From 78f16f0248f5a6da09e98bc645f10505299c7d7f Mon Sep 17 00:00:00 2001
From: Stefan Wahren <info@lategoodbye.de>
Date: Thu, 4 Oct 2012 22:30:53 +0200
Subject: [PATCH] New defines for purge behavior (echo cancelation)

---
 mbus/mbus-protocol-aux.c | 7 +++++++
 mbus/mbus-protocol-aux.h | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/mbus/mbus-protocol-aux.c b/mbus/mbus-protocol-aux.c
index 57758eb..dd6ddb5 100755
--- a/mbus/mbus-protocol-aux.c
+++ b/mbus/mbus-protocol-aux.c
@@ -1467,6 +1467,13 @@ mbus_recv_frame(mbus_handle * handle, mbus_frame *frame)
     }
 
     result = handle->recv(handle, frame);
+    
+    /* frame valid, but wrong direction */
+    if (mbus_frame_direction(frame) == MBUS_CONTROL_MASK_DIR_M2S)
+    {
+        /* purge echo and retry (echo cancelation) */
+        result = handle->recv(handle, frame);
+    }
 
     if (frame != NULL)
     {
diff --git a/mbus/mbus-protocol-aux.h b/mbus/mbus-protocol-aux.h
index 5b63188..02694d9 100755
--- a/mbus/mbus-protocol-aux.h
+++ b/mbus/mbus-protocol-aux.h
@@ -70,12 +70,17 @@
 #define MBUS_PROBE_COLLISION 2
 #define MBUS_PROBE_ERROR     -1
 
+#define MBUS_FRAME_PURGE_S2M  2
+#define MBUS_FRAME_PURGE_M2S  1
+#define MBUS_FRAME_PURGE_NONE 0
+
 /**
  * Unified MBus handle type encapsulating either Serial or TCP gateway.
  */
 struct _mbus_handle {
     int fd;
     int max_retry;
+    char purge_first_frame;
     char is_serial; /**< _handle type (non zero for serial) */
     int (*open) (struct _mbus_handle *handle);
     int (*close) (struct _mbus_handle *handle);