.. index:: pair: group; Receive Offload for TCP packets
.. _doxid-group__offload-receive__offload:

Receive Offload for TCP packets
===============================

.. toctree::
	:hidden:

Check that when LRO or GRO is enabled, received TCP packets are coalesced into bigger ones before they reach OS.



#. Set **rx-checksum**, **rx-lro**, **rx-gro** and **rx-gro-hw** features on the IUT interface according to values of **rx_csum_on**, **lro_on**, **gro_on**, **gro_hw_on** and **rx_vlan_strip_on** test parameters.

#. Try to disable adaptive Rx interrupt coalescing and set **rx_coalesce_usecs** to a big value on the IUT interface to make sure that LRO or GRO often coalesces incoming packets.

#. Make sure TSO is enabled on Tester if possible, so that packets are sent as fast as possible from it.

#. If **rx_vlan_strip_on**, create VLANs, assign addresses and use it for traffic checks below.

#. Establish connection between a pair of TCP sockets on IUT and Tester.

#. Enable ``TCP_NODELAY`` option on the Tester socket so that packets are sent as soon as possible from it.

#. Create a CSAP on IUT to capture packets sent from Tester.

#. Send a lot of data from Tester in multiple bursts with help of **rpc_pattern_sender()**, receiving it all on IUT with **rpc_pattern_receiver()**.

#. Process packets captured by CSAP on IUT. Check that larger-than-MSS packets are encountered if and only if either **gro_on** and/or gro_hw_on are ``TRUE`` or both **lro_on** and **rx_csum_on** are ``TRUE``.
   
   * If LRO is enabled (i.e. both **lro_on** and **rx_csum_on** are ``TRUE``) and 'sfc' driver is tested, check that the first large packet is received after a number of packets specified by **lro_slow_start_packets** driver module parameter.



.. 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>`

	*
		- rx_csum_on

		- If ``TRUE``, Rx checksum offload is enabled.

	*
		- lro_on

		- If ``TRUE``, LRO is enabled.

	*
		- gro_on

		- If ``TRUE``, GRO is enabled.

	*
		- gro_hw_on

		- If ``TRUE``, Hardware GRO is enabled.

	*
		- rx_vlan_strip_on

		- If ``TRUE``, VLAN strip is enabled.