Refactor connection process (#1016)

* Refactor connection process

fluffy/network/wire/portal_protocol.nim

@@ -505,16 +505,18 @@ proc findContent*(p: PortalProtocol, dst: Node, contentKey: ByteList):
           id = dst.id
         return err("Trying to connect to node with unknown address")
 
-      let socketRes = await p.stream.transport.connectTo(
-          nodeAddress.unsafeGet(), uint16.fromBytesBE(m.connectionId))
-      if socketRes.isErr():
-        # TODO: get proper error mapped
-        return err("Error connecting to uTP socket")
-      let socket = socketRes.get()
-      if not socket.isConnected():
-        socket.close()
-        return err("Portal uTP socket is not in connected state")
+      let connectionResult = 
+        await p.stream.connectTo(
+          nodeAddress.unsafeGet(),
+          uint16.fromBytesBE(m.connectionId)
+        )
 
+      if connectionResult.isErr():
+        error "Utp connection error while trying to find content",
+          msg = connectionResult.error
+        return err("Error connecting uTP socket")
+      
+      let socket = connectionResult.get()
       # Read all bytes from the socket
       # This will either end with a FIN, or because the read action times out.
       # A FIN does not necessarily mean that the data read is complete. Further
@@ -570,17 +572,20 @@ proc offer*(p: PortalProtocol, dst: Node, contentKeys: ContentKeysList):
       error "Trying to connect to node with unknown address",
         id = dst.id
       return err("Trying to connect to node with unknown address")
+      
+    let connectionResult = 
+      await p.stream.connectTo(
+        nodeAddress.unsafeGet(), 
+        uint16.fromBytesBE(m.connectionId)
+      )
 
-    let clientSocketRes = await p.stream.transport.connectTo(
-      nodeAddress.unsafeGet(), uint16.fromBytesBE(m.connectionId))
-    if clientSocketRes.isErr():
-      # TODO: get proper error mapped
-      return err("Error connecting to uTP socket")
-    let clientSocket = clientSocketRes.get()
-    if not clientSocket.isConnected():
-      clientSocket.close()
-      return err("Portal uTP socket is not in connected state")
+    if connectionResult.isErr():
+      error "Utp connection error while trying to offer content",
+        msg = connectionResult.error
+      return err("Error connecting uTP socket")
 
+    let clientSocket = connectionResult.get()
+ 
     for contentKey in requestedContentKeys:
       let contentIdOpt = p.toContentId(contentKey)
       if contentIdOpt.isSome():

fluffy/network/wire/portal_stream.nim

@@ -41,7 +41,7 @@ type
     {.gcsafe, raises: [Defect].}
 
   PortalStream* = ref object
-    transport*: UtpDiscv5Protocol
+    transport: UtpDiscv5Protocol
     # TODO:
     # Decide on what's the better collection to use and set some limits in them
     # on how many uTP transfers allowed to happen concurrently.
@@ -99,6 +99,34 @@ proc addContentRequest*(
 
   return connectionId
 
+proc connectTo*(
+  stream: PortalStream, 
+  nodeAddress: NodeAddress, 
+  connectionId: uint16): Future[Result[UtpSocket[NodeAddress], string]] {.async.} =
+  let socketRes = await stream.transport.connectTo(nodeAddress, connectionId)
+
+  if socketRes.isErr():
+    case socketRes.error.kind
+    of SocketAlreadyExists:
+      # This error means that there is already socket to this nodeAddress with given
+      # connection id, in our use case it most probably means that other side sent us
+      # connection id which is already used.
+      # For now we just fail connection and return an error. Another strategy to consider
+      # would be to check what is the connection status, and then re-use it, or 
+      # close it and retry connection.
+      let msg = "Socket to " & $nodeAddress & "with connection id: " & $connectionId & " already exists"
+      return err(msg)
+    of ConnectionTimedOut:
+      # Another strategy for handling this error would be to retry connecting a few times
+      # before giving up. But we know (as we control the uTP impl) that this error will only
+      # be returned when a SYN packet was re-sent 3 times and failed to be acked. This
+      # should be enough for us to known that the remote host is not reachable.
+      let msg = "uTP timeout while trying to connect to " & $nodeAddress
+      return err(msg)
+
+  let socket = socketRes.get()
+  return ok(socket)
+
 proc writeAndClose(
     socket: UtpSocket[NodeAddress], stream: PortalStream,
     request: ContentRequest) {.async.} =