[dpdk-dev] [PATCH v3 3/3] gso: update documents for UDP/IPv4 GSO

[Jiayu Hu <jiayu.hu@intel.com>]

This patch updates the programmer guide and testpmd user guide for
UDP/IPv4 GSO.

Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
---
 doc/guides/prog_guide/generic_segmentation_offload_lib.rst | 10 ++++++++++
 doc/guides/testpmd_app_ug/testpmd_funcs.rst                |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/doc/guides/prog_guide/generic_segmentation_offload_lib.rst b/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
index 9959f0d..0cfc119 100644
--- a/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
+++ b/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
@@ -43,6 +43,7 @@ Limitations
 #. Currently, the GSO library supports the following IPv4 packet types:
 
  - TCP
+ - UDP
  - VxLAN
  - GRE
 
@@ -146,6 +147,15 @@ TCP/IPv4 GSO
 TCP/IPv4 GSO supports segmentation of suitably large TCP/IPv4 packets, which
 may also contain an optional VLAN tag.
 
+UDP/IPv4 GSO
+~~~~~~~~~~~~
+UDP/IPv4 GSO supports segmentation of suitably large UDP/IPv4 packets, which
+may also contain an optional VLAN tag. UDP GSO is the same as IP fragmentation.
+Specifically, UDP GSO treats the UDP header as a part of the payload and
+does not modify it during segmentation. Therefore, after UDP GSO, only the
+first output packet has the original UDP header, and others just have l2
+and l3 headers.
+
 VxLAN GSO
 ~~~~~~~~~
 VxLAN packets GSO supports segmentation of suitably large VxLAN packets,
diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
index 0d6fd50..6f2de24 100644
--- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst
+++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst
@@ -1059,6 +1059,13 @@ By default, GSO is disabled for all ports.
 
    testpmd> csum set tcp hw <port_id>
 
+   UDP GSO is the same as IP fragmentation, which treats the UDP header
+   as the payload and does not modify it during segmentation. That is,
+   after UDP GSO, only the first output fragment has the original UDP
+   header. Therefore, users need to enable HW IP checksum calculation
+   and SW UDP checksum calculation for GSO-enabled ports, if they want
+   correct checksums for UDP/IPv4 packets.
+
 set gso segsz
 ~~~~~~~~~~~~~
 
-- 
2.7.4