IB/mad: Validate MADs for spec compliance

Validate MADs sent by userspace clients for spec compliance with
C13-18.1.1 (prevent duplicate requests and responses sent on the
same port).  Without this, RMPP transactions get aborted because
of duplicate packets.

This patch is similar to that provided by Jack Morgenstein.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Jack Morgenstein <jackm@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/include/rdma/ib_mad.h b/include/rdma/ib_mad.h
index 5ff7755..585d28e 100644
--- a/include/rdma/ib_mad.h
+++ b/include/rdma/ib_mad.h
@@ -75,6 +75,7 @@
 #define IB_MGMT_METHOD_TRAP_REPRESS		0x07
 
 #define IB_MGMT_METHOD_RESP			0x80
+#define IB_BM_ATTR_MOD_RESP			cpu_to_be32(1)
 
 #define IB_MGMT_MAX_METHODS			128
 
@@ -247,6 +248,12 @@
 };
 
 /**
+ * ib_response_mad - Returns if the specified MAD has been generated in
+ *   response to a sent request or trap.
+ */
+int ib_response_mad(struct ib_mad *mad);
+
+/**
  * ib_get_rmpp_resptime - Returns the RMPP response time.
  * @rmpp_hdr: An RMPP header.
  */