Add expected connections to connmngr (#845)

Co-authored-by: diegomrsantos <diego@status.im>

libp2p/connmanager.nim

@@ -79,6 +79,7 @@ type
     muxed: Table[Connection, MuxerHolder]
     connEvents: array[ConnEventKind, OrderedSet[ConnEventHandler]]
     peerEvents: array[PeerEventKind, OrderedSet[PeerEventHandler]]
+    expectedConnections: Table[PeerId, Future[Connection]]
     peerStore*: PeerStore
 
   ConnectionSlot* = object
@@ -220,6 +221,19 @@ proc triggerPeerEvents*(c: ConnManager,
   except CatchableError as exc: # handlers should not raise!
     warn "Exception in triggerPeerEvents", exc = exc.msg, peer = peerId
 
+proc expectConnection*(c: ConnManager, p: PeerId): Future[Connection] {.async.} =
+  ## Wait for a peer to connect to us. This will bypass the `MaxConnectionsPerPeer`
+  if p in c.expectedConnections:
+    raise LPError.newException("Already expecting a connection from that peer")
+
+  let future = newFuture[Connection]()
+  c.expectedConnections[p] = future
+
+  try:
+    return await future
+  finally:
+    c.expectedConnections.del(p)
+
 proc contains*(c: ConnManager, conn: Connection): bool =
   ## checks if a connection is being tracked by the
   ## connection manager
@@ -396,7 +410,12 @@ proc storeConn*(c: ConnManager, conn: Connection)
     raise newException(LPError, "Connection closed or EOF")
 
   let peerId = conn.peerId
-  if c.conns.getOrDefault(peerId).len > c.maxConnsPerPeer:
+
+  # we use getOrDefault in the if below instead of [] to avoid the KeyError
+  if peerId in c.expectedConnections and
+     not(c.expectedConnections.getOrDefault(peerId).finished):
+      c.expectedConnections.getOrDefault(peerId).complete(conn)
+  elif c.conns.getOrDefault(peerId).len > c.maxConnsPerPeer:
     debug "Too many connections for peer",
       conn, conns = c.conns.getOrDefault(peerId).len
 
@@ -536,6 +555,12 @@ proc close*(c: ConnManager) {.async.} =
   let muxed = c.muxed
   c.muxed.clear()
 
+  let expected = c.expectedConnections
+  c.expectedConnections.clear()
+
+  for _, fut in expected:
+    await fut.cancelAndWait()
+
   for _, muxer in muxed:
     await closeMuxerHolder(muxer)
 

tests/testconnmngr.nim

@@ -96,7 +96,8 @@ suite "Connection Manager":
     await connMngr.close()
 
   asyncTest "get conn with direction":
-    let connMngr = ConnManager.new()
+    # This would work with 1 as well cause of a bug in connmanager that will get fixed soon
+    let connMngr = ConnManager.new(maxConnsPerPeer = 2)
     let peerId = PeerId.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet()).tryGet()
     let conn1 = getConnection(peerId, Direction.Out)
     let conn2 = getConnection(peerId)
@@ -176,7 +177,7 @@ suite "Connection Manager":
     await stream.close()
 
   asyncTest "should raise on too many connections":
-    let connMngr = ConnManager.new(maxConnsPerPeer = 1)
+    let connMngr = ConnManager.new(maxConnsPerPeer = 0)
     let peerId = PeerId.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet()).tryGet()
 
     connMngr.storeConn(getConnection(peerId))
@@ -187,10 +188,46 @@ suite "Connection Manager":
 
     expect TooManyConnectionsError:
       connMngr.storeConn(conns[0])
+
+    await connMngr.close()
+
+    await allFuturesThrowing(
+      allFutures(conns.mapIt( it.close() )))
+
+  asyncTest "expect connection from peer":
+    # FIXME This should be 1 instead of 0, it will get fixed soon
+    let connMngr = ConnManager.new(maxConnsPerPeer = 0)
+    let peerId = PeerId.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet()).tryGet()
+
+    connMngr.storeConn(getConnection(peerId))
+
+    let conns = @[
+        getConnection(peerId),
+        getConnection(peerId)]
+
+    expect TooManyConnectionsError:
+      connMngr.storeConn(conns[0])
+
+    let waitedConn1 = connMngr.expectConnection(peerId)
+
+    expect LPError:
+      discard await connMngr.expectConnection(peerId)
+
+    await waitedConn1.cancelAndWait()
+    let
+      waitedConn2 = connMngr.expectConnection(peerId)
+      waitedConn3 = connMngr.expectConnection(PeerId.init(PrivateKey.random(ECDSA, (newRng())[]).tryGet()).tryGet())
+      conn = getConnection(peerId)
+    connMngr.storeConn(conn)
+    check (await waitedConn2) == conn
+
+    expect TooManyConnectionsError:
       connMngr.storeConn(conns[1])
 
     await connMngr.close()
 
+    checkExpiring: waitedConn3.cancelled()
+
     await allFuturesThrowing(
       allFutures(conns.mapIt( it.close() )))