Add monotonic_offset to the ServerStatistics message

Send a base level of traffic between all nodes which should be
forwarding messages between each other.  This helps replay, and also
gives us enough information to estimate the monotonic clock offset
between nodes.  That lets us sort out latencies between nodes.

Change-Id: I9b10243aca2444e201d0d8c0a551e29560d0e147
diff --git a/aos/network/sctp_server.h b/aos/network/sctp_server.h
index a3086d9..b702aa8 100644
--- a/aos/network/sctp_server.h
+++ b/aos/network/sctp_server.h
@@ -46,11 +46,19 @@
   void SetStreamPriority(sctp_assoc_t assoc_id, int stream_id,
                          uint16_t priority);
 
+  void SetMaxSize(size_t max_size) {
+    max_size_ = max_size;
+    // Have the kernel give us a factor of 10 more.  This lets us have more than
+    // one full sized packet in flight.
+    max_size = max_size * 10;
+    PCHECK(setsockopt(fd_, SOL_SOCKET, SO_RCVBUF, &max_size,
+                      sizeof(max_size)) == 0);
+  }
+
  private:
   struct sockaddr_storage sockaddr_local_;
   int fd_;
 
-  // TODO(austin): Configure this.
   size_t max_size_ = 1000;
 
   int ppid_ = 1;