doc: add missing loopback option in testpmd guide

This patch adds a missing topology "loop" mode for port-topology
option in testpmd guide. The testpmd "loop" option
(PORT_TOPOLOGY_LOOP)  was added to testpmd parameter
port-topology back in 2014, but it seems that it was never added
to the testpmd guide. This patch adds it in the testpmd guide.

Fixes: 3e2006d6186c ("app/testpmd: add loopback topology")
Cc: stable@dpdk.org
Signed-off-by: Rami Rosen <ramirose@gmail.com>
Acked-by: Bernard Iremonger <bernard.iremonger@intel.com>

diff --git a/doc/guides/testpmd_app_ug/run_app.rst b/doc/guides/testpmd_app_ug/run_app.rst
index f717bd3..4495ed0 100644 (file)
--- a/doc/guides/testpmd_app_ug/run_app.rst
+++ b/doc/guides/testpmd_app_ug/run_app.rst
@@ -196,7 +196,7 @@ The commandline options are:
 
 *   ``--port-topology=mode``
 
-    Set port topology, where mode is ``paired`` (the default) or ``chained``.
+    Set port topology, where mode is ``paired`` (the default), ``chained`` or ``loop``.
 
     In ``paired`` mode, the forwarding is between pairs of ports, for example: (0,1), (2,3), (4,5).
 
@@ -204,6 +204,8 @@ The commandline options are:
 
     The ordering of the ports can be changed using the portlist testpmd runtime function.
 
+    In ``loop`` mode, ingress traffic is simply transmitted back on the same interface.
+
 *   ``--forward-mode=mode``
 
     Set the forwarding mode where ``mode`` is one of the following::