[dpdk-dev] [PATCH v6] doc: add GRO limitations in prog_guide

[Jiayu Hu]

This patch adds GRO limitations in the programmer guide.

Fixes: 2c900d09055e ("doc: add GRO guide")
Cc: stable at dpdk.org

Signed-off-by: Jiayu Hu <jiayu.hu at intel.com>
---
changes in v6:
- add VLAN limitation
changes in v5:
- remove fix commit 9e0b9d2ec0f4
changes in v4:
- update MBUF->l2_len/... requirement
changes in v3:
- add MBUF limitation
changes in v2:
- add fix commits
- add more limitations

 doc/guides/prog_guide/generic_receive_offload_lib.rst | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/doc/guides/prog_guide/generic_receive_offload_lib.rst b/doc/guides/prog_guide/generic_receive_offload_lib.rst
index 9c6a4d0..5b3fb91 100644
--- a/doc/guides/prog_guide/generic_receive_offload_lib.rst
+++ b/doc/guides/prog_guide/generic_receive_offload_lib.rst
@@ -191,3 +191,22 @@ Header fields deciding if packets are neighbors include:
         ignore IPv4 ID fields for the packets whose DF bit is 1.
         Additionally, packets which have different value of DF bit can't
         be merged.
+
+GRO Library Limitations
+-----------------------
+
+- GRO library uses MBUF->l2_len/l3_len/l4_len/outer_l2_len/
+  outer_l3_len/packet_type to get protocol headers for the
+  input packet, rather than parsing the packet header. Therefore,
+  before call GRO APIs to merge packets, user applications
+  must set MBUF->l2_len/l3_len/l4_len/outer_l2_len/outer_l3_len/
+  packet_type to the same values as the protocol headers of the
+  packet.
+
+- GRO library doesn't support to process the packets with IPv4
+  Options or VLAN tagged.
+
+- GRO library just supports to process the packet organized
+  in a single MBUF. If the input packet consists of multiple
+  MBUFs (i.e. chained MBUFs), GRO reassembly behaviors are
+  unknown.
-- 
2.7.4