face: congestion detection in TCP, UDP, and Unix socket transports

refs #4362

Change-Id: Idaa5d65e1f33663d95bad56de42640183b2cda6d
diff --git a/daemon/face/multicast-udp-transport.hpp b/daemon/face/multicast-udp-transport.hpp
index b0fb4d4..e655f4a 100644
--- a/daemon/face/multicast-udp-transport.hpp
+++ b/daemon/face/multicast-udp-transport.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2018,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -71,6 +71,9 @@
                         protocol::socket&& sendSocket,
                         ndn::nfd::LinkType linkType);
 
+  ssize_t
+  getSendQueueLength() final;
+
   static void
   openRxSocket(protocol::socket& sock,
                const protocol::endpoint& multicastGroup,