
         match self {
             ConnectionError::IO(err) => write!(f, "Connection error: I/O error: {}", err),
             ConnectionError::Handler(err) => write!(f, "Connection error: Handler error: {}", err),
-            ConnectionError::ConnectionLimit(l) => {
-                write!(f, "Connection error: Connection limit: {}.", l)
-            }
         }
     }
 }
@@ -60,7 +52,6 @@ where
         match self {
             ConnectionError::IO(err) => Some(err),
             ConnectionError::Handler(err) => Some(err),
-            ConnectionError::ConnectionLimit(..) => None,
         }
     }
 }

core/src/connection/manager.rs

@@ -20,8 +20,8 @@
 
 use super::{
     handler::{THandlerError, THandlerInEvent, THandlerOutEvent},
-    Connected, ConnectedPoint, ConnectionError, ConnectionHandler, ConnectionLimit,
-    IntoConnectionHandler, PendingConnectionError, Substream,
+    Connected, ConnectedPoint, ConnectionError, ConnectionHandler, IntoConnectionHandler,
+    PendingConnectionError, Substream,
 };
 use crate::{muxing::StreamMuxer, Executor};
 use fnv::FnvHashMap;
@@ -439,15 +439,15 @@ impl<'a, I> EstablishedEntry<'a, I> {
     ///
     /// When the connection is ultimately closed, [`Event::ConnectionClosed`]
     /// is emitted by [`Manager::poll`].
-    pub fn start_close(mut self, error: Option<ConnectionLimit>) {
+    pub fn start_close(mut self) {
         // Clone the sender so that we are guaranteed to have
         // capacity for the close command (every sender gets a slot).
         match self
             .task
             .get_mut()
             .sender
             .clone()
-            .try_send(task::Command::Close(error))
+            .try_send(task::Command::Close)
         {
             Ok(()) => {}
             Err(e) => assert!(e.is_disconnected(), "No capacity for close command."),

core/src/connection/manager/task.rs

@@ -23,8 +23,8 @@ use crate::{
     connection::{
         self,
         handler::{THandlerError, THandlerInEvent, THandlerOutEvent},
-        Close, Connected, Connection, ConnectionError, ConnectionHandler, ConnectionLimit,
-        IntoConnectionHandler, PendingConnectionError, Substream,
+        Close, Connected, Connection, ConnectionError, ConnectionHandler, IntoConnectionHandler,
+        PendingConnectionError, Substream,
     },
     muxing::StreamMuxer,
     Multiaddr,
@@ -43,7 +43,7 @@ pub enum Command<T> {
     NotifyHandler(T),
     /// Gracefully close the connection (active close) before
     /// terminating the task.
-    Close(Option<ConnectionLimit>),
+    Close,
 }
 
 /// Events that a task can emit to its manager.
@@ -163,7 +163,6 @@ where
     Closing {
         closing_muxer: Close<M>,
         handler: H::Handler,
-        error: Option<ConnectionLimit>,
     },
 
     /// The task is terminating with a final event for the `Manager`.
@@ -257,15 +256,14 @@ where
                             Poll::Ready(Some(Command::NotifyHandler(event))) => {
                                 connection.inject_event(event)
                             }
-                            Poll::Ready(Some(Command::Close(error))) => {
+                            Poll::Ready(Some(Command::Close)) => {
                                 // Don't accept any further commands.
                                 this.commands.get_mut().close();
                                 // Discard the event, if any, and start a graceful close.
                                 let (handler, closing_muxer) = connection.close();
                                 this.state = State::Closing {
                                     handler,
                                     closing_muxer,
-                                    error,
                                 };
                                 continue 'poll;
                             }
@@ -340,15 +338,14 @@ where
 
                 State::Closing {
                     handler,
-                    error,
                     mut closing_muxer,
                 } => {
                     // Try to gracefully close the connection.
                     match closing_muxer.poll_unpin(cx) {
                         Poll::Ready(Ok(())) => {
                             let event = Event::Closed {
                                 id: this.id,
-                                error: error.map(ConnectionError::ConnectionLimit),
+                                error: None,
                                 handler,
                             };
                             this.state = State::Terminating(event);
@@ -364,7 +361,6 @@ where
                         Poll::Pending => {
                             this.state = State::Closing {
                                 handler,
-                                error,
                                 closing_muxer,
                             };
                             return Poll::Pending;