.. index:: pair: group; TCP Segmentation Offload
.. _doxid-group__offload-tso:

TCP Segmentation Offload
========================

.. toctree::
	:hidden:

Check that when TSO is enabled, larger-than-MSS packets are passed to NIC and split into MSS-sized ones by it.



#. If **tso_on** is ``TRUE``, try to enable related Tx checksum offloadings if they are disabled.

#. Turn TSO on or off on IUT according to **tso_on**.

#. Make sure LRO and GRO are turned off on Tester, so that CSAP captures IUT packets there exactly as they were sent and their sizes can be checked.

#. Establish connection between a pair of TCP sockets on IUT and Tester, setting ``SO_SNDBUF`` on the IUT socket and ``SO_RCVBUF`` on the Tester socket to values large enough for the data to be sent.

#. Create a CSAP on IUT to capture outgoing packets.

#. Create a CSAP on Tester to capture incoming packets.

#. Do **send_calls** times in a loop:
   
   * Pass a single bigger than MTU buffer to send() on the IUT socket.
   
   * Receive and check data on the Tester socket.
   
   * Examine outgoing packets captured by the IUT CSAP. Packets bigger than MSS should be encountered if and only if **tso_on** is ``TRUE``.
   
   * Examine incoming packets captured by the Tester CSAP. All the captured packets except the last one must be of MSS size.



.. rubric:: Parameters:

.. list-table::
	:widths: 20 80

	*
		- env

		- 
		  Testing environment:
		  
		  * :ref:`env.peer2peer <doxid-group__env-peer2peer>`
		  
		  * :ref:`env.peer2peer_ipv6 <doxid-group__env-peer2peer__ipv6>`

	*
		- tso_on

		- Should TCP Segmentation Offload be enabled?

	*
		- min_size

		- 
		  Minimum size of data passed to send() call, in MTU units:
		  
		  * ``2``

	*
		- max_size

		- 
		  Maximum size of data passed to send() call, in MTU units:
		  
		  * ``5``

	*
		- send_calls

		- 
		  Number of send() calls:
		  
		  * ``3``